The association between assisted reproductive technologies and obesity

The associations between different fertility treatments and BMI in children.

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Over the past few decades, millions of children have been born thanks to assisted reproductive technologies (ARTs), which involve manipulating gametes and embryos ex vivo through procedures like intracytoplasmic sperm injection (ICSI) and in vitro fertilization (IVF). Although the number of live babies following these reproductive treatments has increased, little is known about the long-term health effects.

The requirement for an extended period of follow-up, the inclusion of many children born after therapy, and the gathering of detailed clinical data on both parents and children have made it difficult to examine long-term results. Furthermore, it has been challenging to distinguish between the reasons for treatment and the side effects of the medication.

This new study investigated the associations between different fertility treatments and BMI in children aged 5 to 8 years, adjusting for and stratifying by causes of parental infertility.

The study involved 327,301 children born between 2007 and 2012. Thirteen thousand six hundred seventy-five among these were taken after ART 7,7,28 were born after ovulation induction with or without intrauterine insemination, and 305,898 were born after no fertility treatments.

Scientists used specific standards to define overweight and obesity. Then, they compared children born after assisted reproductive technology (ART) with those born after other methods like ovulation induction/intrauterine insemination (OI/IUI). They also compared different techniques within ART, such as intracytoplasmic sperm injection (ICSI) and conventional in vitro fertilization (IVF), as well as frozen-thawed versus fresh embryo transfer.

They looked at the prevalence of overweight or obesity in children aged 5 to 8 years, odds ratios, and differences in BMI z-scores. They adjusted their analysis for factors like parental characteristics, causes of infertility, and more.

When comparing children born after different fertility treatments, the prevalence of obesity was found to be 1.9% in those born after assisted reproductive technology (ART), 2.0% after ovulation induction/intrauterine insemination (OI/IUI), and 2.7% after no fertility treatment.

Adjusting for various factors, there was no significant difference in the prevalence of overweight or obesity between children born after ART and OI/IUI. Similar patterns were observed when comparing intracytoplasmic sperm injection (ICSI) with conventional in vitro fertilization (IVF).

Additionally, obesity was more prevalent after frozen-thawed embryo transfer (2.7%) than after fresh embryo transfer. The associations between fertility treatments and BMI were generally consistent across different infertility causes.

Scientists concluded, “We found no association with BMI at age 5 to 8 years when comparing ART versus OI/IUI or when comparing ICSI versus conventional IVF. However, the use of frozen-thawed embryo transfer was associated with a 1.5-fold increased risk of obesity compared to fresh embryo transfer. Despite an elevated relative risk, the absolute risk difference was low.”

“Our study provides reassuring results for couples who seek help to conceive. Reasons behind our findings for frozen-thawed embryo transfer need further investigation.”

Journal Reference:

  1. Laugesen K, Veres K, Hernandez-Diaz S, Chiu Y-H, Oberg AS, Hsu J, et al. (2023) Overweight or obesity in children born after assisted reproductive technologies in Denmark: A population-based cohort study. PLoS Med 20(12): e1004324. DOI: 10.1371/journal.pmed.1004324

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