What Can Cause Vomiting in Pregnancy?

Many pregnant women experience nausea and vomiting, a combination of symptoms typically known as morning sickness. Despite the fact that morning sickness is one of the most common side effects of pregnancy, medical professionals are still unsure about its cause. Some experts believe that vomiting in pregnancy is a byproduct of hormonal changes. Other possible causes include migraine headaches, genetics, or the heightened sensitivity to sensory stimuli that accompanies pregnancy in some women. Doctors and midwives can monitor a woman's nausea throughout her pregnancy and assist her in finding ways to manage the condition.

Vomiting in pregnancy often begins during the first trimester and typically continues into the second trimester, though some women may have difficulty with nausea during their entire pregnancy. One common explanation for the nausea is that a woman’s hormone levels change significantly during this time, although doctors aren’t sure of the exact mechanism by which the hormone level change contributes to nausea. It has been observed that raised levels of one hormone, human chorionic gonadotropin (HCG), coincide with episodes of nausea in pregnant women, suggesting a connection. Likewise, women who are pregnant with multiple fetuses have higher levels of HCG and often experience more severe morning sickness than women who are carrying only one fetus.

Another possible contributor to vomiting in pregnancy is the extra sensitivity to smells and tastes that many women experience during this time. This sensitivity can trigger nausea or vomiting if a woman is exposed to a food or smell that she finds unpleasant or distasteful. If a woman already has a sensitive stomach or a history of digestive problems, these conditions, plus an increased aversion to certain smells and tastes, can result in nausea or vomiting. There is also some evidence that vomiting in pregnancy has a genetic component, as women whose close female relatives experienced morning sickness during pregnancy often develop it as well.

Some medical professionals have noted that migraine headaches can appear or increase during pregnancy, although some women find that the headaches actually lessen during this time. As nausea is a common migraine symptom, an increase in migraine headaches during pregnancy can include an increase in nausea as well. Women who experience migraines or suspect that they have developed the condition during pregnancy should speak to their doctor about appropriate options for managing migraine episodes.

While inconvenient and uncomfortable, medical professionals generally consider vomiting in pregnancy to be a normal, temporary condition that can be treated with both dietary and lifestyle changes. Some women, however, develop a dangerous condition called hyperemesis gravidarum, in which excessive vomiting can lead to dehydration and malnutrition. A pregnant woman who feels that her vomiting is excessive should notify her doctor or midwife immediately for evaluation and treatment.