Table 2.
Differences in FF between singleton and twin groups
| Fetal Fraction |
Mean ± SD |
Mean ± SD |
Difference (%)a | P |
|---|---|---|---|---|
| MZ + DZ (combined FF) vs. singleton | 12.6 ± 4.8 | 9.5 ± 4.1 | +3.1 (32.4) | <0.0001 |
| MZ vs. DZ (combined FF) | 12.0 ± 5.0 | 12.9 ± 4.7 | −0.9 (7.0) | <0.0001 |
| MZ (combined FF) vs. singleton | 12.0 ± 5.0 | 9.5 ± 4.1 | +2.5 (25.9) | <0.0001 |
| DZ (combined FF) vs. singleton | 12.9 ± 4.7 | 9.5 ± 4.1 | +3.4 (35.4) | <0.0001 |
| DZ (individual FF) vs. singleton | 6.4 ± 2.6 | 9.5 ± 4.1 | −3.1 (32.3) | <0.0001 |
Abbreviations: FF, fetal fraction; DZ, dizygotic; MZ, monozygotic; DZ (both), the sum of the two fetal fractions.
a
% Differences expressed relative to singleton (except MZ vs DZ expressed relative to MZ).