Treatment with antibiotics can significantly increase the risk of miscarriage

Women who take certain types of antibiotics in the early stages of pregnancy may be at an increased risk of miscarriage, scientists suggest.

New data from Canadian scientists

But not all antibiotics work the same way, and some can be safer during pregnancy than others. Canadian researchers found that pregnant women who consumed certain types of antibiotics had a small increase in the risk of miscarriage during the first 20 weeks of pregnancy compared with future mothers who did not take them. The results of this study were published on May 1 in the journal of the Canadian Medical Association.

"The study showed that the most commonly used antibiotics - penicillin, cephalosporin and erythromycin - have no effect on the risk of miscarriage," said lead author Anik Berard, a professor of pharmacy at the University of Montreal in Canada.

The infections that develop in women during pregnancy need to be treated, so it's encouraging to learn that the antibiotics that are most widely used are not the cause of miscarriage in the early stages of pregnancy.

Security Issues

Despite the frequent use of antibiotics during pregnancy for the treatment of various infections, the safety of the effects of these drugs on the fetus remains a problem, the study authors state. This is because previous studies of the relationship between the use of antibiotics during pregnancy and the risk of miscarriage were quite controversial. Some scientists have found a link between the use of certain classes of antibiotics during pregnancy and miscarriage, while others have not confirmed this.

Advantages of using the database

In the new study, the researchers examined data on the course of pregnancy among women from Quebec between 1998 and 2009. This database contains information about pregnant women within the province, which was covered by the Government of Quebec's plan for drug insurance. The database includes data on the vast majority of pregnant women in the province.

Thus, the researchers were confident that they used accurate information about the prescriptions for antibiotics prescribed for future mothers, which allowed them not to depend on women's ability to remember what medications they used, since this is a less reliable indicator.

What antibiotics are dangerous for pregnant women

The researchers compared the cases of more than 8,700 women who had suffered a miscarriage within the first 20 weeks, from 87,000 women, whose pregnancies had no complications. The age of women in the study ranged from 15 to 45 years. It turned out that about 12 500 of them took antibiotics during pregnancy.

The study showed that five classes of antibiotics - macrolides, quinolones, tetracyclines, sulfonamides and metronidazole - can increase the risk of miscarriage if the woman is at an early stage of pregnancy. The scientists noted that one macrolide antibiotic, erythromycin, was not associated with this risk.

These data are consistent with the results obtained in some previous studies, but the relationship between the intake of fluoroquinolones and tetracyclines and the risk of miscarriage was not previously detected. However, at present, obstetricians do not recommend the use of fluoroquinolones and tetracyclines in the early stages of pregnancy, and these results indicate that such advice makes sense.

Low risk

"Although the study showed an increased risk of miscarriages in women who took certain types of antibiotics, in itself it is low," says Professor Berard. The use of many other drugs, such as non-steroidal anti-inflammatory drugs and antidepressants, was also associated with a similar increased risk of miscarriages.

Decreased risk of miscarriage

Another good news is that the common antibiotic, nitrofurantoin, which is most often prescribed if a woman has urinary tract infections, was actually associated with a reduced risk of miscarriage compared to the control group. This study is the first one that indicates this connection, therefore in the future scientists will have to confirm this new conclusion.