Infertility treatments and cyanotic congenital heart defects among livebirths in the USA: findings from a contemporary cohort.

Study question: Is there an elevated risk of cyanotic congenital heart defects (CCHD) among livebirths following infertility treatments?

Summary answer: In this population-based study of single livebirths, infertility treatment (either ART or non-ART) was associated with a higher prevalence of CCHD among livebirths.

What is known already: The use of infertility treatment has been on the rise over the past few decades. However, there are limited studies assessing the risk of major cardiac defects following infertility treatments.

Study design, size, duration: A retrospective cohort study of livebirth data from the National Vital Statistics System (NVSS) was conducted, comprising of 9.6 million singleton livebirths among first-time mothers aged 15-49 years from 2016 to 2022.

Participants/materials, setting, methods: Information on infertility treatment use and CCHD was obtained from the health and medical information section of birth certificates, which was completed by healthcare staff after reviewing medical records. Logistic regression models were used to estimate odds ratios (OR) and 95% CI. Entropy balancing weighting analysis and probabilistic bias analysis were also performed.

Main results and the role of chance: The proportion of births following infertility treatment increased from 1.9% (27 116) to 3.1% (43 510) during the study period. Overall, there were 5287 cases of CCHD resulting in a prevalence of 0.6 per 1000 livebirths. The prevalence was 1.2 per 1000 live births among infertility treatment users (ART: 1.1 per 1000 livebirths; non-ART: 1.3 per 1000 livebirths) while that for naturally conceived births was 0.5 per 1000 livebirths. Compared to naturally conceived births, the use of any infertility treatment (OR: 2.06, 95% CI: 1.82-2.33), either ART (OR: 2.02, 95% CI: 1.73-2.36) or other infertility treatments (OR: 2.12, 95% CI: 1.74-2.33), was associated with higher odds of CCHD after adjusting for maternal and paternal age, race and ethnicity, and education, as well as maternal nativity, marital status, source of payment, smoking status, and pre-pregnancy measures of BMI, hypertension and diabetes. This association did not differ by the type of infertility treatment (ART versus other infertility treatments) (OR: 1.04, 95% CI: 0.82-1.33, P = 0.712), and was robust to the presence of exposure and outcome misclassification bias and residual confounding.

Limitations, reasons for caution: The findings are only limited to livebirths. We did not have the capacity to examine termination data, but differential termination by mode of conception has not been supported by previous studies designed to consider it. Infertility treatment use was self-reported, leading to the potential for selection bias and misclassification for infertility treatment and CCHD. However, the association persisted when systematic bias as well as exposure and outcome misclassification bias were accounted for in the analyses. Information on the underlying etiology of infertility relating to either maternal, paternal, or both factors, data on specific types of ART and other infertility treatments, as well as information on subtypes of CCHD, were all not available.

Wider implications of the findings: In light of the increasing trend in the use of infertility treatment in the USA, and elsewhere, the finding of the current study holds significant importance for the clinical and public health of reproductive-aged individuals. The data show that the use of infertility treatment may expose offspring to elevated odds of severe congenital heart defects such as CCHD studied here. These findings cannot be interpreted causally. While our findings can assist in preconception counseling and prenatal care for pregnancies conceived by either ART or other infertility treatments, they also support some current recommendations that pregnancies resulting from infertility treatments undergo fetal echocardiography screening.

Study funding/competing interest(s): No funding was sought for the study. The authors declare that they have no conflict of interest.

Trial registraion number: N/A.