Association of Short and Long Interpregnancy Intervals with Adverse Birth Outcomes: Evidence from a Cross-Sectional Study in Northwest China

Abstract

Purpose To analyze the effects of a short interpregnancy interval (IPI) (<6 months) and a long IPI (>120 months) on neonatal adverse birth outcomes including low birth weight (LBW), small for gestational age (SGA), preterm birth (PTB), and birth defects in Shaanxi Province. Patients and Methods A stratified multistage random sampling method was used to recruit participants who gave birth between 2010 and 2013 in Shaanxi province. A self-designed questionnaire was used to collect the information of the participants. With the confounding factors controlled, the generalized linear model (GLM) was used to investigate the association between IPI and neonatal birth outcomes. The restricted cubic spline (RCS) function was used to evaluate the dose–response relationship between IPI and birth outcomes. Results A total of 13,231 women were included. The prevalence of LBW, SGA, PTB, and birth defects was 3.24%, 12.96%, 2.93%, and 2.12%, respectively. GLM showed that a short IPI (<6 months) was associated with a higher risk of SGA (RR=1.25, 95% CI: 1.04–1.52) and birth defects (RR=2.55, 95% CI: 1.45–4.47), and a long IPI (≥120 months) was associated with a higher risk of LBW (RR=1.54, 95% CI: 1.01–2.34) and PTB (RR=1.73, 95% CI: 1.08–2.76) than an IPI of 18–23 months. The RCS showed that LBW, SGA, and PTB demonstrated a j-shaped relationship with IPI (P for overall association < 0.001 for these three birth outcomes), and birth defects (P for overall association <0.001) had an inversely non-linear relationship with IPI. Conclusion Both short and long IPIs are associated with an increased risk of adverse birth outcomes.

Association of Interpregnancy Interval With Adverse Birth Outcomes

“…However, a few unmatched studies in China have presented inconsistent results compared with the unmatched analysis. For example, Shi et al 23 used a generalized linear model to explore the association of IPI with adverse perinatal outcomes in Northwest China; they found that a shorter IPI of less than 6 months was associated with higher risks of SGA but not PTB and LBW. A possible explanation for such differences is that different sample sizes and adjustment factors were involved.…”

“…First, the study period was restricted from 2014 to 2020, which resulted in a relatively limited amount of data on long IPI (>60 months), making it difficult to explore the association between long IPI and adverse perinatal outcomes. Second, consistent with previous studies, this study included only live, consecutive, single-birth data. Thus, these results might not apply to women who had experienced a miscarriage or stillbirth between deliveries.…”

“… 18 , 19 , 20 , 21 However, only a few studies explored the association of IPI with adverse birth outcomes among the Chinese population. 22 , 23 Nevertheless, these studies did not account for some unmeasured confounders.…”

“…Several studies involving populations in high-income countries used a sibling-matched design to account for some unmeasured confounders, such as genetic factors and lifestyles . However, only a few studies explored the association of IPI with adverse birth outcomes among the Chinese population . Nevertheless, these studies did not account for some unmeasured confounders.…”

Association between inter‐pregnancy interval and risk of adverse birth outcomes in subsequent pregnancy: A retrospective study from Jordan

“…Similar findings have been reported elsewhere. 2,6 Despite the fact that prolonged IPIs might allow more complete recovery of the mother, 30 researchers have also opined that pregnancy intervals longer than 5 years might lead to poor infant outcomes, such as preterm birth, small-for-gestational-age fetus, LBW, NICU admission, and stillbirth. 12,30 A recent study of adverse consequences associated with an IPI of 60 months or greater has illustrated that physiologic adaptations of the reproductive system regress gradually after a long time if a woman does not conceive another fetus, which in turn may revert the mother's physiology to a state similar to primigravidity.…”