Relationship between vitamin use, smoking, and nausea and vomiting of pregnancy.

Background: Nausea and vomiting in pregnancy (NVP) is a common complaint but risk factors for NVP are not well characterized.

Methods: Occurrence of NVP was studied by questionnaires given to pregnant women at their first visit to the antenatal care unit and were returned around gestational week 28.

Results: Analysis of 3675 completed questionnaires was made.