Race or ethnicity may be a factor in the success of fertility treatment, a new study suggests.

British researchers studied 1,219 white and 226 minority women undergoing their first assisted reproductive procedure. The observational study, published online in The British Journal of Obstetrics & Gynecology, included all women undergoing the procedures at a hospital in Nottingham between 2006 and 2011.

They found that 43.8 percent of white women gave birth to a live baby, compared with 38 percent of Southeast Asians, 23.3 percent of African blacks and 21.4 percent of Middle Eastern women. After controlling for other factors, researchers found that minority women were about 40 percent less likely than white women to have a live birth.

The production of egg cells, the fertilization rate, and the number of embryos transferred were similar among the four groups. But the implantation rate — the rate at which embryos were successfully implanted in the uterus — was significantly lower among ethnic minorities.

The senior author, Dr. Walid E. Maalouf, a lecturer in embryology at the University of Nottingham, warned against drawing firm conclusions from an observational study with a small population, and said that the reasons for the variations were unclear.

“There are probably many factors,” he said, “but the main focus now is underlying pathologies that could be associated with one or another ethnic group.”