Nausea and vomiting in early pregnancy

Nausea and vomiting in pregnancy is commonly known as morning sickness and like all forms of nausea and vomiting it can be very distressing to the women who suffer from the condition.  It is generally treated conservatively.

The aetiology and risk factors associated with nausea and vomiting in pregnancy

Nausea and vomiting is a common phenomenon in early pregnancy, affecting between 50% and 90% of pregnant women.  The symptoms exhibit in the first trimester and peak during the ninth week of gestation^[1].  Morning sickness is generally not deleterious to either the foetus or the mother.  Indeed, it is reported to have positive effects on the pregnancy outcome, being associated with decreased risk of miscarriage, pre-term birth and perinatal death^[2].  There is some support for the hypothesis that morning sickness serves to protect the embryo by causing pregnant women to avoid potentially toxic foods^[3].

Nausea and vomiting in pregnancy is more common among women who are having their first pregnancy, are younger, overweight, less educated and those not employed outside the home^[1].  There is a strong correlation between previous intolerance to oral contraceptives and nausea and vomiting in pregnancy^[4].

Between 0.3% and 2% of pregnant women develop intractable vomiting, termed Hyperemesis Gravidarum (HG)^[5].  HG is associated with symptoms such as weight loss, dehydration and hypokalaemia.  Life threatening complications can occur including oesophageal rupture due to severe vomiting and retinal haemorrhage.  The growth of the foetus can be retarded and foetal death can occur^[6].

The causes of nausea and vomiting in pregnancy

The cause of nausea and vomiting in early pregnancy is not known although it is thought most likely to be hormonal ^[7].  The symptoms parallel the rise in human chorionic gonadotrophin, however a direct link with this hormone has not been established.

The aetiology of HG is also not clear but there are reports of an association of Helicobacter pylori infection (which contributes to gastric ulcers) with HG^[8].

The management of nausea and vomiting in pregnancy

The main management goal is to minimise the risk to the developing foetus, and this normally involves conservative management.  Thus the patient should avoid stimuli known to produce symptoms and should eat small meals more frequently.  Recumbent rest in a dark and quiet environment is often helpful.  In view of the concern over possible teratogenic risks, drug therapy is normally avoided.

The more serious condition of HG usually results in hospitalisation. The initial treatment is appropriate fluid and electrolyte replacement together with vitamins.  Anti-histamines or anti-muscarinics may provide some anti-emetic effect.  It has been advocated that Helicobacter pylori infection should be considered in intractable cases and appropriate antibiotics given^[6].

Summary

• Nausea and vomiting is a common phenomenon in early pregnancy that is commonly known as morning sickness.
• The cause of nausea and vomiting in early pregnancy is not known although it is thought most likely to be related to hormones.
• Nausea and vomiting in pregnancy is generally managed conservatively.
• Between 0.3% and 2% of pregnant women develop a condition of intractable vomiting, termed Hyperemesis Gravidarum (HG).
• The initial treatment of HG is appropriate fluid and electrolyte replacement together with vitamins.

References