Methyl mercury, but not inorganic mercury, associated with higher blood pressure during pregnancy.

Prior studies addressing associations between mercury and blood pressure have produced inconsistent findings; some of this may result from measuring total instead of speciated mercury. This cross-sectional study of 263 pregnant women assessed total mercury, speciated mercury, selenium, and n-3 polyunsaturated fatty acids in umbilical cord blood and blood pressure during labor and delivery. Models with a) total mercury or b) methyl and inorganic mercury were evaluated. Regression models adjusted for maternal age, race/ethnicity, prepregnancy body mass index, neighborhood income, parity, smoking, n-3 fatty acids and selenium. Geometric mean total, methyl, and inorganic mercury concentrations were 1.40µg/L (95% confidence interval: 1.29, 1.52); 0.95µg/L (0.84, 1.07); and 0.13µg/L (0.10, 0.17), respectively. Elevated systolic BP, diastolic BP, and pulse pressure were found, respectively, in 11.4%, 6.8%, and 19.8% of mothers. In adjusted multivariable models, a one-tertile increase of methyl mercury was associated with 2.83mmHg (0.17, 5.50) higher systolic blood pressure and 2.99mmHg (0.91, 5.08) higher pulse pressure. In the same models, an increase of one tertile of inorganic mercury was associated with -1.18mmHg (-3.72, 1.35) lower systolic blood pressure and -2.51mmHg (-4.49, -0.53) lower pulse pressure. No associations were observed with diastolic pressure. There was a non-significant trend of higher total mercury with higher systolic blood pressure. We observed a significant association of higher methyl mercury with higher systolic and pulse pressure, yet higher inorganic mercury was significantly associated with lower pulse pressure. These results should be confirmed with larger, longitudinal studies.

Cord Blood Methylmercury and Fetal Growth Outcomes in Baltimore Newborns: Potential Confounding and Effect Modification by Omega-3 Fatty Acids, Selenium, and Sex.

BACKGROUND: Methylmercury (MeHg) may affect fetal growth; however, prior research often lacked assessment of mercury speciation, confounders, and interactions. OBJECTIVE: Our objective was to assess the relationship between MeHg and fetal growth as well as the potential for confounding or interaction of this relationship from speciated mercury, fatty acids, selenium, and sex. METHODS: This cross-sectional study includes 271 singletons born in Baltimore, Maryland, 2004-2005. Umbilical cord blood was analyzed for speciated mercury, serum omega-3 highly unsaturated fatty acids (n-3 HUFAs), and selenium. Multivariable linear regression models controlled for gestational age, birth weight, maternal age, parity, prepregnancy body mass index, smoking, hypertension, diabetes, selenium, n-3 HUFAs, and inorganic mercury (IHg). RESULTS: Geometric mean cord blood MeHg was 0.94 µg/L (95% CI: 0.84, 1.07). In adjusted models for ponderal index, ßln(MeHg) = -0.045 (g/cm(3)) × 100 (95% CI: -0.084, -0.005). There was no evidence of a MeHg × sex interaction with ponderal index. Contrastingly, there was evidence of a MeHg × n-3 HUFAs interaction with birth length [among low n-3 HUFAs, ßln(MeHg) = 0.40 cm, 95% CI: -0.02, 0.81; among high n-3 HUFAs, ßln(MeHg) = -0.15, 95% CI: -0.54, 0.25; p-interaction = 0.048] and head circumference [among low n-3 HUFAs, ßln(MeHg) = 0.01 cm, 95% CI: -0.27, 0.29; among high n-3 HUFAs, ßln(MeHg) = -0.37, 95% CI: -0.63, -0.10; p-interaction = 0.042]. The association of MeHg with birth weight and ponderal index was affected by n-3 HUFAs, selenium, and IHg. For birth weight, ßln(MeHg) without these variables was -16.8 g (95% CI: -75.0, 41.3) versus -29.7 (95% CI: -93.9, 34.6) with all covariates. Corresponding values for ponderal index were -0.030 (g/cm(3)) × 100 (95% CI: -0.065, 0.005) and -0.045 (95% CI: -0.084, -0005). CONCLUSION: We observed an association of increased MeHg with decreased ponderal index. There is evidence for interaction between MeHg and n-3 HUFAs; infants with higher MeHg and n-3 HUFAs had lower birth length and head circumference. These results should be verified with additional studies.

Selenium and maternal blood pressure during childbirth.

