Inclusion Criteria:  Suffer from 3 consecutive pregnancy losses or three failed embryo transfers characterized by no achieved pregnancy or solely biochemical pregnancies after 3 cycles with minimum 1 embryo transfer of a good-quality embryo in each cycle.  Exclusion Criteria:  Age <18 or >45 years AMH <4.0 pmol/l unless donor egg in previous cycles Significant uterine malformation Known endometrial pathologies including intrauterine endometriosis, adenomyosis, hyperplasia or polyps Known chromosomal abnormalities Pregnancy >9 weeks of gestation at the time collecting the blood sample