Researchers in the U.S. say that babies born by Caesarean section rather than normal birth, are three times more likely to die.
As an increasing number of today's mothers choose to have their babies this way, when there is no medical need for it.
The large study is the first to compare death rates when women chose the procedure in advance in consultation with their obstetricians.
The cases chosen were those of women with no known medical reason for the procedure, or with no special complications during labour.
Marian MacDorman, of the Centres for Disease Control and Prevention in Atlanta, Georgia, who led the study, says neonatal deaths are rare for low-risk women, around one death per 1,000 live births, and even after they adjusted for socioeconomic and medical risk factors, the difference persisted.
Almost a quarter of British babies are born this way and U.S. Caesarean rates increased by 41 per cent between 1996 and 2004, while the rate among low-risk women nearly doubled.
Baby deaths following Caesareans were known to be higher than after normal vaginal births, but the reason was always thought to be that many operations were done as emergencies, when problems arose during labour.
MacDorman says the findings should be of concern for clinicians and policymakers who are observing the rapid growth in the number of primary Caesareans to mothers without a medical indication.
MacDorman, says they are not trying to alarm anyone but advise women considering an elective Caesarean to consult with their doctor.
The team studied more than 5.7 million live births and nearly 12,000 infant deaths in the United States from 1998 to 2001.