Babies born by elective Caesarean section
are much more likely to develop breathing problems, a
Danish study examining 34,000 deliveries suggests.
Researchers found they were up to four
times more likely to have respiratory problems than those
born naturally, or by emergency Caesarean section.
The babies may miss out on hormonal and
physiological changes during labour which help mature
the lungs, they say.
The University of Aarhus study features
in the British Medical Journal.
Almost a quarter of UK births are now
estimated to be Caesarean sections - far above the 10%
to 15% rate recommended by the World Health Organization.
More than half of these were emergency
Caesareans, but despite this experts have been calling
for measures to reduce numbers of elective Caesareans,
warning it is a major operation.
A recent Oxford University study found
that women could be four times more likely to die in childbirth
if they opted for a Caesarean instead of natural birth.
The Danish team examined data on over
34,000 deliveries, adjusting to take account of factors
such as the mother's age, weight, and whether she smoked
or drank alcohol during pregnancy
They found that babies born by elective
Caesarean section had an increased risk of general respiratory
The risk was higher the earlier the Caesarean
A nearly fourfold increased risk was
found at 37 weeks gestation, a threefold increase in risk
at 38 weeks gestation, and a doubling of risk in infants
delivered at 39 weeks gestation.
For example, at 37 weeks, 10% of babies
delivered by elective Caesarean section developed respiratory
problems, compared with 2.8% of infants delivered naturally
or by emergency Caesarean section.
At 38 weeks, the proportion was 5.1%
of elective Caesarean babies compared with 1.7% of those
born naturally or by emergency Caesarean, and at 39 weeks,
2.1% compared with 1.1%.
The risks of serious respiratory problems
showed the same pattern.
The researchers conclude that significantly
fewer babies would develop breathing problems if elective
Caesareans were put off until 39 weeks gestation.
They said: "It is plausible that hormonal
and physiological changes associated with labour are necessary
for lung maturation in neonates and that these changes
may not occur in infants delivered by elective Caesarean
Dr Maggie Blott, a consultant obstetrician
at King's College Hospital, London, said obstetricians
in the UK were advised not to carry out elective Caesareans
before 39 weeks.
She said part of the problem might be
that doctors had to switch support lines to the baby very
quickly during a Caesarean, and it was possible that lung
fluid is not drained away as well as it should be.
She said: "Some babies do develop transient
breathing problems, they usually recover from them, but
occasionally a baby can be very sick indeed.
"A lot of woman are completely unaware
of the fact that a planned Caesarean section can negatively
impact on their baby.
"Any research which reinforces the fact
that Caesareans are not necessarily in the best interests
of the baby is welcome."
Mervi Jokinen, of the Royal College of
Midwives, said Caesarean section rates were too high in
She said it was a major operation, which
had health implications for the mother, as well as the
"The decision to opt for a Caesarean
section should not be taken lightly and should be based
on good medical grounds," she said.