The influence of interpregnancy interval on infant mortality

Abstract

Background In Ohio the infant mortality rate is above the national average and the black infant mortality rate is more than twice the white infant mortality rate. Having a short interpregnancy interval has been shown to correlate with preterm birth and low birth weight, but the effect of short interpregnancy interval on infant mortality is less well established. Objective To quantify the population impact of interpregnancy interval on the risk of infant mortality. Study Design This was a statewide population-based retrospective cohort study of all births (n=1,131,070) and infant mortalities (n=8,152) using linked Ohio birth and infant death records from 1/2007 through 9/2014. For this study we analyzed 5 interpregnancy interval categories: 0 to < 6 months, 6 to < 12 months, 12 to < 24 months, 24 to < 60 months, and ≥ 60 months. The primary outcome for this study was infant mortality. During the study period, 3701 infant mortalities were linked to a live birth certificate with an interpregnancy interval available. We calculated the frequency and relative risk (RR) of infant mortality for each interval compared to a referent interval of 12 to < 24 months. Stratified analyses by maternal race were also performed. Adjusted risks were estimated after accounting for statistically significant and biologically plausible confounding variables. Adjusted relative risk was utilized to calculate the attributable risk percent of short interpregnancy intervals on infant mortality. Results Short interpregnancy intervals were common in Ohio during the study period. 20.5% of all multiparous births followed an interval of < 12 months. The overall infant mortality rate during this time was 7.2 per 1000 live births (6.0 for white mothers and 13.1 for black mothers). Infant mortalities occurred more frequently for births that occurred following short intervals of 0 to < 6 months (9.2 per 1000) and 6 to < 12 months (7.1 per 1000) compared to 12 to < 24 months (5.6 per 1000), (p= <0.001 and <0.001). The highest risk for infant mortality followed interpregnancy intervals of 0 to < 6 months, adjRR 1.32 (95% CI 1.17–1.49) followed by interpregnancy intervals of 6 to < 12 months, adjRR 1.16 (95% CI 1.04–1.30). Analysis stratified by maternal race revealed similar findings. Attributable risk calculation showed that 24.2% of infant mortalities following intervals of 0 to < 6 months and 14.1% with intervals of 6 to < 12 months are attributable to the short interpregnancy interval. By avoiding short interpregnancy intervals of 12 months or less we estimate that in the state of Ohio 31 infant mortalities (20 white and 8 black) per year could have been prevented and the infant mortality rate could have been reduced from 7.2 to 7.0 during this time frame. Conclusion An interpregnancy interval of 12–60 months (1–5 years) between birth and conception of next pregnancy is associated with lowest risk of infant mortality. Public health initiatives and provider counseling to optimize birth spacing has the potential to significantly reduce infa...

Beyond birth outcomes: Interpregnancy interval and injury‐related infant mortality

“…Previous research using 1991 US birth certificate data showed an elevated association between short IPI (defined as <19 months) only and infant mortality . Similarly, more recent state‐based studies using 2003 revised birth certificate data also found similar associations between only short IPI (defined as either <18 months or <12 months) and infant mortality . In contrast to these studies, we observed a significant association between long IPI and increased risk of overall infant mortality.…”

Short interpregnancy intervals and adverse perinatal outcomes in high‐resource settings: An updated systematic review

“…[8][9][10][11]21,22,25,[27][28][29][34][35][36][37][38][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62] The majority of studies were conducted in the United States (n = 18), 11,21,25,[27][28][29][36][37][38]49,51,[54][55][56][57][58][59]62 78% of which used U.S. birth certificate data (n = 14). 11,21,…”

“…Nine of the 32 studies met criteria for good internal validity, [8][9][10][11]22,28,34,35,46 18 fair 21,25,27,29,36,37,[47][48][49][50][51][52][53][54]57,58,60,61 and five poor 38,55,56,59,62 (Table 1). Most studies included a limited set of covariates for adjustment, and no study accounted for all the study design considerations outlined above.…”

Policy change is not enough: engaging provider champions on immediate postpartum contraception

“…1 These unintended pregnancies are significantly more likely to have short interpregnancy intervals (<18 months apart) compared with pregnancies reported as intended (unadjusted odds ratios, 4.3 and 1.8, respectively). 1 Short interpregnancy intervals also increase risks for poor maternal and infant outcomes, 2–4 which makes the reduction in short-interval unintended pregnancies a public health priority.…”