Supporters of minimal in vitro fertilization say it’s a gentler, less expensive option. Critics say it produces fewer embryos and requires more treatment cycles.

Do lower doses of fertility drugs lead to better patient outcomes following in vitro fertilization?

Experts aren’t so sure.

While the popularity of “minimal stimulation in vitro fertilization” (minimal IVF) has grown, it produces fewer embryos and lower rates of live births than conventional in vitro fertilization (IVF) protocols.

IVF is a form of assisted reproductive technology that’s used to treat infertility as well as assist gestational surrogacy.

In IVF, eggs are extracted from a woman’s ovaries and manually combined with sperm outside of their body.

The resulting embryos can be transferred to the woman’s uterus. They can also be frozen for later use or donated.

In conventional IVF protocols, women receive multiple injections of two hormones, known as gonadotropins, to help stimulate their production of mature eggs.

In minimal IVF protocols, women receive lower doses of injectable gonadotropins, which tends to result in fewer retrieved eggs and fewer fertilized embryos.

Proponents of minimal IVF say it provides a gentler, lower cost alternative to conventional IVF.

Some also suggest it may help reduce the incidence of ovarian hyper stimulation syndrome (OHSS), a potential complication of gonadotropin therapy.

But other researchers and clinicians have challenged those claims.

For example, authors of a recent review article published in the journal Reproductive Biology and Endocrinology concluded that:

“Regarding occurrence of severe OHSS, oocyte/embryo quality, pregnancy/live birth rates and cost, [conventional IVF] is at least comparable or sometimes superior over [minimal stimulation IVF].”

Further research is needed to compare conventional IVF and minimal IVF in different subgroups of patients, they said.

Dr. Vitaly Kushnir is the director of continuing medical education at the Center for Human Reproduction in New York.

According to Kushnir, descriptions of “gentle” and “patient friendly” are “marketing gimmicks” with no scientific basis.

Patients typically receive fewer injections of fertility drugs in each cycle of minimal IVF, compared with conventional IVF protocols.

But since minimal IVF produces lower rates of pregnancy, many women need to undergo more treatment cycles to become pregnant.

“You could argue that mini IVF is less gentle,” Kushnir told Healthline. “You’ve saved the patient medication injections, but you’ve put her through more egg retrievals, and you’ve prolonged the process of getting pregnant.”

In a recent analysis of national IVF data, Kushnir found that minimal IVF was popular among older women.

However, these women were less likely to have success with the procedure.

He found the use of minimal IVF increased with age, while live births following minimal IVF decreased with age.

Although advancing age was also associated with declining rates of live births following conventional IVF, the decline was more pronounced with minimal IVF.

According to the Society for Reproductive Technology, in people under the age of 35, the live birth rate in 2015 was 41 percent following a fresh cycle of conventional IVF, and 23 percent following a fresh cycle of minimal IVF.

In women ages 35 to 37, the live birth rate fell to 31 percent following conventional IVF, and 14 percent following minimal IVF.

In women over the age of 42, only 1.4 percent successfully gave birth after a fresh cycle of minimal IVF.

According to Kushnir, the majority of minimal IVF cycles in the United States are performed by a small number of clinics.

“Two or three clinics account for more than half of all the mini IVF cycles in the U.S. That’s basically their business model, is they offer mini IVF as the primary type of treatment,” he said.

Some other clinics also use minimal IVF but only in select patients.

“We use it, for example, for patients who have no insurance coverage who can’t afford regular IVF,” Kushnir explained. “A regular IVF cycle would give them superior results, but they can’t get there, so we offer mini IVF as a service to them.”

For the majority of women, Kushnir said conventional IVF is the better option.

Demonstrating the drawbacks of minimal IVF, Kushnir pointed to the situation in Japan, where minimal IVF is more common.

In a recent review, Kushnir and colleagues found the overall fresh cycle of the live birth rate in the United States from 2012-2013 was 29 percent, while in Japan it was only 5 percent.

“In the U.S., we do fewer IVF cycles each year than they do in Japan, even though we have a much higher population. And the main reason for that is that the patients have to go through so many cycles because of the strategy that they’re using,” he said.

“It serves as a good model as to what happens when not just a clinic, but a whole country, shifts strategy,” he added.

According to Kushnir, more research is needed to identify subgroups of women who are good candidates for minimal IVF.

Investigators also need to determine the best protocol for minimal stimulation, which is not well-defined.