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RMD Open 2026;12:e006593. doi:10.1136/rmdopen-2025-006593ORIGINAL RESEARCHImpact of postpartum on patients with rheumatoid arthritis and spondyloarthritis: an ancillary analysis of the GR2 prospective cohortMarie Hornez , 1 Anna Molto ,2,3 Maxime Leroy, 4 Béatrice Banneville,5 Rakiba Belkhir,6 Elodie Chauvet,7 Marion Couderc , 8 Emmanuelle Dernis,9 Valérie Devauchelle- Pensec, 10,11 Aline Frazier,12 Laure Gossec , 5 Elisabeth Gervais, 13 Hubert Marotte ,14 Christophe Richez,15,16 Jérémie Sellam,17 Raphaele Seror , 6 Véronique Le Guern,18 Gaëlle Guettrot-Imbert,18 Nathalie Costedoat- Chalumeau ,18 René-Marc Flipo,19 Jean- Guillaume Letarouilly 20To cite: Hornez M, Molto A, Leroy M, et al. Impact of postpartum on patients with rheumatoid arthritis and spondyloarthritis: an ancillary analysis of the GR2 prospective cohort. RMD Open2026;12:e006593. doi:10.1136/ rmdopen-2025-006593► Additional supplemental material is published online only. To view, please visit the journal online (https:// doi. org/ 10. 1136/rmdopen- 2025- 006593). Received 9 December 2025 Accepted 31 March 2026 For numbered affiliations see end of article.Correspondence toDr Jean- Guillaume Letarouilly;Jeanguillaume. letarouilly@chu- lille. frEpidemiology© Author(s) (or their employer(s)) 2026. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ Group.ABSTRACTObjective To describe disease activity and treatments received during the postpartum period, breastfeeding rates and their possible impact on rheumatoid arthritis (RA) and spondyloarthritis (SpA) activity.Method This ancillary study from the French multicentre prospective cohort (GR2-NCT02450396) included pregnant women with RA and SpA with at least one postpartum visit from October 2014 to October 2022. Disease activity, flares, treatments and breastfeeding rates were described. Factors associated with the occurrence of a flare were evaluated by survival analysis. Disease activity was compared according to breastfeeding duration (never, <6 months and ≥6 months).Results Ninety-four RA and 124 SpA patients were studied. In RA patients, the proportion of patients presenting with at least one flare was significantly higher during the first 6 months postpartum compared with pregnancy (62.0% vs 43.5%; p=0.02). For SpA patients, there was no difference in disease activity at 6 months postpartum compared with pregnancy (40.7% vs 40.7%; p=0.999). Disease activity in postpartum was similar between the different breastfeeding status in both diseases. 13/91 (14.3%) RA patients and 29/123 (23.6%) SpA patients continued a biologic Disease-Modifying Antirheumatic Drug (bDMARD) during the whole pregnancy and the postpartum. 78/91 RA and 94/123 SpA patients delivered without any DMARDs, and among them, 43/78 (55.1%) and 56/94 (59.6%) (re)started a bDMARD postpartum.Conclusion RA patients were more likely to flare during early postpartum, while SpA patients remained stable. bDMARD continuation during pregnancy was more frequent in SpA patients, and half of the patients restarted bDMARD during postpartum.INTRODUCTIONRheumatoid arthritis (RA) and spondy- loarthritis (SpA) are the most frequent inflammatory rheumatic diseases (IRD) in women of childbearing age.1 2 The postpartum period is a time of great physical and emotionalWHAT IS ALREADY KNOWN ON THIS TOPIC⇒ It has been classically reported that pregnancy has a beneficial effect on rheumatoid arthritis (RA) dis- ease activity, with frequent spontaneous remission, but with flares during the postpartum period. Data are limited in spondyloarthritis (SpA) disease activ- ity during pregnancy, and virtually non-existent for the postpartum period. Only a few studies have ad- dressed the impact of breastfeeding on RA, and even fewer on SpA. We aimed to describe disease activity, treatments received during the postpartum period, and breastfeeding rates and their possible impact on inflammatory rheumatic disorders activity.WHAT THIS STUDY ADDS⇒ Patients with RA were more likely to flare during early postpartum compared with pregnancy, while patients with SpA remained stable. Breastfeeding was not associated with a difference in disease activity scores in patients with RA or SpA. A few patients maintained biologic Disease-Modifying Antirheumatic Drug (bDMARD) during pregnancy and half resumed or started it in the postpartum period.HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY⇒ This study provides additional data on the postpar- tum period, which remains poorly described, partic- ularly regarding breastfeeding and its relationship with disease activity. It highlights the importance of further informing the use of bDMARDs during preg- nancy and in the early postpartum period. ### Page 2 2 Hornez M, et al. RMD Open 2026;12:e006593. doi:10.1136/rmdopen-2025-006593RMD OpenRMD OpenRMD Openchange for women. These changes need to be considered in our patients with chronic inflammatory rheumatism. It has been classically reported that pregnancy has a benefi- cial effect on RA disease activity, with frequent spontaneous remission3 but with flares during the postpartum period.4 However, more recent studies based on larger prospective cohorts have found lower remission rates than previously described.5 6 Concerning the effect of pregnancy on SpA disease activity, data are limited and virtually non-existent for the postpartum period.7 Also, only a few studies have addressed the impact of breastfeeding on RA, and even fewer on SpA. 8 9 Breast- feeding rates in RA patients have been reported to be lower compared with the general population,10 the main reason for discontinuation being the (re)start of Disease-Modifying Antirheumatic Drugs (DMARDs). 