MHRA (Medicines & Healthcare products Regulatory Agency)  has recently published a warning regarding the use of ondasetron in early pregnancy.leading to a small but significant risk of cleft lip. – LINK HERE

“Recent epidemiological studies report a small increased risk of orofacial malformations in babies born to women who used ondansetron in early pregnancy.^{1 4} Key evidence was an observational study of 1.8 million pregnancies in the USA of which 88,467 (4.9%) were exposed to oral ondansetron during the first trimester of pregnancy. The study reported that ondansetron use was associated with an additional 3 oral clefts per 10,000 births (14 cases per 10,000 births versus 11 cases per 10,000 births in the unexposed population).¹ These data were recently reviewed within Europe and considered to be robust.”

Patients with vomiting in early pregnancy requiring antiemetics you can review the guidance on “Hyperemesis Gravidarum”