A prospective survey of serial maternal serum zinc levels and pregnancy outcome.

Serum zinc levels were monitored serially in pregnant women. Compared with those of age-matched nonpregnant women, their serum zinc levels were significantly decreased in the first trimester (p less than 0.005) and further decreased in the second trimester (p less than 0.005) but then remained unchanged until delivery. Cord blood zinc levels and the ratio of cord blood to maternal serum zinc at delivery were significantly higher in preterm than term (greater than or equal to 37 weeks) infants (p less than 0.05, p less than 0.05). The maternal serum zinc level in the second trimester was not related to the birth weights of the infants. Mothers with serum zinc levels of less than 65 micrograms/dl in the last trimester showed a higher incidence of birth weights of less than the 50th percentile (p less than 0.005) and also of less than the 25th percentile (p less than 0.005) on term delivery. The incidences of birth weights of less than the 10th percentile on term delivery were similar for mothers with serum zinc levels of greater than or equal to 65 micrograms/dl. This observation suggested that a relatively lower birth weight may be associated with lower maternal serum zinc levels in the third trimester, but an additional factor (factors) is also involved in the outcome of low birth weight infants.