In Vitro Fertilization: what is it and when is it recommended?

If you talk to a group of 100 people born in the United States, chances are two of them were born as a result of In vitro fertilization (IVF), according to Zev Williams, director of the Columbia University Fertility Center.

“In many ways, in vitro fertilization is actually one of the great triumphs of medicine modern (…) One thing that is useful to know is how common it is. About 2% of births in the US are the result of In Vitro Fertilization: more than 8 million babies have been born with this technology,” she says.

Another important technology for the in vitro fertilization process is embryo cryopreservation which is the freezing after fertilization of the egg.

The Alabama Supreme Court ruled last Friday that frozen embryos are children and would be protected under the state's Wrongful Death of a Child Act.

Alabama Supreme Court's Unprecedented Ruling on Frozen Embryos Could Affect In Vitro Fertilization Treatments, Critics Warn

As infertility experts warn about the impact of failed assisted reproduction, other experts spoke to CNN to share what people should know about IVF and egg freezing.

What is In Vitro Fertilization?

In Vitro Fertilization occurs when an egg is removed from a woman's body and combined with sperm in a laboratory before being implanted, explains Eve Feinberg, associate professor of obstetrics and gynecology at the Feinberg School of Medicine, Northwestern University.

To achieve this, patients undergo eight- to 10-day fertility injections with hormones that help their eggs mature, says Mamie McLean, an infertility specialist at Alabama Fertility in Birmingham. Egg retrieval procedures are performed on an outpatient or inpatient basis and sometimes under conscious sedation, McLean adds.

After fertilization, doctors observe the development of the embryos.

Feinberg says what we often see is that human reproduction is actually inefficient.

If 10 eggs are exposed to sperm, about seven will be fertilized, he notes. Of those seven, only 25% to 50% will grow in the laboratory long enough to be considered a more mature embryo called a blastocyst, adds Feinberg.

From then on, depending on the patient's age, the blastocyst has between a 10% and 60% chance of becoming a baby, he says.

When is In Vitro Fertilization useful?

In Vitro Fertilization was first developed in the 1970s to help women who had blocked fallopian tubes, the part of the reproductive system where sperm and egg converge, says McLean.

It has since been expanded to help conception in many other contexts, such as for people with recurrent miscarriages, male infertility, those using surrogacy and those for whom other fertility treatments have failed, he adds.

“It’s our most successful treatment,” says McLean.

The technology has also allowed couples with genetic diseases to test their embryos and transfer only those that would not be affected by these diseases, Williams says.

Why freeze embryos?

Freezing embryos is useful for genetic testing, Feinberg says.

Doctors collect cell samples from embryos to test them for diseases or genetic abnormalities, but these tests can take two to four weeks to perform, he notes. Meanwhile, freezing eggs keeps them viable while healthcare professionals investigate genetic factors.

Patients can also choose to freeze embryos when they do not intend to become pregnant immediately, explains Feinberg. There are generally higher success rates when fertilized embryos are frozen, not just the egg, he adds.

They may also have IVF for medical reasons, such as before chemotherapy for cancer, which can damage the ovaries. Or also because they are not at the right stage in life to conceive, but want to have a better chance of getting pregnant in the future, says Feinberg.

If an IVF cycle results in multiple embryos, freezing them can keep those that didn't implant viable for future use, says McLean.

And while in the past it was common to implant multiple embryos, freezing embryos allows doctors to preserve others for future use so that one embryo can be implanted at a time, which is much safer for the patient and the future baby. explains Williams.

Why not just fertilize one egg?

“The science behind IVF really shows that a single fertilized egg is not enough,” says Feinberg.

If his patients say they want two or three children, Feinberg encourages freezing two to four embryos for each, he says.
When a frozen embryo is warmed for implantation, there is a survival rate of about 95%, meaning that 5% will not survive, Feinberg details.

Most patients require at least two or three transfers before becoming pregnant, McLean adds.

Doctors now try to limit the number of times they retrieve eggs and stimulate a patient's ovaries because doing so carries considerable health risks and costs, he notes.

But families can choose to limit the number of eggs fertilized to create embryos and, before undergoing in vitro fertilization, talk to their doctor about their personal moral and ethical considerations, McLean explains.