Embryo transfer is an important aspect of in vitro fertilization, referring to the actual placing of a fertilized egg inside the female’s womb, or uterus. While embryo transfer is not always associated with in vitro fertilization, they are often used together with the purpose of helping women become pregnant. This method is also often used with animals as well, in ranches, farms and so on. However, there are certain factors that influence the types of embryo transfer that occur, and we’ll have a look at them in what follows.
First of all, an embryo transfer can be done with the help of fresh egg cells, meaning the eggs have been harvested some days previous and left for fertilization between two to six days, or it can happen with the help of frozen eggs, which are egg cells that have been harvested some time ago – perhaps months, or years previously – and which were placed in embryo cryopreservation. With the first method, the embryo transfer practically occurs during the same menstrual cycle, whereas the second method entails taking eggs out of preservation and thawing them for immediate use. The great news is that there have been recorded no abnormalities in children born with the help of preserved eggs, and they grew as normally and healthily as those born with the help of fresh embryos or through normal reproduction.
On the contrary, children born with the help of embryo transfer with vitrified blastocysts often had higher birthweight rates than those born from blastocysts which had not been frozen. Vitrification is a method of egg cryopreservation which uses some cryoprotectants to decrease the egg’s freezing temperature and to protect it from other damage. With normal pregnancies, the uterus prepares itself to nurture the egg, but with embryo transfer some additional treatments or procedures may be needed. For example the woman may be given some estrogen preparations in the first two weeks of fertility treatments and then she will take a combination of progesterone and oestrogen so that the lining of the uterus can be ready to receive the embryo.
In most in vitro fertilization procedures, the embryo transfer occurs three days after the fertilization of the egg with sperm has occurred, when the egg is at an eight-cell stage. In other instances, the doctors opt for blastocyst transfer, which entails letting the embryo develop for five or six days before being inserted in the uterus. When a woman has more difficulty in getting pregnant, her doctors may apply both these procedures at a few days’ distance to increase chances of success.