Interpregnancy Interval and Childbirth Outcomes in California, 2007-2009.

Objectives The goals of interconception care are to optimize women's health and encourage adequate spacing between pregnancies. Our study calculated trends in interpregnancy interval (IPI) patterns and measured the association of differing intervals with birth outcomes in California. Methods Women with "non-first birth" deliveries in California hospitals from 2007 to 2009 were identified in a linked birth certificate and patient discharge dataset and divided into three IPI birth categories: <6, 6-17, and 18-50 months. Trends over the study period were tested using the Cochran-Armitage two-sided linear trend test. Chi square tests were used to test the association between IPI and patient characteristics and selected singleton adverse birth outcomes. Results Of 645,529 deliveries identified as non-first births, 5.6 % had an IPI <6 months, 33.1 % had an IPI of 6-17 months, and 61.3 % had an IPI of 18-50 months. The prevalence of IPI <6 months declined over the 3-year period (5.8 % in 2007 to 5.3 % in 2009, trend p value <0.0001).Women with an IPI <6 months had a significantly higher prevalence of early preterm birth (<34 weeks), low birthweight (<2500 g), neonatal complications, neonatal death and severe maternal complications than women with a 6-17 month or 18-50 month IPI (p < 0.005). Comparing those with a 6-17 month vs 18-50 month IPI, there were increased early preterm births and decreased maternal complications, complicated delivery, and stillbirth/intrauterine fetal deaths among those with a shorter IPI. Conclusions for Practice In California, women with an IPI <6 months were at increased risk for several birth outcomes, including composite morbidity measures.