The eGFRcystatin C/eGFRcreatinine-ratio is associated with maternal morbidity in hypertensive disorders in pregnancy and may indicate optimal timing of delivery.

A low eGFR_{cystatin C}/eGFR_creatinine-ratio is characteristic of a group of serious kidney disorders called 'Selective Glomerular Hypofiltration Syndromes'. This study examines if such a low ratio can also be used to evaluate the risk for women with hypertensive disorders in pregnancy to develop severe maternal morbidity. All women discharged from the perinatal ward at the Skåne University Hospital in Lund during the period of 1-9-2016 to 31-8-2017 under one of the diagnoses within hypertensive disorders in pregnancy were considered for inclusion in the study. After delivery and discharge from the hospital, records from included patients were reviewed and all registered measures of renal function were analysed. An eGFR_{cystatin C}/eGFR_creatinine-ratio ≤0.60 in a sample drawn not earlier than three days before delivery was considered as defining a high risk for severe maternal morbidity. A strong association (p-value: 0.035) between severe maternal morbidity and an eGFR_{cystatin C}/eGFR_creatinine-ratio ≤0.60 was found in a subgroup of 32 women diagnosed with 'preeclampsia with severe features'. A total of 69 women were included in the study. Fifty were defined as high-risk and seventeen of them (34%) developed severe maternal morbidity. Among the nineteen women defined as low-risk only two (10.5%) developed severe maternal morbidity (p-value: 0.051). A low eGFR_{cystatin C}/eGFR_creatinine-ratio seems promising as a predictive marker for maternal morbidity in hypertension in pregnancy. Its performance as a tool in the monitoring of progressing disease should be evaluated further in larger cohorts. Delivery before the eGFR_{cystatin C}/eGFR_creatinine-ratio decreases to, or below, 0.60 might help avoid maternal complications.