ESPE Abstracts (2016) 86 RFC7.2

Reference Values for External Genitalia Size and Steroid Hormone Levels in Female Neonates

Sarah Castetsa, Ingrid Plottonb, Kim-An Nguyena, Franck Plaisanta, Malika Prudona, Sophie Laboriea, Marie Souillotb, Sylvain Rochec, René Ecochardc, Olivier Clarisa, Yves Morelb, Marc Nicolinoa & Claire-Lise Gaya


aLyon University Pediatric Hospital, Lyon, France; bLyon University Hospital, Lyon, France; cClinical Investigation Center, Lyon, France


Background: Prenatal androgen exposure can lead to variable virilization of external female genitalia. The lack of a consensus definition of clitoromegaly and the limited data available on normal steroid levels in female neonates makes its diagnosis difficult.

Objective and hypotheses: The aims of this study were (i) to define reference sizes for external female genitalia in term and preterm neonates as a function of gestational age and birth weight; and (ii) to determine reference values for steroid hormones in female neonate serum.

Method: We measured the clitoris (length, width) and the anogenital ratio for three-day-old female neonates born at a gestational age of 24 to 42 weeks. For neonates born after 35 gestational weeks the concentrations of nine steroids were analyzed by LC/MSMS, the main ones being testosterone (Testo), delta4 androstenedione (Delta4), 17-hydroxyprogesterone (17OHP), dihydroepiandrostenedione (DHEA), and dihydrotestosterone (DHT).

Results: For the 452 full-term female neonates included, the mean clitoris length is 3.6 mm (P95=6 mm), the mean clitoral width is 4 mm (P95=7 mm), and the mean anogenital ratio is 0.45 (P95=0.58). Preterm neonates are still being included. The normal values in nmol/l for the main steroids are as follows:

Table 1.
N=452TestoDHTDelta417OHPDHEA
Mean<0.1250.0830.7420.9567.157
P25-P95<0.1250.056–0.1540.251–1.5220.226–2.2991.059–22.2

Conclusion: These results suggest (i) a definition of clitoridomegaly in full term neonates as a clitoris longer than 6 mm; (ii) an anogenital ratio greater than 0.6 is an indicator of possible in utero virilization. A set of reliable LC/MSMS-based reference values for steroid concentrations in female neonates are proposed.