WEDNESDAY, Nov. 25, 2015 (HealthDay News) -- Taking progesterone supplements in the first trimester of pregnancy may not improve the odds of motherhood for women with a history of miscarriage, a new study finds.
Researchers found that among more than 800 women with one or more unexplained miscarriages, those who received the hormone in early pregnancy were no less likely to miscarry than those who received a placebo.
The live birth rate was 65.8 percent among women taking vaginal progesterone and 63.3 percent in those taking a placebo, the researchers found.
"After more than 60 years of debate, we now know that progesterone treatment in early pregnancy isn't the answer for women with unexplained recurrent losses," said lead researcher Dr. Arri Coomarasamy, a professor of gynecology at the Institute of Metabolism and System Research at University of Birmingham in England.
Researchers can now direct their efforts to exploring other treatments that really can reduce the risk, he said.
Coomarasamy said the results will likely disappoint many thousands of women and couples affected by miscarriage. About 1 percent of couples have recurrent miscarriages, he noted.
"Many hoped that this research would confirm progesterone as an effective treatment that would promise an increased chance of a 'take-home' baby next time. Sadly, it does not," Coomarasamy said.
The report was published Nov. 26 in the New England Journal of Medicine.
When a fetus dies in the womb before 20 weeks of pregnancy, it's termed a miscarriage. According to the March of Dimes, about 10 to 15 percent of pregnancies end in miscarriage, usually in the first trimester (first 13 weeks of pregnancy).
Supplemental progesterone is often given when these women get pregnant again, but previous studies have not demonstrated a clear benefit, said Dr. Jennifer Wu, an Ob-Gyn at Lenox Hill Hospital in New York City.
"Patients with a history of unexplained recurrent miscarriage are often desperate for treatment and a good outcome," Wu said.
"The results of this study should be carefully weighed when a patient with adverse obstetric history gets pregnant," she said.
The 826 women in the trial were randomly assigned to receive vaginal progesterone supplements or placebo. Nearly two-thirds had their baby, regardless of treatment, the researchers said.
Coomarasamy said there were no significant negative effects of progesterone for women or for their babies. This is important for women taking progesterone for other reasons, such as fertility treatment, he said.
Despite the findings, Dr. Edward McCabe, chief medical officer at the March of Dimes, is not ready to give up on progesterone for preventing miscarriage.
"The limitations of the current trial include how the progesterone was given. Perhaps oral or intramuscular could be more effective than vaginal," he said.
In addition, treatment was started after pregnancy was confirmed, McCabe said. "Progesterone might be more effective if given before or at the time of conception," he said.
Future trials should address timing and route of administration, he said.
The causes of miscarriage aren't totally understood, but chromosome problems account for more than half of first-trimester miscarriages, the March of Dimes says.
Another cause is blighted ovum, which occurs when a fertilized egg implants in the uterus but doesn't develop into a full-term baby.
Miscarriage also has been linked to smoking, alcohol and drug use, and the mother's health. Conditions such as diabetes, lupus and other autoimmune diseases, and thyroid disease can increase the odds of miscarriage, according to the March of Dimes.
For more on miscarriage, visit the March of Dimes.