Serum insulin-like growth factor-I (IGF-I) and growth in children born after assisted reproduction

Concern has been raised about the safety of assisted reproduction techniques for the offspring.

The objective of the study was to investigate postnatal growth and growth factors in children born after intra-cytoplasmatic sperm injection (ICSI) and in vitro fertilization (IVF).

The study had two cohorts: a population-based longitudinal infant cohort 0-36 months [236 ICSI, 173 IVF, 1530 naturally conceived (NC)], and a cross-sectional child cohort at 5 yr (68 ICSI, 67 IVF, 70 NC).

Anthropometrical measurements were made at birth, 3, 18, 36 (infant cohort), and 60 months (child cohort), and blood samples were collected at 3 or 60 months.

Serum IGF-I, IGFBP-3, height, weight, head and abdominal circumference, body mass index, and fat folds were the main outcome measures.

Anthropometrical measurements showed no significant differences between ICSI and IVF children and controls in either cohort. However, singleton ICSI girls [3.4 (0.6) kg, P = 0.008] had a slightly lower birth weight than IVF [3.5 (0.5) kg] and NC girls [3.5 (0.5) kg]. Birth weights of singleton boys [3.6 (0.5) kg], twin boys [2.6 (0.6) kg], and twin girls [2.4 (0.5) kg] did not differ between types of conception. In the infant cohort in 3-month-old singletons, serum IGF-I was lower in ICSI [78 (26) ng/ml] than NC boys [94 (27) ng/ml, P < 0.001] and IVF [74 (34) ng/ml], compared with NC girls [93 (43) ng/ml, P = 0.011]. ICSI children were also smaller than their target height (sd score) at 3 yr of age [mean -0.91 (1.2)], compared with NC children [-0.61 (0.9), P = 0.033]. In the child cohort, target height attainment (sd score) and growth factors did not differ among the three groups.

The overall growth pattern of ICSI and IVF children in both cohorts was normal. Our findings of subtle differences in target height attainment and serum IGF-I levels between infants born after assisted reproduction techniques and controls may not be clinically significant. However, these observations indicate that further systematic follow-up of growth and puberty in these children is needed.