Scientists in the US have taken significant strides in solving the mysteries surrounding human birth. Their achievements answer questions related to fertility in women which would make it easier for them to conceive
COUPLES seeking parenthood- or not it
all - shall heave a sigh of relief that they
would not make a mistake, after all.
Going by tradition, the few days before
and after ovulation (the release of ovum
from the ovary) constitute the most fertile period in a woman's monthly biological cycle. Researchers have disproved this popular belief by establishing that a woman's most fertile period
lasts for six days, ending on the day of
ovulation (The New England Journal of
Medicine, Vol 333, No 23).
Ovulation occurs approximately
once a month around the l4th day of
the 28-day menstrual cycle, in response
to a stimulatory cocktail of hormones.
Conception which takes place only
around the time of ovulation, occurs
when an egg is dislodged from its protective follicle in the ovary and becomes
available for fertilisation by a sperm.
The egg is either fertilised by a sperm
leading to pregnancy or is removed
from the reproductive tract through
menstrual bleeding.
Even though the fertilisation of an
egg by a sperm was a well -understood
process, relatively little was known
about the period which could be
regarded as the most fertile. Experts
varied in their estimates. However, with
the recent developments there remains
Do more scope for such speculation.
"Our data seems to indicate that the
day of ovulation marks the culmination
of the fertile period," says Allen I
Wilcox, head of the research team at the
National Institute of Environmental
Health Sciences (NIEHS) in the US. two
hunded twenty-one healthy women
planning a child were studied over a
four-year (1982-85) period. The urine
samples of these women were analysed
on a daily basis for the presence
and relative abundance of various
harmones. These results were
compared to reports of sexual
activity submitted by them regularly. Researchers reached the
conclusion that nearly all pregnancies occured during the six-
day period that ended on the day
of ovulation.
In addition, the research also
attempted to provide information on the length of time for
which the sperm and eggs remain
viable. "The rapid drop in the
probability of conception after
ovulation, suggests a short survival time for eggs or perhaps a
change in cervical mucus following ovulation that obstructs the
entry of new sperm," speculate
researchers at the NIEHS.
The results confirm that the sperm
retain the ability to fiertilisc an egg Lip
to
five days after entering the fiernale reproductive tract - a period somewhat
longer than what was earlier believed.
This also shatters the earlier theory that
fertilisation by older sperm results in a
higher rate of spontaneous abortions.
The misconceptions floated by some
Popular books believing in the ability to
influence the sex of the child through
sexual intercourse have also been ]aid
bare by these findings. Notable among
such books is How to Choose the Sex of
Your Baby written by L B Shettles, which states that intercourse timed to
coincide with ovulation is more likely to
produce mate offspring. "We found no
association between the sex of the baby
and the timing of intercourse," conclude the researchers.
Could infertile couples benefit from
the results of the study? "It can alleviate
a bit of the anxiety they feel when they
think they must have intercourse on a
certain day or all is lost," says Howard A
Zacur of the US-based Johns Hopkin
Medical Institution. Besides placing a
question mark on our traditional
wisdom, these findings provide crucial
tips for practising 'natural family
planning'.
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