First trimester maternal serum lysosomal enzymes: implications for carrier testing and prenatal diagnosis

Carrier detection for lysosomal storage diseases is sometimes possible by evaluating maternal serum levels of specific enzymes. However, lysosomal enzymes (LE) can be modified by maternal hormonal changes in pregnancy or embryonic contributions. Maternal serum was obtained prospectively in the follicular phase and at 2-5 and 7-11 weeks after conception from 13 infertility patients with precisely known ovulation dates. Eleven enzyme activities were determined fluorimetrically using 4-methylumbelliferyl substrates. Using repeated measures ANOVA, alpha-N-acetyl-glucosaminidase (p less than 0.05), hexosaminidase A (p less than 0.005) and hexosaminidase A and B (p less than 0.005) increased during the first trimester, and 8 enzymes did not change significantly. Our data show differing patterns of LE in the first trimester. These may be explained by: (1) variability of maternal reaction to hormonal changes of pregnancy, or (2) variable embryonic contributions suggesting differential ontogeny and placental transfer of these enzymes. The increase in levels of the 3 specific LE in maternal serum may interfere with the accuracy of carrier testing in early pregnancy, but pregnancy should not interfere with the other 8.