Development of the fetal uterus between 19 and 38 weeks of gestation: in-utero ultrasonographic measurements

In-utero assessment of the internal female genitalia is important for deter mination of fetal gender in fetuses with suspected genital tract anomalies. We therefore measured fetal uterine transverse width and circumference fro m 19 weeks of gestation until term, using transvaginal and transabdominal h igh-resolution ultrasound techniques in order to establish nomograms, A pro spective, cross-sectional study on 180 normal singleton pregnancies was per formed. Data were obtained for 140 normal fetuses. The mean +/- SD uterine width and circumference were 12.9 +/- 4.1 mm (95% confidence interval 12.1- 13.7), and 40.2 +/- 12.5 mm (95% confidence interval 37.9-72.5) respectivel y, Uterine size as a function of gestational age was expressed by the regre ssion equations: uterine width (mm) = 12.9 + 0.7 x gestational age (weeks), and uterine circumference (mm) = 40.2 + 2.1 x gestational age. The correla tion coefficients, r = 0.885 and r = 0.888, for uterine width and circumfer ence, by gestational age respectively, were highly statistically significan t (P < 0.001). A nomogram of uterine width and circumference per gestationa l week, and the 95% prediction limits were defined. The present data offer baseline measurements of the fetal uterus that may allow intrauterine asses sment of the female genital tract and associated fetal gender.