It will be wise to start taking multivitamins ahead of the pregnancy, since the  nerve system starts to develop in the first three weeks ( which is the time we are not aware of the pregnancy).

the best choice would be to take multivitamin for pregnant women, because the dosage of each mineral and vitamin is the correct one. Most of the dietary supplement companies offer such multivitamins which you can find in every health food shop and most pharmacies.

Farther more I suggest you take Omega 3 supplement which is good for the fetus's nerve system development and for preventing early labor, in some cases. 

Have a healthy good pregnancy.

Sharon