Phentermine is a prescription appetite suppressant used for short-term weight management. It works by influencing the central nervous system to reduce hunger and can increase energy expenditure. When considering any medication during pregnancy, it is important to understand its potential effects on the developing fetus and the pregnant individual.
Phentermine Use During Pregnancy: Current Guidance
Phentermine is not recommended for use during pregnancy. The U.S. Food and Drug Administration (FDA) classifies phentermine as a Pregnancy Category X drug. This means studies show fetal abnormalities or clear human fetal risk, where the risks outweigh any potential benefits. Intentional weight loss during pregnancy offers no benefit and may harm the fetus, as minimum weight gain is recommended.
Potential Risks to Mother and Baby
The primary reason phentermine is not recommended during pregnancy stems from its classification and the general medical guidance against weight loss during gestation. Phentermine is a sympathomimetic amine, sharing pharmacological activity with amphetamines. While extensive human studies on phentermine alone during pregnancy are limited, information from studies on stimulants or other anti-obesity medications can provide some context. Some available data on phentermine exposure in early pregnancy do not consistently suggest an increased chance of birth defects.
However, other reports link anti-obesity drug use, including phentermine, to infants being larger for gestational age or having a higher birth weight, potentially leading to delivery complications like shoulder dystocia. Concerns have also included thickened heart valves and brain cysts in exposed infants, though a direct causal link is not established. One case report also correlated phentermine use with stroke in a developing fetus.
For the pregnant individual, phentermine’s known side effects include increased heart rate and elevated blood pressure, posing additional health risks during pregnancy. There may also be an increased risk of gestational hypertension, especially with higher stimulant doses. Some studies on stimulant use during pregnancy suggest associations with preterm birth and low birth weight, though specific data for phentermine are not conclusive.
Essential Steps for Pregnant Individuals
Individuals who discover they are pregnant while taking phentermine should discontinue the medication under healthcare provider supervision. An immediate consultation with an obstetrician or prescribing physician is necessary for personalized advice, considering medication exposure timing and duration.
Given that many birth defects can develop early in pregnancy, often before a person is aware of their pregnancy, individuals using phentermine who are planning to conceive should consider using effective contraception. Healthcare providers can then guide individuals on appropriate weight management strategies during pregnancy. These strategies typically involve a balanced nutritional plan and suitable physical activity, rather than pursuing intentional weight loss. A minimum weight gain is generally recommended for all pregnant individuals to support healthy fetal development. Maintaining open communication with healthcare providers ensures comprehensive prenatal care and contributes to a healthy pregnancy outcome.