Pregnancy week by week

Nausea during early pregnancy, also called morning sickness, might be a good sign. Studies have shown that women with nausea and vomiting during the first trimester have a lower risk of miscarriage than do women without these symptoms.

What's the connection? Nausea and vomiting during early pregnancy might indicate you are experiencing the climb in hormones needed for a healthy pregnancy.

Research suggests that nausea and vomiting during pregnancy might be due to the effects of a hormone produced by the placenta called human chorionic gonadotropin (HCG). Pregnant women begin producing HCG shortly after a fertilized egg attaches to the uterine lining. Women with severe morning sickness (hyperemesis gravidarum) have higher HCG levels than other pregnant women do. Women pregnant with twins or multiples also have higher HCG levels and are more likely to experience morning sickness. Similarly, estrogen, another hormone that increases during pregnancy, is associated with an increase in the severity of nausea and vomiting during pregnancy.

However, high pregnancy hormone levels aren't consistently associated with nausea and vomiting.

It's also possible that nausea and vomiting during pregnancy are signs of viable placental tissue.

Keep in mind, however, that a lack of nausea and vomiting during pregnancy isn't cause for concern. Some women with healthy pregnancies never experience morning sickness.

• Miscarriage and stress
• Pregnancy acne