Peripheral natural killer cell activity as a predictor of recurrent pregnancy loss: a large cohort study

Objective: To determine the predictive value of preconceptional peripheral blood natural killer (pNK) cell activity in patients with recurrent pregnancy loss (RPL). Design: Cohort study. Setting: University department. Patient(s): A total of 552 patients with a history of two to six consecutive miscarriages. Intervention(s): None. Main Outcome Measure(s): The predictive value of preconceptional pNK cell activity for subsequent miscarriage was analyzed using multivariable logistic regression analysis, with age, number of previous miscarriages, and presence/absence of previous live births and bed rest as covariates. Result(s): Age and number of previous miscarriages, but not high pNK cell activity, were found to be independent risk factors for a subsequent miscarriage. No effect of bed rest and previous live birth on the likelihood of live birth was observed (odds ratios 1.28 [95% confidence interval 0.81-2.02] and 0.91 [0.52-1.59], respectively). Conclusion(s): Elevated pNK cell activity was found to not be an independent risk factor for subsequent miscarriage. Clinicians should not measure the plasma NK activity as a systematic recurrent pregnancy loss examination, because its clinical significance is yet to be established. (Fertil Steril (R) 2013;100:1629-34. (C)2013 by American Society for Reproductive Medicine.)