Women's Health Specialists of St. Louis
Obstetrics and Gynecology

Articles - Morning Sickness

Most women will experience some nausea in pregnancy. In fact, morning sickness is often what most women recognize as a symptom of pregnancy. The symptoms usually begin five weeks after the last menstrual period, peak at ten weeks, and then abate by the end of the first trimester. In less than 5% of women, the symptoms will persist until term. Though called morning sickness, the discomfort may occur at any time or persist throughout the day. Often women will notice that there are certain triggers which cause symptoms. These triggers may include certain smells (smoke, food, and perfume), brushing teeth, physical motion (driving), and supplements containing iron (prenatal vitamins). It is not clear why morning sickness occurs in pregnancy and what benefit it has. Some have suggested that it may prevent women from making food choices that might be potentially harmful to the pregnancy during formation of the internal organs in the first trimester. It is also not clear as to which physiologic changes of pregnancy cause morning sickness. The severity of nausea is most closely associated with the rise in human chorionic gonadotropin (HCG). HCG is a pregnancy hormone which begins to rise around 5 weeks of gestation and reaches a peak at 10 weeks. This correlates well with when most women experience nausea in pregnancy. It also explains why nausea is often more severe in women with twin pregnancies or pregnancies that have an overproduction of HCG. It doesnt explain, however, why some women have severe nausea and vomiting in pregnancy despite having a normal pregnancy with normal levels of HCG. Interestingly, women who experience nausea in pregnancy are less likely to have a miscarriage. This is probably because the rise in HCG is an indication of a normal pregnancy.

Severe nausea and vomiting of pregnancy is referred to as hyperemesis gravidarum. This diagnosis is made when the vomiting is severe enough to require hospitalization for dehydration or if the patient losses 5% of her body weight. When women experience intractable vomiting, sources for other possible causes of vomiting will need to be investigated. Interestingly, even women who experience this level of vomiting will often give birth to healthy and normal weight babies. Women who have a history of severe motion sickness or an acute sense of smell are at greater risk for severe morning sickness. Other possible risk factors are chronic illnesses including depression. Management of morning sickness typically involves avoidance of triggers and dietary manipulation. Changes in diet may include eating small frequent meals (avoid having an empty stomach), eliminating spicy foods, and eating what sounds good. Some women may have a decrease in symptoms with 1 gram of ginger daily and/or supplements with vitamin B6 10-25mg three times daily. Though there is no treatment for morning sickness, anti-nausea medications are available. Thankfully, the majority of women will have resolution of symptoms by the first trimester. If nothing else, the saving grace is that these symptoms are most commonly associated with normal healthy babies.