Selection criteria and Study selection
Studies were selected if the pregnancy outcomes of RPL couples with
abnormal chromosomal were reported. RPL couples had two or three more
miscarriages before 20 weeks. Carriers were defined as the chromosomal
abnormalities in any one of the couples with RPL. Chromosomal
abnormalities included structural and numerical abnormalities and
excluded normal polymorphisms such as pstk, qh and pss. Karyotype
analysis was the technological means used to distinguish carriers and
noncarriers. The PGD was performed in a polar body biopsy or blastomere
biopsy using either fluorescent in situ hybridization (FISH),
comparative genomic hybridization (aCGH) or a single nucleotide
polymorphism array (SNP) array. The primary outcome was the live birth
rate (LBR) per couple, and secondary outcome was the miscarriage rate
per couple. All the cohort studies described the pregnancy outcomes
after natural conception or after PGD for carriers and noncarriers. Two
independent investigators (S.L. and JJ.H.) extracted the data and
compared the results, and all disagreements were resolved by discussion.