Nausea with or without vomiting in pregnancy is commonly referred to as morning sickness. American Family Physician, a peer-reviewed journal of the American Academy of Family Physicians, reports that about 80 percent of pregnant women are affected by morning sickness. Though hormones are sometimes thought to be the cause of morning sickness, the exact culprit has yet to be identified.
Human Chorionic Gonadotropin (hCG)
Human chorionic gonadotropin is a hormone released by the placenta that increases in a woman's body during pregnancy. The National Institutes of Health points out that rapidly increasing levels of hCG are thought to contribute to pregnant women's nausea early in pregnancy. Women carrying multiples may experience even more significant nausea and vomiting. The hCG levels tend to level off by the end of the first trimester, or about the 13th week of pregnancy. This is also the time when most women get relief from morning sickness.
Sense of Smell
A woman's senses become more acute very early in pregnancy. This includes her senses of taste and smell. BabyCenter.com points out that certain aromas may be unpleasant or overly strong during the early part of pregnancy. This can contribute to gagging or feeling nauseated.
Estrogen
Estrogen is another hormone that increases rapidly in the early part of pregnancy and is sometimes thought to be the cause of nausea. However, American Family Physician suggests that evidence to support hormones as the cause of morning sickness is still not strong enough to draw a definitive conclusion.
Stomach Issues
Digestive issues are common in pregnancy, and this can include a more sensitive stomach. BabyCenter.com suggests some women may respond to stress with nausea and vomiting. Other women may have a bacterial infection of the stomach called Helicobacter pylori. This bacterium has been linked to extended nausea and vomiting. When a woman feels nauseated she is likely to avoid food, especially protein. This can exacerbate the symptoms because the acids in the stomach have nothing to keep them active.
Dana Ericson, certified nurse midwife, recommends that pregnant women eat a protein-based snack every two hours. She recommends consuming between 90 and 110 grams of protein daily, especially during the first trimester. This amount helps to alleviate the mother's nausea and provides ample protein for the development of the placenta.
Molar Pregnancy
In some cases a woman may have more nausea or vomiting because of pregnancy abnormalities. The National Institutes of Health suggests that this can include molar pregnancy, which occurs when a rare mass forms in the uterus instead of a fetus. This condition is rare.
