Placenta previa and the risk of intrauterine growth restriction (IUGR): a systematic review and meta-analysis

Background: Whether placental location confers specific neonatal risks is controversial. In particular, whether placenta previa is associated with intra-uterine growth restriction (IUGR)/small for gestational age (SGA) remains a matter of debate. Methods: We searched Medline, EMBASE, Google Scholar, Scopus, ISI Web of Science and Cochrane database search, as well as PubMed (www.pubmed.gov ) until the end of December 2018 to conduct a systematic review and meta-analysis to determine the risk of IUGR/SGA in cases of placenta previa. We defined IUGR/SGA as birth weight below the 10th percentile, regardless of the terminology used in individual studies. Risk of bias was assessed using the Cochrane Handbook for Systematic Reviews of Interventions. We used odds ratios (OR) and a fixed effects (FE) model to calculate weighted estimates in a forest plot. Statistical homogeneity was checked with the I-2 statistic using Review Manager 5.3.5 (The Cochrane Collaboration, 2014). Results: We obtained 357 records, of which 13 met the inclusion criteria. All study designs were retrospective in nature, and included 11 cohort and two case-control studies. A total of 1,593,226 singleton pregnancies were included, of which 10,575 had a placenta previa. The incidence of growth abnormalities was 8.7/100 births in cases of placenta previa vs. 5.8/100 births among controls. Relative to cases with alternative placental location, pregnancies with placenta previa were associated with a mild increase in the risk of IUGR/SGA, with a pooled OR [95% confidence interval (CI)] of 1.19 (1.10-1.27). Statistical heterogeneity was high with an I-2=94%. Conclusion: Neonates from pregnancies with placenta previa have a mild increase in the risk of IUGR/SGA.