When trying to conceive, the main vitamin recommended to take is folic acid, as it helps with the development of the baby's nervous system in the early stages of pregnancy. It is advised to start taking folic acid about 3 months before trying to get pregnant. Your partner can also take steps to improve fertility, such as not smoking, maintaining a healthy weight, managing stress, and reducing alcohol intake. It is important to prioritize these lifestyle changes for both partners before considering any additional supplements.