Objective: The purpose of this study was to investigate the frequency of confined placental mosaicism (CPM) in placentas from liveborn infants.
Study design: A retrospective analysis of 51 placentas from small-for-gestational-age (SGA), live born infants (birthweight below 5th centile), and 45 placentas from normally grown infants at term was performed. Aneuploidy for chromosomes 15, 16, and 18 was analyzed with QF-PCR (polymorphic markers) and FISH (centromeric probes).
Results: No trisomic sample was detected with either method. FISH revealed 1 case of monosomy 16 in the SGA group, which was not confirmed by PCR. On the other hand, PCR analysis showed allelic imbalances, ie, deviation of the 1:1 peak ratio > 20%, in 5 cases (4 in the SGA and 1 in the control group; P = .157).
Conclusion: Trisomic CPM in liveborn SGA infants is much less frequent than previously appreciated. The occurrence and eventual biologic significance of the observed allelic imbalances needs to be further investigated.