11 Conflicting results have been found concerning the effect of breast- feeding on RA and SpA, with some studies reporting more active disease in breastfeeding patients, 12 13 while more recent studies have reported opposite results. 14–16 Treatment possibilities for patients with RA and SpA during preconception, pregnancy and postpartum have significantly increased over the past decades. Although national and international societies (ie, British Society for Rheumatology (BSR) and British Health Profes- sionals in Rheumatology (BHPR),17 European Alli- ance of Associations for Rheumatology (EULAR)18 and American College of Rheumatology (ACR))19 have published guidelines for the management of DMARDs during these three periods, namely recommending continuing compatible DMARDs (ie, hydroxychloro- quine, sulfasalazine and TNF alpha inhibitors (TNFi)) if needed to control disease activity, the decision to continue/stop is still a challenge in clinical practice for many rheumatologists. Therefore, we conducted an ancillary analysis of the GR2 prospective cohort study with the following aims: (1) to describe the disease activity during the postpartum period in patients with RA and SpA, (2) to describe treat- ments prescribed during this period and (3) to evaluate the rate and effect of breastfeeding on disease activity in these patients during postpartum.PATIENTS AND METHODS PopulationThe GR2 (‘Groupe de recherche sur la Grossesse et les Maladies Rares’, NCT02450396) is an ongoing prospec- tive observational French cohort study launched in October 2014 involving 63 centres. It is part of the Euro- pean network of pregnancy registers in Rheumatology20 supported by Foundation for Research in Rheuma- tology 21 and follows EULAR recommendations regarding core data sets for pregnancy registers in rheumatology.22 The cohort has been described elsewhere, 23 24 but briefly, GR2 includes women with autoimmune diseases (eg, systemic lupus erythematosus and antiphospho- lipid syndrome) and IRD (eg, RA and SpA) with either a pregnancy wish or pregnant. Patients are followed yearly until pregnancy occurs if included via the preconcep- tional module, and every trimester during the pregnancy and then 12 months after birth. Diagnosis of the disease (ie, RA and SpA) was based on the rheumatologist’s opinion. To be eligible for this study, women had to be≥18 years old, have been included in the GR2 cohort at or before 12 weeks gestation, with an RA or SpA diag- nosis and with a live birth before October 2022 (date of database extraction) with at least one visit postpartum. In case of more than one pregnancy in a patient, the anal- ysis included only the first pregnancy that fitted these criteria.Data collectionData were collected during preconceptional visits when available (only the last visit preceding the pregnancy was considered here), regular visits during pregnancy and visits at 6 and 12 months postpartum. Data were prospectively collected in an electronic case report form; they included demographic, clinical, labora- tory and treatment characteristics. Breastfeeding status (ongoing, completed and never breastfed) was collected at delivery and each available postpartum visit.Disease activity evaluationAt each visit, disease activity was assessed by the disease activity score 28 joints CRP (DAS28-CRP)25 for RA and both Bath Ankylosing Spondylitis Disease Activity Index (BASDAI)26 and axial SpA DAS CRP (ASDAS-CRP)26 for SpA. Patients self-reported flares since the last visit. Flares were subsequently confirmed by the physician. Investigator global assessments and number of tender joints were also systematically collected and included in the analysis. Different thresholds for disease activity were used:► For SpA: a BASDAI <2 was used for remission and BASDAI ≥4 for high disease activity. 26 For ASDAS-CRP, the official cut-offs were used (ie, <1.3 for inactive disease, 1.3 and 2.1 for moderate disease activity and >2.1 for moderate to high activity). 26► For RA, DAS28- CRP was used. The cut-off for remis- sion was 2.6, for low activity between 2.6 and 3.2, and for medium to high activity >3.2. 25 When DAS28- CRP could not be calculated due to missing CRP data, disease activity was assessed using the Clinical Disease Activity Index. The cut-off for remission was 2.8, for low activity between 2.8 and 10, and for medium to high activity >10. 