It’s a conundrum as old as time itself: you have a pregnant female who presents with anything (abdominal pain, toothache, ingrown toenail) and you order a urinalysis. The results are frustratingly murky – a few bacteria, no white blood cells, no nitrites or leukocyte esterase. What’s a good provider to do?
There are three main types of urinary tract infections in pregnancy:
1. Asymptomatic Bacteriuria – these are infections with no symptoms that are caused by bacteria present in a woman’s system before she even became pregnant. This can lead to pyelonephritis if left untreated. Take-home message: bacteria in the urine? Treat.
2. Acute cystitis or urethritis – your bread and butter urinary tract infection
3. Pyelonephritis – when the UTI has spread to the kidney. This can lead to preterm labor if not treated appropriately.
For years the go-to antibiotic which was thought to have little side effect in pregnancy was Macrobid (nitrofurantoin). Unfortunately, that’s no longer the case (and hasn’t been for quite some time).
In 2009, a study concluded that nitrofurantoin was associated with birth defects, including cleft lip and hypoplastic left heart syndrome among others (1). There were some limits to the study; for instance, women were asked about antibiotic use after pregnancy so there was potential for recall bias, antibiotic prescribing was not confirmed by checking the medical record, etc. Importantly, other antibiotics (such as cephalosporins and penicillins) were not associated with an increased risk of birth defects.
Other studies, however, have found that first-trimester use of nitrofurantoin was not associated with any major malformations.
The American College of Obstetricians and Gynecologists (ACOG) has the following policy statement:
“Commonly used antibiotics, such as penicillins, erythromycin, and cephalosporins, have not been found to be associated with an increased risk of birth defects. However, the evidence regarding an association between the nitrofuran and sulfonamide classes of antibiotics and birth defects is mixed. As with all patients, antibiotics should be prescribed for pregnant women only for appropriate indications and for the shortest effective duration. Prescribing sulfonamides or nitrofurantoin in the first trimester is still considered appropriate when no other suitable alternative antibiotics are available…”
Bonus:
Remember that in pregnant women with G6PD deficiency, nitrofurantoin can cause hemolytic anemia.
Conclusion:
Reach for cephalexin (keflex), amoxicillin-clavulanic acid (augmentin), or erythromycin. Put down the nitrofurantoin and step away…
References:
1. Arch Pediatr Adolesc Med. 2009 Nov;163(11):978-85.
