Morning sickness

Morning sickness, also called nausea and vomiting of pregnancy (NVP), affects between 50 and 85 percent of all pregnant women. It is also sometimes experienced by women who take birth control pills or hormone replacement therapy. It is not confined to the morning: nausea can occur at any time of the day, though it most commonly occurs soon after waking. There is insufficient evidence to pin down a single (or multiple) cause but the leading theories include:

• An increase in the circulating level of the hormone estrogen. Estrogen levels may increase by up to a hundredfold during pregnancy.
• An increase in progesterone relaxes the muscles in the uterus, which prevents early childbirth, but may also relax the stomach and intestines, leading to excess stomach acids.
• An increase in human chorionic gonadotropin.
• An increase in sensitivity to odors.
• Eating vegetables. One theory is that the small amounts of toxins vegetables produce to deter insect infestation are normally harmless to humans but extremely dangerous to embryos; therefore, becoming nauseated during pregnancy was an evolutionary measure to protect the embryo. Other studies, however, have linked consumption of fruits and vegetables to higher birth weights, which tend to mean healthier babies.

For 50% of all sufferers, it ends by the 16th week of pregnancy. Studies have shown that women who suffer from morning sickness are less likely to have miscarriages.