OBJECTIVE: To study whether fertility treatment or subfertility is associated with long-term growth in the offspring.

DESIGN: A prospective follow-up study including 1,773 singletons participating in the Lifestyle During Pregnancy Study at the age of 5.

SETTING: Research centers.

PATIENT(S): A total of 3,478 mother-child pairs were sampled from the Danish National Birth Cohort, and 1,773 completed the outcome measurements. A total of 69 children were born after fertility treatment, whereas 132 were born to subfertile parents conceiving spontaneously but after a time to pregnancy of more than 12 months. The remaining 1,572 children were born to parents conceiving spontaneously within 12 months. At the age of 5, the children participated in a follow-up including anthropometric measurements. Information on important covariates with respect to family background, maternal prenatal exposures, perinatal outcomes, and postnatal parental lifestyle characteristics were obtained from the Danish National Birth Cohort, the 5-year follow-up, and Danish health registers.

INTERVENTION(S): None.

MAIN OUTCOME MEASURE(S): Adjusted mean differences in body weight, height, body mass index (BMI), and head circumference at age 5.

RESULT(S): Compared with spontaneously conceived children born to fertile parents, no systematic differences were observed for body weight, height, BMI, or head circumference at age 5 in children conceived after fertility treatment or to subfertile parents conceiving spontaneously.

CONCLUSION(S): There were no differences in child anthropometrics at 5 years between children conceived after fertility treatment or by subfertile parents compared with that of children born to fertile parents. However, children born after fertility treatment may show catch-up growth during childhood.