Morning sickness is not confined to the morning: nausea can occur at any time of the day, though it most commonly occurs soon after waking, perhaps due to the fact that the stomach is empty at that time.
Morning sickness usually starts in the first month of the pregnancy, peaking in the 5th to 7th weeks, and continuing until the 14th to 16th week. For 50% of all sufferers, it ends by the 16th week of pregnancy.
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