Around the third or fourth week after conception -- week five or six of pregnancy -- many women begin to experience periodic nausea, often called morning sickness. The primary cause of this nausea is that hormone levels rise quickly in early pregnancy. The hormone hCG is one of those most directly responsible for morning sickness.
HCG
The hormone hCG, or human chorionic gonadotropin, isn't one you normally have circulating in your bloodstream if you're not pregnant. Instead, it's produced by tissues in your developing baby and helps to let your body know that you're pregnant. A developing baby starts secreting hCG within just a few days of conception, and levels of the hormone rise quickly, doubling around every 48 to 72 hours.
HCG Effects
HCG has many effects upon your body, but the one most directly responsible for feelings of nausea and queasiness is that hCG slows your digestive tract significantly, explain Heidi Murkoff and Sharon Mazel in their book "What To Expect When You're Expecting." This helps you to extract nutrients from your food more efficiently, but it also means food sits in your digestive tract longer, which can lead to nausea.
HCG and Health
Thankfully, as uncomfortable as morning sickness can be, it's actually associated with improved maternal and fetal outcomes. A 2000 study conducted by Dr. Samuel Flaxman and Dr. Paul Sherman, published in the "Quarterly Review of Biology," notes that morning sickness appears to reduce exposure of both mother and baby to environmental toxins. As such, women with high hCG who experience more morning sickness tend to have healthier babies.
Time Frame
HCG levels start rising as early as the third week of pregnancy and generally reach levels sufficient to cause symptoms by the sixth week. Murkoff and Mazel explain that while over half of all pregnant women will experience morning sickness to some degree, most will have fewer symptoms, if any at all, by the twelfth week of pregnancy, as their bodies becomes accustomed to the higher hormone levels.
Prevention/Solution
Because you can't control your hCG levels, there's nothing you can do to prevent morning sickness, but you can treat symptoms and help to lessen the severity. Murkoff and Mazel recommend ginger, either eaten in food or in the form of a tea or candy. They also recommend eating several small meals throughout the day, since keeping your blood sugar stable seems to help reduce symptoms of nausea.
References
- "What to Expect When You're Expecting"; Heidi Murkoff and Sharon Mazel; 2008
- "Quarterly Review of Biology"; Morning Sickness: A Mechanism for Protecting Mother and Embryo; Samuel Flaxman and Paul Sherman; June 2000
