(614) Placental histology of term and preterm birth in a prospectively collected community sample

Placental histology such as chronic inflammation (CI), acute inflammation (AI), and maternal vascular malperfusion (MVM) have been associated with preterm birth (PTB). However, most studies are retrospective and originate from samples that are submitted for pathological evaluation, creating the potential for selection bias and misleading results. The purpose of this study is to compare the prevalence of placental pathology among patients with a PTB and term birth in a prospectively collected community sample.

Study Design:

This is a secondary analysis of 2,146 participants in a prospective randomized controlled trial of group prenatal care vs routine prenatal care.  Participants were included if placental pathology examination was completed per study protocol.  Demographic and clinical characteristics were obtained by chart review. Chi squared analysis was completed to examine the differences in demographic characteristics and prevalence of histology type (CI, MVM, AI, and fetal vascular malperfusion (FVM)) by term vs PTB. In an exploratory analysis, we examined placental pathology in pregnancies identified as spontaneous PTB.

Results:

There were 1,133 participants with any pathologic exam, of which 626 had complete sampling. 11.1% of participants delivered preterm and patients who delivered preterm were more likely to have preeclampsia and gestational diabetes and deliver via c-section (Table 1). AI in the placenta was more common among term deliveries (p < 0.01, Table 2) and MVM was more common among PTB (p < 0.01). There were no differences in CI or FVM between term and PTB and only 11% of term deliveries were considered histologically normal with no placental lesions identified. In a descriptive analysis of those identified strictly as spontaneous PTB (n=24), MVM remained prevalent at 79.2%.

 

Conclusion:

MVM was more prevalent in PTB than term birth and AI was more common in term birth in this prospectively collected community sample. Further study is needed in the contribution of MVM in preterm birth, particularly in spontaneous PTB.