Evidence suggests selenium concentrations outside the nutritional range may worsen cardiovascular health. This paper examines the relationship between selenium and maternal blood pressure (BP) among 270 deliveries using umbilical cord serum as a proxy for maternal exposure levels. Multivariable models used linear splines for selenium and controlled for gestational age, maternal age, race, median household income, parity, smoking, and prepregnancy body mass index. Non-parametric analysis of this dataset was used to select spline knots for selenium at 70 and 90 µg/l. When selenium was <70 µg/l, increasing selenium levels were related to a non-statistically significant decrease in BP. For selenium 70-90 µg/l, a 1 µg/l increase was related to a 0.37 mm Hg (95% confidence interval (CI): 0.005, 0.73) change in systolic and a 0.35 mm Hg (0.07, 0.64) change in diastolic BP. There were very few selenium values >90 µg/l. Other studies indicate that the maternal/cord selenium ratio is 1.46 (95% CI: 1.28, 1.65). This u-shaped relationship between selenium and BP is consistent with a dual role of selenium as an essential micronutrient that is nonetheless a toxicant at higher concentrations; however, this needs to be studied further.

Body burdens of mercury, lead, selenium and copper among Baltimore newborns.

Umbilical cord blood or serum concentrations of mercury, lead, selenium and copper were measured with inductively coupled plasma mass spectrometry in a population of 300 infants born in Baltimore, Maryland. Geometric mean values were 1.37 µg/L (95% confidence interval: 1.27, 1.48) for mercury; 0.66 µg/dL (95% CI: 0.61, 0.71) for lead; and 38.62 µg/dL (95% CI: 36.73, 40.61) for copper. Mean selenium was 70.10 µg/L (95% CI: 68.69, 70.52). Mercury, selenium and copper levels were within exposure ranges reported among similar populations, whereas the distribution of lead levels was lower than prior reports; only one infant had a cord blood lead above 10 µg/dL. Levels of selenium were significantly correlated with concentrations of lead (Spearman's ρ=0.20) and copper (Spearman's ρ=0.51). Multivariable analyses identified a number of factors associated with one of more of these exposures. These included: increase in maternal age (increased lead); Asian mothers (increased mercury and lead, decreased selenium and copper); higher umbilical cord serum n-3 fatty acids (increased mercury, selenium and copper), mothers using Medicaid (increased lead); increasing gestational age (increased copper); increasing birthweight (increased selenium); older neighborhood housing stock (increased lead and selenium); and maternal smoking (increased lead). This work provides additional information about contemporary prenatal element exposures and can help identify groups at risk of atypical exposures.

Iron deficiency anemia and depleted body iron reserves are prevalent among pregnant African-American adolescents.

Anemia is prevalent among pregnant adolescents, but few data exist on biochemical indicators of iron status in this group. We hypothesized that among an at-risk population of African-American, pregnant adolescents, the degree of iron depletion and deficiency would be marked, and that iron deficiency anemia would comprise the majority of the observed anemia. To examine this, blood samples were collected from 80 girls (< or =18 y old) attending an inner city maternity clinic, 23 of whom were studied longitudinally in the 2nd and 3rd trimesters depending on contact at the clinic. Sample sizes for the biomarkers varied according to the blood volume available at the time the assays were completed. Descriptive statistics were applied to characterize iron status, and multivariate regression and logistic analyses were used to identify significant determinants of iron status. Depleted iron stores (ferritin < or = 15 microg/L) were indicated for 25% (n = 44) and 61% (n = 59) of adolescents during the 2nd and 3rd trimesters, respectively. Serum folate (39.3 +/- 15.4 nmol/L, n = 60), RBC folate (2378 +/- 971 nmol/L, n = 60), and serum vitamin B-12 concentrations (313 +/- 163 pmol/L, n = 60) were within normal ranges. Adolescents with serum transferrin receptor:serum ferritin ratios (R:F ratio) > 300 during the 2nd trimester were 12.5 times (95% CI 2.83, 55.25) more likely to be classified with iron deficiency anemia during the 3rd trimester (P = 0.0002) than those with lower ratios. Estimates of body iron were lower in those tested after wk 26 of gestation (P < 0.0001), and reserves were depleted in 5.0% vs. 31.3% of the 2nd (n = 40) and 3rd (n = 48) trimester cohorts, respectively. In conclusion, iron-deficiency anemia was prevalent among these pregnant minority adolescents. Targeted screening and interventions to improve diet and compliance with prenatal iron supplementation are warranted for this at-risk group.