Association between gestational age at delivery and lymphocyte-monocyte ratio in the routine second trimester complete blood cell count

Background: We aimed to determine whether routine second trimester complete blood cell (CBC) count parameters, including neutrophil-lymphocyte ratio (NLR), lymphocyte-monocyte ratio (LMR), and platelet-lymphocyte ratio (PLR), could predict obstetric outcomes. Methods: We included singleton pregnancies for which the 50-g oral glucose tolerance test and CBC were routinely performed between 24 and 28 weeks of gestation in our outpatient clinic from January 2015 to December 2017. The subjects were divided into three groups according to their pregnancy outcomes as follows: group 1, spontaneous preterm births, including preterm labor and preterm premature rupture of membranes; group 2, indicated preterm birth due to maternal, fetal, or placental causes (hypertensive disorder, fetal growth restriction, or placental abruption); and group 3, term deliveries, regardless of the indication of delivery. We compared the CBC parameters using a bivariate correlation test. Results: The study included 356 pregnancies. Twenty-eight subjects were in group 1, 20 in group 2, and 308 in group 3. There were no significant differences between the three groups in neutrophil, monocyte, lymphocyte, and platelet counts. Although there was no significant difference in NLR, LMR, and PLR between the three groups, LMR showed a negative correlation with gestational age at delivery (r =-0.126, p =0.016). Conclusion: We found that a higher LMR in the second trimester was associated with decreased gestational age at delivery. CBC parameters in the second trimester of pregnancy could be used to predict adverse obstetric outcomes.