Some people may be wondering whether it’s wise to undergo assisted reproduction after recent media headlines about these technologies increasing the risk of birth defects. In fact, millions of babies have now been born worldwide after use of assisted reproductive technologies, and nothing has gone wrong with the vast majority.
The technologies used to help people conceive are mainly in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI). In IVF, the woman’s eggs are collected, as is sperm from the male partner or donor. Both are left in a culture dish in a laboratory to allow the egg to be fertilized by the sperm.
ICSI involves use of a single sperm to inseminate the egg, not millions of sperm as are used in conventional IVF. This procedure is often used when the male produces small numbers of sperm or when conventional IVF has not worked for unknown reasons.
There have been many studies in Australia and overseas designed to assess the safety of these technologies. It’s generally found that about one in 20 babies conceived naturally will have a birth defect. And, if IVF or ICSI is used to conceive, the risk of defects goes up – but by not very much.
In a recent Victorian study of 3,312 IVF and 3,634 ICSI pregnancies with a single baby rather than twins, we found the risk of birth defects was slightly higher for ICSI (one in 15) than for IVF (one in 16). So for every 100 babies conceived with use of either IVF or ICSI, 93 or 94 will not have a birth defect.
We didn’t find the difference between outcomes for IVF and ICSI that the South Australian study responsible for recent headlines did. Neither have many other people who have done research in this area.
In fact, the SA study’s finding of an increased risk after ICSI (but not IVF) is unexpected and difficult to explain. Their numbers were not as large as ours for IVF and ICSI and they lumped together many minor defects with the more severe ones.
Unlike the SA study, other researchers have concluded that the micro-injection procedure used in ICSI to mix a single sperm with an egg, didn’t add to the risk of the fetus having a birth defect over and above that associated with IVF.
The Victorian study was large enough to allow for examination of specific types of birth defects after IVF and ICSI. We found that there was a particular group of birth defects occurring and they were ones that formed during the first four weeks of pregnancy, before organs start developing. These are called blastogenesis defects and can affect the formation and fusion of the spine, the gastrointestinal tract (gut) and other parts of the body.
The frequency with which these specific defects usually occur is very low, but can be as high as one in 110 babies after assisted reproduction. What seems to reduce this risk and the risk of other birth defects is the timing of the embryo transfer from the laboratory to the woman’s uterus.
Our study showed very clearly that a fresh embryo transfer (usually occurring within days of the egg pick-up for IVF or ICSI) carried a far greater risk of birth defects than an embryo that had been frozen and thawed prior to transfer. Thawed embryo transfer usually occurs in a natural menstrual cycle, months after the egg-pick up – well beyond the time when all the hormones required to retrieve the eggs for IVF or ICSI have disappeared from a woman’s body.
The frequency of blastogenesis defects with a fresh embryo transfer was one in 100 but if a thawed transfer was used, only one in 250 births was affected.
People seeking treatment to improve their chance of having a baby need to be aware of the slightly increased risk of birth defects. Australian data are providing strong evidence for the use of embryos that have been frozen after IVF and then thawed before their transfer to the womb. At the moment, there’s not very convincing evidence to suggest that IVF is safer than ICSI, so expect to hear more.