Neonatal uterine morphology as seen on real-time US.

The uterus in the neonate is prominent and readily identified on ultrasonography (US). The neonatal uterus is larger than the prepubertal uterus as a result of residual stimulation from maternal hormones. The uterus was visualized in 31 of 35 (89%) infant girls examined with real-time US. Mean uterine length was 3.4 cm. The majority of the uteri were tubular or spade-shaped, with the anteroposterior diameter of the cervix equal to or greater than the anteroposterior diameter of the fundus. The endometrial cavity was visualized in 30 (97%), a myometrial halo in nine (29%), and a small amount of endometrial fluid in seven (23%) of the uteri.