27Statistical analysisBaseline characteristics were described in the two groups (patients with SpA or RA). Categorical vari- ables were described as frequency (percentage). Quantitative variables were reported as mean and SD in case of a normal distribution or median and ### Page 3 3Hornez M, et al. RMD Open 2026;12:e006593. doi:10.1136/rmdopen-2025-006593EpidemiologyEpidemiologyEpidemiologyinterquartile range (ie, 25th and 75th percentiles) otherwise. The normality of the distributions was evaluated by a Shapiro- Wilk test and using histo- grams. All analyses were performed separately by subgroup. Bivariate comparisons were performed according to patients’ breastfeeding status (ongoing, completed and never breastfed) at 6 and 12 months by Kruskal-Wallis test for quantitative variables and Fisher exact test for categorical variables. The change in activity indices between pregnancy and 12 months was eval- uated by paired Student’s t-test or Wilcoxon signed-rank test for quantitative variables or by McNemar’s test for qualitative variables. The likelihood of breastfeeding during the postpartum period was described using the Kaplan-Meier method. Risk factors for flare were identified using a multi- variate Cox regression model, factors included in the model were chosen according to the clinical relevance. The proportional hazard assumption was checked by examining the Schoenfeld residuals. 28 Effect sizes were expressed as HRs and 95% CI. Statistical analyses were performed using R software (V.4.1). All statistical tests were two-sided, with a type I error of 5%.RESULTS Population characteristicsThis study included 218 patients with 218 pregnancies (one pregnancy per patient), including two twin preg- nancies: 94 patients with RA and 124 patients with SpA (figure 1). The main characteristics of our population are summarised in table 1. The mean age at pregnancy was 32.0 (±5.0) years for RA patients and 31.8 (±5.0) years for SpA. Among patients with RA, 41/89 (46.1%) patients had erosions, 66/92 (71.7%) were rheumatoid factor positive and 65/92 (70.6%) had ACPA. Most SpA patients had axial involvement (95/124, 76.6%). 17/92 (18.5%) patients with RA had preterm delivery.Disease activityRheumatoid arthritisAmong the 94 patients with RA, disease activity data during postpartum were available in 92 and 91 patients for the first 6 months and 6–12 months postpartum, respectively. Among them, 57/92 (62.0%) reported at least one flare within the first 6 months postpartum and 55.4% within the first 3 months. Afterwards, between the 6 and 12 months period, 32/91 (35.2%) patients reported at least one flare.Figure 1 Flowchart of patient selection. RA, rheumatoid arthritis; SpA, spondyloarthritis. ### Page 4 4 Hornez M, et al. RMD Open 2026;12:e006593. doi:10.1136/rmdopen-2025-006593RMD OpenRMD OpenRMD OpenThe proportion of patients with RA reporting a flare was significantly lower during pregnancy compared with the first 6 months postpartum (43.5% vs 62.0%; p=0.02) (table 2). There was no significant difference in DAS28 scores during pregnancy and postpartum. Investigator-rated Visual Analogue Scale (VAS) between patients who did or did not experience relapses during the first 6 months postpartum was at the limit of statistical significance between the two groups, with a trend towards higher scores in those who experienced a relapse (1.6 vs 2.9 p=0.073).Table 1 Population characteristics and outcomeBaseline characteristics Spondyloarthritis N=124 Rheumatoid arthritis N=94Mean age at pregnancy, y (SD) 31.8 (5.0) 32.8 (5.0) Mean duration of rheumatic disease, y (SD) 10.31 (6.1) 12.3 (7.7) Axial SpA (%) 95 (76.6) – Peripheric SpA (%) 58 (46.8) – HLA-B27 positivity (%) 58 (46.8) – Erosive RA (%) – 41/89 (46.0) RF positive (%) – 66/92 (71.7) ACPA positive (%) – 65/92 (70.7) Parity (%)Primiparous 46/59 (78.0) 32/40 (80.0)Multiparous 13/59 (22.0) 8/40 (20.0) Vaginal delivery (%) 95/116 (81.9) 60/83 (72.3) Caesarean section (%) 21/116 (18.1) 23/83 (27.7) Mean term at delivery, w (SD) 38.9 (1.8) 38.3 (2.1) Preterm (%) 7/123 (5.7) 17/92 (18.5) Data are expressed in mean and SD or number and percentages. ACPA, anti-citrullinated protein antibody; RA, rheumatoid arthritis; RF, rheumatoid factor; SpA, spondylarthritis; w, week; y, years.Table 2 Comparison of activity during pregnancy and postpartum at 6 monthsN Spondyloarthritis Rheumatoid arthritis Pregnancy Postpartum (M6) P value N Pregnancy Postpartum (M6) P valueReported flare (%) 118 48 (40.7) 48 (40.7) 0.999 92 40 (43.5) 57 (62.0) 0.020Activity (%) 71 0.436 64 0.349Remission 23 (32.4) 27 (38.0) 44 (68.8) 37 (57.8)Low 28 (39.4) 19 (26.8) 7 (10.9) 12 (18.8)Moderate/high 20 (28.2) 25 (35.2) 13 (20.3) 15 (23.4) CRP (mg/L) 43 7.0 (3.3; 13.1) 3.2 (1.4; 5.1) 0.014 54 4.8 (2.3; 10.2) 2.6 (1.0; 9.8) 0.371 ASDAS- CRP 29 2.3 (1.7; 2.8) 2.2 (1.1; 3.0) 0.865 – – – – BASDAI 70 2.5 (1.3; 4.0) 2.0 (1.0; 4.0) 0.562 – – – – Tender joint count 62 0.0 (0.0–0.0) 0.0 (0.0–0.0) 0.163 – – – – DAS28- CRP – – – – 54 2.1 (1.6; 3.0) 2.4 (1.5; 3.1) 0.409 CDAI – – – – 25 4.0 (1.0; 12.0) 5.0 (2.0; 17.0) 0.230 VAS investigator 40 1.40 (0.7–3.1) 2.0 (0.0–3.0) 0.657 50 1.0 (0.0–3.4) 2.0 (0.0–3.7) 0.435 Data are expressed in median and interquartile or number and percentages. Disease activity was defined for SpA according to BASDAI or ASDAS-CRP: BASDAI<2 for remission and BASDAI≥4 for high activity; ASDAS-CRP<1.3 for inactive disease, 1.3 and 2.1 for moderate disease activity, and >2.1 for moderate to high activity; DAS28-CRP<2.6 for low activity, DAS28-CRP>2.6 and <3.2, and DAS28-CRP>3.2 for medium to high activity, CDAI<2.8 for low activity, CDAI>2.8 and <10, and