New research suggests that the use of assisted reproductive technology (ART) may mediate around one quarter of the association between twin births and a pre-pregnancy body mass index (BMI) of 30-40.
In a comprehensive cohort study encompassing over half a million deliveries, the percentage of women conceiving through ART rose with increasing BMI, with ART linked to nearly a 12-fold higher rate of twin delivery.
ART was identified as the explanation for 23% of the association between obesity class I (BMI, 30-34.9) and class II (BMI, 35-39.9) and twin delivery. Surprisingly, ART did not mediate this association in patients with class III obesity (BMI ≥ 40).
Study author Jeffrey N. Bone, a graduate student and statistician at the University of British Columbia, shared his surprise at the findings. He stated that various epidemiological explanations and types of bias were assessed but did not significantly alter the primary findings.
The study, published in JAMA Network Open, examined the link between BMI and twin births and the potential mediating role of ART in this association. The retrospective cohort study included all live births and stillbirths in British Columbia from 2008 to 2020, totaling 524,845 eligible deliveries, with 392,046 women having complete pre-pregnancy BMI data.
The results indicated that ART mediated 23% of the association between obesity and twin delivery, except for class III obesity. The study emphasized the need for further exploration and understanding of the factors influencing twin births in women with high BMI.
The study’s limitations included a significant proportion of missing data, lack of information on chorionicity, and the absence of data on race and ethnicity. Despite these limitations, the findings provide valuable insights into the complex relationship between BMI, ART, and twin deliveries.
