Is Bactrim Safe During Pregnancy?

What does the evidence say about bactrim during pregnancy?

1. ACOG considers sulfamethoxazole-trimethoprim a first-line option for urinary tract infections in the second and third trimester, and permits its use in the first trimester when no acceptable alternative is available. 1
2. A cohort study of 71,604 pregnancies found that first-trimester TMP-SMX use for a urinary tract infection was associated with a higher risk of overall congenital malformations, major cardiac defects, and cleft lip or palate compared with beta-lactam antibiotics, while nitrofurantoin and fluoroquinolone risk was comparable to beta-lactams; when TMP-SMX is medically necessary, the chapter describes the benefit as strongly outweighing the risk. 2
3. TMP-SMX should be avoided if feasible in the late third trimester because of a theoretical risk of newborn kernicterus, a severe form of jaundice, an entirely separate caution from nitrofurantoin, which is generally avoided closer to delivery, at 36 to 37 weeks, for a theoretical risk of newborn hemolytic anemia. 2
4. Trimethoprim may lower the level of folic acid in the body, so healthcare providers often recommend increased folic acid supplementation, in the range of 400 to 800 micrograms daily, during first-trimester use, and some earlier studies suggesting higher rates of heart, neural tube, or cleft defects lacked adequate controls for other factors. 3
5. Trimethoprim-sulfamethoxazole passes into breast milk only in small amounts and is considered acceptable during breastfeeding for healthy, full-term infants past the newborn period, but alternate antibiotics are recommended for infants with G6PD deficiency, jaundice, illness, or prematurity, because of a risk of bilirubin displacement and kernicterus. 4

Is bactrim safe in each trimester?

• First trimester. First-trimester use is generally reserved for when there's no acceptable alternative, since trimethoprim can lower folic acid levels right when neural tube development is happening. If your provider does prescribe it now, ask whether you should increase your folic acid intake, guidance points to 400 to 800 micrograms daily, while you're taking it.
• Second trimester. This is when ACOG considers Bactrim a first-line option for a urinary tract infection, alongside other antibiotics your provider may choose based on your urine culture and local resistance patterns.
• Third trimester. Still considered first-line earlier in the third trimester, but many clinicians shift away from it in the final weeks before delivery, due to a theoretical, unproven concern that sulfa antibiotics used right before birth could raise the chance of severe newborn jaundice.