The exact cause of nausea and vomiting in pregnancy (NVP) is unknown. However, a number of theories have been suggested which are outlined below.
Hormones
Changes in hormone levels during the early stages of pregnancy may cause short-term nausea and vomiting.
During pregnancy, oestrogen levels rise and tend to be at their highest in the first three months, when the symptoms of NVP are at their worst.
Rising levels of oestrogen may heighten your sense of smell, which may explain why certain smells can trigger the onset of symptoms.
Evolutionary adaptation
Evolutionary adaptation is a change that occurs in an organism in order to make it better adapted to its environment.
Some scientists believe that NVP is an evolutionary adaptation that has occurred in order to protect women and their baby from food poisoning.
Pregnant women with NVP often do not feel like eating foods that can potentially become contaminated, such as meat, poultry, and eggs, instead preferring foods which have a low risk of contamination, such as bread, or crackers.
