New research at the Yale School of Medicine essentially puts a time stamp on a woman's biological clock.
Researchers said they've found what actually causes the quality of women's eggs to decline.
Doctors said the best time for a woman to get pregnant is between the ages of 21 and 32.
"After this decade, there is going to be a slow decline in the quality of the eggs," said Dr. Pasquale Patrizio, director, Yale Fertility Center.
In reality, more women are putting off having children until their late 30s and even early 40s. Patrizio said that can be quite a venture.
"This biological clock, this continual running of time, it's really what intrigued us to try and understand," he said.
Researchers said they recently examined the sharp decline in egg quality, particularly in women ages 40 and older.
"In a nutshell, what the research has brought forward is that the process of vascularization of blood supply to each single follicle is the main determinant of egg aging," Patrizio said.
In other words, as the ovaries become older, the blood supply diminishes. As fast as that blood supply diminishes, the rate of errors that can happen to the egg increases.
Doctors said it's because the cells are not properly supplies anymore, a process commonly referred to as apoptosis.
"If our findings are correct, we should probably decrease the number of days in which the eggs are sitting in the ovary, which are not properly receiving a good blood supply," Patrizio said.
Patrizio said future studies may involve testing whether or not changing the type of ovarian stimulation may slow down or even stop the aging process of the eggs.
Regardless, more research needs to be done.
"I would definitely advise women who are thinking about postponing motherhood, to freeze eggs before it is too late," Patrizio said.
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