CDAI>10 for medium to high activity. Values in bold indicate statistical significance. ASDAS, Ankylosing Spondylitis Disease Activity Score; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; CDAI, Clinical Disease Activity Index; DAS28-CRP, Disease Activity Score based on 28 tender and swollen joints and C reactive protein; Tender joint count, count on 44 articulations; VAS, visual analogue scale. ### Page 5 5Hornez M, et al. RMD Open 2026;12:e006593. doi:10.1136/rmdopen-2025-006593EpidemiologyEpidemiologyEpidemiologyFor the 15 patients who were included preconception- ally (and had available postpartum data), DAS28-CRP was significantly higher during the preconception period compared with the 1-year postpartum visit (2.6 vs 1.8; p=0.007).SpondyloarthritisAmong the 124 SpA patients, disease activity data during postpartum were available in 118 patients (both at 6 and 12 months); 48 (40.7%) patients reported at least one flare within the first 6 months postpartum, most of them (64.8%) during the first 3 months. There were no significant differences in activity (reported flares, BASDAI and ASDAS-CRP) at 6 months postpartum compared with pregnancy (table 2). However, CRP was significantly higher during pregnancy than 6 months post- partum (7 mg/L vs 3.2 mg/L; p=0.014). At 1-year postpartum, while BASDAI and ASDAS were comparable to pregnancy, reported flares were significantly less frequent than in preg- nancy (13.4% vs 40.3%; p<0.001). All DASs and flares during postpartum in SpA are detailed in online supplemental table.TreatmentsFor the 91 patients with RA and 123 SpA patients for whom data on treatment were available, 46 (50.5%) and 85 (69.1%), respectively, were treated with biologic DMARDs (bDMARDs) at conception and during the first trimester. Only 13 (14.3%) RA patients continued a bDMARDs during the whole pregnancy and the postpartum. Among the 78 (85.6%) RA patients who delivered while not receiving any bDMARD, 37 (47.4%) resumed a bDMARD, and 6 (7.7%) initiated a bDMARD for the first time, mainly (44.2% of cases) during the first month postpartum. Details of treatment resumption and type of bDMARDs are detailed in tables 3 and 4. In total, 56/91 (61.5%) patients were treated postpartum with bDMARDs. On average, 35/90 (38.9%) of patients started methotrexate in the postpartum period and 8/90 (8.9%) patients were treated with sulfasalazine during pregnancy and continued this treatment during the postpartum period. At delivery, 12/94 patients (12.8%) received corticosteroid therapy with a stable average dose of 8.2 mg/day (±3.8), only two had a bDMARD associated. After delivery, 12 courses of corticosteroids were initiated with a mean maximum dose of 12.0 mg/day (±11.0). Only 29 (23.6%) SpA patients continued a bDMARD during the whole pregnancy and the postpartum. Among the 94 (76.4%) SpA patients without treatment at delivery, 54 (57,4%) resumed, and 2 started a bDMARD post- partum, in 42% of cases during the first month. Details of treatment resumption and type of bDMARDs are detailed in tables 3 and 4. In total, 85 (69.1%) patients were treated postpartum with bDMARDs. Methotrexate was initiated on average during the third month post- partum. 3/123 (2.4%) patients were treated with sulfas- alazine during pregnancy and continued this treatment during the postpartum period. 28/122 (22.9%) patients received NSAIDs postpartum.Factors associated with postpartum flaresMean DAS28-CRP during pregnancy (HR=1.4 (1.1 to 1.9); p=0.016) and resuming or starting bDMARDs during post- partum (HR=2.4 (1.3 to 4.3); p=0.005) were independently associated with a higher likelihood of flare during post- partum in the multivariate survival analysis for patients with RA (table 5). There were no identified factors associated with postpartum flares in patients with SpA.BreastfeedingRatesData on breastfeeding were available for 82 RA and 113 SpA patients. Thus, 46/82 (56.1%) patients with RA breastfed at delivery, and among those who did not, the main reason was the choice of the mother (50.0%). For SpA patients, 62 (54.9%) breastfed at delivery (figure 2), and among those who did not, the main reasons for notTable 3 bDMARDs during postpartumSpondyloarthritis N=123 Rheumatoid arthritis N=91Ongoing during pregnancy and postpartum (%) 29 (23.6) 13 (14.3) Started postpartum (%) 2 (1.6) 6 (6.6) Stopped during pregnancy and resumed postpartum (%) 46 (37.4) 26 (28.6) Stopped before pregnancy and resumed postpartum (%) 8 (6.5) 11 (12.1) Number total of patients treated postpartum (%) 85 (69.1) 56 (62.2) Data are expressed in number and percentages. bDMARDs, biologic Disease-Modifying Antirheumatic Drugs.Table 4 Type of bDMARDs received postpartumSpondyloarthritis N=85 Rheumatoid arthritis N=56Etanercept (%) 20 (23.5) 21 (37.5) Certolizumab (%) 33 (38.8) 24 (42.9) Adalimumab (%) 18 (21.2) 1 (1.8) Infliximab (%) 6 (7.1) 1 (1.8) Golimumab (%) 5 (5.9) 0 Others (%) 2 (2.3) 1 (1.8) Data are expressed in number and percentage. Others: rituximab, belimumab (patient with concomitant systemic lupus erythematosus), ustekinumab. bDMARDs, biologic Disease-Modifying Antirheumatic Drugs. ### Page 6 6 Hornez M, et al. RMD Open 2026;12:e006593. doi:10.1136/rmdopen-2025-006593RMD OpenRMD OpenRMD Openbreastfeeding