Monday, July 25, 2016
Low maternal zinc concentrations during pregnancy increase the risk of premature birth
Zinc is important for the growth and development of cells in infants. Maternal zinc insufficiency during pregnancy predisposes to abortion, stillbirth, intrauterine foetal growth restriction, and premature birth. The risk for premature birth rises with maternal zinc insufficiency. A study published in The Journal of Nutrition focused on the association between maternal blood zinc concentration during pregnancy and the risk of premature birth.
The study was based on a large population-based birth cohort study that enrolled 3081 mother and single child pairs in China. Blood samples from 1069 pregnant women were collected in the 1st trimester (4–12 weeks of gestation), and 2012 samples were collected in the 2nd trimester. Blood zinc levels were analysed, and women were categorised as having low (less than 76.7 µg/dL), medium (76.7–99.6 µg/dL), or high (more than 99.7 µg/dL) zinc levels.
Factors such as age, body mass index (BMI) before pregnancy, the number of times the women were pregnant, or the monthly income was similar for all the 3 groups. Maternal zinc concentrations were lower in women with lower pre-pregnancy BMI (less than 18.5 kg/m2) compared to those with normal BMI (18.5–24.9 kg/m2). Maternal zinc concentrations were lower in women in the gestation period 33.0–34.9 and 35.0–36.9 weeks compared to those with a higher gestational age (more than 37.0 weeks of gestation).
As the maternal blood zinc concentration decreased, the risks of premature birth and low-birth-weight infants gradually increased. Risk factors such as the age of the mother during delivery, the number of times the women got pregnant, monthly income, or pre-pregnancy BMI were not associated with the risk of premature birth.
However, the risk of premature birth was associated with low and medium maternal zinc concentrations. Women with low or medium zinc concentration during the 1st trimester had a significantly higher risk of premature birth, while maternal zinc levels in the 2nd trimester did not influence the rate of premature birth.
The study indicated that maternal zinc concentration during pregnancy is inversely associated with the risk of premature birth. However, this study has some limitations. The cause for low maternal zinc was not investigated; the classification of pre-term birth was done based on the mother’s last menstrual period and not based on ultrasound scanning reports. Maternal micronutrient deficiencies, such as folate and vitamin D deficiency, which increase the risk of premature birth, were not investigated.