Nifedipine During Pregnancy: Safety and Uses

What does the evidence say about nifedipine during pregnancy?

1. Nifedipine is used during pregnancy for high blood pressure, irregular heartbeat, and chest pain, and separately, at a different dosing schedule, to briefly delay preterm labor before 37 weeks. 1
2. Research on first-trimester nifedipine exposure has produced mixed findings: some studies found a small increase in the risk of birth defects, while others found no increased risk, so the overall first-trimester risk is not clearly established. 2
3. In a study of preterm labor patients given oral nifedipine (30 mg followed by 30 mg every 6 hours for up to two days), labor was successfully delayed in 84.78% of cases, with the most common side effects being low blood pressure (18.84%) and a fast heart rate (14.49%), both described by the authors as easily managed. 3
4. A systematic review comparing nifedipine with other tocolytic medications found nifedipine extended pregnancy by an additional 11 percentage points beyond 34 weeks compared with ritodrine, with a safety profile that compared favorably with alternatives, particularly around the risk of fluid in the lungs. 4
5. Nifedipine passes into breast milk in small amounts, and no problems have been reported in nursing infants exposed this way, though uncontrolled high blood pressure itself carries serious risks, including harm to the placenta, kidneys, and heart, which is why stopping the medication without medical guidance is not recommended. 1

Is nifedipine safe in each trimester?

• First trimester. Nifedipine's first-trimester safety data is mixed. If you take it for chronic high blood pressure and become pregnant, don't stop on your own; your provider will weigh the uncertain data against the real risks of uncontrolled blood pressure.
• Second trimester. In the second trimester, nifedipine continues to be an option for blood pressure management, and providers may also reach for it briefly if preterm labor starts, though its use for labor is more of a third-trimester scenario.
• Third trimester. In the third trimester, short courses of nifedipine are commonly used to delay preterm labor for up to 48 hours, often to allow time for other interventions like corticosteroids for the baby's lungs, alongside its ongoing use for blood pressure if needed.