Avoid, if possible or use appropriately: Antibiotics in early pregnancy increases risk of spontaneous miscarriage.

courtesy: fortworthent.net

Use of certain antibiotics in early pregnancy increases the risk of miscarriage, says the results of new nested case control study published in current issue of Canadian Medical Association Journal on May 1, 2017.

Macrolides (excluding erythromycin), quinolones, tetracyclines, sulfonamides and metronidazole consumption increases the odds of spontaneous abortion during early pregnancy as compared to cephalosporin, penicillin or no antibiotics at all.

 Antibiotics are widely prescribed throughout pregnancy and existing literature provides conflicting views on their use.

Flory T. Muanda, M.D and her colleagues analyzed data from Quebec Pregnancy Cohort (1998–2009) and identified 182 369 pregnancies that met the inclusion criteria.

The women were between 15–45 years of age and was continuously covered by insurance for at least a year before the pregnancy. Out of these cohort of women, 8702(4.7%) suffered spontaneous pregnancy loss before 20 weeks of gestation and were considered as cases.

For every case ending in abortion, the researchers identified 10 control patients who matched the case by age, year of pregnancy and gestational dating.

Antibiotic exposure was identified by information obtained from Quebec Public Prescription Drug Insurance Plan. All women who filled atleast one prescription for any type of antibiotic between the first day of gestation and the abortion date or just before pregnancy but it’s use extended around the conception period were considered as exposed.

To study the baseline risk of abortion among the general population, a category was formed of patients who were pregnant with no antibiotic exposure.

About 12,446 (13%) patients consumed antibiotics during pregnancy, of which 1428 ended in spontaneous abortion (16.4% of all pregnancies ending in spontaneous abortion).

The mean gestational age at abortion was 14.1week.

Among the control group, 11,018 (12.6%) of patients were exposed to antibiotics.

Those women who had abortion were a year older than the control group, more likely to visited hospital ER and reported consuming more medicines in general.

Interpretation:

• After accounting for the confounders, it was seen that nitrofurantoin, erythromycin, penicillins, or cephalosporins were the safest to prescribe with no increased risk of abortion.
• Use of macrolides (excluding erythromycin), quinolones, tetracyclines, sulfonamides and metronidazole during early pregnancy was associated with an increased risk of spontaneous abortion.
• The odds of suffering spontaneous abortion were greatest with Norfloxacin (odds ratio 4.81) and Levofloxacin (odds ratio 3.28) as compared to no antibiotic.
• Safety of Nitrofurantoin supports its use as an alternative to trimethoprim–sulfamethoxazole for the treatment of urinary tract infection during pregnancy.
• The study findings supported the current guidelines of not using tetracyclines and quinolone class of drugs in pregnancy.
• Metronidazole exposure was also associated with 70% increased risk of spontaneous abortion, which is similar to a previous Medicaid cohort study that showed a 67% increased risk of spontaneous abortion.

The study has a very large sample size and documented information about exposure and the outcome, eliminating recall bias. The study design also minimized selection bias.

Severity of infection, tobacco/ alcohol use, folic acid intake may serve as confounders and may account for some of the findings, but the researchers took measures like using 2 active comparator groups to address these confounders.

The article full text can be accessed here.