Chromosome and interphase analysis of placental mosaicism in intrauterine growth retardation.

Confined placental mosaicism is found in a higher percentage of cases of unexplained intrauterine growth retardation (IUGR) than in those of normal pregnancies. To test this hypothesis of cytogenetically abnormal placental cells associated with IUGR, we identified patients in whose fetuses IUGR was suspected during the antepartum period by clinical and serial ultrasonography and Doppler examinations and confirmed by immediate neonatal physical examination. At birth placental biopsy samples and cord blood were collected and coded. Similar specimens were obtained from non-IUGR pregnancies during that period to avoid bias in evaluation of results. These specimens were processed for standard cytogenetic studies and fluorescent in situ hybridization (FISH) of interphase cells to detect any chromosomal mosaicism in a double-blind fashion. Results were obtained on 26 IUGR placentas. Of these placentas, 22 were cytogenetically normal on standard karyotype analysis and interphase fluorescent studies. Four placentas were shown to have some chromosomal aneuploidy: one with the same chromosome anomaly in multiple cells and the other with multiple single-cell aneuploidy. Of these placentas, cytogenetic and FISH studies showed one to have a monosomy 21 cell line, two placentas showed mosaicism on karyotyping, which was not confirmed by FISH, and one placenta had a suggested chromosomal instability. All placentas had normal anatomy regardless of the chromosome findings and no chromosome anomalies were seen in any of the infants. Non-IUGR placentas showed no chromosomal-confined mosaicism and all had normal findings on placental pathologic examination.