Infertility treatment and the growth of children from birth to 12 years of age: A national cohort study

Abstract

Background Children conceived through infertility treatments may have altered birth outcomes and growth patterns compared to those conceived naturally. However, evidence on long-term growth trajectories, particularly distinguishing singletons and multiples, remains inconsistent. This study aimed to compare childhood growth trajectories from birth to 12 years of age between children conceived via infertility treatments and those conceived naturally, using a large national birth cohort. Methods We analyzed the follow-up data (6 months to 12 years of age) from the Taiwan Birth Cohort Study, an ongoing, nationwide, longitudinal study of children. Our final sample included 20,507 singletons (20,306 naturally conceived [NC], 104 via intrauterine insemination [IUI], 97 via in vitro fertilization [IVF]) and 950 multiples (670 NC, 68 IUI, 212 IVF). We used linear mixed models with random coefficient cubic splines for age to assess the growth trajectories for weight, height, and body mass index (BMI) by infertility treatment status and logistic regression to analyze risk of rapid weight gain, overweight, obesity, and underweight. Results Children conceived via IUI or IVF showed lower weight, height, and BMI in pooled analyses; however, these differences were largely attributable to the higher proportion of multiple births in the infertility treatment groups. After stratification by plurality, most differences were attenuated and not statistically significant, with the exception of slightly lower weight (−0.353 kg; p = 0.039) among IUI-conceived multiples. The risk of rapid weight gain (6 months–2 years) and underweight, overweight, or obesity (5.5–12 years) did not differ significantly by the conception mode after plurality was controlled. Conclusions After accounting for plurality, children conceived through infertility treatments showed similar growth trajectories to those conceived naturally. These findings are reassuring for families using infertility treatments and highlight the importance of minimizing multiple births in assisted reproduction to support optimal child growth and health outcomes.