Havent been taking prenatal vitamins regularly. how dangerous is this?

Depends on your diet: The main benefit of taking prenatal vitamins is to dramatically reduce the risk of neural tube defects (a birth defect) by taking adequate folic acid in the first month of pregnancy. However, if your diet has adequate folate or folic acid you'll be fine- it's found in many foods, esp. beans, greens & fortified cereals. Even if you did not take vits the risk is low-but folic acid lowers it greatly.