The study tests the success rates of common fertility drugs

Betsy Kilmartin and her husband tried to conceive a child for nine months without success. They saw a doctor to find out what might be causing the problem and found there was no specific biological cause – it was what was considered unexplained infertility.

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“It’s hard, you’re on an emotional roller coaster,” Kilmartin told CBS News.

She used clomiphene, or Clomid, to stimulate egg production and increase her chances of pregnancy. A new study shows that the drug, which has become one of the standard treatments for unexplained infertility, may be the best choice for couples like the Kilmartins.

A study published in the New England Journal of Medicine examined 900 couples who had trouble conceiving for at least a year despite normal reproductive function. The study tested different medications that may increase the chances of a healthy pregnancy, seeking the greatest success of a live birth with the least chance of having multiple, one of the major risk factors for fertility drugs.

The researchers were particularly interested in comparing two common drugs that promote extra egg release to a new treatment using an aromatase inhibitor called letrozole, which has shown promising pregnancy rates without increased birth defects in other studies. The study was conducted at 12 clinics in the United States by the National Institute of Child Health and Human Development. The women in the study were between 18 and 40 years of age and had male partners with sperm counts healthy enough for artificial insemination.

Although in vitro fertilization is also an option for women who have difficulty conceiving, it is much less common because it is expensive and most insurance does not cover the process; The use of a drug to promote ovary stimulation is the most common therapy.

This study tested three ovarian stimulant drugs that increase the odds of pregnancy by releasing more eggs: clomiphene and clotted tablets, and an injectable hormone called gonadotropin. The two pills were blindly tested against each other.

The results? “Clomid was far more efficient than letrozole, achieving a live birth rate of 23 percent,” Dr. Tomer Singer of Lenox Hill Human Reproduction told CBS News. “The letrozole group only reached 18 percent.”

The rate of getting pregnant with multiples – twins or triplets – differed significantly between medications. The clomiphene group had the lowest number of babies born with pregnancy, at 5.7 percent, compared to 14.3 percent in the letrozole group and 13.4 percent in the gonadotropin group.

“Letrozole treatment offered no benefit over clomiphene treatment,” study author Esther Eisenberg of the Fertility and Infertility Branch of the National Institute of Child Health and Human Development at EHNY Kennedy Shriver said in a statement. “Women in the letrozole treatment group had fewer live births but four times more multiple pregnancies than women in the clomiphene group.”

Treatments with injected gonadotropin resulted in the highest number of births, 32 percent, but many were multiple – twins or even triplets. The gonadotropin group had 24 twins and 10 triplets, while those born to women in the other drug groups were all twins.

Pregnancies with multiple fetuses may involve more complications, which often leads to much lower birth weights and preterm births.

“There is a higher rate of c-sections, more diabetes, more pre-eclampsia,” Singer said.

Limitations of the study may have slightly affected outcomes, including the fact that because gonadotropin is injectable rather than a pill, it was not possible to blindly study the other drugs. In addition, the study was designed to compare current treatments using clomid or gonadotropin as a result versus the new letrazole instead of studying the three drugs separately. Finally, no control group was included because the researchers considered it would be unethical to deny the actual treatment to couples seeking fertility help after attempting to conceive between one and three years.

However, the study’s researchers believe the evidence is strong that current standard therapy using clomiphene remains the most effective way to stimulate the ovaries and increase the chances of healthy pregnancy for couples with unexplained infertility.

After her treatment with Clomid, Kilmartin became pregnant with her son Lucas, who is now almost two years old. “I love children, I’ve always wanted to be a mother,” Kilmartin said. It seemed like an eternity would come.

After another round of treatment, the couple’s second child is now waiting.