Hormone levels could be culprit behind low birth weight, preeclampsia in assisted reproduction
The researchers, led by Kirk P. Conrad, M.D., a professor in the College of Medicine’s departments of physiology and functional genomics and of obstetrics and gynecology, are examining the effects of a hormone produced in pregnancy called relaxin.
The hormone spurs many physiological changes, including dilating the blood vessels in women’s skin, kidneys and heart. But when women become pregnant with medical assistance, or in vitro fertilization, the hormone is produced in a higher quantity — or sometimes not at all. Conrad and his colleagues are trying to determine whether the absence or abundance of relaxin affects the normal ways a woman’s heart, blood vessels and kidneys change during pregnancy. This could possibly lead to obstetrical complications such as preeclampsia, a condition marked by high blood pressure.
Women who become pregnant without medical assistance usually produce an egg from a single site within the ovary, called a follicle. The follicle then changes into what is called a corpus luteum, a glandular structure that produces the relaxin hormone.
“The corpus luteum is a major source of reproductive hormones that circulate in the blood in the first eight weeks of pregnancy until the placenta can take over. In the case of relaxin, the corpus luteum is the only source to produce the hormone,” said Conrad, principal investigator of the study.
When women undergo medically induced ovulation, their own eggs are harvested, fertilized and then implanted back into their bodies. Because administered hormones stimulate the production of many eggs, there are many follicles in their bodies, which turn into corpus lutea. The extra corpus lutea produce extra relaxin.
Women who use donor eggs to become pregnant, however, do not develop follicles that turn into corpus lutea. Their ovaries produce no relaxin. Conrad and his colleagues are studying whether excess or absent relaxin may lead to exaggerated or deficient dilation of blood vessels in the women’s kidneys, skin and heart.
There is emerging evidence that women who become pregnant through medical assistance are at a higher risk for developing preeclampsia, and delivering babies who are lower in weight for the number of weeks they were in the womb before birth. Stanford researcher Valerie Baker, M.D., who is part of the team, is investigating this connection.
“Whether this is because of absence or excess of relaxin, respectively, in the donor egg recipients or in the standard in vitro fertilization patients who undergo ovarian stimulation is presently not known,” Conrad said. “There are other potential explanations. It could be a combination of factors.”
Conrad is hoping to study women who get pregnant without medical assistance to establish a baseline against which they can compare women who become pregnant through medical assistance. The researchers measure heart and kidney function before a woman’s pregnancy, six times during the pregnancy, and then once about six months after pregnancy. Aside from blood tests, the study is noninvasive.
“The problem with spontaneous pregnancies is that oftentimes, we can connect with women, but they’re already pregnant,” Conrad said. “But we need to investigate the women before they become pregnant so we have baseline data. We need women who are very in tune with exactly when they want to get pregnant.”
Conrad, along with UF researchers Mark Segal, M.D., Ph.D., Maureen Keller-Wood, Ph.D., Yueh-Yun Chi, Ph.D., R. Stan Williams, M.D., and Stanford researcher Valerie Baker, are halfway through a five-year National Institutes of Health grant that is funding their study of pregnancies conceived by assisted reproduction techniques.
Women in the Gainesville area who are planning to become pregnant and who are interested in being part of the study should call Kevin Bishop, ARNP, at 352-594-1583 or 877-506-2736 before going off birth control. Compensation of up to $250 for each visit is available for time and for some travel.