An sFlt-1:PlGF ratio of 655 is not a reliable cut-off value for predicting perinatal outcomes in women with preeclampsia.

Objectives: The ratio of soluble fms-like tyrosine kinase 1 (sFlt-1) to placental growth factor (PlGF) is increased in preeclampsia. This study evaluated perinatal outcomes in cases with an sFlt-1:PlGF ratio above 655.

Study Design: We retrospectively analyzed data from all consecutive women with singleton pregnancies who presented with clinically manifest preeclampsia and underwent immediate sFlt-1:PlGF assessment. Cases with an sFlt-1:PlGF ratio ≥ 655 were matched 1:1 for gestational age to controls with a ratio < 655.

Main Outcome Measures: The 5-min Apgar score and the arterial cord pH.

Results: There was a significant association of sFlt-1:PlGF ratios ≥ 655 with fetal distress (40% in cases vs. 3.3% in controls; p < .01) and neonatal sepsis (23.3% vs. 0%; p = .02), but not with impaired Apgar score (9 vs. 9 at 5 min; p = .45) or lower arterial cord pH (7.24 ± 0.09 vs. 7.26 ± 0.08; p = .73). Perinatal mortality (20% vs. 16.7%; p = .9), intrauterine growth restriction (IUGR; 30% vs. 13.3%; p = .2), and small-for-gestational-age fetuses (SGA; 30% vs. 16.7%; p = .35) were proportionally distributed among cases and controls. IUGR and SGA diagnoses were most common in cases with sFlt1:PlGF ratios ≥ 1000, as was respiratory distress.

Conclusions: An sFlt-1:PlGF ratio above 655 is not predictive of impaired perinatal outcomes, and insufficiently reliable for predicting outcomes in cases with clinical signs of preeclampsia. Our data suggest that an extremely high sFlt-1:PlGF ratio above 1000 might be more useful.