Approximately 50 to 75 percent of pregnant women experience it ... and exactly zero percent enjoy it. Morning sickness is one of the most unpleasant side effects of pregnancy. Considered by many to be a misnomer (given the fact that the nausea and vomiting of pregnancy can hit at any time during the day or night—or all day and all night), morning sickness varies in intensity from person to person, and even from one pregnancy to the next. Nausea can kick in before four weeks gestation and usually tapers off right around the beginning of the second trimester at 13 weeks. For some women, though, queasiness lingers to some degree throughout the pregnancy, or comes and goes. "I was sick before I even knew that I was pregnant, and finally I went for a test," recalls Sherry Clouet of San Diego, California. "I was thrilled by the news of my pregnancy, but I felt just awful, spending most of my day lying on the couch resting between sprints to the toilet."
There's no known cause of morning sickness, although several factors are implicated. Some doctors believe that the sudden and dramatic physical changes that take place in a woman's body early in pregnancy could be behind the nausea.
The most widely accepted theory is that morning sickness is caused by the buildup of hCG (human Chorionic Gonadotropin) in the body. This hormone is produced after implantation occurs and continues to increase until about the twelfth week of pregnancy, at which point the levels begin to drop.
Others believe that morning sickness is caused by progesterone; the dominant hormone during pregnancy. Progesterone relaxes the muscles of the stomach, hence slowing down digestive processes and the emptying of the stomach, which leads to increased stomach acid.
Why Me but Not Her?
Most women experience some morning sickness, but the degree may differ greatly from one person to the next. Some are more sensitive to stimuli than others. A woman is more likely to have nausea or vomiting if these situations apply:
- She has a history of nausea/vomiting as a side effect from taking birth control pills. Increased levels of estrogens can cause the "queasies" even before pregnancy.
- She has a history of motion sickness.
- She suffers from nausea with migraines.
- She is pregnant with twins or multiples. The higher levels of hCG and hormones that accompany a twin or higher order multiple pregnancy can make nausea worse, although some women who are pregnant with multiples experience no nausea at all.
- There may be a genetic predisposition to morning sickness during pregnancy. Did your mother or sister have the "queasies?" If so, there's a higher chance you will, too.