The world’s first IVF baby, Louise Brown, was born in 1978. Since then, more than five million IVF babies have been born worldwide.
IVF is actually a sequence of infertility treatments, involving a number of important steps. These include ovarian stimulation where a woman takes fertility drugs, usually in the form of daily injections, to stimulate her ovaries to produce multiple eggs. The woman is then sedated and the eggs are retrieved using ultrasound guidance. The goal is to collect a safe number of eggs, usually between 8 and 10. Once the eggs are collected, they are mixed with sperm in the lab and left to incubate. Usually, high percentages of the eggs will fertilize and form embryos. Hopefully, many eggs will fertilize properly and then go on to develop into embryos—this laboratory culture process usually takes about five days. Once an embryo has become mature (the “blastocyst” stage), each embryo is tested to see if it appears to be genetically normal. This is done by removing a few cells from each embryo and sending them to a reproductive genetics laboratory for preimplantation genetic screening (PGS). The embryos are then frozen until the results are back and the process of preparing the uterus to receive one of these normal embryos has been completed.
To prepare the uterus, the woman takes other fertility medications to build up the lining of her womb so it is ready to receive and accommodate the resulting embryos.
The embryo is then “transferred” to the woman’s womb. While it is up to individual clinics to decide how many embryos are transferred, it is usually just one to two. The best practice is to limit the number transferred in order to avoid multiple pregnancies (twins and triplets) which are high-risk pregnancies. Any additional genetically normal embryos remain frozen so that they can be used later if that needs to be done.
At Gen 5 Fertility, we almost always transfer only one embryo, because, after genetically testing using PGS and then only transferring normal embryos, pregnancy rates are very high. Thus, we almost always only do single embryo transfers (SET) because it is much safer to carry one rather than two (or more) fetuses. And because there is a minimal increase in pregnancy rate rate by transferring a second embryo.
In very exceptional cases (usually in older women), up to two embryos may be transfer.