The Department of Health recommends babies are breastfed for the first six months

The study by the Swansea University team suggests the drugs may slow down milk production, the same effects as high doses of painkilling drugs.

The findings may help to explain the limited success of efforts to increase breastfeeding rates in the UK.

The Department of Health recommends babies are breastfed for the first six months, and it has set a target of increasing breastfeeding rates by 2% each year. But in the UK under half of babies are exclusively breastfed, with a quarter only receiving formula milk from birth.

The research found use of the drugs oxytocin or ergometrine were associated with an overall 7% decline in the proportion who started breastfeeding within 48 hours of giving birth.

Among women who were not given the drugs, two-thirds started breastfeeding within 48 hours of giving birth. Those given a shot of oxytocin the breastfeeding rate was 59.1% and among those who were given an additional shot of ergometrine the rate fell to just 56.4%.

Lead researcher Dr Sue Jordan says ‘The potentially life-saving treatments to prevent bleeding after birth must not be compromised on the basis of this study but further studies are required to establish ways to minimize any effects on breastfeeding rates. In the meantime what we would like to see would be provision of extra help for new mothers trying to establish breastfeeding by making sure to allow enough time for the effect of drugs given in labour to subside.’