A team of researchers at the University of Maryland School of Medicine in Baltimore and the Eastern Virginia Medical School in Norfolk has shown that low estrogen levels during pregnancy can impair fetal ovary development and reduce the number of follicles (eggs) a female is born with.
"Low estrogen levels during pregnancy mean the female baby will be born with fewer eggs," says Dr. Gene Albrecht Ph.D., professor of Obstetrics, Gynecology and Reproductive Sciences at the University of Maryland School of Medicine and co-investigator for the study. Because women are born with all of the eggs they will ever have during their reproductive life, the findings may help to explain adult fertility problems and the early onset of menopause.
The study, presented at the national conference of Experimental Biology in Orlando, involved pregnant baboons. One-third of the baboons received a drug to reduce estrogen levels by as much as 95 percent. The control group received no treatment and maintained normal levels of the hormone throughout the study. In a third group, estrogen levels were reduced and then restored to make sure that any changes were the result of estrogen deprivation.
In the baboons with very low estrogen, the female offspring were born with underdeveloped ovaries and about half the normal number of follicles (eggs).
In addition, there was a higher number of abnormal or "broken" eggs. Ovarian and follicle development was normal in the other groups.
"Women naturally lose eggs throughout their reproductive life," says Gerald J. Pepe, Ph.D., professor and Chair of Physiological Sciences at the Eastern Virginia Medical School. "But if a woman has fewer eggs to begin with, there will be fewer eggs available for reproduction, especially as a woman grows older and nears menopause."
During menopause, the ovaries stop releasing eggs, menstruation ends, and estrogen levels decline. In addition to promoting bone strength in women, estrogen helps to regulate the female reproductive cycle and is important to the maintenance of a healthy pregnancy."Our research suggests that doctors should pay more attention to estrogen levels during pregnancy, and consider estrogen replacement therapy for expectant mothers with low estrogen levels," says Dr. Albrecht, who is also director of the University of Maryland Center for Studies in Reproduction. "It could help prevent future fertility problems for the child and decrease the chance of miscarriage."
In addition to ovary and follicle problems, estrogen deprivation also had an adverse effect on fetal development of the adrenal glands. Researchers found that the gland's production of cortisol, which is critical to the body's response to stress, was cut by half in the group whose mothers had low estrogen levels.
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