One of the main vitamins considered useful in pregnancy is Vitamin B6. Doctors do prescribe multi-vitamin capsules during pregnancy and most of the time; a pregnant woman can fulfill her needs with these. But in case this does not appear to help there are a lot of other foods that will fulfill the need.
Cereal is a particularly rich source of Vitamin B6 as is banana, baked potatoes, salmon and spinach. One thing that must be kept in mind is that potato contains a lot of pesticide and may not be healthy for mother or child. Hence either organic potato must be used or they must be abandoned altogether.
Ginger is another food that seems to be very adept at reducing nausea. In fact ancient Indian sages recommended a healthy glass of ginger milk when pregnant. Another spice that can help is the clove. Just chewing on one slowly reduces the nausea.
Pregnancy is a joyous time and need not be hampered by nausea if the correct steps are taken.