Hyperglycosylated hCG and pregnancy failures

Considerable evidence indicates that one third of early pregnancy failures, spontaneous abortions and biochemical pregnancies, are due to chromosomal abnormalities, and two thirds are due to inappropriate implantation. These findings led us to investigate the role of hyperglycosylated hCG, an important pregnancy implantation signal, in pregnancy failures. We used urinary hCG determinations to evaluate a total of 127 pregnancies on the day of implantation, as marked by a positive urinary hCG. These included 81 normal term pregnancies, 18 spontaneous abortion pregnancies, and 28 biochemical pregnancies. Of the normal term pregnancies, the mean±standard deviation concentration of hyperglycosylated hCG was 5.4±4.3 mIU/ml equivalents, and the percentage of hyperglycosylated hCG was 88±17%. All term pregnancies produced hyperglycosylated hCG>51%. Of the 18 cases that spontaneously aborted, both the mean hyperglycosylated hCG (1.9±2.0 mIU/ml equivalents) and the percentage of hyperglycosylated hCG (41±33%) were significantly lower than in the normal pregnancy group. Only 4/18 spontaneously aborting pregnancies produced more than 51% hyperglycosylated hCG on the day of implantation. Similarly, of the 28 biochemical pregnancies, both the mean hyperglycosylated hCG (0.63±1.3 mIU/ml equivalents) and the percentage of hyperglycosylated hCG (21±29%) were significantly lower than in the normal pregnancy group. Only 4/28 pregnancies produced more than 51% hyperglycosylated hCG. Low hyperglycosylated hCG concentrations are associated with pregnancy failure. Whether this association is a primary cause of pregnancy failure or is simply a marker for an abnormal conceptus requires further investigation.