Fig. 1

The STR results of case 1–4. None of the STR loci of the amniocytes in four cases showed MCC. A In fetus 1, the chr2 had two STR loci. TPOX was a single peak with no information, and D2S1338 had three fluorescence peaks (19/21/24) with areas of 5246/1279/5020, and two (19 and 21, indicated by the blue arrows) were the same as the mothers’. B In case 2, the STRs of chr15 in uncultured amniocytes had three fluorescence peaks (12/14/21 with areas ratio of 1: 1: 0.4), and two (12 and 14, indicated by the blue arrows) were the same as the mothers’. The STRs of cultured amniocytes had two fluorescence peaks (12/14) with an area ratio of 1.2. C The STR showed a bias in area ratios of multiple bimodal peaks with higher paternal in case 3. The alleles ratios of paternal and maternal were about 1.3–1.5 and excluded the possibility of paternal heterodisomy. D In fetus 4, the four single-peak STRs of chr20 were identical to one of her mother’s alleles, indicating her maternal origin