For children conceived with assisted reproductive technology (ART), early-life weight differences did not appear to persist into adolescence, the researchers reported.
Compared with those conceived naturally, children conceived with ART tended to be shorter and weigh less in early childhood, said Ahmed Elhakeem, PhD, of the University of Bristol in England, and colleagues.
However, as shown in their study in JAMA Network Open, these weight differences for ART-conceived children were evident only in infancy and then slowly dissipated throughout childhood. More specifically, adjusted mean changes in weight were no longer significant by age 14:
- <3 months: -0.27 standard deviation units (95% CI -0.39 to -0.16)
- 17 to 23 months: -0.16 SD units (95% CI -0.22 to -0.09)
- 6 to 9 years: -0.07 SD units (95% CI -0.10 to -0.04)
- 14 to 17 years: -0.02 SD units (95% CI -0.15 to 0.12)
“Results appeared independent of multiple births and were at least partially mediated by birth weight and gestational age, particularly at younger ages,” the researchers noted.
They added that the findings should be “reassuring as the changes in early growth were small, although there is a need for additional follow-up and studies with larger numbers at older ages to investigate the possibility of increased obesity in adulthood.”
However, not all children conceived with ART tend to be smaller babies. Elhakeem’s group found that this smaller size was only seen among those conceived by fresh – not frozen – embryo transfer versus natural conception. The difference in weight at ages 4 to 5 years was -0.14 (95% CI -0.20 to -0.07) SD units for fresh embryo transfer versus natural conception and 0.00 (95% CI -0 .15 to .15) SD units for frozen embryo transfer versus natural conception.
This was not so surprising, as Elhakeem’s group said that this finding was consistent with previous research on the topic related to lower birth weight in offspring conceived through fresh embryo transfer versus natural conception, plus higher birth weight. birth and heavy weight for pregnancy. -age of offspring conceived through frozen-thawed embryo transfer compared to those conceived through fresh embryo transfer.
These differences in early size extended beyond the weight of children conceived via fresh embryo ART, the investigators reported. These children also tended to have smaller waist circumference, total body fat percentage and fat mass index. Although as with body weight, these differences diminished by adolescence.
“There was little evidence that the differences were driven by parental subfertility, given similar results when we compared offspring conceived with ART to those who were [naturally conceived] with parents who became pregnant after 12 months of trying and for whom conception occurred within a shorter period from the start of trying,” Elhakeem’s group noted.
A total of 26 study groups were included in the meta-analysis, which included data on 158,066 offspring — 4,329 of whom were conceived by ART. The cohorts came from Europe, Asia-Pacific and North America and mainly included children born after 2002.
The study was funded by the European Research Council under the European Union’s Horizon 2020 research and innovation programme, the Medical Research Council, the British Heart Foundation and the Bristol Health Research Biomedical Research Centre.
Elhakeem reported no discovery; other co-authors reported several disclosures, including several relationships with commercial entities.