 Nausea and vomiting of pregnancy (NVP, or morning sickness) are associated with a decreased risk.Several possible causes have been suggested for morning sickness but there is still no agreement.NVP may represent a defense mechanism which discourages the mother's ingestion of foods that are harmful to the fetus; according to this model, a lower frequency of miscarriage would be an expected consequence of the different food choices made by women experiencing NVP.