Morning Sickness in Early Pregnancy
Pregnancy morning sickness is believed to be caused by the hormonal, metabolic and chemical changes that take place during early pregnancy. Beginning around six weeks after the first day of your last menstrual cycle, and lasting until the second trimester, nausea can strike at any time and affects between 60 percent and 80 percent of pregnant women. However, women who are carrying twins or other multiples, or who are feeling slightly run down are more likely to experience pregnancy morning sickness.
While you may be feeling everything but grateful about this classic symptom, scientists believe there is an upside to morning sickness. Studies have shown that women with little or no nausea or vomiting are two to three times more likely to miscarry because their levels of pregnancy-related hormones may not be high enough to support a pregnancy. (Some good news to take to the bathroom with you!)
Note: Some scientists believe pregnancy morning sickness serves as a defense mechanism that encourages pregnant women to avoid alcohol, tobacco, coffee and other substances that could be harmful to their developing babies. There's just one small issue with this theory: human genetic evolution has occurred over thousands of years, but most of the substances that pregnant women feel queasy have only been around for the last few hundred years. Hmmmm...