The Relationship Of Maternal And Umbilical Cord Blood Zinc Level Associated With Small For Gestational Age Infants:A Birth Cohort Study

Objectives To describe the serum zinc（Zn）level in maternal and umbilical cord blood in Ma’anshan city and to explore the association between serum Zn level during pregnancy and cord blood with small for gestational age（SGA）.Methods Based on Ma’anshan Birth Cohort Study（MABC）,a total of 3 474 pregnant women were recruited from May 2013 to September 2014.Follow up the women during their first,second and third trimesters of pregnancy and use self-made questionnaire to collect information on social and demographic characteristics.Blood samples were collected in three pregnancy period and umbilical cord blood samples were collected at birth.3 243 mother-infant entered the final analysis.Serum concentrations of Zn was assayed by inductively coupled plasma mass spectrometry（ICP-MS）.Blood samples in the first,sceond,third trimester and cord blood we assayed were 2 957,3 087,2 925 and 2 707 cases,respectively.Serum Zn in maternal and umbilical cord blood were defined as low,medium and high level according to P25 and P75 of Zn level,respectively.We performed all statistical analyses with SPSS（version 13.0）.The wilcoxon symbolic rank sum test of paired samples was used to compare the differences of serum Zn level in first,second,third and umbilical cord blood.χ² test were used to compare continuous and categorical variables in groups,respectively.And multi-factor non-conditional logistic regression model was conducted to evaluate the association between serum Zn level in pregnancy and umbilical cord blood with SGA.Results Serum Zn level in P₅₀(P₂₅-P₇₅)during the first,second,third trimesters and cord blood were separately 1 016.18（907.09,1 145.60）,813.36（732.47,897.89）,814.96（723.21,920.47）,and 903.44（808.71,1 015.64）μg/L.The prevalence of Zn deficiency during maternal and cord serum was 1.5%（44/2 957）,15.9%（492/3 087）,19.8%（580/2 925）and 6.5%（176/2 707）,respectively.The prevalence of total SGA was 9.7%（314/3 243）.After maternal demographic characteristics and pregnant exposure adjusted,compared to high-level serum Zn group,low-level serum Zn group during first trimesters increased the risk of SGA OR（95% CI）was 1.51（1.04,2.18）.Then,after Hg and Cd concentration further adjusted,low-level serum zinc group during first trimesters increased the risk of SGA OR（95% CI）was 1.53（1.06,2.21）.There was no statistically significant association between low serum Zn concentration and SGA in the middle,third trimesters and umbilical cord blood group（all P>0.05）.The prevalence of total large for gestational age（LGA）was 16.5%（536/3 243）.Low-level serum Zn group during maternal and umbilical cord blood had no statistically significant effect on LGA,OR（95% CI）were 1.10（0.83,1.46）,0.84（0.63,1.12）,0.97（0.71,1.31）and 0.79（0.57,1.07）,respectively.Conclusion Zn nutritional status of pregnant women in Ma’anshan city is at a good level.The low serum Zn level in the first trimester increased the risk of SGA.