These are questions for a qualified medical person. Sorry. We're just folks. When you're pregnant, everything changes. I can tell you that ginger and garlic aren't used for blood sugar really. They're used for a lot of things, but not so much that. Ginger, however, is a blood thinner, so again, you'll have to check with your doc. I know it's used for morning sickness so it's probably fine for at least temporary use, but as to regular use when pregnant, I just don't know. It's also an antiinflammatory and circulatory aid. None of the vitamins you mention will lower blood perssure. One B vitamin, niacin, might or it might not, but if you're pregnant, you have to be careful with it. And if you're going to miscarry, you have to be careful about blood thinners because there might be bleeding problems. Folate and DHA are always recommended for pregnancy, but again, if you're about to miscarry, you must follow your doc's advice. There are good blood pressure remedies. The main one is hawthorn, but is usually used with other herbs as well, but here we are again, some aren't probably good to take if you're pregnant. Good luck with it, hope you get the outcome you want, and find a caring professional who can expertly answer your very complex questions.
I would not be taking a vitamin E supplement. It alters blood clotting.
Garlic is relatively non-toxic and will reduce blood pressure.
I would ask your physician about taking 1000 mg of omega-3 fish oil.
Garlic doesn't lower blood pressure. It has been thought to fight cholesterol, but that hasn't shown up in recent studies. And fish oil, again, is a blood thinner, so I'd still be wary without speaking to a doc if this person is about to miscarry, with the attendant risk of bleeding.