A: Morning sickness varies from woman to woman and pregnancy to pregnancy. Some women experience classic "morning sickness" which happens in the morning hours, may or may not include vomitting, and is usually in the first 12 to 13 weeks of pregnancy. Some women experience more of an afternoon sickness, also in the first trimester. Some women have sickness the entire pregnancy. Morning sickness is neither a good or bad "symptom" and has no bearing on how healthy a pregnancy is....however, severe weight loss as a result of illness may be dangerous to a developing fetus and should be treated either at home or in a hospital setting.