Objectives
The Neutrophil-to-Lymphocyte Ratio (NLR) is a recognised marker of inflammation and infection, but evidence regarding its role in pregnancy is limited.
Placental inflammation and infection is frequently implicated in spontaneous preterm birth (sPTB), particularly in the early preterm period when neonatal outcomes are poorest.
Our aim was to characterise NLR levels from routine booking bloods and prior to late miscarriage or early sPTB. We evaluated its relationship to placental histology, investigating its role as a simple, low-cost marker of inflammation.
Methods
This was a planned sub-analysis of a larger prospective cohort study investigating markers of sPTB. Our cohort was comprised of asymptomatic high-risk women attending a Prematurity Surveillance Clinic between 2002-2015, with late miscarriage or sPTB, available placental histology and timely blood results.
Placental histology was categorised as either inflammatory (e.g. chorioamnionitis) or non-inflammatory (reflecting normal or vascular pathology). NLR was calculated from routine full blood count (FBC) at booking and prior to delivery. Receiver Operating Characteristic (ROC) curves were plotted and Area Under the Curve (AUC) calculated for predicting inflammation.
Results
NLR was significantly raised at delivery compared to antenatal booking bloods (n=156, NLR 8.8 versus 3.69, p<0.0001, 95% CI 4.1 to 6.2).
70% (109/156) of women had inflammatory placental lesions. Mean delivery NLR was significantly raised compared to those with normal or vascular placentas (9.81 versus 6.53 p = 0.0021, 95% CI -5.35 to -1.21). Delivery NLR had AUC of 0.67 for predicting inflammation (SE 0.048, 95% CI 0.58 – 0.77)
Conclusion
In high-risk women, NLR is raised at early delivery, compared to booking. Delivery NLR is significantly higher in women with placental inflammation, compared to those with normal or vascular placental findings.
NLR, calculated from routine FBC may inform prognosis and management for women in threatened preterm labour.