A Synopsis of AFP's "Nausea and Vomiting of Pregnancy"

A Synopsis of
Nausea and Vomiting of Pregnancy
HOWARD ERNEST HERRELL, MD, East Tennessee State University, Johnson City, Tennessee
Am Fam Physician. 2014 Jun 15;89(12):965-970
http://www.aafp.org/afp/2014/0615/p965.pdf

     Three quarters of pregnant women experience nausea and vomiting. It starts by week four, peaks by week nine, and resolves by the end of the first trimester. Risk factors include lower education, lower income, older patients, multiple gestations, a history of motion sickness, a history of migraines, and nausea associated with OCP use. When nausea and vomiting affect electrolyte levels, it is known as hyperemesis gravidarum. Patients may have up to three episodes of vomiting per day. The cause of nausea and vomiting is unknown but may be due to HCG levels. High levels of HCG are associated with multiple gestation, twin pregnancy, or molar pregnancy. If the nausea and vomiting is uncomplicated, it is related to a lower risk of miscarriage, a lower risk of preterm delivery, a lower risk of growth restriction, and a lower risk of fetal death. If there is weight loss associated with the nausea and vomiting (or refractory symptoms), then there is an increase risk of growth restriction or lower birth rate. Parenteral or enteral nutrition may be needed of the nausea and vomiting are sever enough to require hospitalization. 
     When a pregnant patient presents with nausea and vomiting, infection and surgical conditions are first ruled out. If the cause is dehydration, then fluid replacement is given. Thiamine is added if a dextrose containing solution is used (to protect against wernicke's encephalitis). The first therapy that is tried for nausea and vomiting is vitamin B6. If that does not help, then doxylamine is given. The combination of these two medications can reduce the symptoms by up to 70%. If the symptoms don't resolve then promethazine can be added. Dimenhydrinate may be substituted for doxylamine. If symptoms persist, then other medications are considered. Ondansetron has comparable effectiveness as promethazine, but it is expensive. Metoclopramide can be considered but there is a risk of tardive dyskinesia and should not be used earlier than 10 weeks gestation. Methylprednisolone may be helpful but is contraindicated for use before 10 weeks because of a risk of cleft lip.