Causes of Morning sickness

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The exact cause of morning sickness is unknown, but it is probably linked to hormone changes that occur naturally in pregnant women. There is a sudden rise of a hormone called human chorionic gonadotrophin (HCG) during early pregnancy, which controls the production of other pregnancy hormones. Levels of this hormone rise rapidly during the first six weeks, are greatest at approximately 10 weeks, and begin to fall at approximately 12 weeks.

Symptoms can be made worse by emotional stress, some foods, smells, fumes, smoke, or travelling. Some researchers think that pregnant women become more sensitive to smells as a natural protective measure; it may makes them more aware of things in the environment that are harmful for the unborn baby.

Morning sickness is associated with a healthy pregnancy, and is linked to a lower miscarriage rate and larger healthier babies. It is uncertain why this is the case; one hypothesis suggests that reduced food intake at the beginning of the pregnancy causes a corresponding increase in the size of the placenta, which ensures better nutrition for the baby for the rest of the pregnancy, reducing the risk of miscarriage.