The number of newborn babies in Switzerland suffering from respiratory distress (RD) has doubled in the past 30 years, according to paediatric researchers.
A study shows that the increase may be attributed to the larger number of caesarean sections carried out nowadays.
Deaths among newborns have dropped in the past three decades in Switzerland. Mortality from RD – a lung disorder that makes it hard to breathe - has also fallen: in the 1970s, one in six died, while today that figure has tailed off to one in 29.
But at the same time, the number of babies admitted to hospital units suffering from RD has doubled over the same period, rising from 1.9 to 3.8 per cent.
For those who ended up in neonatology units, that figure increased from just under one third to over half of all admissions, according to the study, published in the latest issue of paediatric research journal Acta Paediatrica.
Hans Ulrich Bucher, the head of the neonatology unit at Zurich University and study co-author, has trouble explaining why.
"That's a question that we can't completely answer," he told swissinfo. "It's the first time in industrialised countries that this phenomenon has been described – so we are slightly puzzled."
Bucher and his colleagues analysed data from almost all the country's neonatology services, comparing with figures from the Federal Statistics Office and similar studies from 1974, 1984 as well as 1994.
Bucher, who is also head of the Swiss Society of Neonatology, says that although no firm connection between caesareans and breathing problems has been proven, research has shown that there is a connection with elective procedures.
"This is well documented and this could explain at least half of the additional cases of babies with respiratory problems," said Bucher.
But he said that caesareans were "the most likely explanation".
Studies have in the past demonstrated that caesareans carried out before a woman goes into labour put the development of a baby's lungs back two weeks.
In other words, a child that comes into the world this way after 35 weeks will have the same lungs as a 33-week-old baby born naturally.
The results uncovered by Bucher and his colleagues also show that contrary to what most people believe, it is not premature babies with low birth weight that are the most affected by RD.
It is in fact babies weighing more than 2.5 kilograms that have suffered the most.
According to the World Health Organization, caesareans are medically justified in ten to 15 per cent of births.
But in Switzerland, the number of these births climbed from just five per cent in 1974 to 30 per cent in 2004. Many western countries have similarly high rates.
Studies have also shown that children born by caesarean have three times more breathing problems than other babies. Around 60 per cent of hospital admissions for children are also related to respiratory difficulties.
Bucher said the main message of the published research was that the problem as documented in the study was avoidable.
"I'm not against all caesareans, but elective caesareans, which... are unfavourable for the baby because the baby is not prepared to be born," he said.
Separate statistics have shown that caesareans also have a cost, usually twice that of a normal birth, while one night spent by a baby in a neonatology unit runs into several hundreds of Swiss francs.
But experts say the money is well spent. Most children pull through with no ill effects.
Childbirth facts (2006)
Number of children per woman in Switzerland: 1.44 (1964: 2.7)
Currently foreign women have more children: 1.9 per woman vs. 1.3 children per Swiss woman
Number of boys per 100 girls: 106.1
Mean age of childbirth (in years): 30.4 years