Birth-to-pregnancy intervals and adverse perinatal outcomes among African-born women in Washington State

Background: Short birth-to-pregnancy (BTP) intervals are associated with adverse perinatal outcomes. The number of African-born blacks currently living in the U.S. exceeds 1.6 million. However, little is known about BTP intervals and the risk factors and outcomes related to short BTP intervals among African-born women living in the U.S. Objectives: The objectives of this study were to: (1) Investigate risk of short BTP and BTP-related risk factors and perinatal outcomes among African-born black women in Washington State, and (2) evaluate whether short BTP intervals modify the relationship between maternal birth country and race and perinatal outcomes among African-born black, U.S.-born white, and U.S.-born black women. Methods: This was a retrospective cohort study using data from linked birth certificate and hospital discharge records for 18,984 consecutive, singleton birth pairs to African-born black (n=3,312), U.S.-born white (n=7,839) and U.S.-born black women (n=7,833) in Washington State from 1992-2013. Short BTP interval was defined as <6 months between date of delivery of preceding live birth and conception date of a subsequent pregnancy. Logistic regression models were used to determine adjusted odds ratios (aOR) and 95% confidence intervals (CI). Effect modification was evaluated using stratified analyses. Results: Women with short BTP intervals comprised 10.0% of African-born women, 4.3% of U.S.-born white women, and 6.8% of U.S.-born black women. African-born women had 3-fold and 1.5-fold higher risk of short BTP intervals compared with U.S.-born white women (aOR 3.44; 95%CI: 2.53-4.68) and U.S.-born black women (aOR 1.49; 95%CI: 1.28-1.74). Among African-born women, those who were born in Eastern Africa (aOR 3.17; 95%CI: 1.92, 5.24), nulliparous (aOR 1.37; 95%CI: 1.01-1.86), had ≤ high school education (aOR 1.92; 95%CI: 1.41-2.61), and previous vaginal delivery (aOR 1.78; 95%CI: 1.29-2.44) were at higher risk for short BTP intervals. Among women with normal BTP interval, African-born black women had almost two-fold higher risk of having low birthweight (aOR 1.89; 95%CI: 1.10-3.23) infants compared with U.S.-born white women. This association was not observed among women with short or intermediate BTP intervals. Conclusions: African-born black women are at higher risk for short BTP intervals than U.S.-born white and black women. We identified several risk factors that may contribute to short BTP among African-born black women. Given the link between short BTP intervals and adverse perinatal outcomes, additional efforts are needed to better understand factors affecting pregnancy spacing among African-born women.