Intense pregnancy-related nausea and vomiting affects about 0.3% to 3% of pregnancies. It exposes the mother to dehydration, electrolyte and metabolic abnormalities and serious complications. The woman loses weight, usually with a loss exceeding 5% of her pre-pregnancy weight. This vomiting is resistant to dietary measures, as well as to doxylamine, a first-choice H1 antihistamine (despite its limitations) in mild nausea and vomiting in a pregnant woman.
Priority treatment of severe vomiting during pregnancy consists of non-drug measures, chiefly parenteral rehydration combined with rest.
Of the antiemetic drugs with proven efficacy in other situations, metoclopramide is the one for which we have the longest experience during the first trimester of pregnancy, with no major signal of an increased malformation rate. But after the first trimester, the long-term consequences of exposure to metoclopramide are not known.
If metoclopramide proves ineffective, corticosteroids should be used with caution, and only exceptionally and for a very short period, with a rapid reduction of the dose. Ondansetron does not appear to be more effective than metoclopramide, but during the first trimester of pregnancy it does seem to expose the unborn child to a risk of sometimes severe malformations. The use of some drugs, such as domperidone, metopimazine, alizapride, droperidol and haloperidol, should be ruled out altogether (pregnancy or not), because they expose patients to disproportionate or insufficiently known adverse effects.
©Prescrire 1 February 2020
"Severe vomiting with dehydration during pregnancy. Antiemetics have little place" Prescrire Int 2020; 29 (212): 48-49. (Pdf, subscribers only).
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