A team of Danish researchers conducted a study to determine if there is a link between antibiotics and miscarriage. The findings reveal that miscarriage increases by an estimated 60 percent in women, who consume antibiotics throughout pregnancy.
The researchers focused on antibiotic use during early pregnancy ‘only’. The number of weeks the medicine was utilized was not factored into the study. Antibiotics are most often prescribed for over a 5 to 10 day period.
All pregnant women have a miscarriage baseline risk of 6 to 7 percent. So, if the pregnant female is not exposed to antibiotics during her pregnancy, she will still have a 6 to 7 percent risk of miscarriage. With antibiotic exposure, the risk factor increases to 9 to 10 percent, which is only a slight increase.
The research team examined the effects of infection on pregnancy and the link between antibiotics and miscarriage is several ways.
First, the multivariate model utilized for the study was adjusted accordingly for the existence and type of infection.
Second, the study restricted the study population to women with an infection and ‘users of antibiotics’, while comparing the effects of cephalosporin and penicillin on pregnancy.
Thirdly, the study was further restricted to only women, who had been diagnosed with a Urinary Tract Infection (UTI), the most common type of infection diagnosed in pregnant women. The restriction decreased the sample size, but the researchers were still able to see the estimates of risk (OR) were continual, increasing validity.
With the nature of the study, the researcher was not able to rule out that infection played a huge role in their findings. However, they were encouraged that their findings were consistent to previous studies and current health care guidelines, which specify that tetracycline and quinolone should not be taken during pregnancy.
Antibiotics have a unique mechanism of action, which varies from one type to another. Nonetheless, previous animal studies have revealed that some antibiotics may influence inflammation and DNA, which could account for the link between these drugs and miscarriage.
The findings reveal that erythromycin, Cephalosporin and Penicillin, the most commonly used antibiotics in pregnant women, are not connected with an increased risk of miscarriage. It was also discovered that nitrofurantoin (Macrobid), commonly utilized to treat UTI, actually decreases the risk of miscarriage – the researchers note that further studies are required to validate this finding, since this is the first study to reveal this discovery. The findings corroborated previous studies with the exception of nitrofurantoin.
The findings were also consistent with the health care guidelines, which state that tetracycline and quinolone should not be taken during pregnancy.
Infections must be treated during pregnancy, but clinicians need to carefully identify the safest and best treatment option. The researchers were reassured that the first line of antibiotics and treatment, cephalosporin and penicillin, for infections in pregnant women were not linked to increased risk of miscarriage.
The study was published in the journal CMAJ on May 1, 2017.