Calcium deficiency has been associated with preeclampsia.²⁰ In numerous controlled trials, oral calcium supplementation has been studied as a possible preventive measure.^21 22 2324 While most trials have found a significant reduction in the incidence of preeclampsia with calcium supplementation,^212227282430 One study reported that calcium supplementation reduced both the severity of preeclampsia and the mortality rate in the infants.²³

An analysis of double-blind trials46 found calcium supplementation to be highly effective in preventing preeclampsia. However, a large and well-designed double-blind trial and a critical analysis of six double-blind trials concluded that calcium supplementation did not reduce the risk of preeclampsia in healthy women at low risk for preeclampsia.³² For healthy, high-risk (in other words, calcium deficient) women, however, the data show a clear and statistically significant beneficial effect of calcium supplementation in reducing the risk of preeclampsia.^{3228233623383940242443 44 4546}

The National Institutes of Health recommends an intake of 1,200 to 1,500 mg of elemental calcium daily during normal pregnancy.⁴⁷ In women at risk of preeclampsia, most trials showing reduced incidence have used 2,000 mg of supplemental calcium per day.²² Nonetheless, many doctors continue to suggest amounts no higher than 1,500 mg per day.

Pregnant women with preeclampsia have significantly lower plasma coenzyme Q10 levels, when compared with women with healthy pregnancies. In a double-blind study at women who were at high risk of developing preeclampsia, supplementing with coenzyme Q10 reduced the incidence of preeclampsia by 44%. The amount used was 200 mg per day; treatment was begun during the twentieth week of pregnancy and continued until delivery.³⁹

Women with preeclampsia have been shown to have elevated blood levels of homocysteine.^40,41,42,43 Research indicates elevated homocysteine occurs prior to the onset of preeclampsia.⁴⁴ Elevated homocysteine damages the lining of blood vessels,^{41,46,44,48,49,50,51} which can lead to the preeclamptic signs of elevated blood pressure, swelling, and protein in the urine.⁵²

In one preliminary trial, women with a previous pregnancy complicated by preeclampsia and high homocysteine supplemented with 5 mg of folic acid and 250 mg of vitamin B6 per day, successfully lowering homocysteine levels.⁴⁰ In another trial studying the effect of vitamin B6 on preeclampsia incidence, supplementation with 5 mg of vitamin B6 twice per day significantly reduced the incidence of preeclampsia. Women in that study were not, however, evaluated for homocysteine levels.⁵⁴ In fact, no studies have yet determined whether lowering elevated homocysteine reduces the incidence or severity of preeclampsia. Nevertheless, despite a lack of proof that elevated homocysteine levels cause preeclampsia, many doctors believe that pregnant women with elevated homocysteine should attempt to reduce those levels to normal.

Fish oil supplementation has been proposed to lower the incidence of preeclampsia.^52,53 However, controlled clinical trials suggest that fish oil does not reduce symptoms⁵⁴ or protect against preeclampsia.^55,56

Magnesium deficiency has been implicated as a possible cause of preeclampsia.^{57,58,59,60,61} Magnesium supplementation has been shown to reduce the incidence of preeclampsia in high-risk women in one trial,⁶² but not in another double-blind trial.⁵⁸

Women who are deficient in vitamin B2 (riboflavin) are more likely to develop preeclampsia than women with normal vitamin B2 levels.⁶³ These results were observed in a developing country, where vitamin B2 deficiencies are more common than in the United States. Nevertheless, insufficient vitamin B2 may contribute to the abnormalities underlying the disease process.

Women with preeclampsia have been shown to have elevated blood levels of homocysteine.^64,65,66,67 Research indicates elevated homocysteine occurs prior to the onset of preeclampsia.⁶⁸ Elevated homocysteine damages the lining of blood vessels,^{65,70,68,72,73,74,75} which can lead to the preeclamptic signs of elevated blood pressure, swelling, and protein in the urine.⁷⁶

In one preliminary trial, women with a previous pregnancy complicated by preeclampsia and high homocysteine supplemented with 5 mg of folic acid and 250 mg of vitamin B6 per day, successfully lowering homocysteine levels.⁶⁴ In another trial studying the effect of vitamin B6 on preeclampsia incidence, supplementation with 5 mg of vitamin B6 twice per day significantly reduced the incidence of preeclampsia. Women in that study were not, however, evaluated for homocysteine levels.⁷⁸ In fact, no studies have yet determined whether lowering elevated homocysteine reduces the incidence or severity of preeclampsia. Nevertheless, despite a lack of proof that elevated homocysteine levels cause preeclampsia, many doctors believe that pregnant women with elevated homocysteine should attempt to reduce those levels to normal.