Lead associated with high blood pressure during pregnancy

A French study reports that higher lead levels measured in women halfway through their pregnancy are associated with pregnancy-induced high blood pressure.

A recent study links higher blood lead levels with high blood pressure in pregnant women, suggesting that lead exposure may increase the risk of developing hypertension during pregnancy.

All of the women in the study had blood levels below the level considered “acceptable” by most health agencies. The association suggests that the level – 10 micrograms per deciliter (µg/dL) – may need to be lowered.

Prior studies have associated elevated lead levels with hypertension and other indicators of vascular disease in women during late-pregnancy or those who are not pregnant. This new study is the first to find a similar relationship in mid-pregnancy.

Lead was measured in blood collected from 971 women between the 24th and the 28th week of gestation. Women were placed into the case or control groups based on monthly blood pressure measurements.

Of the subjects, 106 developed pregnancy-induced hypertension. Lead levels were significantly higher in those women when compared to the other women in the study.

Researchers reported that women with pregnancy-induced hypertension (PIH) had mean blood lead levels of 2.2 µg/dL relative to 1.9 µg/dL in women with normal blood pressure. According to national data (National Health and Nutrition Examination Survey), more than 25 percent of women have blood lead levels above 2.2 µg/dL in the United States.

In addition, every 1 µg/dL increase in blood concentration was associated with a 3-fold increase in the likelihood of PIH. The blood lead levels were weakly, but significantly, associated with systolic blood pressure.

Blood levels of other metals – cadmium, manganese and selenium – were also measured but only elevated lead levels were significantly correlated with blood pressure. This relationship persisted even after controlling for potential confounders, including dietary habits, smoking history, and socio-economic status.

Blood pressure normally rises in mid-pregnancy but approximately 10 percent of mothers-to-be develop PIH. The condition Increases the risk of preeclampsia which is characterized by high blood pressure during pregnancy accompanied by measureable proteins in the urine. It is also a risk factor for intrauterine growth retardation (abnormally slow fetal growth) and stillbirth. Preeclampsia can also lead to maternal seizures (also named eclampsia).

Lead exposure varies by region in the United States. It is higher in places with older buildings, because they are more likely to contain lead-based paint and plumbing capable of leaching lead. Areas with numerous industrial sites also can have higher environmental lead levels.

Lead can cause other health problems when exposure occurs at low levels, including memory impairment and increased risk of cancer.

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