Black women with high blood pressure during pregnancy have higher homocysteine levels

This difference may contribute to the higher rates of the hypertension condition known as preeclampsia among black women and indicate future risk for cardiovascular disease, said lead author Thelma E. Patrick, Ph.D., R.N., an assistant professor at the University of Pittsburgh School of Nursing and an assistant investigator at Magee-Womens Research Institute.

“There is a higher incidence of preeclampsia in black women and we know that when black women experience the disorder they are more likely to have a more severe form that shows up as early as six months into pregnancy,” Patrick said.

It’s unclear if the differences are due to diet, lifestyle or heredity.  But, since high homocysteine levels have been linked to diets low in folic acid and vitamins B6 and B12, Patrick said the finding suggests that it may be necessary to increase folic acid intake among blacks.

Epidemiological studies of non-pregnant populations have shown that too much homocysteine in the blood is related to a higher risk of coronary heart disease and stroke, though no causal link has been established, she said.

Blood homocysteine levels are strongly influenced by diet and genetic factors.  Folic acid and vitamins B6 and B12 help break down homocysteine.  Folic acid is found in green, leafy vegetables such as spinach, turnip greens and kale, while B6 and B12 come from grains and other types of food.  Folic acid, B6 and B12 can be found in prenatal vitamins.  Because low folic acid is also associated with birth defects in the nervous system, the United States requires cereal and bread to be fortified with folic acid.

Preeclampsia affects an estimated 3 to 5 percent of U.S. pregnancies.  The onset of the disorder is detected by an increase in blood pressure and can cause protein in the urine — a sign of potential kidney damage and severe water retention resulting in swelling in the hands and feet.  The condition can also affect circulation in the small vessels of the brain and the liver, causing headaches, double vision or abdominal pain.  Preeclampsia can endanger the lives of mothers and babies, and is a common reason for premature birth, Patrick said.

Researchers examined 85 white women and 78 black women who gave birth at Magee-Womens Hospital.  Thirty-four white women and 26 black women had preeclampsia.

The researchers found that homocysteine levels were higher in both black and white women with preeclampsia compared to those with uncomplicated pregnancies.  Black women with  preeclampsia had the highest homocysteine levels: 8.7 micromoles per liter (umol/L); while the levels were 7.6 umol/L for black women with normal pregnancy; 7.5 umol/L for white women with preeclampsia and 5.5 umol/L for white women without preeclampsia.

There were no differences in folic acid or B12 levels within racial groups, but there were differences in those levels between races.  Folic acid was higher in white women compared to black women, whereas B12 was higher in black women compared to white women, Patrick said.  That finding is intriguing because both folic acid and B12 are needed to break down homocysteine.

“I had assumed folic acid and B12 tracked until this,” she said.  “In searching the literature, I found a study of postmenopausal women that found the same thing: homocysteine was elevated in black women and their folate was down but their B12 was increased.”

The discovery of another study with similar results indicates that it probably is not a fluke, Patrick said.  “We need to test this further either through supplementation or by controlling diet or weight to see if the same thing happens,” she said. 

Co-authors are Robert W. Powers, Ph.D.; Ashi R. Daftary, M.D.; Roberta B. Ness, M.D., M.P.H.; and James M. Roberts, M.D.

The study was partly funded by the National Institutes of Health.