Is spironolactone safe during pregnancy?

What does the evidence say about spironolactone during pregnancy?

1. Spironolactone is a potassium-sparing diuretic that's also prescribed off-label for hormonal acne and excess hair growth, and product labeling is split: some manufacturers advise against any use in pregnancy while others allow it when benefits outweigh risks. 1
2. Animal studies have linked early spironolactone exposure to feminization of male offspring because of the drug's antiandrogen activity, though it isn't yet known whether this translates to human pregnancies. 1
3. In a documented case, a pregnant woman who was accidentally given spironolactone 240 mg a day for one week at 16 weeks gestation delivered a healthy male infant with normal genitalia, since that exposure came after the window when external genitalia finish forming around 14 weeks. 2
4. Spironolactone is poorly excreted into breast milk, with a nursing infant estimated to receive only about 0.2% of the mother's daily dose, and documented breastfeeding cases haven't reported adverse effects in the infant. 3
5. Oral spironolactone produced roughly six times greater acne improvement than placebo across randomized trials, which is why it's a common off-label prescription for hormonal acne, though those trials were conducted in women who were not pregnant. 4

Is spironolactone safe in each trimester?

• First trimester. Spironolactone crosses into fetal circulation during the window when a male fetus's external genitalia are still forming, and animal research links early antiandrogen exposure to feminization. This is the highest-sensitivity period, so unplanned first-trimester exposure is worth a prompt call to your prescriber rather than a wait-and-see approach.
• Second trimester. External genitalia development is essentially complete by 14 weeks, and a documented case of a week-long accidental exposure at 16 weeks ended in a healthy, unaffected infant. That single case is reassuring but not proof of safety, so ongoing second-trimester use still needs your prescriber's sign-off.
• Third trimester. Human safety data specific to third-trimester spironolactone use are limited in the available literature. Product labeling is inconsistent, with some manufacturers advising against any use in pregnancy and others allowing it if benefits outweigh risks, so this stays a decision to make with your prescriber.