Hydrochlorothiazide Pregnancy and Breastfeeding Warnings

Brand names: Aquazide H, Carozide, Diaqua, Esidrix, Ezide, Hydro Par, HydroDIURIL, Inzirqo, Loqua, Microzide, Oretic

Hydrochlorothiazide Pregnancy Warnings

This drug should be used during pregnancy only if the benefit outweighs the risk to the fetus.

AU TGA pregnancy category: C
US FDA pregnancy category: Not assigned

Risk summary: No data are available on the use of this drug in pregnant women to inform a drug-related risk.

Comments: The routine use of diuretics during pregnancy is not indicated or recommended.

Animal studies have failed to reveal evidence of fetal harm. There are no data from controlled human studies, but retrospective reviews have shown an increased risk of malformations associated with thiazide diuretics. In addition, use of thiazide diuretics during pregnancy has been associated with fetal or neonatal electrolyte abnormalities, jaundice, and/or thrombocytopenia.

The Collaborative Perinatal Project monitored 50,282 mother-child pairs, of whom 233 were exposed to thiazide or related diuretics during the first trimester. An increased risk of malformations was found for thiazide diuretics. Use of thiazides after the first trimester does not seem to carry this risk. Thiazide diuretics may, however pose metabolic risks to the mother and fetus (hyponatremia, hypokalemia, thrombocytopenia, hyperglycemia), and may have a direct effect on smooth muscle, resulting in inhibition of labour.

Data from the U.S. Michigan Medicaid Birth Defects Study has revealed an association between the use of hydrochlorothiazide and congenital abnormalities. This was a retrospective study of 229,101 completed pregnancies between 1985 and 1992, of which 567 were exposed to hydrochlorothiazide at some time during the first trimester, and 1,173 were exposed to the drug at any time during pregnancy. Of the 567 pregnancies, there were 24 total and 7 cardiovascular birth defects (22 and 6 were expected, respectively). There were no observations of cleft palate, spina bifida, limb reduction, or hypospadias. The one instance of polydactyly did not achieve statistical significance. These data are consistent with an association between the use of hydrochlorothiazide and birth defects, although other factors, including underlying disease(s) of the mother are not accounted for.

Cases of neonatal thrombocytopenia associated with antepartum administration of thiazide diuretics have been reported.

AU TGA pregnancy category C: Drugs which, owing to their pharmacological effects, have caused or may be suspected of causing, harmful effects on the human fetus or neonate without causing malformations. These effects may be reversible. Accompanying texts should be consulted for further details.

US FDA pregnancy category Not Assigned: The US FDA has amended the pregnancy labeling rule for prescription drug products to require labeling that includes a summary of risk, a discussion of the data supporting that summary, and relevant information to help health care providers make prescribing decisions and counsel women about the use of drugs during pregnancy. Pregnancy categories A, B, C, D, and X are being phased out.

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Hydrochlorothiazide Breastfeeding Warnings

Manufacturer recommendation: Use is not recommended and a decision should be made to discontinue breastfeeding or discontinue the drug, taking into account the importance of the drug to the mother.

Excreted into human milk: Yes

According to LactMed this drug has been used without apparent harmful effects in the nursing infant at doses of 50 mg daily or less. Large doses may cause intense diuresis resulting in a decrease in breastmilk production.

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Further information

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