Very low maternal serum chorionic gonadotropin levels in association with fetal triploidy.

OBJECTIVE: The objective of this study was to identify the parental origin of the extra haploid set of chromosomes in triploid pregnancies and to correlate the parental origin to very low levels of human chorionic gonadotropin and unconjugated estriol levels (multiple of the median < or = 0.20) and normal alpha-fetoprotein levels.

STUDY DESIGN: Three triploid pregnancies were ascertained retrospectively, and three pregnancies were identified prospectively. Maternal sera samples were analyzed for levels of alpha-fetoprotein, human chorionic gonadotropin, and unconjugated estriol. Deoxyribonucleic acid analysis was performed on parental bloods and fetal fibroblasts in two prospectively identified pregnancies to establish the parental origin of the extra set of chromosomes.

RESULTS: Levels of alpha-fetoprotein were normal in all pregnancies. Levels of human chorionic gonadotropin were very low in five of six of pregnancies, and unconjugated estriol levels were low in three of six pregnancies. Deoxyribonucleic acid analysis indicated maternal origin of the extra haploid set of chromosomes in two triploids.

CONCLUSION: When the extra haploid set of chromosomes are maternally derived, some triploid pregnancies exhibit very low levels of maternal serum human chorionic gonadotropin and unconjugated estriol with normal levels of alpha-fetoprotein.