To understand in vitro fertilization, it is necessary to understand the natural conception process. In the middle of a normal menstrual cycle, an egg is released from the ovary into the fallopian tube. Fertilization occurs in the fallopian tube, where the fertilized egg remains for several days while dividing and becoming an early embryo. A few days later, the embryo enters the uterus and implants in the uterine wall.
In vitro fertilization can be thought of as a fallopian tube bypass. The ovaries are stimulated with injectable fertility drugs to make multiple eggs. Transvaginal ultrasounds and blood tests done during this time help determine when the eggs are mature. At this point, they are retrieved through the vagina with a minor procedure that requires only a mild anesthetic. The eggs are put in a petri dish and exposed to the husband’s sperm.
The next day, the eggs are examined to see if fertilization has been successful. If so, they are left in the petri dish to divide and become early embryos. After several days, one or more embryos are placed in the woman’s uterus in a simple procedure that is generally no more uncomfortable than a Pap test. Extra embryos are assessed by the IVF laboratory personnel. If they are viable they may be frozen for future use by the couple.