were the choice of the mother (60.8%), or a contraindication (17.6%). Breastfeeding mean duration was 12.9±10.0 weeks for patients with RA and 14.3±10.9 weeks for patients with SpA.Activity and treatmentsDisease activity measures were similar between patients who breastfed at 6 months and those who never breastfed or discontinued breastfeeding before 6 months post- partum, whatever the condition (ie, RA or SpA). Sixteen of the 46 (34.8%) RA breastfeeding patients and 19/62 (30.6%) patients with SpA received bDMARD while breastfeeding. Ten patients with RA discontinued breastfeeding coincidentally with resuming treatment. For SpA patients, there did not appear to be any relation- ship between the resumption of treatment and discontin- uation of breastfeeding.DISCUSSIONThis study confirms the higher likelihood of postpartum flares in RA compared with the pregnancy period, with 62% of patients presenting a flare, especially during the first 3 months postpartum. However, this was not found in patients with SpA, for whom no difference was found in disease activity during pregnancy and postpartum except for the CRP level, which was higher during pregnancy. Furthermore, only 47% of patients with RA and about 57% of patients with SpA patients resumed bDMARD during the postpartum period, and about 30% of patientsTable 5 Multivariate survival analyses of flare occurrence over follow- upHR (95 CI) P valueSpA (n=112)Breastfeeding at delivery 0.86 (0.52 to 1.41) 0.548Maternal age 1.00 (0.96 to 1.05) 0.869bDMARD resumed post-partum 1.10 (0.67 to 1.80) 0.712Immunosuppressants 1.75 (0.81 to 3.79) 0.152 RA (n=67)Breastfeeding at delivery 1.54 (0.85 to 2.77) 0.151Maternal age 1.00 (0.94 to 1.05) 0.868bDMARD resumed post-partum 2.36 (1.30 to 4.28) 0.005Immunosuppressants 1.23 (0.67 to 2.25) 0.502DA28 CRP 1.42 (1.06 to 1.90) 0.016HR per 1-year increase in maternal age and per 1-point increase in DAS28-CRP. DAS28- CRP<2.6, for low activity, DAS28-CRP>2.6 and <3.2 and DAS28-CRP>3.2 for medium to high activity; HR per 1-year increase in maternal age and per 1-point increase in DAS28- CRP. Values in bold indicate statistical significance. bDMARD, biologic Disease-Modifying Antirheumatic Drugs; DAS28-CRP, Disease Activity Score based on 28 tender and swollen joints and C reactive protein; RA, rheumatoid arthritis; SpA, spondyloarthritis.Figure 2 Probability of continuing breastfeeding over the course of postpartum period. (A) Breastfeeding in SpA patients. (B) Breastfeeding in RA patients with RA patients. Survival data were censored at 12 months for those still breastfeeding at the 12 month visit. RA, rheumatoid arthritis; SpA, spondyloarthritis. ### Page 7 7Hornez M, et al. RMD Open 2026;12:e006593. doi:10.1136/rmdopen-2025-006593EpidemiologyEpidemiologyEpidemiologymaintained their treatment until delivery. Finally, breast- feeding was not associated with a difference in DASs in patients with RA or SpA. It is generally accepted that RA improves during pregnancy and relapses during postpartum.4 However, most of these studies were retrospective and not based on any biological markers or validated scores, such as DAS28-CRP. In 2008, one of the first prospective studies using DAS28-CRP found patients with improved disease activity during pregnancy, particularly in the third trimester.5 There was a rebound of activity in the postpartum period for 39% of patients. A meta-analysis performed in 2018 on prospective studies with 237 preg- nancies also showed an improvement in disease activity during pregnancy for an average of 60% of patients, lower than previously described in the literature (about 90%), 6 and 47% of patients presented increased disease activity in the postpartum period. In a study comparing the Preconception Counselling in Active RA (PreCARA) cohort to a historic reference cohort on RA during preg- nancy (PARA cohort), disease activity was also globally stable during pregnancy and remained stable until the first 6 months of postpartum. 29 In our study, we observe a discordance between self-reported flares and disease activity assessed using validated indices. This finding may be explained by including a possible overestimation of flares based on patient self- report or missing data regarding inflamma- tory markers, particularly CRP, which may have limited the sensitivity of activity assessments. Notably, when comparing investigator global assessment (VAS) between patients who experienced a flare and those who did not within the first 6 months postpartum, a difference close to the threshold of statistical significance was observed (p=0.073). There may be a correlation with the fact that the indices are assessed at the time of the consultation, whereas the relapses reflect those that have occurred since the previous visit. Concerning patients with SpA, we noticed a higher number of flares during pregnancy compared with 1 year after delivery for patients with SpA. SpA patients may present active disease or stable or even reduced disease activity.7 For example, in a 2022 German study investigating outcomes during pregnancy in 304 women with axial SpA from European registries, disease activity measured with BASDAI remained stable throughout pregnancy and postpartum (below 4).30 In a 2018 Norwe- gian study of 166 patients with axial SpA, a significant increase in BASDAI in the second trimester compared with the postpartum period was described (mean BASDAI 3.97 vs 3.46, p=0.005). 