Pregnancy outcomes don't differ among women who use a vaginal hormone gel during in vitro fertilisation or a hormone shot, according to a new study.
The results may encourage more doctors and women to use the hormone gel, which tends to be much less painful than the shot that's injected into the muscle, according to the study's lead author.
"Progesterone in oil is much less expensive but it is notoriously painful and usually requires that a second person do the injection, while vaginal gel is more expensive but tolerated much better in most patients who can self-administer the drug," Dr Daniel B. Shapiro of Reproductive Biology Associates in Atlanta, Georgia, told Reuters Health by email.
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Progesterone is typically produced by the ovaries to prepare the lining of the uterus to accept an embryo. During IVF, women take pills to stop progesterone production so they do not ovulate. They need to somehow replace the hormone.
"The gold standard of care has been intramuscular progesterone," said Dr. Frederick Licciardi, a fertility specialist in the Department of Obstetrics and Gynaecology at NYU Langone's Fertility Centre in New York City.
"In the past, people have been a little bit leery about going away from the gold standard with good reason, because you're dealing with a pregnancy," said Licciardi, who was not involved in the new study.
Outcomes not significantly different
Shapiro and his colleagues designed their study to answer a simple question: Does the way progesterone is delivered affect pregnancy outcomes of IVF using frozen embryos?
The analysis included 920 frozen embryo IVF cycles. Of those, 682 used progesterone shots and 238 used vaginal progesterone gel.
About 40% involved transfer of just a single embryo.
Outcomes were not significantly different between the IVF cycles that used the progesterone shots or the vaginal progesterone gel, the researchers write in the journal Human Reproduction.
Implantation rates were about 46% regardless of the type of progesterone used. Clinical pregnancy rates were about 62% with the shot and about 61% with the gel. Live birth rates were about 50% with the shot and 49% with the gel.
"Since there is no clinical difference in outcome, the decision about which to use boils down to cost, convenience and comfort," Shapiro said.
We want you to have a baby
He and his colleagues caution that the results of their study are limited by the fact that they looked back at data on IVF and the women were not randomly assigned to use either the shot or gel.
Actavis, which makes progesterone products, provided funds for the study. Several of the authors have financial relationships with the company and one author is an employee. Dr. Berger is on the advisory boards of Actavis and Merck.
"This is not going to be the definitive study, but it's still going to be very good," Licciardi said.
He added that while the study found the two methods are statistically equal, some doctors may see the few percentage point differences and still encourage using the shots.
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"It comes down to the patient," Licciardi said. "We want you to have a baby. That's what you want, that's what we want. Are we going to do something that's going to decrease that – even by a few percentage points?"
In other countries and some US medical centres, fertility doctors have moved away from using the shot, said Dr Brian M. Berger, medical director of the donor egg and gestational carrier programme for Boston IVF.
"The rest of the world thinks we are basically barbaric for using intramuscular progesterone because they have largely abandoned it," said Berger, who wasn't involved in the new study. "The United States is probably the last holdout country for using intramuscular progesterone."
"We all use it, but we don't use it for everybody," Licciardi said. "Some of us have a bias to use the shots. Let's stick with the gold standard . . . If you don't do well with the shot, then we'll try the gel."
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