[Blood manganese levels among pregnant women and the associated factors in three counties of northern China].

OBJECTIVE: To explore the levels of blood manganese concentration in pregnant women in 1st and 2nd trimester and the associated factors in three counties of northern China.

METHODS: We carried out a cross-sectional investigation in three counties of northern China in 2010. Two hundred and seventy three pregnant women whose gestational age was less than 28 weeks were recruited, their demographic characteristics and information on exposure to indoor air pollution from coal combustion and dietary during one month before pregnancy till the date of investigation were collected with questionnaires by face-to-face interview, their fasting venous whole blood samples were collected with vacuum blood collection tube containing heparin lithium at the Maternal and Child Health Hospital in the three counties. Their blood manganese concentrations were measured with inductively coupled plasma mass spectrometry (ICP-MS). Nonparametric tests were used to compare the concentrations among the groups and multivariate unconditional Logistic regression model was used to adjust the confounding factors.

RESULTS: The geometric mean of blood manganese of the women was 16.78 (95%CI: 16.14-17.45) μg/L, and the median (interquartile range) was 16.59 (13.68-20.44) μg/L. According to the reference range of general healthy adult female's manganese concentration in the whole blood 3.39-20.67 μg/L, the proportion of manganese concentration lower than normal, normal, higher than normal were 0%, 76.6% and 23.4%, respectively. Medians of blood manganese concentrations among the women in Yushe, Dai and Xianghe were 17.51 (13.96-22.04), 16.92 (13.78-21.45) and 15.43 (12.25-17.56) μg/L, respectively (P<0.05), and multivariate analysis found that the risk of higher than normal in Yushe County was 6.15 (95%CI: 1.21-31.35) times the risk in Xianghe county. Blood manganese concentrations were higher in women who were farmers, had lower income per month, and consumed more vinegar and less peppers, pork, beef and mutton during the month before investigation (all P<0.05), the adjusted odds ratio (AOR) between these factors and high blood manganese concentration were not statistically significant No statistical associations were found between blood manganese levels and indoor air pollution from coal combustion for both of crude odds ratrio (COR) and AOR (P>0.05).

CONCLUSION: The blood manganese concentration among pregnant women in the three counties is similar to the women in some other studies abroad and quite different from the findings of several domestic researches. The risk of blood manganese concentration higher than normal in Yushe county was higher than Xianghe county. The relationships between high manganese concentration and exposure to indoor air pollution from coal combustion or dietary need further research in the future.