Background:
Since the first in vitro fertilization (IVF) in 1978, assisted reproductive technology (ART) has led to over 10 million births worldwide.
There are four types of embryo transfers, depending on whether they are fresh or frozen, and on their developmental stage.
Fresh cleavage stage embryos are transferred on day 2 or 3 following fertilization and typically contain four to eight relatively large, undifferentiated cells. Fresh blastocyst embryos are transferred on day 5 or 6 after fertilization. At this point, they have developed over a hundred cells and have differentiated into two types: the inner cell mass, which develops into the fetus, and the outer cell layer, which forms the placenta.
Globally, more children are now born through assisted reproductive technology using frozen-thawed embryo transfer than fresh embryo transfer.
Research suggests that ART-conceived offspring may face increased risks of cardiovascular, musculoskeletal, chromosomal, urogenital diseases, and cancers. Might they also be at increased risk for ADHD?
Study:
Taiwan’s single-payer health insurance covers over 99% of people and records all their healthcare activity. Since 1998, it has kept an ART database for all couples registered for IVF treatment.
A Taiwanese research team reviewed all records for the five-year period from 2013 through 2017, ultimately analyzing 3,125 live singleton births from fresh cleavage stages, 1,332 from fresh blastocysts, 1,465 from frozen cleavage stages, and 4,708 from frozen blastocysts, alongside 878,643 naturally conceived singleton births.
The team controlled for the following potential confounders: pregnancy-induced hypertension, chronic hypertension, diabetes mellitus, gestational diabetes mellitus, unhealthy lifestyle, placenta previa, placenta abruption, preterm premature rupture of membrane, and postpartum hemorrhage.
Results:
With these adjustments, cleavage stage embryo transfers, whether fresh or frozen, were associated with a seven-fold higher rate of ADHD diagnosis in offspring than natural conception.
Frozen blastocyst embryo transfers were likewise linked to a seven-fold increase in ADHD diagnoses in offspring compared to natural conception. Notably, fresh blastocyst transfers showed a 19-fold increase, likely due to the smaller number of cases in this category.
The team concluded, “Compared to natural conception, ART is associated with higher risks, particularly for preterm birth, ADHD, and developmental delay.”
Conclusion:
This large national cohort suggests that ART-conceived singletons face higher rates of several adverse outcomes, including preterm birth, ADHD, and developmental delay. Clinicians and prospective parents should therefore weigh these potential associations when counseling and planning care, prioritize optimized ART protocols and perinatal management, and ensure early developmental surveillance for ART-conceived children so concerns can be identified and addressed promptly.
It is important to note that the findings also point to the likely contribution of underlying parental infertility in these developmental outcomes. Future research should aim to disentangle parental- versus procedure-related risks to clarify absolute risk magnitudes. As always, associations of this time should not be interpreted as causal due to the inability of observational studies to rule out all possible confounding factors.
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