Vaginal delivery in women with a low-lying placenta: a systematic review and meta-analysis.

Background: Low-lying placentas are positioned close to the internal os of the cervix. The preferred way of delivery within this group is unclear.

Objectives: To review the literature on the success of a vaginal delivery with a low-lying placenta.

Search Strategy: We searched OVID EMBASE and MEDLINE for studies on vaginal delivery with a low-lying placenta.

Data Collection And Analyses: Data was extracted on successful vaginal delivery and emergency caesarean section due to haemorrhage. We distinguished between different distances between the cervical os and the placenta (internal os distance, IOD); 0-10, 11-20, and >20 mm. A meta-analysis of proportions was made for successful vaginal delivery and emergency caesarean section at every cut-off value. Maternal morbidity (i.e. antepartum blood loss, postpartum haemorrhage and blood transfusion) at different cut-off values was evaluated.

Main Results: Of the 999 articles retrieved, 10 articles met our inclusion criteria. A vaginal delivery was successful at an IOD of 0-10 mm in 43%, at an IOD of 11-20 mm in 85%, and at an IOD of >20 mm in 82%. A shorter IOD had a higher chance of antepartum haemorrhage, whereas a larger IOD needed postpartum blood transfusion more often. Postpartum haemorrhage did not depend on IOD.

Conclusion: A low-lying placenta is not a contraindication for a trial of labour, and the morbidity in these women is not increased. However, women with a low-lying placenta have a higher chance of an emergency caesarean section compared with women with a placenta outside the lower uterine segment. Therefore, shared decision-making is mandatory in case of a trial of labour.

Tweetable Abstract: This systematic review demonstrates the possibility of a vaginal delivery in women with a low-lying placenta within 20 mm of the cervix.