Nausea and vomiting in pregnancy

Nausea and vomiting in pregnancy (toxicosis): Your complete guide

Nausea, often called "morning" sickness, is one of the earliest and most well‑known symptoms of pregnancy. Although this condition can be very exhausting, in the vast majority of cases it is a sign of a healthy, normally developing pregnancy. It is not merely discomfort, but a complex physiological process indicating your body’s adaptation to the new state.

Why nausea occurs: Hormonal surge

The exact causes of toxicosis are still subject to scientific debate, but the main "culprit" is considered to be the hormonal surge that takes place in your body after conception. The key players in this drama:

• Human chorionic gonadotropin (hCG): This is the same "pregnancy hormone" that pregnancy tests detect. Its level rapidly doubles every few days in early weeks, reaching a peak around weeks 9‑10. It is believed that the high hCG level is the primary trigger of nausea.
• Estrogen: The level of this hormone also rises sharply and can intensify the feeling of nausea and heighten the sense of smell.
• Heightened sense of smell: Suddenly the smell of coffee, favorite perfume, or fried onions becomes unbearable? That’s also the work of hormones. Increased sensitivity to odors is a protective mechanism, but it also provokes nausea attacks.

There is also an evolutionary theory that toxicosis is a protective mechanism that shielded pregnant women from potentially harmful foods during the most critical period of fetal organ development. You can read about other pregnancy symptoms in our dedicated section.

When does it start and (the main question) when does it end?

Toxicosis usually begins around the 6th week of pregnancy, peaks roughly at week 9, and in most women gradually subsides by the end of the first trimester (approximately weeks 12‑13). The placenta takes over the main hormonal function, and the condition stabilizes. Effective ways to ease this condition are detailed in our recommendations and in the blog "10 ways to survive toxicosis".

Important: In a small number of women, nausea can persist into the second trimester, and sometimes even until delivery. It is important to distinguish ordinary toxicosis from the more serious condition — hyperemesis gravidarum, whose warning signs we discuss in a separate section.

Does toxicosis harm the baby?

This question worries every mother who cannot eat properly. Rest assured: with mild to moderate toxicosis your baby is completely safe. Nature is very wise: the fetus receives all necessary nutrients from your body’s reserves. That is why taking prenatal vitamins is so important during this period.