Estimation of Reference Values for External Genitalia Parameters in North Indian Preterm and Term Female Newborns

To establish gestation-wise normative data of external genitalia measurements in North Indian term and preterm female newborns.

In this cross-sectional descriptive study, institutionally-born female neonates between 28-42 wk gestation were consecutively enrolled between 24-72 h of life. Newborns with major congenital malformations, chromosomal anomalies, multifetal gestation and birth injuries were excluded. Data on various genital measurements were collected [Clitoral length (CL), clitoral width (CW), ano-clitoral distance (AGD_AC), ano-fourchette distance (AGD_AF) and anogenital ratio (AGR)].

One hundred ninety-eight of 508 neonates (39%) were preterm and 310 (61%) were term. Mean (± SD) CL and CW were 4.6 ± 1.8 mm and 3.9 ± 1.6 mm, respectively. Mean (± SD) values for AGD_AF, AGD_AC and AGR were 9.3 ± 1.8 mm, 30.2 ± 3.9 mm, and 0.31 ± 0.05, respectively. According to these results, term female newborns with CL more than 7 mm and/or CW more than 6 mm (95^th centile) warrant evaluation for clitoromegaly. An anogenital ratio greater than 0.45 should be considered as a sign of virilization in a female neonate. Gestation-wise percentile charts for CL, CW, AGD_AF, AGD_AC and AGR were generated.

The percentile values defined in the study can serve as local normative data for accurate interpretation of genital measurements in North Indian female newborns and enable health care professionals for early identification of genital virilization.