Parental human leukocyte antigens and implantation failure after in-vitro fertilization.

At present, it is well accepted that maternal recognition of paternally derived fetal antigens occurs during normal pregnancy and may be beneficial for implantation and maintenance of gestation. Thus, we have investigated the compatibility of human leukocyte antigens (HLA) in couples with successive failed in-vitro fertilization (IVF) cycles. Study group 1 included 50 couples with prior primary infertility who had not achieved a pregnancy after > or = 3 (range 3-7, mean 3.7) IVF cycles where at least two embryos (mean 3.3, range 2-4) were transferred in each attempt. An infertile control group (group 2) included 50 infertile couples undergoing IVF with the same indications as couples in group 1, who achieved a viable pregnancy with their first IVF attempt. The results were compared with those found in a population sample including 100 men and 100 women from the local population (group 3). We found a statistically significant (P < 0.05) excess of HLA sharing (> or = 2 antigens) between partners in group 1 as compared to groups 2. There was a trend toward increased HLA sharing in group 1 when groups 1 and 3 were compared. We conclude that some cases of implantation failure after IVF and embryo transfer might be caused by underlying close histocompatibility between partners.