How Does In Vitro Fertilization Work?

Infertility, defined as the inability of becoming pregnant after 1 year of unprotected sex, is an issue faced by a lot of women. The most widespread method of solving this particular issue is in vitro fertilization, more commonly known as IVF. But how does in vitro fertilization work?

How Does In Vitro Fertilization Work

The first successful IVF took place in 1978 in England, materializing by the birth of Louise Brown. This success has represented the starting point of a new revolutionary treatment in the couple`s sterility and has led to the development of a new technology, assisted reproduction.

IVF has made possible thousands of healthy babies from couples that were previously considered infertile. Long term studies indicate the fact that there`s no increased risk of congenital malformations or abnormalities in babies born through this procedure.

What Is the Procedure for In Vitro Fertilization?

In vitro fertilization consists of a series of complex procedures used to treat fertility or genetic problems and help in conceiving a child. This involves harvesting mature eggs from ovaries and fertilizing them in a laboratory.

Unlike the simplest procedure of artificial insemination where sperm is introduced inside the uterus and the conception occurs naturally, IVF involves combining the eggs and sperm outside the body. Once the embryo/embryos form, they are inserted inside the uterus. Statistically speaking, only 5% of infertile couples resort to this procedure, resulting in the birth of over 200.000 children only in the U.S., so it`s the most efficient form of assisted reproductive technique.

IVF can be used by a couple to conceive a biological child or using donated eggs, embryos or sperm. The donors can be known or anonymous. The embryo can also be implanted in the uterus of a surrogate mother. The chances of having a healthy child using IVF depend on many factors, such as age or infertility causes. In addition, in vitro fertilization might be time consuming, invasive and expensive. In case that more than 1 embryo is implanted in the uterus, IVF can lead to a multiple pregnancy.

Infertility Causes that May Lead to IVF

When it comes to infertility, this procedure may be an option for:

  • Severe endometriosis.
  • Low sperm count (oligospermia).
  • Low ovarian reserve.
  • Uterine & fallopian tube issues (unexplained uterine tubes, premature ovarian failure, uterine fibroids).
  • Ovulation issues.
  • Issues with antibodies that damage the eggs or sperm.
  • The inability of sperm to penetrate or survive in the cervical mucus
  • Vasectomy/tubectomy
  • Advanced maternal age (over 38 years).
  • Inexplicable fertility issues.
  • 2 – 4 cycles of ovarian stimulation with failed intrauterine insemination.
  • Genetic hereditary disease.
  • Fertility preservation after cancer
  • Other medical conditions

It should be mentioned that IVF is never the first step in treating infertility. Instead, it`s intended for situations where other methods, like artificial insemination, fertility medications or surgery don`t work.

How Does In Vitro Fertilization Work?

IVF comprises several steps. Before applying this method, the couple needs to perform several clinical investigations and blood tests to determine the fact health state and type of infertility. A spermogram will also be performed as well.

After the investigations, the assisted reproductive treatment is started by the ovarian stimulation of the woman. Egg harvesting is done under transvaginal ultrasound guidance.

Next is the fertilization of the eggs with the partner`s sperm and after a period of embryo development, they are inserted in the uterine cavity.

Your doctor may help you better understand how in vitro fertilization really works, the potential risks and if this infertility treatment method is suited for you or not.

Ovarian Stimulation

For ovarian stimulation, it`s necessary for every woman to follow a treatment. The combination of drugs, dosages, and type of treatment are individualized and adjusted depending on the lab and clinical results of each couple in order to produce as many eggs as possible.

Egg Harvesting

Egg harvesting is scheduled in a certain moment in the maturation of ovarian follicles. This is performed by transvaginal puncture of the follicles. After each punctured follicle, an egg from the follicular fluid is searched in the lab. Aspiration of the follicle content is performed under ultrasound control under short-term general anesthesia.


A few hours after the harvesting of eggs and special processing of sperm that removes prostate fluid and concentrates the best possible sperm in terms of mobility and morphology, it`s cultured together with the eggs in a special culture environment.

The following day, fertilization is controlled by spotting 2 pronuclei (2 small spheres) inside the egg.

Embryo Transfer

The procedure of embryo transfer is made 2 or 3 days after harvesting the eggs. It`s quite simple and painless, it lasts only a few minutes and can be watched on the monitor by both parents.

The selected embryos will be displayed on the monitor of the couple and then with a soft catheter, 2 – 4 embryos are inserted in the uterine cavity.

The number of transferred embryos depends on several factors:

  • The total number of fertilized eggs.
  • The quality of the eggs.
  • The woman`s age.
  • The couple`s option for a possible multiple pregnancy.

The main goal of some medical clinics is to transfer as few embryos as possible without, however, reducing the chances of success of the procedure.

Success Rate for IVF

Success rates for IVF depend on a series of factors, including infertility, maternal procedure and the place where the procedure takes place. According to Society of Assisted Reproductive Technologies, the approximate chance of giving birth to a baby after this procedure is as it follows:

  • 41% – 43% for women under the age of 35.
  • 33% – 36% for women aged 35 to 37.
  • 23% – 27% for women aged 38 to 40.
  • 13% – 18% for women aged 41+.

A report from the U.S. from 2009 shows that a pregnancy obtained averagely in 29.4% from in all cycles, the percentage of cycles that resulted in live births averaging to 22.4%.

After the Procedure

After the embryo transfer takes place, the woman is advised to rest throughout the remaining of the day (if the ovarian hyperstimulation syndrome exists, complete bed rest is required), and all the usual activities can be resumed the following day. – Visit this webpage!

It`s also necessary an oral or intravenous treatment with progesterone (8 to 10 weeks after the embryo transfer) that aids in thickening the uterine lining (the embryo implants faster). If progesterone has a level that is too low, the pregnancy may be lost. Then, in 12 to 14 days after the last stage of IVF, a pregnancy test will be performed at the medical clinic. It`s recommended to talk to your doctor if:

  • Your body temperature is higher than 38° C.
  • Any massive bleeding occurs.
  • You experience blood in your urine.


  • It`s the oldest assisted reproductive technology method and there are no medical problems associate with it.
  • Doesn`t cause cancer as a result of ovulation induction treatment.
  • The way is performed is constantly improving (the cryopreservation led to identical pregnancy rates with those associated with fresh embryos).


  • It`s expensive and requires energy and time (visits to the medical clinic, tests, etc.) A lot of couples might experience depression or stress.
  • Because more than 1 embryo is introduced in the uterus, there`s a 20% chance of giving birth to twins or more babies. Multiple pregnancies are associated with risks of miscarriage, premature birth and other complications. – More info!
  • Risk of ectopic pregnancy – the embryo implants in one of the uterine tubes or abdominal cavity. This may cause severe issues to the mother.
  • Oocyte harvesting also has risks such as infection, reactions to the anesthetic, bleeding or damage to the structures adjacent to the ovaries (the intestines or bladder).
  • Possible complications for the baby, like premature birth, low birth weight or increased risks of birth defects.
  • The risk of ovarian hyperstimulation syndrome as a result of the way the body responds to the fertility drugs (10% – 20% may experience a rapid weight gain – 4,5 kg in 3 to 5 days, bloating, reduced urination and in some cases shortness of breath, dizziness, vomiting, pelvic pain or nausea.
  • It may not work – 20% of IVF cycles are canceled before harvest because there aren`t enough follicles developed or due to the risk of ovarian hyperstimulation syndrome.
Image courtesy of PregnancyTips.org

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