458 Maternal passive-smoking during pregnancy. the effect on pregnancy outcomes and placental-pathology. A prospective case-control study

Abstract

The effect of maternal passive smoking (MPS) during pregnancy is difficult to investigate and was poorly studied before. This study was designed to investigate the effects of MPS during pregnancy- on placental pathology and pregnancy outcomes. We performed a prospective case-control study. We recruited low-risk laboring women at 37+0 to 41+0 weeks between 9/2019-7/2020. MPS was defined as exposure to a spouse that reported in-house tobacco smoking of > 20 cigarettes/day in the absence of maternal active smoking. In an attempt to "purify" the effect of MPS - we excluded cases with preeclampsia, diabetes, suspected fetal growth restriction (FGR), preterm labor, and illicit drug use. Maternal characteristics, pregnancy outcomes, and placental pathology were compared between the MPS group and a control group matched for gestational age, maternal age, and delivery date. Placental lesions were classified according to “Amsterdam” criteria. The study was powered to detect a 33% difference in placental malperfusion lesion and was calculated as 115 cases in each group. Multivariable regression analysis was performed to identify independent associations with placental malperfusion lesions. In labor, the MPS group (n=115) had higher rates of meconium-stained amniotic fluid (MSAF, p<0.001) and non-reassuring fetal heart rate (NRFHR) that necessitated immediate delivery (p=0.03), compared to controls (n=115). Neonates in the MPS group had higher rates of undiagnosed FGR (p=0.01) and NICU admissions (p=0.004). In placental pathology, the MPS group had higher rates of placental hypoplasia (p=0.02) and fetal vascular malperfusion (FVM) lesions (p=0.04). In regression analysis MPS was associated with FVM lesions independent of background confounders (aOR=2.3 95% CI 1.26-6.34). In otherwise low-risk pregnancies, MPS was associated with higher rates of MSAF, NRFHR, undiagnosed FGR, and NICU admissions, probably mediated via placental FVM. These worrisome findings mandate patient counseling and further investigation in larger population-based studies.View Large Image Figure ViewerDownload Hi-res image Download (PPT)