Four rounds of in vitro fertilization couldn't help Sara Conyers conceive, according to the U.K.'s  Daily Mail.

But the fifth time was the charm for Conyers, 33, who now has twins. Conyers says the only way she could get pregnant was with the help of an experimental fertility method called intralipid infusion, Conyers, who lives in the U.K., told The Daily Mail.

The procedure, more commonly used in the U.K. than in the U.S.,  is used to supplement   another fertility treatment ,such as in vitro fertilization.  The woman is intravenously given a fat solution consisting partly of soybean oil and egg yolk.

Some experts who tout its success say  it can prevent miscarriage by limiting activity of overactive so-called natural killer immune cells found in the body that would otherwise destroy the embryo.

But many fertility experts in the U.S. are not so sure about its effectiveness, since there are no definitive studies to suggest that the method works or is even safe.

"Before I can endorse this theoretical therapy for my patients, I need at least some evidence," said Dr. Michael Murray, director of reproductive endocrinology and infertility at Northern California Fertility Medical Center.

This procedure is one of many that some of Murray's patients ask him about,  who are "grasping at straws for a solution to their recurrent miscarriages," he says.

And some experts agreed, comparing the fertility-boosting procedure to others that are seemingly inexpensive with unknown risks for side effects, such as herbal supplements.

Previous studies done on animals or in lab dishes have found conflicting results about whether intralipid infusion works. Studies are also conflicted about the role that natural killer cells play in fertility.

"Most of the time when IVF fails, it is due to the quality of the embryos that were transferred and not the immune environment in the uterus," said Dr. Tamer Yalcinkaya, section head of reproductive endocrinology and infertility at Wake Forest Baptist Medical Center.

If the scientific evidence supported the claims, intralipid infusion may benefit women with good quality embryos who have undergone previous IVF cycles but haven't yet been able to conceive, said Yalcinkaya.

As for Conyers' multiple unsuccessful IVF tries followed by one supplemented by intralipid infusion that worked, some experts say it's hard to tell what part of that equation turned out to be the tipping point for Conyers.

"Success of a repeat IVF cycle may be a chance event and does not necessarily indicate that the need of an intervention was the cause of that improvement," said Yalcinkaya.