02:27 - Source: CNN
Myths of pregnancy
CNN —  

Vaginal bleeding during pregnancy can be a sign of an impending miscarriage. Doctors sometimes prescribe progesterone, a hormone essential to a healthy pregnancy, to prevent miscarriage.

New research says that vaginal suppositories of progesterone given to pregnant women experiencing bleeding in the first trimester did not result in a significantly higher incidence of live births than a placebo.

However, one small group of women benefits from this treatment, according to Dr. Arri Coomarasamy, lead author of the study and director of Tommy’s National Centre for Miscarriage Research at the University of Birmingham in the UK.

“Our study shows that high-risk women, by that we mean women who are bleeding in early pregnancy and have a previous history of miscarriage, can benefit from vaginal progesterone treatment,” Coomarasamy wrote in an email. “Our study found a 5% higher livebirth rate in this group of women if they used progesterone compared with placebo.”

One in 5 pregnancies ends in miscarriage, according to the study, published Wednesday in the New England Journal of Medicine.

A common occurrence during pregnancy

Use of vaginal progesterone to prevent miscarriage can be traced to the mid-1950s, Coomarasamy noted. The practice isn’t common in the United Kingdom, Coomarasamy said, but much more common globally.

“Bleeding in pregnancy is very common, affecting 1 in 5 women,” Coomarasamy said. “A third of women who bleed in early pregnancy will sadly miscarry.”

His new research examined the use of progesterone in greater detail than in past studies, which had too few patients or poor methodology and so could not be considered conclusive, he said.

More than 4,000 women, recruited from 48 UK hospitals, were randomly assigned to receive vaginal suppositories containing either 400 milligrams of progesterone or placebo twice daily from the time they began bleeding through 16 weeks of gestation. Three-quarters of the progesterone group had a live, full-term birth (1,513 women), while 72% in the placebo group did so (1,459).

The results indicate no real benefit in using progesterone for most women experiencing early pregnancy bleeding, but the treatment was helpful for a small subgroup of women who had miscarried before.

“Reassuringly, there was no evidence of harm from the use of progesterone in our study,” Coomarasamy said.

Raising even more questions

Dr. Scott Sullivan, a professor and director of maternal-fetal medicine at the Medical University of South Carolina, said the new study is both “excellently designed” and “excellently executed.”

“Both conclusions are important,” said Sullivan, who was not involved in the research. “For a low-risk person or a first-time mom, this treatment doesn’t seem to work, but for the 1% of people who have a strong history of miscarriages, it seems like it did help.”

Still, there is a catch, he said: “Every well-done study, you end up with five or 10 new questions. That’s just the nature of research.”

The issue is that progesterone comes in different types – natural or synthetic – and different forms – oral, vaginal or injectable. And this study looked at only one type and form: 400 milligrams of micronized (more easily absorbed) natural progesterone given as vaginal suppositories (Utrogestan, made by Besins Healthcare).

It is still unknown whether other types and forms of progesterone would prevent miscarriage.

“You really cannot infer that just because the vaginal doesn’t work, the oral also doesn’t work,” Sullivan said. He believes that many doctors will rightly conclude that although this type of vaginal suppositories didn’t prevent miscarriage, it may not mean the same is true of another type or form of progesterone; many may continue prescribing based on insufficient evidence.

“Honestly, we don’t have a lot of great treatments” when women bleed early in their pregnancies, he said. “We tell people to take some days off, to prop her feet up, to watch the bleeding. Of course, doctors want to help, and patients want something. There’s nothing that we have that we can say ‘I know that this will help you.’ “

No ‘magic bullet’ to stop a miscarriage

“Miscarriages are really wrenching experiences for women and their families. It’s important that women who are facing miscarriage or who have had a miscarriage talk to their doctors and discuss possible treatment and prevention efforts,” Sullivan said.

“We don’t have a magic bullet right now to stop miscarriages, but it’s this type of research that brings us closer to that,” he said. “We need more studies.”

It’s clear today that the hormone progesterone, produced by the ovaries, is needed to prepare the womb for implantation of the embryo. Later, the placenta develops and produces progesterone, which suppresses contractions and prevents labor before the end of pregnancy.

But in the 1930s, scientists had only just begun to recognize the physiological function and the rising and falling levels of various hormones during pregnancy, according to Dr. Michael F. Greene, chief of obstetrics at Massachusetts General Hospital in Boston.

“By 1940, it was also recognized that an initial rise in these hormones followed by a premature fall was associated with spontaneous abortion,” Greene wrote in an editorial published alongside the new study in the New England Journal of Medicine.

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During the 1950s, advertisements combined with the medical literature made treatment of a threatened miscarriage with hormones and vitamins “virtually imperative,” Greene wrote. “In retrospect, it is likely that the initial rationale for hormonal therapy – that is, the observed fall in pregnancy hormone levels before pregnancy loss – was, in fact, a consequence rather than a cause of pregnancy failure.”