In Vitro Fertility Goddess.
Tuesday 11 November 2008
Source: American Society for Reproductive Medicine
Using frozen rather than freshly collected embryos produce healthier babies, new research has found.
Three separate studies published this week found that children born from frozen embryos before they are transferred to the womb are less likely to be underweight, premature and recorded lower rates of stillbirth or early death than those conceived during fresh treatment cycles.
Scientists in Australia, the US and Finland have also dismissed the myth that cycles using embryos are more risky.
Their findings are very significant at a time when women are encouraged to use just one fresh embryo at a time. This means they can now rest at ease knowing that their frozen embryos can be safely stored for later use, hence avoiding the urge for multiple implants and risky multiple births.
But the findings pose an important dilemma for parents and fertility clinics because fresh cycles result in more successful pregnancies: 31% for women under 35 compared with only 20.1% for frozen cycles.
While the studies have failed to find conclusive evidence as to why babies born from frozen embryos are healthier, they have advanced several hypotheses.
One possibility is that some frozen embryos generally fail to survive thawing which weeds out those that are of poor quality. Another reason could be that women who generate a large number of good quality embryos are more likely to have frozen cycles and also have a lower risk of complicated pregnancies.
Another explanation could stem from the fact that women using fresh embryos could still be under the influence of hormonal drugs used to stimulate their ovaries into producing extra eggs. Either of these hypotheses may interfere with the endometrial lining of the womb and the formation of the placenta, therefore increasing the risk of experiencing a complicated pregnancy.
But using frozen embryos doesn'only benefit the baby, it also has health benefits for the mother as it means she will avoid ovarian hyperstimulation syndrome or OHSS which is triggered by the powerful drugs used to stimulate the ovaries, a condition which can be fatal in rare cases. Fertility doctors usually abandon an IVF attempt using fresh embryos if a patient begins to develop symptoms because the hormonal disruption of pregnancy can make OHSS worse.
Sarah Williams
