Differences in growth, adiposity are not long term in children conceived through ART

Children conceived through assisted reproductive technology — or ART — were “shorter, lighter and thinner” compared with naturally conceived children at birth through early adolescence, data published in JAMA Network Open showed.

However, the differences in body fat and height between children conceived through ART and those who were conceived naturally grew smaller with age.

“Ever since the first ART birth in 1978, research focus has been on improving live-birth rates,” Ahmed Elhakeem, PhD, a senior research associate in epidemiology at the University of Bristol in England, and colleagues wrote. “Now that ART is acknowledged as an effective procedure for infertility treatment, attention has shifted toward identifying and reducing any adverse effects of ART on maternal or offspring health.

“Besides perinatal outcomes, long-term associations between ART conception and offspring growth and adiposity remain largely unknown, with the few studies that have examined these mostly limited by small sample size, short follow-up and limited adjustment for confounders or overadjustment for possible mediators,” they added.

Elhakeem and colleagues collected data on children’s growth and adiposity over time from 26 population-based cohort studies conducted in Europe, Asia-Pacific and North America. Heterogeneity was low to moderate between most cohorts.

To assess the impact of ART, the researchers analyzed the length/height, weight and BMI data of children born between 1984 and 2018 by age group, with up to 158,066 children per age group. Child measurements were reported for ages 0.6 months through 27.4 years.

BMI measurements

Children conceived through ART had a smaller mean length/height compared with naturally conceived children at younger ages; at age younger than 3 months, the mean difference was –0.27 standard deviation (SD) units (95% CI, –0.4 to –0.14). With age, the mean difference grew smaller; the mean difference was –0.03 SD units (95% CI, –0.17 to 0.1) at age 14 to 17 years and –0.06 SD units (–0.24 to 0.12) at age older than 17 years.

A similar trend was detected with weight. ART-conceived children were significantly lighter compared with naturally conceived children when they were aged younger than 3 months (mean difference, –0.27 SD units; 95% CI, –0.39 to –0.16). The difference was attenuated at the ages of 17 to 23 months (mean difference, –0.16 SD units; 95% CI, –0.22 to –0.09), 6 to 9 years (mean difference, –0.07 SD units; 95% CI, –0.1 to –0.04) and 14 to 17 years (mean difference, –0.02 SD units; 95% CI, –0.15 to 0.12).

Analyses of ART methods revealed that children conceived through fresh embryo transfer (ET) had smaller mean length/height, weight and BMI measurements vs. naturally conceived children. The mean difference in these measurements was smaller between children conceived through frozen-thawed ET and those conceived naturally. For instance, the mean difference in weight between children conceived through fresh ET and those conceived naturally was –0.14 SD units (95% CI, –0.2 to –0.07) at age 4 to 5 years; between children conceived through frozen-thawed ET and those conceived naturally, the mean difference in weight was 0 SD units (95% CI, –0.15 to 0.15) at 4 to 5 years.

Body fat measurements

Mean measurements for waist circumference, total body fat percentage and fat mass index were smaller among children conceived with ART vs. naturally during childhood and adolescence. However, the mean measurements were higher in adulthood for ART-conceived children compared with those conceived naturally, although the confidence intervals were wider. For example, the mean difference in fat mass index between ART-conceived and naturally conceived children at age older than 17 years was 0.23 SD units (95% CI, –0.04 to 0.5).

“Overall, our findings are reassuring since differences in early growth were small, although there is a need for additional follow-up and studies with larger numbers into older ages to investigate the possibility of greater adiposity in adulthood,” Elhakeem and colleagues wrote.