Antibiotics During Pregnancy Linked to Miscarriage

As if being pregnant did not come with enough worry, a new study found that certain antibiotics are linked to an increased risk of spontaneous abortion, or miscarriage — a terrifying finding for any expectant mother.

The study, published in the Canadian Medical Association Journal, compared rates of miscarriage with the prescription of certain types of antibiotics to treat maternal infections during pregnancy. By definition, a spontaneous abortion, or miscarriage, is the loss of an unborn child before the 20th week of gestation.

The research team from the Université de Montréal used data from the Quebec Pregnancy Cohort from the years 1998 and 2009. The cohort is a combination of four databases that house data on approximately 290,000 pregnancies during those years, including information on pregnancy histories, socioeconomic factors, lifestyle data, and more.

In the years studied, there were 8,702 miscarriages suffered by women between 15 and 45 years of age. For each miscarriage, ten other pregnancies (for a total of 87,020 "controls") were included to develop meaningful statistical data using the large population of information available. Of the women who miscarried, 1,428 women had taken antibiotics during early pregnancy.

Overall, the risk of miscarriage for women who do not take antibiotics during early pregnancy is about 6 to 7 percent. The figures from this study indicate the risk of spontaneous abortion for women who took antibiotics in early pregnancy is boosted to 9 or 10 percent.

So What Does the Study Really Mean?

The study was extensive and incorporated a lot of data. In the end, it suggested that using certain antibiotics early in pregnancy are linked to an incrementally increased risk of miscarriage.

During pregnancy, women are exposed to pathogens like bacteria and viruses, just as they are when not pregnant. As a result, they may suffer a respiratory, urinary tract infection (UTI), or a sexually transmitted disease (STD). Antibiotics are frequently used to treat these common infections.

While the take-home point of this study seems frightening, the study also noted that use of erythromycin and nitrofurantoin, often prescribed for UTIs during pregnancy, are "not associated with an increased risk of spontaneous abortion." Other commonly used drugs like penicillins and cephalosporins were also not deemed high risk during pregnancy.

So what was deemed a high-risk prescription? The study linked "quinolones, tetracyclines, sulfonamides, and metronidazole" with an increased risk of miscarriage. Doctors prescribe these antibiotics for various types of infections.

The study authors also noted possible confounders, or issues, that could cloud their findings include some lifestyle choices like smoking or alcohol use.

They also noted the severity of infections suffered could have affected their findings. The infections could have been severe enough to impact the viability of pregnancy, so a miscarriage could have occurred not from antibiotic use but due to the infection they were trying to treat.

We feel confident that confounding by infection severity cannot fully explain our findings, although residual confounding cannot be completely ruled out.

Pregnancy & Infections — They Happen

Because pregnancy causes big hormonal swings, UTIs are not rare during pregnancy, and there is not much you can do if you are prone to them when pregnant. There are other steps you can take to stay out of the way of pathogens during pregnancy and reduce the chance that you will need a prescription.

Despite best efforts, germs get around and infections happen. Summed up, advice from the Centers for Disease Control and Prevention for avoiding illness during pregnancy includes:

• Wash your hands frequently, especially around food, young children, or sick people.
• Avoid unpasteurized products.
• Do not handle cat litter, rodents (pet or wild), or their droppings.
• Work with your doctor to stay current on vaccinations.
• Get tested for STDs and avoid infection, as well as get informed about group B strep.

Points on preventing infections during pregnancy from the CDC.

The biggest danger to you, or your unborn child, is poor medical care during pregnancy. Be sure to see your healthcare practitioner regularly and ask about the right antibiotics for you, should you have an infection.

On balance, the danger caused by an antibiotic, in most cases, is far less than the damage, potential miscarriage, or early delivery caused by an untreated maternal infection. As the saying goes, "healthy mom, healthy baby."

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