Objective The objective was to determine if anterior placental location increased the risk of postpartum haemorrhage (PPH) and retained placenta in women previously delivered by caesarean section.
Design Prospective cohort study.
Setting Fetal medicine unit, Uppsala University hospital, Sweden.
Population. Four hundred women previously delivered by caesarean section.
Methods Ultrasound scans were performed at gestational week 28-30. Placental location, myometrial thickness and three-dimensional vascularisation index (VI) were recorded. Data on maternal age, parity, BMI, smoking, gestational week at delivery, induction, delivery mode, Oxytocin, preeclampsia, PPH, retained placenta and birth weight was obtained.
Main Outcome Measures PPH (≥ 1000 ml) and retained placenta.
Results Twenty-four women (11.6%) of 213 with anterior placentas had PPH compared to 13 (7.3%) with placentas in other locations. This difference was not significant. No significant risk increase was found for retained placenta in women with anterior placentae. Of the 23 women with low anterior placentae six (26.1%) had PPH compared to 38 (10.3%) with other placental locations (p = 0.032). Three women (13.0%) with low anterior placentae had retained placenta compared to 11 (2.9%) with other locations (p = 0.04). All women but one with low-lying anterior placentae and PPH and all with retained placentae had placenta praevia.
Conclusion Low anterior placentae in women previously delivered by caesarean section increased the risk of PPH and retained placenta, mostly due to placenta praevia. Other anterior locations of the placenta may add to the increased risk of PPH.