Maternal and neonatal outcomes in pregnancies with sFlt-1/PlGF >85: exploring the predictive value of sFlt-1 and PlGF

To evaluate the outcomes of pregnancies with elevated soluble fms-like tyrosine kinase-1 to placental growth factor (sFlt-1/PlGF) ratios >85 and determine whether the individual components of the ratio are independently associated with adverse maternal and neonatal outcomes.

Retrospective analysis was conducted at a tertiary obstetric unit in central London, UK on singleton pregnancies with sFlt-1/PlGF ratios >85 recorded between November 2021 and February 2024.

Gestational age (GA) at pre-eclampsia diagnosis and delivery, birthweight, and indication for iatrogenic delivery were analysed in relation to the magnitude of the sFlt-1/PlGF ratio and the individual sFlt-1 and PlGF values. Non-linear regression modelling was applied.

Seventy five cases were included. The median interval from the first ratio >85 to delivery was 10 days. PlGF showed a non-linear association with GA at time of preeclampsia diagnosis, best described by a logistic growth curve (R² = 0.43). For GA at delivery, the relationship with PlGF followed an exponential growth curve, where lower PlGF was associated with earlier delivery (R² = 0.58). High sFlt-1 levels were significantly associated with maternal indications for preterm delivery, whereas low PlGF levels correlated significantly with fetal indications for delivery.

An sFlt-1/PlGF ratio >85 alone does not necessitate immediate delivery. Our findings suggest two potential overlapping pre-eclampsia phenotypes: high sFlt-1 aligning with maternal vascular dysfunction, and low PlGF indicating predominantly utero-placental disease. These findings support more tailored antenatal surveillance and management strategies based on the individual biomarker profiles, rather than the ratio alone.