How Does In-Vitro Fertilization Work?

In-vitro fertilization, usually referred to as IVF, is a technique that was pioneered in England in the late 1970s. This assisted fertilization technique, which produced the world's first “test tube baby,” has become a staple of infertility treatments whose long term effectiveness is well established. In fact, the original test tube baby turned thirty last year and now has kids of her own!


The term in-vitro was originally quite literal, meaning “in glass” – referring to the test tube in which egg and sperm were artificially joined. Now the term refers to any procedure that is preformed outside the body – glass may or may not be involved. Today, in most cases, actual fertilization takes place in a Petri dish, not a test tube.


Initially, the IVF procedure was indicated in cases of fallopian abnormalities. As a brief biology lesson, remember that the fallopian tubes are the tubes linking the ovaries and the uterus. Sperm travel up the fallopian tubes to reach an egg for fertilization, and the fertilized egg must travel down the fallopian tube to reach the uterus where it will hopefully implant and develop into a baby. A woman who had abnormalities in her fallopian tubes could benefit from an embryo that was fertilized outside the body and implanted into the uterus.


It was quickly discovered, however, that IVF worked just as well as for couples who faced sperm motility issues. In traditional IVF procedures, the sperm are introduced to the egg in a laboratory setting and then implanted into the mother. Of course, there are several steps that have to occur before and after this process.


Initially, the egg donor, who may or may not be the woman who is to carry the baby, is given a series of medications to stimulate egg production. This is done over a ten day period under close monitoring. When both the blood tests and ultrasound show a good number of eggs, they are harvested trans-vaginally with an ultrasound-guided needle, usually under some form of sedation. The process generally produces between ten and thirty eggs.


Next, the sperm are harvested from the sperm donor in a much less surgically involved manner. The man ejaculates into a plastic cup used to catch the semen. The sample must then be kept at body temperature and delivered as quickly as possible to the laboratory. The “fun” may have then ended for the donors, but it has only begun in the laboratory.


Introducing the sperm to the egg isn’t as simple as mixing the two together and stirring. The sperm sample and the eggs have to be prepared by stripping all extraneous cells and cellular debris away from the eggs and the sperm. Only two cells, one egg and one sperm, are placed together in the Petri dish. In cases of poor sperm motility, a sperm will be selected and injected directly into the egg.


Next, an incubation period of about eighteen hours will take place. The newly fertilized eggs are examined under a microscope and cells with two nuclei are selected and transferred to another vessel where they are incubated for another six to eight hours on a special growth media.


At this point, the embryos have reached the six-to-eight cell stage and are judged for quality and selected for implantation. But before that happens, they are transferred to another growth media and are allowed to grow until they become a ball of cells, termed a blastocyst. Waiting until this stage before implanting the blastocysts results in more successful pregnancies.


The embryos are again graded by the doctor. This time, they are judged on the number of cells, the kind of growth and degree of fragmentation. It’s interesting to note that the number of blastocysts to be transferred depends on the number available, the age of the woman and other diagnostic factors. In addition, the total number implanted is regulated by the medical authorities of the countries where the IVF is being performed in order to prevent higher order multiple pregnancies.


Although this treatment has worked for many infertile couples, it’s important to note that IVF isn’t a panacea. For example, if the infertility is rooted in implantation issues, IVF isn’t an option, nor is it an option in cases of abnormality in sperm production. Still, it remains a powerful tool in the arsenal of fertility treatments and it’s worth looking into if you’re having problems with infertility.