9 The disease activity of SpA remained stable before pregnancy to 1 year postpartum, and lower disease activity was found in the postpartum period. However, other studies have shown opposite results.7 We found that CRP level was significantly higher during pregnancy than in the 6 months postpartum in SpA patients. While it could be a marker of activity during pregnancy, it much probably corresponds to a physiolog- ical increase in CRP described during pregnancy.30 This had already been described in 2022, the German study from European registries. 31 CRP level was higher in the second trimester (mean 9 mg/L) of pregnancy compared with before and after pregnancy (mean 5 mg/L). In addition, apart from the biological markers that can be compromised (CRP and ESR), there is a lack of valida- tion of the clinical markers and scores used for our patients with inflammatory rheumatism during pregnancy.32 Regarding treatment, we observed in our study that despite the stability of the disease in the postpartum period, 57.4% of our patients with SpA resumed bDMARD in the 6 months postpartum. This could also be an indi- rect marker of activity during postpartum, especially as 28% of patients treated during pregnancy discontinued their bDMARD in the third trimester. This result was similar in the 2018 Norwegian study, 9 with only 38% of patients on bDMARD 6 months after delivery, 11% on csDMARD, 7% on corticosteroids and 44% on NSAIDs, despite a low disease activity. The number of patients treated with TNF- inhibitors was higher in the 2022 study based on European registries, with 21% patients treated in the third trimester and 42.3% in the postpartum period.31 For patients with RA, only 47.4% resumed bDMARD during the postpartum period, mainly in the first month. A Dutch study based on the PreCARA cohort published in 2022 found results comparable to ours for RA: 46% of patients were treated with TNFi at 6 months postpartum, 25% on methotrexate, and 40% on corticosteroids. 33 There was a clear increase in these rates compared with the older PARA cohort. 5 10 However, about 60% of patients treated at the beginning of pregnancy stopped their bDMARD in the first or third trimester, with only 14% of our patients with RA receiving bDMARD at delivery. Resumption of bDMARD during postpartum was asso- ciated with the risk of flare in the first 6 months of post- partum in patients with RA probably because the flare itself led to the resumption of bDMARD. Several studies have observed a significant association between discontinuing bDMARD before or during preg- nancy and higher activity in postpartum. 34–37 Also, in these studies, disease activity during pregnancy itself was also associated with a greater risk of flare in postpartum. In our study, we observed that DAS28- CRP during preg- nancy was associated with a higher risk of flare during the first 6 months of postpartum (HR=1.42 (1.06 to 1.90); p=0.016). Thus, maintaining a bDMARD during preg- nancy, particularly in patients with an active RA before or during pregnancy, would be of interest to limit the risk of flare during postpartum. Finally, the rate of breastfeeding at delivery was about 55% in patients with SpA and 56% in patients with RA, which is lower than the general population in France (about 70%). 38 39 In our study, about 33% of them continued breastfeeding at 6 months postpartum. The ### Page 8 8 Hornez M, et al. RMD Open 2026;12:e006593. doi:10.1136/rmdopen-2025-006593RMD OpenRMD OpenRMD Openaverage duration of breastfeeding observed in our two populations was slightly lower than the general population (about 14 weeks for SpA and 12 weeks for RA vs 15 weeks in the general population), 40 which is, in general, the duration of maternity leave in France (ie, 12 weeks postpartum). A Dutch study conducted from 2002 to 2008 in patients with RA and included in the PARA registry also found a lower rate of breastfeeding than the general population: at 4–6, 12 and 26 weeks postpartum, 43%, 26% and 9% were breastfeeding. 10 This work was continued in 2022 with the PreCARA study and showed a breastfeeding rate comparable to the general population, with 70% at delivery, 60% at 4–6 weeks, 39.8% at 12 weeks and 26% at 26 weeks. 33 Another study was conducted in 2021 in the USA on 295 patients with rheumatic diseases, including 100 patients with RA or SpA. 41 At delivery, 84% of the patients tried to breastfeed. At the postpartum visit, that is, about 7.6 weeks, two-thirds of them continued breastfeeding. Resumption of bDMARDs has been reported as a widespread reason to stop breastfeeding. 10 33 41 In our study, around 30% of our two populations received a bDMARD while breastfeeding. In the PreCARA study, one reason for the higher breastfeeding rate compared with the historical cohorts was better knowledge of the treatments used during postpartum, particularly TNFi. 33 We found no significant differences in activity between breastfeeding patients, those who had breastfed and those who never had breastfed throughout postpartum. The effect of breastfeeding on the activity of RA and SpA is discussed in the litera- ture. A rebound in activity has been reported in some studies in RA patients who are breastfeeding, espe- cially after a first pregnancy. 