349 Understanding racial-ethnic disparities in preterm birth sub-types

Abstract

To determine if there are racial-ethnic disparities in preterm birth (PTB) subtypes (spontaneous or medically indicated) after controlling for known risk factors. Retrospective cohort study including singleton pregnancies from 2011-2018 within Kaiser Permanente Northern California (KPNC). Women with missing data on gestational age at delivery or maternal race-ethnicity were excluded. Spontaneous PTB (sPTB) was defined as spontaneous onset of labor or preterm premature rupture of membranes less than 37 weeks gestation. Medically indicated PTB (mPTB) was defined as all other PTB that were not spontaneous. The primary outcome was PTB by subtype, and exposure was race-ethnicity. Covariates included demographic factors (maternal age at delivery, pre-pregnancy BMI, parity, insurance status), and PTB risk factors (diabetes, hypertension, history of PTB, cervical insufficiency, uterine anomalies, cervical shortening, smoking and illegal drug use during pregnancy). Bivariate and multivariate logistic regression analyses were performed. A total of 295,210 pregnancies met inclusion criteria. Overall PTB rate was 6.6% (N=19,357). Compared to White women (5.4%), Black women had almost double the risk of PTB at 9.5%, while Asian/Pacific Islander women had a 7% rate and Hispanic women had a 6.9% rate of overall PTB. Of all PTB, 44.2% were mPTB and 55.8% were sPTB. After adjusting for maternal demographics and medical conditions associated with PTB, all non-White racial-ethnic categories were independently associated with increased relative risks of both mPTB and sPTB (Table 1). Black race was associated with the highest relative risk of mPTB at 1.46 (95% CI 1.32-1.61, Table 1), while Asian/Pacific Islander race was associated with the highest relative risk of sPTB at 1.30 (95% CI 1.23-1.39, Table 1). There are racial and ethnic disparities in PTB within KPNC overall, and by PTB subtype. Further examination of the drivers of PTB disparities by subtype can help direct further efforts to reduce these disparities.