Maternal Serum Magnesium Concentration And Fetal Growth: A Prospective Birth Cohort Study

ObjectivesTo understand the association between serum magnesium and cord blood serum magnesium concentration and birth weight in pregnant women in different pregnancy in order to provide a basis for reasonable diet and dietary supplement supplementation for pregnant women.MethodsThe birth cohort analysis was used and pregnant women who were admitted to the Maanshan Maternal and Child Health Hospital from May 2013 to September 2014 were selected as research objects to establish Ma'anshan Birth Cohort?MABC?.3474pregnant women were included that met the inclusion criteria.Questionnaires were collected during the early pregnancy and the second trimester,samples from pregnant women were colleted,and cord blood was collected at the time of delivery.In the analysis,39 cases of twins,75 cases of arrested embryo,45 cases of spontaneous abortion,30 cases of therapeutic abortion,10 cases of stillbirth,2 cases of ectopic pregnancy,8 cases of small for gestational age infant?SGA?,early pregnancy,and 7cases of pregnant women that lacked serum in early pregnancy,in the second trimester and in the umbilical cord were excluded and the number of women who were included in the analysis was 3 258.Mann-Whitney U test,Kruskal-Wallis H test and Bonferroni method were used to analyze the difference of serum magnesium concentration in early pregnancy,mid-term and cord blood of pregnant women with different demographic characteristics,and the differenceofserummagnesiumconcentrationindifferentpregnancy.Double-objective logistic regression model was used to investigate the effects of serum magnesium concentration in cord blood in early pregnancy and second trimester on low birth weight and small for gestational age infant.The restricted cubic spline model was used to analyze the association of serum magnesium concentration in cord blood?ln-Mg?with low birth weight and macrosomia after natural logarithm transformation.The percentile regression model was used to analyze the effect of percentile of serum magnesium concentration on birth weight of the newborn.ResultsThe study analyzed 2973 cases in the early pregnancy,3104 cases in the second trimester,and 2723 cord blood samples.The median concentration of magnesium in the second trimester was 20.44 mg/L,the concentration range of P₁₀0 to P₉₀0 was18.13-23.26 mg/L,the median concentration of magnesium in the second trimester was19.48 mg/L,and the concentration range of P₁₀0 to P₉₀0 was 17.21-22.15 mg/L,the median concentration of magnesium in the cord blood phase was 15.38 mg/L,the concentration range of P₁₀0 to P₉₀0 was 15.38-20.23 mg/L,showing a downward trend.The average birth weight of the infant was 3.36±0.45 kg,the average length of birth was50.01±1.99 cm,the fetal head circumference was 34.49±1.54 cm,and the chest circumference was 33.49±1.54 cm.Higher serum magnesium concentration in early pregnancy was affected by intrahepatic cholestasis and drinking habits;in the second trimester,older age,mainly physical labor and drinking alcohol became risk factors for higher blood magnesium in pregnant women;There was a statistically significant association between high serum magnesium concentration in cord blood and pregnant women with BMI<18.5 kg/m²before pregnancy,ICP,age more than 30 years,and preterm birth.High serum magnesium concentration in cord blood was a risk factor for low birth weight.The adjusted OR was 2.53?95%CI:1.20⁵.33?;the serum magnesium concentration in cord blood was above P₉₀(P₉₀=20.23 mg/L)and the adjusted OR value was 1.51 after SGA?95%CI:1.04 to 2.21?.The percentile regression model showed that the cord blood magnesium concentration was lower percentile?below 10%quantile?,and the change in cord blood magnesium concentration had a greater effect on the birth weight of the newborn.ConclusionsThe serum magnesium concentration of pregnant women showed a downward trend with the progress of pregnancy.Serum magnesium concentration in early pregnancy and second trimester has no predictive effect on low birth weight infants.Cord blood magnesium concentration higher than P₉₀0 is a risk factor for SGA.When the cord blood magnesium concentration is lower than the percentile,it has a greater impact on the birth weight of the newborn.