What Are the Causes of Nausea in Pregnancy?

Nausea occurring during pregnancy, commonly called “morning sickness,” is an uncomfortable and annoying byproduct that can strike at any time of day. You may or may not vomit, and the symptom can begin as early as two weeks into the pregnancy; atthough, it is usually limited to the first trimester. Charles Q. Choi, from MSNBC Health, reports that, despite the discomfort “morning sickness” causes pregnant women, it may indicate a positive sign of a healthy pregnancy.

Human Chorionic Gonadotropin

hCG, or human chorionic gonadotropin, is a hormone produced by the placenta in early pregnancy. OTC pregnancy urine dipstick tests and your health care provider confirm pregnancy by the elevation of hCG levels in the urine and blood. According to Dr. Goodwin in “Nausea and Vomiting of Pregnancy: State of the Art 2000,” the hormone rapidly rises to its peak concentration around the first eight to 12 weeks of pregnancy. This time period directly associates with the maximal amount of nausea experienced through the first trimester.


Another hormone also dramatically rising in early pregnancy is estrogen, which helps maintain pregnancy and stimulate maturation of the fetus. The Mayo Clinic suggests that increased levels of estrogen cause the stomach to empty more slowly, which, in turn, may be the culprit causing nausea.

Sensitive Nose

An enhanced and heightened sense of smell experienced by pregnant women can also cause uncomfortable nausea. Things undetected by other noses can be overwhelmingly strong for you, and these aromas may initiate the gag reflex. Cigarette smoke, certain perfumes or raw and cooked foods are common triggers of nausea.

About this Author

Based in Chicago, Jojo Genden is passionate about sharing her health and wellness expertise through writing since 2008. She holds a Bachelor of Science in biology from Rockford College, and a Bachelor of Science in nursing from Edinboro University of Pennsylvania. Genden is a registered nurse in the state of Illinois with a background in intensive care.