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.