Adverse pregnancy outcomes associated with maternal syphilis infection

Syphilis infections affect many pregnant women worldwide every year. The increasing rates of maternal and congenital syphilis infections in recent years in the United States necessitates further investigation into the adverse effects of syphilis infection on maternal and neonatal health.

We sought to examine the association of maternal syphilis infection with adverse pregnancy and perinatal outcomes.

We performed a retrospective cohort study of women with singleton pregnancies who delivered between 23 and 42 weeks in California between 2007 and 2011. We compared demographic characteristics and pregnancy outcomes between pregnant women with syphilis and without syphilis. Maternal outcomes of interest included gestational hypertension, pre-eclampsia, gestational diabetes, preterm delivery, cesarean delivery, induction of labor, and severe maternal morbidity. Neonatal outcomes included neonatal intensive care unit admission, congenital anomaly, congenital syphilis, small for gestational age, stillbirth, neonatal death, infant death. Descriptive statistics were assessed using chi-square/Fisher's Exact tests. Multivariable logistic regression was used to estimate the association between syphilis and adverse pregnancy and perinatal outcomes. Statistical comparisons with a p-value of less than .05 and 95% CI that did not cross the null were considered statistically significant.

Among a cohort of 2,566,246 women, there were 991 pregnancies complicated by maternal infection with syphilis (0.04%). We found during multivariable logistic regression that syphilis infection was significantly associated with preterm delivery (aOR: 1.27, 95% CI: 1.05-1.54), NICU admission >24 h (aOR: 2.54, 95% CI: 2.13-3.04) and stillbirth (aOR: 5.01, 95% CI: 3.16-7.92) after adjusting for a number of potential confounders including maternal age, race/ethnicity, education, parity, prenatal visits, body mass index, smoking and insurance status.

Maternal syphilis infection in pregnancy is associated with specific adverse pregnancy outcomes, even after adjusting for potential confounders. These data can be used to counsel patients with syphilis in pregnancy, and in developing approaches to clinical care. Due to the increased risk of stillbirth, perhaps such patients should receive antenatal testing. Further research is necessary to investigate the mechanisms of morbidity.