Previous research has suggested that taking antibiotics could help to delay the onset of labour and reduce the need for assistance with breathing in women whose waters have broken prematurely.
But a study funded by the Medical Research Council (MRC), found that babies had a greater risk of developing disabilities if their mothers were given antibiotics when their waters had not broken and they showed no signs of infection.
The DoH has sent letters to all GPs in England informing them of the results of the trial.
Cerebal palsy: antibiotics risk
What is the research?
The results are based on a follow-up study of the 2001 ORACLE trial, involving 4,221 mothers at risk of having a premature birth.
The trial looked at women whose waters had broken and those who showed signs of going into premature labour whose waters had not broken.
The trial did not include pregnant women showing signs of infection, for whom antibiotics are the correct treatment.
The mothers were randomly assigned to receive placebo plus erythromycin, placebo plus co-amoxiclav, both antibiotics or double-placebo.
The mothers took the tablets for 10 days or until they gave birth, whichever was sooner.
The follow-up study looked at 3,196 of their children for signs of impairment using a questionnaire to measure functioning, health problems and educational attainment.
For mothers whose waters broke early, taking antibiotics did not affect their child's functioning or behaviour.
But the risk of functional impairment increased by 18 per cent for children of mothers who had received erythromycin before their waters broke.
Co-amoxiclav, with or without erythromycin, did not increase functional impairment risk.
But the risk of cerebral palsy roughly doubled for children whose mothers took antibiotics before their waters broke. Children had a 3.3 per cent chance of developing cerebral palsy if their mothers took erythro- mycin, compared with 1.7 per cent if they had not.
There was a 3.2 per cent chance of developing cerebral palsy for children whose mothers took co-amoxiclav, and 1.9 per cent for those who had not.
What do the researchers say?
Lead researcher Dr Sara Kenyon, from the University of Leicester, said: 'Before the ORACLE trial, there was evidence of short-term benefits of antibiotics in premature labour.
'But we did not know what the long-term outcomes would be. It is unclear why the follow-up showed this unexpected increase in cerebral palsy in babies born to the women whose waters had not broken.'
Dr Catherine Elliott, head of clinical research support and ethics at the MRC, said: 'The results were unexpected and the MRC is considering what further research could shed more light on these findings.'
What do other researchers say?
In a letter to GPs, England's CMO Sir Liam Donaldson said pregnant women should not worry about taking antibiotics to treat infections, but that antibiotics should not be routinely given to women who are in premature labour.
- Giving antibiotics to women without infections in premature labour could increase the risk of having a child with functional impairment and cerebral palsy.
- Pregnant women should still take antibiotics if they have an infection.
- A helpline set up by the researchers is on 0800 085 2411 from 9.30am to 4.30pm, Monday to Friday.