
Extremely common, pregnancy nausea is one of the most unpleasant symptoms of pregnancy. Approximately 70-80% of all pregnant women will experience mild to moderate nausea and about 50% will experience vomiting.
While this symptom is normally referred to as morning sickness, only 17% of pregnant women will experience nausea only in the morning. Nausea will more often occur throughout the day - morning, noon, and night.
Generally pregnancy nausea begins around week 8, but it can start much earlier in some women. By week 13 the severity usually reduces, but it can continue in some women for longer. Hospitalisation is needed for women who have continuous severe vomiting which may cause dehydration and further pregnancy complications. This type of severe pregnancy nausea is referred to as hyperemesis gravidarum.
It is still not clearly understood why nausea and vomiting occur in such a natural process as pregnancy. However, considering the commoness of this complaint, there has to be a very good reason why so many women have such an unpleasant start to an event which is so joyous.
One theory behind pregnancy nausea is that it offers a protection against foods that may be contaminated with pathogens or contain chemicals that can be harmful to the developing embryo or fetus. This therefore explains why women commonly have a strong aversion to raw meats, seafood, coffee, eggs, alcohol, cigarette smoke, and strong smelling vegetables.
However, the nausea and vomiting often continue, suggesting other reasons for its occurrence. Human and animal studies have shown reduced energy intake early in pregnancy is associated with increased placental weight. This suggests therefore, that as nausea and vomiting reduce energy intake, placental growth is stimulated, ensuring a healthy and developed placenta is established. Further research is still needed in this area.
Other theories behind the cause of nausea and vomiting in pregnancy include hormonal changes, stress, fatigue, hunger and blood glucose level changes.
While the reasons behind nausea and vomiting in pregnancy are not clear, women who experience it have a significantly lower risk of miscarriage than those who do not. Other positive outcomes that have been reported include decreased risk of preterm birth, low birth weight and perinatal death.
Part two discusses ways to effectively manage your pregnancy nausea.
References available upon request