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A team at The National Maternity Hospital, Holles Street,
looked at more than 8,000 births, searching for an
answer
to something long understood by midwives - that boys cause
more problems than girls. The results are published
this morning
in the British Medical Journal.
"As a humorous explanation for women in difficult labour,
doctors often say, 'Oh, it must be a boy'," explained
Dr Maeve Eogan, specialist registrar at Holles Street, who
carried out the research with Dr Michael O'Connell, Dr Michael
Geary and Dr Declan Keane. "That was the basis of the
research; we wanted to see whether we were blaming males needlessly."
Now it's official - males really do cause more problems during
labour, according to Dr Eogan's results. "We found that
women who carried male infants had longer labours, more foetal
distress and were more likely to require assistance during
delivery.
"Some of these things can be explained because males
are larger and have larger head circumferences" but this
factor didn't fully explain the differences, she said. It
may be that there was some "inherent vulnerability"
in male babies. "They are more vulnerable to the effects
of labour."
The team looked at first-time mothers who went into natural
labour between 1997 and 2000. Male births were much more likely
to require the use of oxytocin, a hormone which stimulates
contractions.
"Of the women carrying male infants, 70 per cent of them
had completely normal deliveries, compared to 76 per cent
of females."
Baby-boy labour averaged more than six hours, while average
baby-girl labour lasted less than six hours. Forceps were
needed in 23 per cent of boy births, but only 19 per cent
of girl births.
"If there is evidence of an unusual foetal heart trace
, we would then go on to do a foetal blood sample," Dr
Eogan explained. Some 19.5 per cent of baby boys were sampled
in this way, compared to 16.5 per cent of girls, her research
found.
And while 6 per cent of boys were delivered by Caesarean section,
only 4 per cent of girls were born this way.
She had no answers about why this should be so. "The
biological mechanisms can only be speculated on. We don't
know why. "It is one of those unknown variables,"
she concluded.
By Dick Ahlstrom, Science Editor
© The Irish Times
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Childbirth