This prospective cohort study examined whether maternal first-trimester blood levels of oestradiol (E) and testosterone (T), measured at 6–8 weeks (E1, T1) and 10–11 weeks (E2, T2), were associated with newborn head circumference (HC), length, and birthweight in 47 mother-neonate pairs.
Maternal E1 (6–8 week oestradiol) was positively associated with neonate HC in multiple regression, independent of T1, E2, T2, and maternal anthropometrics; the effect was stronger in male neonates (n=24) than female neonates (n=23). Maternal age was negatively related to HC. No other sex steroids independently predicted HC.
Very small sample (n=47) limits statistical power and generalizability. Only two early first-trimester time points were measured, leaving later gestational hormonal exposure unexamined. Study design is observational, so causality cannot be established.
These findings are primarily research-oriented rather than immediately actionable clinically. Clinicians should be aware that early first-trimester maternal oestradiol may influence fetal brain growth proxy measures, with potentially greater effects in male fetuses — a consideration for future neurodevelopmental research.
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