The following news story is from Reuters News Service
ovulate more than once a month, study says
Last Updated: 2003-07-08 17:00:20 -0400 (Reuters Health)
By Maggie Fox
WASHINGTON (Reuters) - No wonder the rhythm method does not work
so well for birth control -- scientists in Canada said on Tuesday
they had found women sometimes ovulate several times in a single
Their finding, if verified, would overturn the traditional wisdom
that women produce an egg cell once a month. It would also help
explain why "natural" methods of birth control, based
on the idea that ovulation can be predicted, often fail.
"We are literally going to have to re-write medical textbooks," said
Dr. Roger Pierson, director of the Reproductive Biology Research
Unit at the University of Saskatchewan, who led the study.
"It's exactly why the rhythm method doesn't work."
Scientists have long known that humans have unique cycles of ovulation.
Many animals come into heat -- a time when all the males around
know through smells and visual signals that a female is ovulating
and ready to conceive.
Not so with humans, who have "concealed" ovulation.
Standard medical science says a woman has a cycle running roughly
28 days in which an egg ripens, is released by the follicle, drops
into the fallopian tube, and then is either fertilized or shed
Writing in the journal Fertility and Sterility, Pierson and colleagues
found this did not always happen.
"We weren't expecting this. We really weren't," Pierson
said in a telephone interview.
DAILY ULTRASOUND SCANS
In the study, Pierson, veterinarian Gregg Adams and graduate student
Angela Baerwald did daily, high-resolution ultrasound scans on
63 women for a month, which allowed them to see the follicles very
"We had 63 women with normal menstrual cycles. Of those 63,
only 50 had normal ovarian cycles," Pierson said.
Thirteen of the women ovulated multiple times, in various different
ways. And of the other 50, 40 percent had up to three waves of
activity by the follicles, any one of which could result in the
production of an egg.
The women's hormone levels did not match this activity, Pierson
said. "Hopefully this will help women explain how they got
pregnant when they really didn't want to be pregnant, and it certainly
will help us design better fertility therapies."
Apparently, measuring hormones in the blood is not enough to predict
what a woman's reproductive system is up to.
"The hormones do what they are going to do and the ovaries
just follow their merry path," Pierson said.
"We always thought that menstrual cycles and ovarian cycles
were one and the same. It turns out they are just like two political
parties -- sometimes they go along hand in hand for the good of
the country and sometimes they go along their separate ways."
Pierson's team plans longer-term studies to see if the women's
patterns are consistent from month to month.
"We don't know what's causing it -- we don't know if it is
the weather or exposure to men or grapefruit juice or what," Pierson
The findings, which were first seen in cattle and horses, help
explain some things that have puzzled obstetricians, Pierson said.
"It really explains how we get fraternal twins wi
th different conception days," Pierson said. "Clinically,
we see this all the time. We see women come in with twins and when
we do an ultrasound we see one is at one 10 weeks development and
another at seven."
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