Diuretics, often called “water pills,” increase urine production to help the body eliminate excess fluid and salt. While commonly used to treat conditions like high blood pressure and heart failure, their use during pregnancy is generally avoided. Routine prescription of diuretics to manage the mild, common swelling that occurs during a healthy pregnancy is not recommended, as it poses unnecessary risks to both the mother and the developing fetus. Medical professionals only consider their use in rare circumstances where the mother has a severe, pre-existing condition and the benefits outweigh the potential harms.
Why Diuretics Are Generally Avoided
A healthy pregnancy requires a significant, natural increase in the mother’s circulating fluid volume, known as plasma volume expansion. This biological change is necessary to support placental perfusion and meet the metabolic demands of the growing fetus. By the late third trimester, total blood volume may increase by up to 45% above non-pregnant levels.
Fluid retention, or edema, is a common and expected side effect of this essential volume increase, affecting up to 80% of healthy pregnant women. Diuretics actively reduce the body’s fluid volume, directly interfering with this required physiological expansion. Reducing this necessary volume of blood and plasma could compromise the maternal-fetal circulatory system, making diuretics unsuitable for treating typical, mild swelling in a normal pregnancy.
Potential Risks of Diuretic Use During Pregnancy
The primary concern with using diuretics when not medically indicated is the potential for reduced blood flow to the placenta. Diuretics decrease the mother’s plasma volume, which reduces uteroplacental perfusion. This decreased blood flow is associated with restricted fetal growth because the fetus receives fewer nutrients and less oxygen.
Diuretics also pose significant metabolic risks for the mother. These medications can cause an imbalance of electrolytes, specifically low levels of potassium (hypokalemia) and sodium (hyponatremia). Electrolyte disturbances can affect the function of the mother’s heart and nerves. Specific types, such as thiazide diuretics, have been linked to maternal metabolic risks like hyperglycemia (high blood sugar).
Specific concerns exist regarding certain diuretic classes, such as spironolactone, which has antiandrogenic properties. This effect could impact the genital development of a male fetus, a concern raised in animal studies. Furthermore, diuretic use has been associated with neonatal complications, including thrombocytopenia (low platelet count) and jaundice in the newborn.
Managing Common Pregnancy Swelling Without Medication
For the mild to moderate swelling typical of pregnancy, several non-pharmacological strategies provide safe and effective relief. One effective method involves strategically elevating the legs above the level of the heart for 15 to 20 minutes, multiple times per day. This position allows gravity to assist the venous return of fluid pooled in the lower extremities.
Wearing medical-grade compression stockings is another recommended intervention. These stockings apply pressure to the legs, preventing fluid accumulation in the tissues and improving circulation. Expectant mothers should look for knee-high garments with a pressure rating between 15 to 20 mmHg and put them on early before swelling begins.
Maintaining adequate hydration is a beneficial approach, as it helps the body manage fluid balance efficiently. Reducing the intake of highly processed foods and excessive salt can also minimize water retention. Simple lifestyle adjustments, such as exercising gently and sleeping on the left side, further promote circulation by moving the enlarging uterus off the large vein that returns blood to the heart.
Medical Conditions Requiring Diuretics
Despite the general avoidance of diuretics, their use may be necessary and lifesaving in rare and serious maternal medical conditions. These situations involve conditions where the risk posed by the underlying maternal disease is far greater than the potential risks of the medication. For example, pre-existing severe cardiac disease, such as heart failure, may require a diuretic like furosemide to prevent a life-threatening complication such as acute pulmonary edema.
If a woman is already taking a diuretic for a chronic condition, such as hypertension, the medication may be continued or a safer alternative substituted under strict medical guidance. Sometimes, a diuretic is prescribed to replace another drug, such as an ACE-inhibitor, which is dangerous to the fetus later in pregnancy. These situations require close monitoring by high-risk specialists, including additional fetal growth scans, to ensure the baby is thriving despite the medication exposure.