IVF (In Vitro Fertilization) is an Assisted Reproductive Technology (ART) where eggs and sperm are combined in a laboratory, and the resulting embryo is transferred to the uterus. Millions of children have been born through IVF, leading to ongoing research into their health and development compared to naturally conceived children. Scientists study both short-term outcomes at birth and long-term health status to distinguish between effects caused by the IVF procedure and those caused by the underlying factors that led parents to seek fertility treatment.
Short-Term Outcomes at Birth
IVF-conceived children historically show a higher incidence of adverse short-term outcomes, including prematurity (delivery before 37 weeks) and low birth weight (less than 2,500 grams). These outcomes were largely driven by the high rate of multiple births, such as twins or triplets, common in early ART practices when multiple embryos were transferred.
Multiple gestations inherently carry an elevated risk of complications for both mother and child, which largely drove the initial adverse IVF statistics. Twin pregnancies, for example, are associated with higher rates of preterm birth and low birth weight compared to singletons, regardless of conception method. As clinics adopted single embryo transfer (SET), the rates of multiple births fell, and short-term risks for IVF singletons decreased considerably.
When comparing IVF singletons to naturally conceived singletons, the increased risks of prematurity and low birth weight are less pronounced but still present. These risks are often connected to the parents’ underlying infertility or aspects of the IVF process itself. Even after adjusting for maternal factors, studies show IVF singletons may still have a slightly higher risk of being born preterm or with a lower birth weight.
Understanding Congenital Anomalies
Data shows a slight increase in the relative risk of major congenital anomalies (structural birth defects) for IVF-conceived children. While the general population risk is typically 3% to 5%, IVF has been associated with a 25% to 50% relative increase. It is important to emphasize, however, that the absolute risk remains low.
The vast majority of children born through ART are healthy, even though the proportion of affected babies is slightly higher in the IVF group. Specific organ systems studied include the cardiovascular system (25% to 40% of anomalies) and the genitourinary system (10% to 60%). The gastrointestinal and musculoskeletal systems are also sometimes implicated.
The slight risk elevation is not uniform across all ART methods; some studies suggest Intracytoplasmic Sperm Injection (ICSI) may carry a higher risk for certain defects, such as hypospadias, compared to conventional IVF. Data on congenital anomalies are often limited by methodological challenges requiring very large study populations. Counseling emphasizes the low absolute risk while acknowledging the slight relative increase compared to spontaneous conception.
Long-Term Developmental and Health Status
Long-term research focuses on neurodevelopmental outcomes, including cognitive ability and behavioral health. Large-scale studies generally find reassuring results, with IVF children tracking within the normal range for cognitive function and IQ scores. Initial concerns about conditions like cerebral palsy were often explained by the higher rates of prematurity and low birth weight associated with earlier IVF practices.
The association between IVF and specific neurodevelopmental disorders like Autism Spectrum Disorder (ASD) and Attention Deficit Hyperactivity Disorder (ADHD) is complex and inconsistent. While some studies suggested a modest link, researchers conclude that any slight increase is likely confounded by underlying parental factors, such as the cause of infertility or parental age, rather than the IVF procedure. Most literature shows no significant difference in long-term neurodevelopmental outcomes.
Studies examining cardiometabolic health in IVF-conceived adolescents and young adults have yielded mixed findings. Some research reports slightly higher blood pressure levels in ART offspring, while other studies find no differences. Specific techniques like ICSI have been linked to a greater tendency toward adiposity and insulin resistance. Overall, long-term metabolic risks are still being actively investigated but do not currently point to a widespread major health concern.
Disentangling Procedure Risks from Infertility Factors
A major challenge is determining whether adverse outcomes stem from the IVF procedure or from the characteristics of the parents requiring ART. Underlying causes of infertility—such as advanced parental age, pre-existing conditions, or male factor issues—are powerful confounding variables. The need for IVF suggests pre-existing subfertility, which may carry a genetic or biological risk independent of laboratory techniques.
Researchers are working to isolate the effect of specific laboratory manipulations, such as ICSI, which bypasses the natural selection process of sperm. ICSI, often used for male factor infertility, has been weakly associated with higher risks of certain neurodevelopmental disorders, potentially due to genetic factors related to the male infertility itself. Cryopreservation (freezing) of embryos or eggs is also under scrutiny, though current data suggests oocyte cryopreservation does not add significant risk to birth defects.
The consensus suggests that the causes of parental infertility, such as endometriosis or male factor issues, are often stronger predictors of adverse outcomes than the IVF process itself. For instance, women with infertility due to endometriosis or anovulation have increased risks of preterm birth, independent of the IVF technique used. This highlights that observed differences are often attributable to the patient population rather than the technology.