Placental cord insertion distance from the placental margin and its association with adverse perinatal outcomes

Detection of an abnormal placental cord insertion (PCI)-either marginal or velamentous-can be assessed in the midtrimester. Marginal PCIs are defined as occurring at a distance of <2 cm from the placental edge; velamentous PCIs occur when the placental cord inserts into the fetal membrane. Velamentous PCIs have been associated with a number of perinatal and obstetric complications, such as low birth weight, intrauterine fetal demise, admission to the neonatal intensive care unit (NICU), peripartum hemorrhage, and emergent cesarean delivery (CD). Less clear is whether there is an association between marginal PCI and adverse outcomes associated with placental function. The aim of this study was to examine the association between PCI distance from the placental edge and adverse perinatal and maternal outcomes. This was a retrospective study conducted at a single urban facility where routine measurements of PCI distance were conducted during fetal anatomy ultrasounds between July 2011 and July 2013. Included were patients with singleton gestations who underwent fetal anatomy ultrasounds and delivered at the facility. Excluded were those who had multiple gestations, delivered before 24 weeks' gestation, had a neonate with unknown birth weight or unknown gestational age, or did not have their PCI location and measurement documented. Measurements of the sonographic distance from the placental margin to the PCI site in centimeters were recorded and then classified as normal, marginal, or velamentous. The analysis included 1443 patients, the majority of whom were White (62.1%), nulliparous (58.9%), and privately insured (98.7%). For the entire study population, the mean PCI distance from the nearest placental edge was 4.4 ± 1.4 cm. Only 21 (1.5%) of the 1428 patients had abnormal PCI sites: 15 were marginal, and 6 were velamentous. No associations were observed between PCI distance and CD (P = 0.98), peripartum hemorrhage (P = 0.76), preeclampsia (P = 0.52), 5-minute Apgar score <7 (P = 0.42), and intrauterine fetal demise (P = 0.66). There were significantly shorter PCI distances in patients with NICU admissions than those without (4.1 ± 1.5 vs 4.4 ± 1.4 cm; odds ratio, 0.85; 95% confidence interval, 0.73-0.98, P = 0.02). A significant association was also observed between PCI distance and birth weight (β = 22.97, SE = 9.33, P = 0.01), but this did not hold up after being adjusted for gestational age (β = 12.58, SE = 7.59, P = 0.10). No difference in PCI distance was observed between the 50 patients (3.5%) diagnosed with fetal growth restriction (FGR) versus those without FGR (4.2 ± 1.4 vs 4.5 ± 1.4 cm, P = 0.18), and the area under the curve was 0.57 (95% confidence interval, 0.49-0.65). These findings suggest that although PCI distance may be associated with admission to the NICU, it was not associated with CD, preeclampsia, and other adverse events, nor was it predictive of FGR.