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.