Placental histopathology lesions and pregnancy outcome in pregnancies complicated with symptomatic vs. non-symptomatic placenta previa

The mechanisms involved in bleeding in cases of placenta previa (PP) and the effect on pregnancy outcome is unclear.

We aimed to compare pregnancy outcome and placental histopathology in pregnancies complicated with symptomatic (bleeding) vs. non-symptomatic PP, and to study the effects of the co-existence of histopathological retro-placental hemorrhage (RPH) in cases of symptomatic PP on neonatal and maternal outcomes.

Labor and maternal characteristics, neonatal outcome and placental histopathology lesions of pregnancies with PP, delivered between 24 and 42weeks, during 2009-2015, were reviewed. Results were compared between PP who had elective cesarean delivery (CD) (previa group) and PP with bleeding necessitating emergent CD (symptomatic previa group). Placental lesions were classified to lesions consistent with maternal malperfusion or fetal thrombo-occlusive disease (vascular and villous changes), and inflammatory lesions.

Compared to the previa group (n=63), the symptomatic previa group (n=74) was characterized by older patients (p<0.001), higher rate of smokers (p=0.005), thrombophilia (p=0.038), and preterm deliveries (p<0.001). Placentas within the symptomatic previa group were smaller, with higher rates of weight<10th% (p=0.02), RPH (p<0.001) and villous changes related to maternal malperfusion (p=0.023). As compared to symptomatic PP without RPH, co-existence of RPH was associated with higher rate of adverse neonatal outcome (p<0.001) and maternal blood transfusion (p=0.02). On multivariate regression analysis, composite adverse neonatal outcome was found to be dependent on coexisting RPH (OR=2.8, 95%CI 1.2-11.7, p=0.03), and low gestational age (OR=3.1, 95%CI 1.6-4.9, p=0.02).

Symptomatic placenta previa is associated with increased placental malperfusion lesions suggesting an association of maternal malperfusion with abnormal placental separation. The coexisting finding of RPH with symptomatic placenta previa can be seen as a marker for more extensive/severe placental separation, hence the association with maternal transfusion requirements and poorer fetal outcome.