13 One of the hypotheses was that breastfeeding maintains a higher level of prolactin during the postpartum period, which could contribute to the higher activity of the disease in these patients. 16 However, this is controversial; other studies have not shown this relationship or even found a protective effect of breastfeeding. 14–16 Furthermore, the role of prolactin as a pro or anti-inflammatory effect remains debated. 42 One reason why disease activity may be higher in breastfeeding patients is that they may delay resuming treatment during breastfeeding. With the improved knowledge of treatment during breastfeeding, this effect should no longer be seen. 33 The strengths of our study are the multicentre design, the number of patients, especially for patients with SpA, which is higher than many early studies in the literature, and the prospective recruitment. Very few studies have focused on postpartum, particularly on the management of DMARD or the effect of breast- feeding on disease activity, making our work original. The main limitation is the missing data, namely on disease activity measurements, such as CRP and DASs. Furthermore, the number of visits during pregnancy was not identical across patients, and few patients were included preconceptionally. However, we aimed to minimise this bias by using an average of disease activity during pregnancy to compare them with disease activity in postpartum. Another limitation is the self-reported definition of disease flare, which may lead to an overestimation of flares. We were unable to use a variation of objective activity markers (DAS28-CRP and BASDAI/ASDAS) due to a lack of data during pregnancy and postpartum. In conclusion, patients with RA experienced signifi- cantly more flares in the first 6 months of postpartum compared with the pregnancy period. In contrast, patients with SpA remained stable. Additionally, only 14.3% of patients with RA and 23.6% of patients with SpA continued treatment until delivery. Breastfeeding was not associated with increased or decreased disease activity in patients with RA or SpA. Yet only 47% of patients with RA and about 57% of patients with SpA resumed bDMARD during postpartum. The use of bDMARDs during pregnancy may be appropriate for some patients with active disease, with the potential benefit of lowering postpartum flare risk, while care- fully weighing risks and benefits. Further studies could reinforce the data on the safe use of bDMARDs during pregnancy and breastfeeding and thus better define the best therapeutic strategy to adopt during pregnancy and postpartum.Author affiliations1 Service de Rhumatologie, Université de Lille, CHU Lille, Lille, France 2 Centre for Research in Epidemiology and Statistics, Université Paris Cité; Université Sorbonne Paris Nord; INSERM; INRAE, Paris, France 3 Service de Rhumatologie, Hôpital Bichat, APHP, Paris, France 4 Department of Biostatistics, CHU Lille, Lille, France 5 Service de Rhumatologie, Sorbonne Université and Pitié Salpêtrière Hospital, Paris, France 6 Service de Rhumatologie, Université Paris-Saclay, Assistance Publique-Hôpitaux de Paris, Hôpital Bicêtre, Le Kremlin-Bicetre, France 7 Service de Médecine Interne, CHU Montpellier, Montpellier, France 8 Service de Rhumatologie, CHU Gabriel Montpied, Clermont-Ferrand, France 9 Service de Rhumatologie, CHU Caen, Caen, France 10 Service de Rhumatologie, UMR1227, Lymphocytes B et Autoimmunité, Université de Bretagne occidentale, Inserm, CHU Brest, LabEx IGO, Brest, France 11 Rheumatology Unit, Centre National de Référence des Maladies Auto-Immunes Rares (CERAINOM), CHU, Brest, France 12 Service de Rhumatologie, Université Paris Cité, AP-HP, Hôpital Lariboisière, Paris, France 13 Service de Rhumatologie, CHU Poitiers, Poitiers, France 14 Service de Rhumatologie, Université Jean Monnet Saint-Étienne, CHU Saint-Etienne, Mines Saint-Etienne, INSERM, SAINBIOSE U1059, Saint-Étienne, France 15 Service de Rhumatologie, National Reference Center for Systemic Autoimmune Rare Diseases, Bordeaux University Hospital, Hôpital Pellegrin, Bordeaux, France 16 CNRS, Immunoconcept, UMR 5164, Bordeaux University, Bordeaux, France 17 Service de Rhumatologie, Hôpital Saint-Antoine; Assistance Publique–Hôpitaux de Paris (AP-HP); Sorbonne Université, Paris, France 18 Service de Médecine Interne, Centre de Référence Maladies Autoimmunes et Systémiques Rares Île de France, APHP Hôpital Cochin, Paris, France 19 Service de Rhumatologie, Université de Lille, CHU Lille, FHU PRECISE, Lille, France 20 Service de Rhumatologie, Université de Lille, CHU Lille, FHU PRECISE, U1286 - INFINITE - Institute for Translational Research in Inflammation, Lille, France ### Page 9 9Hornez M, et al. RMD Open 2026;12:e006593. doi:10.1136/rmdopen-2025-006593EpidemiologyEpidemiologyEpidemiologyAcknowledgements We thank Doctor Lija James for language revision of this manuscript. We thank Ada Clarke for her assistance in managing the e-case report form and collecting data. We thank the patients for agreeing to participate in the study