Chromosome abnormalities in the placenta and spontaneous abortions.

Data are presented confirming that placental chromosome abnormalities are more important than fetal chromosome abnormalities in determining fetal loss. Improved methodologies for studying chromosome abnormalities in spontaneous abortion (SAB) are presented that include results for 141 cases (gestational ages 6-24 weeks) with karyotypic study on placental as well as fetal tissue. Experience in two laboratories gave a success rate of >90% of specimens with identifiable placental tissues, an average turnaround time of 10 days for those that produced chromosome results, male-to-female ratio of >50% (indicating no impact of maternal cell contamination), and 30% of cases had chromosome abnormalities. More significantly, two cases (5% of all abnormal cases) showed an abnormal karyotype limited to the placenta. This illustrates the need to examine the placenta in cases of SAB and the importance of technical issues in laboratory studies.