Doctors are ignoring guidance notes and are routinely prescribing powerful narcotics to pregnant women. Around 14 per cent of expectant mothers in America are given the painkillers-the rate is probably lower in Europe-but nobody knows the affect this may be having on the developing fetus.
The use of narcotics during pregnancy has trebled in the past 20 years, even though manufacturers warn against their use because of the potential harm to the woman or the unborn child.
The US's National Institutes of Health reckons that 14 per cent of pregnant women in America are now routinely prescribed a narcotic to help them deal with pains, and research is urgently needed to discover if it is harming the unborn child.
Narcotic usage in pregnancy is "significantly higher" in the US than in Europe, they say.
The researchers made their surprise discovery when they carried out an analysis of narcotic use in the US. Between 1991 and 2009, 200 million prescriptions were handed out for the powerful painkillers in the US, and this included 14 per cent of 530,000 pregnant women who were part of the analysis.
Typical usage was for less than a week, and most commonly for back pain. Around 2.2 per cent of the women were dispensed a narcotic three times or more during the pregnancy.
(Source: Anesthesiology, 2014; 1: doi: 10.1097/ALN.0000000000000172)