Background and objectives Identifying virilisation of the genitalia in female newborns early during the neonatal period is important to diagnose pathologies. However, there is no clear threshold for clitoromegaly or for the anogenital ratio. The objective of this study was to define reference values for the external genitalia of full-term and pre-term female neonates.
Design This was a prospective study of all females born in the study centre between May 2014 and July 2016. Clitoral length and anogenital ratio were measured in 619 newborns with a gestational age of 24+2 to 41+3 weeks during their first 3 days of life. Associations between the values at day 3 and gestational age, birth weight and other newborn characteristics were examined by linear regression.
Results The mean clitoral length at day 3 of life was 3.69±1.53 mm (n=551; 95th percentile, 6.5 mm; maximum, 8 mm), and the mean anogenital ratio was 0.42±0.09 (95th percentile, 0.58). There was no significant variation with gestational age or birth weight, and no significant difference between the results at day 0 and day 3.
Conclusion These results suggest that clitoromegaly can be defined as a clitoral length >6.5 mm. Values ≥8 mm should prompt further investigations. An anogenital ratio >0.6 should be considered a sign of virilisation. Since clitoral size does not vary with gestational age or birth weight, clitoromegaly should not be attributed to prematurity.
- paediatric practice
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Contributors SC conceptualised and designed the study, drafted the initial manuscript, collected data, co-ordinated and supervised data collection, analysed the data, and reviewed and revised the manuscript. CL-G conceptualised and designed the study, reviewed the initial manuscript, collected data, analysed the data, and reviewed and revised the manuscript. K-AN, FP and MBP collected data and reviewed and revised the manuscript. CV, IP, OC and MN designed the study and reviewed and revised the manuscript. SR and RE designed the study, performed the statistical analysis, and reviewed and revised the manuscript. BK designed the study and supervised data collection. All authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.
Funding This work was funded by grants from the Société Française d’Endocrinologie Pédiatrique (SFEDP, prix FERRING) and from the Fond de dotation de l'ALLP.
Competing interests None declared.
Patient consent for publication Parental/guardian consent obtained.
Ethics approval The study was approved by the local ethics committee (Comité de Protection des Personnes Sud-Est II, no. ID-RCB 2014-A00571-46). Written consent was not required because measurements were performed as part of usual non-invasive physical examinations.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available on reasonable request. Anonymised data are available on request from the corresponding author.