What causes morning sickness

The feelings of nausea do not happen only in the morning. Most women find they ease as the day goes on, but, for some women, they may continue all day.

Nausea during pregnancy is normally associated with an increase in estrogen levels, low blood sugar counts, and a greater susceptibility to some smells.

The exact reason is unknown, but factors may include:

  • a rise in hormones, especially estrogen, progestorone, human chorionic gonadotrophin (HCG), and cholecystokinin, leading to changes in digestive activity
  • a fall in blood sugar, resulting from the placenta's need for energy

Another theory on what contributes to nausea in early pregnancy is related to the sense of smell. A woman's sense of smell is more sensitive in pregnancy, and this could increase the feelings of nausea.

It is most likely to occur during the first 3 months of pregnancy, and it often subsides once into the second trimester.

Research has suggested that nausea and vomiting during pregnancy are a good sign, and they are associated with a lower risk of pregnancy loss.