Ultrasound evaluation of the uterus in the uncomplicated postpartum period: a systematic review

Abstract

The aim of this systematic review and meta-analysis was to define the means and the upper limits of normal for endometrial thickness and uterine measurements in uncomplicated pregnancies at different postpartum periods. A search was conducted in the Medline, Embase, Cinahl, and Clinicaltrials.gov databases up to January 30, 2020. We included studies reporting sonographic parameters of the uterus in the normal postpartum period. The continuous variables were expressed as means with standard deviations. The upper limits of normal were defined as the 95th percentile. Clinically significant differences in the uterine measurements between subgroups were defined as ≥2 cm; significant differences in the uterine volume were defined as >10%. The primary outcome was the endometrial thickness; others sonographic parameters that were analyzed were the uterine anteroposterior diameter, longitudinal diameter, width, and volume. A total of 5260 articles were identified. Of these, 80 were assessed for their eligibility for inclusion and 32 studies were included in this systematic review. These studies included 3106 women (55% multiparas and 82% with vaginal deliveries) who underwent transabdominal and/or transvaginal ultrasound from the first postpartum day to a maximum of 6 weeks postpartum. The upper limit of normal (95th percentile) for the endometrial thickness was 25 mm by 7 days postpartum and this continued to decrease (18 mm at 14 days, 12 mm at 4 weeks, and 9 mm at 6 weeks) in a similar manner for all the women regardless of parity or mode of delivery. All the other uterine measurements also gradually decreased during the puerperium for all the women regardless of parity or mode of delivery. These upper limits of normal for the postpartum endometrium and uterine measurements in uncomplicated pregnancies provide clinical guidance for the sonographic evaluation of women with complicated postpartum courses.