Many of the supplements you were taking while trying to conceive can be stopped once you get a positive pregnancy test. There may also be a few new ones you need to add.
The most important supplements to continue are a prenatal multivitamin and vitamin D. The supplements you can typically stop include DHEA, vitamin C, vitamin E, and melatonin. Whether to continue taking some of the other supplements depends on your specific circumstances, as covered in depth in chapters 1 through 8 of my new pregnancy book, It Starts with the Bump.
As one example, continuing with myo-inositol can be helpful if you have insulin resistance or PCOS because doing so can likely reduce the chance of miscarriage associated with insulin resistance. Taking myo-inositol in the second and third trimester can also help prevent and manage gestational diabetes.
Continuing NAC and/ or alpha-lipoic acid may be helpful if you have a history of miscarriage that may have been caused by immune or clotting issues. This is covered in more detail in chapter 6 of It Starts with the Bump, along with a discussion of the controversies over supplemental progesterone.
You may also need to add choline, omega-3s, calcium, and additional iron, with the dosage depending on your diet and in the case of iron, your lab tests. This is covered in chapters 1 through 3.
The book also covers many other important topics, such as managing the worry and anxiety that often crops up when you are pregnant after a difficult path, strategies to ease nausea, back pain, and other pregnancy symptoms, important lab tests, and exercises to help prepare for labor and delivery.