and patient associations for their strong support. We also thank the French Society of Rheumatology (SFR), the French Society of Internal Medicine (SNFMI), and the filière de santé des maladies auto- immunes et auto-inflammatoires rares (FAI2R) for their scientific and technical support. The GR2 study has received grants from patient associations (Lupus France; association des Sclérodermiques de France, association Gougerot Sjögren, Association Francophone contre la Polychondrite chronique atrophiante), from the AFM-Telethon, the SNFMI, the SFR, the CMEL commission for Research and Innovation of Cochin Hospital, the Ministère de la Santé (the Clinical Research Contract—Database CRCBDD17003), Foundation for Research in Rheumatology, ORRICK society (Prix Véronique ROUALET), and an unrestricted grant from UCB (the company had no role in the initiation, planning, conduct, data assembly, analysis or interpretation of the study). The Direction de la Recherche Clinique et du Développement provided logistic and administrative support.Contributors J- GL and MH conceived and designed the study. MH collected the clinical data and drafted the manuscript. Statistical analysis was performed by ML. All authors critically reviewed the manuscript, contributed to revisions and approved the final version of the paper. MH and J-GL act as guarantors of this manuscript.Funding The GR2 study was supported by Lupus France, association des Sclérodermiques de France, Association Gougerot Sjogren, Association Francophone contre la Polychondrite chronique atrophiante, AFM-Telethon, the French Society of Internal Medicine and Rheumatology, Cochin Hospital, the French Health Ministry, FOREUM, the Association Prix Veronique Roualet, and UCB. The funder didn’t influence the results/outcomes of the study despite author affiliations with the funder.Competing interests AM has received an unrestricted research grant from UCB and Pfizer to her institution, consulting fees from Janssen and Gilead, and honouraria for presentations from AbbVie, Bristol Myers Squibb, Biogen, Pfizer, UCB and Lilly, was supported by AbbVie, Janssen, BMS and Pfizer for attending meetings or travel, and is an advisory board member for Janssen and UCB. MC received travel fees from Janssen Pharmaceuticals, UCB and Pfizer. ED received consulting fees from BMS, Celgene, Lilly, Merck Sharp & Dohme (MSD), Novartis and UCB; honouraria for lectures from AbbVie, BMS, Janssen Pharmaceuticals, Lilly, Medac, MSD, Novartis, Roche-Chugai, Sanofi, UCB, Celgene, Amgen and Galapagos; and travel fees from AbbVie, BMS, Janssen Pharmaceuticals, Lilly, Medac, MSD, Novartis, Roche-Chugai, Sanofi, UCB, Celgene, Amgen and Galapagos. LG has received consulting fees from AbbVie, Amgen, Biogen, BMS, Celltrion, Eli Lilly, Galapagos, Janssen, MSD, Novartis, Pfizer, Sandoz, UCB Pharma, CR has received an unrestricted research grant from Lilly and Biogen to his institution, consulting fees from AstraZeneca, GSK and Novartis, and was supported by AbbVie, Lettre du Rhumatologue and UCB, for attending meetings or travel. NC-C has received an unrestricted research grant from UCB and Roche to her institution, but no personal fees. R-MF is a member of the advisory board at Pfizer, MSD, AbbVie, Janssen, Celltrion, BMS and Sanofi. He received honorary fees from Pfizer, MSD, AbbVie, Janssen, Celltrion, BMS, Sanofi, Lilly, Galapagos, Novartis, Nordic Pharma, Roche-Chugai. J-GL reports speaker fees from AbbVie, Amgen, Biogen, BMS, Galapagos, Janssen, Lilly, Novartis and Pfizer, consulting fees from AbbVie, Celltrion, Janssen and MSD, and research grants from Pfizer. All other authors declare no competing interests.Patient consent for publication Not applicable.Ethics approval This study involves human participants but CPP Ile de France VI, Groupe Hospitalier Pitié-Salpêtrière, 29 August 2012. Participants gave informed consent to participate in the study before taking part.Provenance and peer review Not commissioned; externally peer-reviewed.Data availability statement Data are available upon reasonable request.Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.Open access This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non- commercial. See: https://creativecommons.org/licenses/by-nc/4.0/.ORCID iDsMarie Hornez https://orcid.org/0009-0002-2635-4264 Anna Molto https://orcid.org/0000-0003-2246-1986 Marion Couderc https://orcid.org/0000-0002-2001-1132 Laure Gossec https://orcid.org/0000-0002-4528-310X Hubert Marotte https://orcid.org/0000-0003-1177-9497 Raphaele Seror https://orcid.org/0000-0002-5523-1856 Nathalie Costedoat- Chalumeau https://orcid.org/0000-0002-1555-9021 Jean- Guillaume Letarouilly https://orcid.org/0000-0003-2793-6303REFERENCES1 Fakih O, Prati C, Wendling D, et al. Differences in distribution by department of prevalence and incidence of spondyloarthritis and inflammatory bowel diseases declared to the French National Health Insurance and their evolution between 2008 and 2018. Joint Bone Spine 2022;89:105289.2 Pina Vegas L, Drouin J, Dray-Spira R, et al. Prevalence, mortality, and treatment of patients with rheumatoid arthritis: A cohort study of the French National Health Data System, 2010-2019. 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