Objective To evaluate the effect of inter-pregnancy interval (IPI) on early neurodevelopmental disorders in children.

Methods A prospective cohort study was conducted among 421 pairs of mothers and infants, a subset of the Peking University Birth Cohort in Tongzhou (PKUBC-T), who registered and delivered in Tongzhou Maternal and Child Health Care Hospital from 2018 to 2019. Demographic information, pregnancy behavior patterns and IPI were collected during the prenatal visit. Ages and Stages Questionnaive-3(ASQ-3) questionnaire was used to collect the developmental scores of children. Covariance analysis, multiple linear regression and multiple logistic regression models were used to analyze the association between IPI and early childhood development. Subgroup analysis was further conducted to validate the association.

Results IPI was positively correlated with children individual-social scores. Compared with children whose mother experienced short IPI (IPI < 50.33), those whose mother experienced long IPI (80.94 ≤ IPI) had higher individual-social scores (β=3.350, 95%CI: 0.199, 6.501). IPI was also negatively correlated with the risk of individual-social disorders among children, and this relationship showed a progressive trend with the increase of IPI. Children who in longer IPI group (50.33 ≤ IPI < 80.94 and IPI ≤ 80.94) have lower risk of individual-social disorders6.9%(95%CI: 0.1%, 13.4%)and 8.2%(95%CI: 0.7%, 15.1%)than children who in shorter IPI group (IPI ≤ 50.33).These effects varied across different genders of the newborn, folic acid supplementation during pregnancy, life stress, and exposure to biological factors.

Conclusion The offspring of pregnant women with longer IPI (50.33 ≤ IPI < 80.94 and IPI ≤ 80.94) had a lower risk of individual-social disorders and a higher individual-social score than those with shorter IPI (IPI ≤ 50.33), and the association was influenced by factors such as the gender of newborn, folic acid supplementation during pregnancy, exposure to biological factors, and mental health.