Increased risk of preterm delivery with elevated maternal alpha-fetoprotein and plasma zinc levels in African-American women

Background. This study evaluated the relationship of maternal serum alpha‐fetoprotein (MSAFP) and plasma zinc levels (PZn) to pregnancy outcome. Methods. The subjects for this investigation consisted of 917 African‐American women, who on registration for prenatal care between 7–22 weeks gestational age (GA), had PZn levels determined and also had MSAFP recorded in their charts. Results. MSAFP levels greater than the 90th percentile significantly increased the risk of PTD (adjusted odds ratio or AOR=2.5, 95% C.I.=1.5−4.2) but not of IUGR. There was no significant relationship between maternal PZn level and PTD or IUGR. When subjects were stratified by MSAFP levels, in women with MSAFP greater than the 90th percentile, the AOR for PTD was 4.0 (95% C.I.=1.2−13.5) for women with PZn levels greater than the median vs. those with PZn equal to or less than the median. In women with MSAFP equal to or less than the 90th percentile, there was no such difference. Multiple regression analyses, using GA at birth as the dependent variable, indicated an interaction between MSAFP and PZn levels. Conclusion. In this population, the adverse pregnancy outcome associated with elevated MSAFP was seen only in women with PZn levels greater than the median. The reason for this association is not currently apparent.