How in vitro fertilization IVF works Nassim Assefi and Brian A Levine
In 1978, Louise Brown became the world's first baby to be bornby in vitro fertilization, or IVF. Her birth revolutionized the field of reproductive medicine. Given that approximately one in eightheterosexual couples has difficulty conceiving, and that homosexual couplesand single parents often need al help to make a baby, the demand for IVF has been growing.
IVF is so common, that more than 5 millionbabies have been born through this technology. IVF works by mimicking the brilliantdesign of sexual reproduction. In order to understand IVF, we first need to take a look at the natural process of baby making. Believe it or not, it all starts in the brain. Roughly fifteen days before fertilization can happen, the anterior pituitary gland secretesfollicle stimulating hormone, FSH, which ripens a handful of follicles of the ovary
that then release estrogen. Each follicle contains one egg, and on average, only one follicle becomes fully mature. As it grows and continues to release estrogen, this hormone not only helps coordinategrowth and preparation of the uterus, it also communicates to the brainhow well the follicle is developing. When the estrogen level is high enough, the anterior pituitary releases a surgeof luteinizing hormone, LH,
which triggers ovulation and causes the follicle to ruptureand release the egg. Once the egg leaves the ovary, it is directed into the Fallopian tubeby the fingerlike fimbriae. If the egg is not fertilized by sperm within 24 hours, the unfertilized egg will die, and the entire system will reset itself, preparing to create a new eggand uterine lining the following month.
The egg is the largest cell in the body and is protected by a thick, extracellular shell of sugar and protein called the zona pellucida. The zona thwarts the entry and fusionof more than one sperm, the smallest cell in the body. It takes a man two to three monthsto make sperm, and the process constantly renews. Each ejaculation during sexual intercoursereleases more than 100 million sperm.
But only 100 or so will ultimatelymake it to the proximity of the egg, and only one will successfully penetratethrough the armor of the zona pellucida. Upon successful fertilization, the zygote immediately begins developing into an embryo, and takes about three daysto reach the uterus. There, it requires another three or so days to implant firmly into the endometrium,the inner lining of the uterus. Once implanted, the cells that are to become the placenta