Abstract
Postnatal activation of the pituitary–ovarian axis in female infants is not as well characterized as that of male infants. This paper hypothesized that the effect of prematurity in addition to premature birth may interrupt mid-gestation peak oestrogen stimulation of primordial follicles.
Participants (n= 63) were divided into three groups based on gestational age (GA) (full term, n= 29, GA 37–42 weeks; near-term, n= 17, GA 34–37 weeks; and preterm, n= 17, GA 24–34 weeks). Follow-up occurred monthly from postbirth day 7 (D7) to month 6 (M1–M6) and at 14 months from expected delivery date (corrected month 14, cM14). At each visit, urinary follicle-stimulating hormone (FSH) (adjusted for creatinine) was measured and the antral follicle number was determined by the transabdominal ovarian ultrasound. Serum anti-Müllerian hormone (AMH) was measured on D7, M3 and cM14. In addition, AMH expression was examined in postmortem fetal ovarian samples, beginning at 13 weeks' gestation.
A postnatal surge in FSH concentration was observed in all subjects around postmenstrual week 40, which was more pronounced and longer-lasting in near-term and preterm infants. AMH concentration peaked at M3 with lower concentrations detected in preterm compared with near- and full-term infants. The number of antral follicles correlated positively with AMH, while urinary FSH correlated negatively with antral follicle count and AMH (all P< 0.0001). The detection of follicles was delayed in preterm compared with full-term infants.
This study indicates that postnatal activation of the pituitary–ovarian axis in female infants results in follicular development and a rise in AMH concentration. Results suggest there is delayed follicular development in preterm infants, which may account for the greater FSH surge, as a consequence of a lack of negative inhibition. Limitations of this study include a loss of 10 subjects by cM14 and the challenges of ovarian ultrasound in infants, although AMH correlated well with findings. The long-term significance of postnatal pituitary–ovarian activation in females and the consequences of prematurity are still unclear.