Table 2. Detection of paternally inherited HBB mutations in maternal plasma.

	HBB mutation				Maternal plasma analysis
Case	CD 41/42 (-CTTT)	IVS2 654 (C → T)	nt — 28 (A → G)	CD 17 (A → T)	Standard protocol	SABER	Fetal genotype†	Weeks gestation
1	F	M	—	—	Neg	Neg	*/*	11
2	—	F	—	M	Neg	Neg	*/*	18
3	F	—	—	M	Neg	Neg	*/*	21
4	M	F	—	—	Pos	Pos	F/*	18
5	M	—	F	—	Neg	Pos	F/M	17
6	F	M	—	—	Pos	Pos	F/*	11
7	F	M	—	—	Pos	Pos	F/*	14
8	F	—	—	—	Neg	Neg	*/*	7
9	—	—	—	F	Neg	Pos	F/*	12
10	M	F	—	—	Neg	Neg	*/*	17
11	F	—	—	—	Pos	Pos	F/*	20
12	M & F	—	—	—	N.A.	N.A.	*/*	18

All of the parents are carriers for β-thalassemia and have one HBB mutation. The maternal mutation is not indicated for cases where the maternal mutation is not one of the four HBB mutations studied. F and M, mutations of the father and mother, respectively; —, no mutation; Neg, negative; Pos, positive; N.A., not applicable.

^†The fetal genotype determined by conventional methods is indicated by the inheritance of the paternal mutation F, the maternal mutation M, or the normal allele, *