It's well-known in the fertility community that babies conceived through assisted reproductive technology (ART) are at a slightly increased risk for birth defects. Proving that this increase is technology-driven, however, is complicated.
Thanks to improvements in ultrasound technology and genetic testing, any increased risk to fetal health can be detected early — sometimes within days of fertilization — and closely monitored by clinicians.
How ART Affects Fetal and Maternal Health
Fetal health may be affected by several specific components of ART: the effect of gonadotropins and other fertility drugs used during follicular stimulation, the exposure of reproductive cells and fertilized eggs to clinical procedures involved in assisted reproduction or the transfer of multiple embryos. An undetected anomaly in a parent or donor, such as a sperm defect, can also compromise fetal health.
For the patient trying to become pregnant, injectable fertility drugs may have the immediate side effect of ovarian hyperstimulation syndrome (OHSS). Ultrasound-guided egg retrieval carries risks of infection as well as bowel or blood vessel injury. Finally, embryologists are not always sure which embryo will implant and develop into a fetus.
Multiple Births and IVF
Transferring more than one embryo at a time during ART has long been a common recommendation — and one that patients often encourage — but it may have health consequences.
Having a multiple pregnancy is likelier with in vitro fertilization (IVF), especially when more than one embryo is transferred. High-order pregnancies may affect maternal health by increasing the risk of gestational diabetes, high blood pressure and premature birth. They may cause fetal health complications such as lung development issues, intestinal infections, cerebral palsy or language delay. Simply put, the more embryos that are transferred into the uterus, the greater the risks.
Views on transferring multiple embryos are changing, however. Data collected by the Centers for Disease Control and Prevention (CDC) shows there has been a significant reduction of twin and high-order pregnancies from IVF during the last decade. The American Society for Reproductive Medicine now recommends transferring the minimum number of embryos necessary to provide a high likelihood of pregnancy with the lowest risk of multiple pregnancy. This recommendation requires a delicate balance, but the best way to avoid multiple pregnancy is to transfer only one embryo at a time.
Sperm Abnormalities and ICSI
Intracytoplasmic Sperm Injection (ICSI), a variation on the IVF procedure originally developed for treating male factor infertility, is connected to an increased risk of sex chromosome (X or Y) abnormalities. However, the extent to which this connection is due to the ICSI procedure itself must still be determined.
In general, men with sperm defects are more likely to have chromosomal abnormalities that can be transmitted to their children, but, even so, such disorders are rare.
Maternal Age and Pregnancy Outcomes
The miscarriage rate after natural conception rises as maternal age increases; the same is true after assisted reproduction. According to Reproductive Biology and Endocrinology, the risk of miscarriage after ART is drastically higher for women ages 36 to 40 and older than 40. Much of the increase in risk is due to the age-related increase of chromosomal anomalies in the eggs.
Ectopic Pregnancy with ART
ART carries an elevated risk of an ectopic pregnancy, according to Fertility and Sterility, but this result may be confounded by a woman's history of tubal factor infertility or maternal age. Patients who undergo IVF also have a higher risk for a heterotopic pregnancy, a simultaneous ectopic pregnancy where one embryo implants in the uterus while another implants in a fallopian tube.
The incidence of birth defects in the general population is 2 to 3 percent, and this slightly increases among infertile patients. However, IVF specialists consider postponed conception a likelier cause of risks to fetal health.
