Postpartum Hemorrhage in Patients With a Low-Lying Placenta: A Systematic Review and Meta-analysis

Area of Science:

• Obstetrics and Gynecology
• Maternal-Fetal Medicine
• Reproductive Health

Background:

• A second- or third-trimester diagnosis of low-lying placenta may carry an underappreciated risk for postpartum hemorrhage (PPH) and placenta accreta spectrum (PAS).
• Quantifying this risk and its variation by placental distance from the cervical os and resolution status is crucial for clinical management.

Purpose of the Study:

• To conduct a systematic review and meta-analysis to quantify the risk of PPH and PAS associated with a low-lying placenta diagnosis.
• To assess how this risk varies based on the specific distance of the placenta from the cervical os and whether the low-lying placenta resolves during pregnancy.

Main Methods:

• Systematic searches of major databases (PubMed, ClinicalTrials.gov, EMBASE, Web of Science) were performed up to April 30, 2024.
• Twenty-one studies involving 3,704 patients with low-lying placenta and 2,555 with normal placentation were included, excluding studies before 2000.
• Data extraction and quality assessment were independently performed by three reviewers using the Newcastle-Ottawa Scale.

Main Results:

• Low-lying placenta diagnosis was associated with a significant twofold increased risk of PPH (RR 2.10) compared to normal placentation.
• The incidence of PPH was 16.0% for low-lying placenta cases (1-20 mm from os) versus 5.8% for normal placentation.
• PAS disorders affected 9.0% of all low-lying placenta cases, and a high PPH incidence persisted even with resolved low-lying placenta (8%).

Conclusions:

• Antepartum diagnosis of low-lying placenta is linked to a twofold increased risk of PPH.
• Pooled PPH proportions were 16.6% (1-10 mm) and 17.5% (11-20 mm) for low-lying placenta, with no significant difference between these groups.
• This meta-analysis highlights the need for rigorous monitoring and delivery management for pregnancies with low-lying placenta to reduce maternal morbidity from PPH.