THE VIRGINIAN-PILOT
Copyright (c) 1995, Landmark Communications, Inc.
DATE: Thursday, December 7, 1995 TAG: 9512070343
SECTION: FRONT PAGE: A1 EDITION: FINAL
SOURCE: FROM WIRE REPORTS
DATELINE: BOSTON LENGTH: Medium: 73 lines
A new study pinpoints nature's window of fertility: There are six days in every menstrual month when a woman can get pregnant.
The findings have implications for couples striving to have children, as well as for those who want to avoid them.
Still, it offers no sure-fire formula for people who want children.
``The trick to all this is for couples to know their fertile days,'' said Dr. Allen J. Wilcox. ``There is no good way to do that.''
Perhaps the best advice is: Have sex often.
Until now, estimates of women's fertility ranged from two days in a menstrual cycle to 10 or more.
But the study found that conception is possible if a woman has intercourse on the five days before ovulation as well as on the day her ovaries release a new egg.
Sex before that six-day period almost certainly will not result in pregnancy. And, to the researchers' great surprise, intercourse just one day after ovulation won't, either.
The often-repeated idea that couples should save up and have intercourse on the day closest to ovulation turns out to be false.
On the contrary, the study ``suggests that you increase your chance of pregnancy with increased frequency of intercourse,'' said Wilcox, its lead author.
Ideally, a couple would want to know five days in advance when ovulation will occur and have sex on those days. Many test kits now on the market will reveal when ovulation is occurring, but by then it's almost too late.
However, other kits detect the surge of luteinizing hormone, a signal that ovulation is about to occur. The new findings suggest that when women who want to conceive detect this hormonal surge, they should have intercourse immediately and not wait even a day or two to do so.
``If you have intercourse when you see that surge, it will be just prior to ovulation,'' Klapholz explained. ``That's what these kits tell you to do and that's why they work.''
But timing clearly is not everything.
``Even couples who are very fertile are not fertile in every cycle,'' Wilcox said. ``We don't understand why that is.''
Wilcox and colleagues from the National Institute of Environmental Health Sciences in Research Triangle Park, N.C., published their findings in today's issue of the New England Journal of Medicine.
Wilcox, who also teaches at the University of North Carolina, based his findings on 221 women who wanted to get pregnant. All of them stopped using birth control, collected daily urine specimens and kept records of when they had intercourse.
From this, the researchers could calculate when the women ovulated and when they got pregnant.
The probability of conception ranges from 10 percent when intercourse occurs five days before ovulation to 33 percent when it happens on the day of ovulation itself. Daily intercourse results in the highest chance of pregnancy - 37 percent.
Among other findings of the study:
Contrary to another common belief, there is no evidence that the timing of intercourse influences whether the baby will be a boy or a girl.
Sperm has a fairly short shelf life. Ninety-four percent of pregnancies result from sperm that has lingered less than three days. There were no pregnancies from sperm more than 5 days old.
There is also no sign that aging sperm is more likely to produce babies with defects, although the study was too small to prove this conclusively.
KEYWORDS: FERTILITY STUDY by CNB