Babies conceived through fertility treatment techniques are one-third more likely to have a birth defect than babies conceived without any help from technology
In vitro fertilisation (IVF) has been available to would-be mothers for more than three decades. The process involves fertilising the mother's egg outside of the body and then transferred to the womb. Numerous studies have looked at the potential hazards of these techniques.
Zhibin Hu and colleagues at Nanjing Medical University in China collected the results of 46 studies that compared the number of birth defects among children conceived using IVF technique to children conceived normally.
For more than 124,000 children born through IVF or using ICSI – in which a single sperm is injected directly into the egg – the risk of having a birth defect was 37 percent higher than that of the other children, they found.
"Children conceived by IVF and/or ICSI are at significantly increased risk of birth defects, and there is no risk difference between children conceived by IVF and/or ICSI," the team wrote.
The increase in birth defect risk was apparent across a range of functions and body systems, including the genitals, skeleton, digestive system and the nervous system, the authors reported.
The question of why birth defects appear across many studies to be more common among IVF-conceived babies, however, remains to be answered.
One possibility is that the reasons people have trouble conceiving in the first place could influence their increased risk of having a baby with a birth defect.
It is also possible that the IVF techniques themselves, the jostling and handling of the embryos, or the drugs that go along with fertility treatment, could be a factor.
A third theory is that birth defects only appear to be more common in babies conceived through fertility treatments because they're monitored more closely than other babies.