TOPLINE:

The lateral placental position was associated with higher odds of preterm birth, preeclampsia, small for gestational age (SGA), retained placenta, and non-vertex foetal presentation at birth than the central placental position. After adjustment for confounding factors, a lateral placenta remained independently associated with higher odds of SGA, preterm birth, and retained placenta.

METHODOLOGY:

• Researchers conducted a systematic review and meta-analysis to evaluate the association between the lateral placental position and adverse maternal and perinatal outcomes.
• Following a systematic literature search across various databases, a total of 21 studies (prospective or retrospective cohort studies and case-control studies) comprising 162,727 singleton pregnancies from countries across North America, Europe, Asia, Africa, and Oceania were included.
• Primary outcomes included SGA (defined as a newborn birth weight below the 10th percentile for their gestational age), preterm birth, stillbirth (defined as foetal death at 28 weeks or more), and preeclampsia; secondary outcomes included non-vertex foetal presentation at birth and retained placenta.
• Study quality and the risk for bias were assessed using a validated tool, and between-study heterogeneity was evaluated using standard statistical methods.

TAKEAWAY:

• In pooled analyses of 12 studies each, pregnant women with a lateral placenta had 65% higher odds of preeclampsia (odds ratio [OR], 1.65; 95% CI, 1.25-2.19; I² = 41.0%) and 40% higher odds of delivering SGA babies (OR, 1.40; 95% CI, 1.17- 1.68; I² = 69.0%) than those with a central placenta.
• Pooled analyses of 4 and 10 studies, respectively, showed that those with a lateral placenta had more than twofold higher odds of preterm birth before 34 weeks (OR, 2.10; 95% CI, 1.62-2.72; I² = 0.0%) and 50% higher odds of preterm birth before 37 weeks (OR, 1.50; 95% CI, 1.26-1.80; I² = 60.5%) than those with a central placenta.
• Pooled analyses of six and four studies, respectively, revealed that the lateral placental position was associated with 2.52-fold higher odds of retained placenta (95% CI, 1.60-3.95; I² = 87.7%) and 50% higher odds of non-vertex foetal presentation at birth (95% CI, 1.19-1.89; I² = 28.6%) than the central placental position.
• Importantly, after adjusting for confounders, a pooled analysis of three to four studies showed that a lateral placenta remained independently associated with increased odds of SGA (OR, 1.84; 95% CI, 1.33-2.53; I² = 0.0%), preterm birth before 34 weeks (OR, 2.14; 95% CI, 1.34-3.41; I² = 0.0%) and before 37 weeks (OR, 1.54; 95% CI, 1.11-2.13; I² = 38.8%), and retained placenta (OR, 4.43; 95% CI, 1.70-11.53; I² = 76.1%).

IN PRACTICE:

"[The study] findings suggest that lateral placenta, routinely assessed by ultrasound in the mid-trimester, could serve as an additional perinatal risk indicator to guide closer surveillance," the authors wrote.

SOURCE:

This study was led by Joseph Arkorful, Wilhelmina Children's Hospital, University Medical Center, Utrecht University, Utrecht, Netherlands. It was published online on June 07, 2026, in BJOG: An International Journal of Obstetrics and Gynaecology.

LIMITATIONS:

The analysis included observational studies rather than randomised controlled trials, which may have introduced residual confounding. The retrospective design of the studies and the reliance on existing ultrasound reports rather than standardised assessments likely introduced misclassification bias. Only a few studies were adjusted for confounders when assessing the independent associations.

DISCLOSURES:

This study was supported by a research grant from the University of Cape Coast Directorate of Research Innovation and Consultancy. The authors declared having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.