Long-term growth in offspring of infertile parents: A 20-year follow-up study

INTRODUCTION: Long-term growth has been poorly investigated in boys and girls born to parents receiving fertility treatment. This study aimed to investigate the growth of children born following fertility treatment up to adulthood hypothesizing comparable growth in children born to parents receiving fertility treatment or to subfertile parents conceiving spontaneously to that in children spontaneously conceived by fertile parents.

MATERIAL AND METHODS: In this historical long-term follow-up study the study population consisted of 4151 singletons born at term in the Aarhus Birth Cohort between 1990 and 1992. Parental lifestyle and sociodemographic characteristics together with multiple measurements of weight and height were collected up to 20 years of age (6.1% of children contributed with at least one measurement for height or weight at age 20 years). The main outcome was difference in z-score for height (m) and weight (kg) between children conceived spontaneously (reference) and children conceived following fertility treatment, children conceived spontaneously by subfertile parents, or unplanned. Results were adjusted for pre-pregnancy maternal and paternal body mass index, maternal educational level, smoking during pregnancy, maternal age, and parity.

RESULTS: Singletons conceived following fertility treatment (n = 164; 4.0%) or by subfertile parents (n = 271; 6.5%) had comparable magnitude of weight estimates to children conceived spontaneously (difference in z-score per year 0.0148 [95% CI 0.0026-0.0270] and 0.0069 [95% CI -0.0028 to 0.0165], respectively). Height estimates were also comparable between groups of children conceived following fertility treatment or by subfertile parents (difference in z-score per year 0.0022 [95% CI -0.0075 to 0.0119]) compared with children conceived spontaneously (difference in z-score per year -0.0026 (95% CI -0.0103 to 0.0052). From the beginning of adolescence, we found lower weight for children born to subfertile parents and to parents receiving fertility treatment compared with spontaneously conceived children.

CONCLUSIONS: The main finding was equal long-term growth for children born at term by parents who received fertility treatment or parents waiting more than 12 months to conceive compared with spontaneously conceived children.