What is In Vitro Fertilization?
In Vitro Fertilization literally means fertilization “in glass.” This is a reference to the fact that the first baby born by this process was by an embryo created by fertilization of an egg, surgically removed from the mother and placed in a glass dish (in vitro) with sperm in an incubator. The resulting embryo was transferred into the uterus of her mother through her cervix because both of her fallopian tubes had been damaged by earlier ectopic pregnancies. The first IVF baby, Louise Brown, was born in 1978. In the 40 years since, it is estimated as many as 8 million babies have been born through in vitro fertilization worldwide.
In Vitro Fertilization (IVF) Process
The most common type of assisted reproductive technology (ART) is in vitro Fertilization (IVF). The in vitro fertilization process is multifaceted, but there are a few core stages:
At birth, the ovaries are estimated to carry approximately 2 million eggs. Each month as many a few dozen are awakened, and then one is selected from the group to mature and ovulate. Initially, the eggs are surrounded by a single layer of nurturing cells in a structure called a “primordial follicle,” which is only the diameter of a grain of sand. The follicle is stimulated to mature by a hormone called Follicle Stimulating Hormone (FSH). FSH is made in the area of the brain called the Pituitary, it is in a class of hormones known as “gonadotropins.” FSH drives the nurturing cells surrounding the egg, or oocyte, to multiply and make fluid. Follicular fluid is hormonally complex and causes the egg to mature. The follicle grows to be almost an inch in diameter by the time the egg is ready to fertilize. One of the many hormones in the follicular fluid is a unique estrogen called estradiol (E2). A single follicle will produce levels of E2 of >200 pg/ml when the egg inside is mature and ready to ovulate.
In vitro fertilization involves stimulating the ovaries to make multiple follicles by taking shots of FSH for a period of approximately 10 days. Taking additional FSH in this manner defeats the selection process that normally results in the production of only one mature egg. If a dozen follicles are awakened, the goal is to keep all of them maturing until they are ready to ovulate. The ovaries, with so many mature follicles, each an inch in diameter, are much larger than usual and grow to fill the pelvis.
Egg Retrieval / Aspiration
In order to be able to receive a “new” set of chromosomes from a sperm, the egg has to lose half of its original chromosomes. It releases them in a structure called a “polar body,” which is visible with a special microscope. The process is initiated by Lutenizing Hormone (LH), another gonadotropin. In a natural cycle, the LH surge occurs when E2 levels have remained elevated above 200 pg/ml for greater than 48 hours. In IVF, because multiple follicles are contributing to the overall E2 level, the total rises well above the level that would normally cause ovulation. This would occur well before any of the eggs would be ready to fertilize. Over the past forty years many “stimulation protocols” have been developed for IVF, all of which have to prevent ovulation until all the eggs are ready. The most common protocol today, is called an “Antagonist” in which a third injection of an LH-blocking medication (LH antagonist) is begun about mid-way through the stimulation phase.
At some point, all the follicles reach a mature diameter. Each will be making at least 200 pg/ml of estradiol. It is time to begin the final maturation of the oocyte, getting the egg ready for fertilization.
The embryo transfer itself is not a complicated procedure and is performed in our office. The embryos are placed in a catheter which is inserted through the cervix into the uterine cavity, by visualization from an abdominal ultrasound. The number of embryos transferred depends, but is not limited to, a woman’s age, cause of infertility, pregnancy history, and other factors. If there are additional embryos that are of exceptional quality, they may meet the guidelines for freezing (cryopreservation) for later use. Approximately two weeks after the day of egg retrieval, a pregnancy test is performed.
When is In Vitro Fertilization used?
There is no one benchmark for in vitro fertilization or any fertility treatment, as each person's situation is unique. If you are younger than 35 years of age, you should try to conceive by means of sexual intercourse for six months before considering intervention. If conception does not occur after six months, a fertility consultation is recommended. If you have a family history or are known to be at risk for a medical condition that could impair conception, we would recommend starting with a consultation to evaluate if you are at risk. Contact us today for more information, or to schedule a consultation with our infertility doctors.