Taking common antibiotics during pregnancy may increase the chance of birth defects, major new research warns.Although scientists claim the risk is only small, only three drugs studied were not associated with such links.

Experts suggested the findings were worrying, considering just how many expectant mothers get struck down with infections.The Canadian team is urging doctors to consider prescribing other antibiotics when treating mothers-to-be with bugs.

Senior author Dr. Anick Bérard, from Montreal University, said: “Infections during pregnancy are frequent and should be treated. However, our study highlights safer options for treatment of infections, more specifically urinary tract infections or pulmonary infections, at least during the first trimester of pregnancy.”
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What did they find? Clindamycin, doxycycline, quinolones, macrolides, and phenoxymethylpenicillin were all linked to organ-specific malformations. Amoxicillin, cephalosporins, and nitrofurantoin were all deemed safe, according to the study of nearly 140,000 live births in Canada.

Published in the British Journal of Clinical Pharmacology, the findings were based on data between 1998 and 2008.The same team of researchers were behind a major study in May that established a link between common antibiotics and miscarriages.

Pregnant women who take antibiotics could be putting their unborn children at risk, scientists warned in February.Drugs used to beat infections can interfere with a baby’s immune system long-term, Cincinnati Children’s Hospital Medical Center experts found.

Friendly gut bacteria – which play a pivotal role in the development of a child – are frequently wiped out by the drugs, according to the research.In a study on mice this was found to leave them at higher risk of developing pneumonia – which can be deadly. While many types were also found to be safe, certain forms significantly increased the risk – some more than double.Macrolides and quinolones were suggested triggers of miscarriages, backing up the new found evidence of their link to birth defects.

While nitrofurantoin, which is often used to treat urinary tract infections in pregnant women, was also found to be safe. Prior to that study, research had consistently found that antibiotics could increase the risk of premature birth or low birth weight.

Doctors have previously stressed that it is dangerous to leave infections untreated, especially in pregnant women who have a weakened immune system. In Britain, some of the drugs such as tetracyclines and quinolones come with warnings they should not be taken during pregnancy. But some carry no such warning, or warn only that they should be not taken at high doses.