Interpregnancy Interval and Adverse Pregnancy Outcomes: An Analysis of Successive Pregnancies.

OBJECTIVE: To examine the association between interpregnancy interval and maternal-neonate health when matching women to their successive pregnancies to control for differences in maternal risk factors and compare these results with traditional unmatched designs. METHODS: We conducted a retrospective cohort study of 38,178 women with three or more deliveries (two or greater interpregnancy intervals) between 2000 and 2015 in British Columbia, Canada. We examined interpregnancy interval (0-5, 6-11, 12-17, 18-23 [reference], 24-59, and 60 months or greater) in relation to neonatal outcomes (preterm birth [less than 37 weeks of gestation], small-for-gestational-age birth [less than the 10th centile], use of neonatal intensive care, low birth weight [less than 2,500 g]) and maternal outcomes (gestational diabetes, beginning the subsequent pregnancy obese [body mass index 30 or greater], and preeclampsia-eclampsia). We used conditional logistic regression to compare interpregnancy intervals within the same mother and unconditional (unmatched) logistic regression to enable comparison with prior research. RESULTS: Analyses using the traditional unmatched design showed significantly increased risks associated with short interpregnancy intervals (eg, there were 232 preterm births [12.8%] in 0-5 months compared with 501 [8.2%] in the 18-23 months reference group; adjusted odds ratio [OR] for preterm birth 1.53, 95% confidence interval [CI] 1.35-1.73). However, these risks were eliminated in within-woman matched analyses (adjusted OR for preterm birth 0.85, 95% CI 0.71-1.02). Matched results indicated that short interpregnancy intervals were significantly associated with increased risk of gestational diabetes (adjusted OR 1.35, 95% CI 1.02-1.80 for 0-5 months) and beginning the subsequent pregnancy obese (adjusted OR 1.61, 95% CI 1.05-2.45 for 0-5 months and adjusted OR 1.43, 95% CI 1.10-1.87 for 6-11 months). CONCLUSION: Previously reported associations between short interpregnancy intervals and adverse neonatal outcomes may not be causal. However, short interpregnancy interval is associated with increased risk of gestational diabetes and beginning a subsequent pregnancy obese.

Racial disparity in stillbirth among singleton, twin, and triplet gestations in the United States.

OBJECTIVE: We investigated the relationship between maternal race and stillbirth among singletons, twins, and triplets. METHODS: We conducted a retrospective cohort study on 14,348,318 singletons, 387,419 twins, and 20,953 triplets delivered in the United States from 1995 through 1998. We compared the risk of stillbirth between pregnancies of black and those of white mothers using the generalized estimating equations framework to adjust for intracluster correlation in multiples. RESULTS: The proportion of black infants was 16%, 18%, and 8% among singletons, twins, and triplets, respectively. Crude stillbirth rate among singletons was 6.6 per 1,000 and 3.5 per 1,000 for black and white fetuses, respectively. Among twins, 796 stillbirths (11.6 per 1,000) were recorded for black mothers versus 3,209 stillbirths (10.1 per 1,000) among white mothers, whereas among triplets there were 233 stillbirths, of which 39 stillbirths were black fetuses (24.6 per 1,000) and 194 stillbirths were white fetuses (10.0 per 1,000). Black singletons, twins, and triplets weighed 278 g, 186 g, and 216 g less than white fetuses, respectively (P <.001). Risk of stillbirth was elevated in black fetuses compared with white fetuses among singletons (adjusted odds ratio [OR] 2.9, 95% confidence interval [CI] 2.8-3.0) and twins (OR 1.3. 95% CI 1.2-1.4) but comparable among triplets (OR 1.2, 95% CI 0.7-2.1). This decreasing trend was significant (P for trend <.001). CONCLUSION: The disparity of stillbirths between black and white fetuses still persists among singletons and twins. Among triplet gestations, however, the 2 racial groups have a comparable risk level. Our findings highlight the need for a rigorous research agenda to elucidate causes of stillbirth across racial/ethnic entities in the United States. LEVEL OF EVIDENCE: II-2