By Maureen Salamon
TUESDAY, Oct. 21, 2014 (HealthDay News) -- Black women undergoing in vitro fertilization (IVF) are only about half as likely as white women to become pregnant using the popular assisted reproduction technique, new research indicates, and the racial disparity persists even when donor eggs are used.
In the study, about 31 percent of white patients became pregnant after IVF, compared to about 17 percent of black patients.
Analyzing more than 4,000 IVF cycles over two years to tease out the impact of race, scientists from University of Chicago also found that miscarriage after IVF -- where eggs and sperm are joined in a lab and implanted in the woman's uterus -- occurred twice as often among blacks than whites.
These racial differences remained even though the researchers controlled for factors affecting pregnancy such as age, body-mass index (BMI, a measurement of weight vs. height), hormone levels and smoking. Asian women also experienced somewhat lower live birth rates than whites after IVF, but rates among Hispanic women were comparable to whites.
"We were just struck by these outcomes," said study author Dr. Eve Feinberg, an assistant clinical professor at University of Chicago Medical Center and a physician at Fertility Centers of Illinois. "They had been reported previously in other studies, but our study, which is quite large, really confirmed those other findings."
The study was presented Monday at the American Society for Reproductive Medicine (ASRM) annual meeting in Honolulu. Research presented at scientific meetings typically has not been published or peer-reviewed and results are considered preliminary.
Used in the United States since 1981, IVF is one of the most common forms of assisted reproduction. About 65,000 babies were born in the United States in 2012 through 176,000 assisted reproduction cycles, typically costing upwards of $10,000 apiece, according to the U.S. Centers for Disease Control and Prevention.
In another study being presented at the ASRM meeting, researchers from Columbia University Medical Center in New York found that racial differences for IVF success persisted between white and black women even when donor eggs were used.
In that research, led by Dr. Lisa Carey Grossman, uterine conditions such as fibroids or prior cesarean surgery were taken into account. Because black women have higher incidences of such conditions, the scientists compared black and white egg donor recipients who had similar uterine histories.
Despite that, black women still experienced significantly lower embryo implantation rates than whites -- 30.4 percent compared to 36.3 percent, Grossman said.
Dr. Edward Illions, a reproductive endocrinologist at Montefiore Medical Center in Hartsdale, N.Y., who wasn't involved in the new research, said he has observed the same racial disparities in IVF outcomes in his own practice.
"I'm not actually surprised, because the [medical] literature before this almost uniformly has shown a lower success rate in African-American women compared to Caucasians," said Illions, also an associate professor of clinical obstetrics, gynecology and women's health at Montefiore Institute for Reproductive Medicine.
"In most of the studies also, the BMIs of African-American women have been dramatically higher," he added. "We know from lots of data that women with higher BMIs have worse IVF outcomes, even with donor eggs."
Illions said scientists aren't yet sure why higher BMI is linked to lower IVF success. "It has to do with uterine receptivity," he said, but he added that the exact cause hasn't been pinpointed.
The experts agreed that more large-scale research is needed to determine why racial disparities in IVF outcomes persist.