Help! My Prenatal Vitamins Make Me Sick!

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Many women find prenatal vitamins hard to stomach. I often have patients ask me if they have to take them.

The short answer is, “it depends.”

The necessity of taking prenatal vitamins depends on your nutritional status at the beginning of pregnancy. Are you well nourished, malnourished or obese?

In the U.S., if you are eating a normal, healthy diet, vitamin and mineral supplements are probably not required. When there is a problem with inadequate sources of vitamins or minerals, the first solution is a healthy diet.

However, a prenatal vitamin can be a very important part of your health during pregnancy.

If you are planning pregnancy, it is always a great idea to schedule a pre-pregnancy visit with your obstetrician. We want to make sure that you are up to date with all vaccinations and to check your blood count and iron level. If you meet certain criteria, it may be advisable to check your glucose levels and your levels of vitamin D.

The two most important ingredients of the prenatal vitamin are folic acid and iron.

Folic Acid

I personally feel that pre-conception folate supplementation will reduce birth defects and improve pregnancy outcome. Those of you who are planning pregnancy would do well to take a multi-vitamin with at least 400 ug of folic acid daily for at least a month prior to conception. If you had a prior pregnancy with spina bifida, we would advise 4,000 ug (or 4 mg daily).

Since we know that nausea is very common in the first three months of pregnancy, it would be wise to be sure that your body is well supplied with both macro and micronutrients prior to conception. This would help you to weather any temporary reductions in your food supplies.


Since you are building the blood volume of the fetus, you will need to provide about 1000 mg of iron to the fetal-placental unit over the 40 weeks of pregnancy. Much of this can be achieved with the correct diet, however, taking 30 mg of iron daily can be of great assistance. For some people the iron causes significant GI issues such as nausea or constipation. If your blood count is low, I would encourage you to take the additional iron, drink plenty of fluids and use stool softeners to help decrease unwanted side effects.

In addition to the folic acid and iron, it takes about 30 grams of calcium to build the fetal skeleton and most of this growth occurs during the last 10 weeks. Your diet and prenatal vitamin will certainly provide adequate reserves. Most women do get heartburn during their pregnancy. It is perfectly okay to use Tums or Rolaids and these antacids are loaded with calcium.

If you want to focus on food sources that have the needed vitamins, click here to visit the U.S. Department of Agriculture’s website which features an interactive diet-planning program specifically for women who are pregnant or breastfeeding.

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