Vitamin E in pregnancy: evidence and safety

How does vitamin E work?

Vitamin E is a fat-soluble antioxidant that stops the production of reactive oxygen species formed when fat undergoes oxidation. Beyond that it takes part in immune function and, as shown mainly by laboratory studies of cells, in cell signaling, regulation of gene expression, and other metabolic processes. It also acts on blood vessels: endothelial cells replete with vitamin E better resist blood cell components adhering to the vessel surface, and vitamin E increases the expression of two enzymes that suppress arachidonic acid metabolism, raising prostacyclin release from the endothelium, which dilates blood vessels and inhibits platelet aggregation. That last pathway is the same action behind the coagulation concern at high doses, so the mechanism and the caution are two readings of one effect.

What does the evidence say about vitamin E in pregnancy?

• The RDA is 15 mg a day during pregnancy and 19 mg while breastfeeding, with an upper limit of 1,000 mg for anyone 19 or older. MotherToBaby is explicit that exceeding the RDA is not recommended unless a provider prescribes it. 1
• Vitamin E taken at the RDA and kept below the upper limit is not expected to raise the chance of birth defects. Two studies reported conflicting findings on heart defects, which MotherToBaby calls not enough information to draw conclusions from. 1
• Alpha-tocopherol is the only form of vitamin E recognized to meet human requirements, and high doses interrupt blood coagulation. Adults taking 400 IU (180 mg) of synthetic vitamin E every other day for eight years had an increased risk of hemorrhagic stroke. 2
• Across nine randomized trials of 19,810 pregnant women, vitamin C and E supplements produced identical preeclampsia rates to placebo: 9.6 percent in both groups, relative risk 1.00. 3
• Those same trials found more gestational hypertension in the supplemented groups (21.5 percent versus 19.4 percent) and more premature rupture of membranes (9.6 percent versus 5.6 percent), which is why high-dose vitamin E is no longer a routine recommendation. 3

What's on the label?

Alpha-tocopherol is the only form recognized to meet human requirements, and the liver's alpha-tocopherol transfer protein resecretes only that form out of everything absorbed from food. Natural and synthetic are not interchangeable by weight: the natural compound exists as a single stereoisomer while the synthetic version carries equal amounts of all eight, which makes synthetic alpha-tocopherol only half as active milligram for milligram. The IU conversions follow from that, with 1 mg of natural equal to 1.49 IU and 1 mg of synthetic equal to 2.22 IU. Most supplements supply 67 mg or more, which is 100 IU of natural vitamin E and already far above the 15 mg pregnancy RDA.

What should I know before taking vitamin E?

Please consult your healthcare provider before starting, stopping, or stacking supplements in pregnancy, especially if you take prescription medication, live with a chronic condition, or have a procedure or delivery scheduled. Herbal supplements are not required to demonstrate purity; brands that publish third-party test results give the most confidence in what is actually in the capsule.