|Ovulation Findings Could Fight Fertility
WebPosted Jul 8 2003 06:24 PM PDT Taken from the Globe and Mail
Women may be capable of ovulating several times a month, Canadian scientists have discovered.
Their finding could have important implications for birth control, because it means women may be able to get pregnant at various times during the menstrual cycle. It could also change the way doctors treat infertile women and give them more chances of harvesting eggs, says Roger Pierson, director of the reproductive biology research unit at the University of Saskatchewan.
"We are in the early phases of understanding it, but it is quite a significant departure from what we all thought was going on for the last 50 years or so," Dr. Pierson said in an interview. "We are literally going to have to rewrite medical textbooks."
He studied the results of vaginal ultrasounds performed every day for a month on 63 women, aged 18 to 40. The ultrasound tests produced images of follicles, the cells and fluid that surround eggs as they start to develop.
The theory has been that at the beginning of each menstrual cycle, 15 to 20 follicles begin to grow in the ovaries and that only one egg reaches maturity -- at roughly the middle of the cycle -- and is released, ready to be fertilized. The other eggs die.
But the ultrasound images showed that in almost all of the women, follicle development occurred in waves two or three times during the cycle. That means that not once, but two or three times an eggs was ready to be released.
Most of the women ovulated only once, usually around the middle of their cycle, between the 11th and the 17th day. But many were ready to ovulate two or three times. Most of those chances came after they had ovulated, he said, but some had the potential to ovulate immediately after their menstrual period.
"They have the biological capacity in their ovaries to do it," Dr. Pierson says.
The number of waves of egg development varied from woman to woman. In some cases, follicle development didn't reach the point where the egg would normally be mature enough to release. But all of the women in the study experienced more than one wave of egg maturation.
The researchers don't know whether the pattern for each woman is constant, or whether it changes from month to month.
Some of the women in the study had never been pregnant; others had had as many as three children, but their pattern of egg development and their reproductive history were not linked.
The study found that for 40 per cent of the women in the study, so-called natural family-planning methods might not work, Dr. Pierson said. There was no "safe" time during their cycles to have intercourse, he said. There was always the chance they might ovulate. The researchers also don't know what may cause ovulation earlier or later than usual. Is it possible that seeing an attractive man, or having intercourse, could stimulate the eggs to develop? In animal studies, exposure to pheromones -- chemicals that signal sexual status -- can cause profound swings in ovarian cycles.
"We have no idea about humans," says Dr. Pierson, but he added that being prepared to ovulate more than once a cycle makes sense from an evolutionary point of view because it could improve the odds of procreating.
Other researchers say the paper is solid, and may help in treating women with fertility problems, or explain unplanned pregnancies.
"It really gives us as a new idea about how the menstrual system works," said Bruce Murphy, a reproductive biologist at the University of Montreal. "It may explain why my mother had four kids using the rhythm method."