Nausea and Vomiting in Pregnancy

Introduction

Nausea and vomiting in pregnancy can lead to dehydration, electrolyte imbalances, and poor maternal nutrition, making treatment crucial 1

First-line treatments for nausea and vomiting of pregnancy include Vitamin B6 (pyridoxine) supplementation, Doxylamine-pyridoxine combination, and Phenothiazines, as recommended by the European Association for the Study of the Liver Clinical Practice Guidelines and the American College of Obstetricians and Gynecologists 2, 3
Second-line treatments include Metoclopramide and Ondansetron (only after 10 weeks gestation), with the combination of ondansetron and metoclopramide considered for enhanced antiemetic effect in severe cases 4, 3
Ondansetron 8mg should be used as a second-line therapy for nausea and vomiting in pregnancy, preferably after 10 weeks gestation, with recognition of a small increased risk of orofacial clefts (from 11 to 14 cases per 10,000 births) 1
The use of the lowest effective dose is recommended to minimize potential risks 1
Methylprednisolone may be considered as a last resort for severe hyperemesis gravidarum, as suggested by the American College of Obstetricians and Gynecologists and the European Association for the Study of the Liver Clinical Practice Guidelines 2, 3

There is a small absolute risk increase of orofacial clefts associated with ondansetron use, from 11 to 14 cases per 10,000 births (0.03% absolute increase) 1
The small absolute risk increase of orofacial clefts should be contextualized against the risks of untreated severe nausea and vomiting, which can lead to dehydration, electrolyte imbalances, and poor maternal nutrition 1
Ondansetron exposure in early pregnancy has been associated with a small absolute increase in risk of congenital defects, including orofacial clefts (0.03% absolute increase) and ventricular septal defects (0.3% absolute increase) 2
Metoclopramide has a better established safety profile in pregnancy, with no significant increase in major congenital defects in meta-analyses of large cohort studies 2, 1, 3

A baseline ECG should be considered before ondansetron use due to the risk of QT prolongation, as suggested by the European Society of Gastroenterology 5
Ondansetron may interfere with oral contraceptives, as noted by the European Society of Gastroenterology 5
Both ondansetron and metoclopramide should be used with caution in patients with cardiac conditions due to the risk of QT prolongation 4
Increased fetal monitoring, including detailed ultrasound examination during the second trimester, should be considered if ondansetron is used after the first trimester 2

Ondansetron may be considered for managing chemotherapy-induced nausea and vomiting (CINV) in pregnant cancer patients, particularly after the first trimester, as recommended by the National Comprehensive Cancer Network 2, 6, 7, 8, 9