Objective: To describe uterine and uterine cavity changes throughout the puerperium, as revealed by ultrasound.
Methods: This was a prospective, longitudinal study in which 42 women with uncomplicated vaginal term deliveries were examined serially by ultrasound on postpartum days 1, 3, 7, 14, 28 and 56. The first four examinations were performed transabdominally and the last two transvaginally. The involution process of the uterus was assessed by measuring the anteroposterior diameter of the uterus and uterine cavity. Morphological findings were recorded. The influence on the involution process of parity, breast-feeding, maternal smoking and infant's birth weight were also evaluated.
Results: The maximum anteroposterior diameter of the uterus diminished substantially and progressively from 92.0 mm on day 1 postpartum to 38.9 mm on day 56. The maximum anteroposterior diameter of the uterine cavity diminished from 15.8 mm on day 1 to 4.0 mm on day 56. However, the anteroposterior diameter of the uterine cavity, 5 cm from the fundus, typically increased on days 7 and 14 postpartum. The position of the uterus and the shape and the appearance of the cavity change in a unique way during the normal puerperium. The uterus was most often retroverted and empty in the early puerperium. Fluid and debris in the whole cavity were seen in the middle part of the puerperium. In late puerperium the cavity was empty and appeared as a thin white line. Endometrial gas was occasionally visualized. No correlation was found between the involution of the uterus and parity, breast-feeding and the infant's birth weight.
Conclusion: Transabdominal sonography is suitable for examination of the uterus during the first 14 days postpartum but from day 28 the transvaginal route is preferable. The uterine body and position, as well as the cavity, are easy to examine by ultrasound. Accumulation of fluid and debris in the uterine cavity is a common and insignificant finding of the involuting uterus. It is located in the cervical area in the early puerperium and in the whole uterine cavity in the middle part of the puerperium. Findings from uncomplicated vaginal deliveries are needed as a reference when the diagnostic efficacy of ultrasound for pathological conditions is to be tested.