The purpose of this study is to

1. Identify a cut-off for the ratio of the serum proteins soluble FMS-like Tyrosine Kinase 1 (sFLT-1) and placental growth factor (PlGF) that identifies women will who develop preeclampsia with severe features within 2 weeks of testing (clinically positive) from those who do not develop preeclampsia with severe features within 2 weeks of testing (clinically negative) among preterm pregnant women with hypertensive disorders of pregnancy.

   And

2. To validate the cut-off the ratio of sFLT-1 and PlGF and to validate the performance of the automated assays used to find the cut-off. Test performance includes positive predictive value, negative predictive value, sensitivity, and specificity.

Subjects will provide blood, urine, and saliva samples at the time of enrollment. Samples will be frozen for batch assessment of sFLT-1 and PlGF levels by automated assays. Clinicians, subjects, and researchers will be blinded to protein level assessment, therefore assay results will not affect clinical management.

Preeclampsia is a leading cause of maternal and fetal morbidity and mortality in the US, and affects about 5% of pregnancies. Despite its morbidity, preeclampsia is challenging to distinguish from worsening chronic hypertension or gestational hypertension. Furthermore, it is challenging to identify who among those with hypertensive disorders of pregnancy will develop preeclampsia with severe features, including kidney, liver, pulmonary, or cerebral injury. The only definitive treatment is delivery of the placenta, and therefore the fetus, which can lead to severe morbidity and mortality to the neonate if delivery is very premature. New methods of risk stratification are needed to identify who among women with hypertensive disorders of pregnancy are at risk of developing preeclampsia with severe features in order to allocate resources (e.g. betamethasone and magnesium for fetal neuroprotection) accordingly.

Several serum proteins (sFLT-1 and PlGF) correlate well with the development of preeclampsia, particularly with preeclampsia with severe features, and may be used to predict the development of preeclampsia with severe features within a certain timeframe. The goal of this study is to identify a cut-off of the sFLT-1/PlGF ratio using automated assays that differentiates women who will develop preeclampsia with severe features from those who will not among women with hypertensive disorders of pregnancy within 2 weeks of testing. The secondary outcomes include time to delivery, the performance of the cut-off to predict adverse maternal and adverse fetal outcomes, and a comparison of the performance of the cut-off with clinical and laboratory factors per American College of Obstetricians and Gynecologists (ACOG) guidelines. Investigators will also look at the levels of sFLT-1 and PlGF in the urine and the saliva to determine if they correlate well with serum levels and may provide a less invasive alternative to serum samples.

Inclusion Criteria:

• Signed informed consent in a pregnant woman ≥ 18 years of age.
• Gestational age 23+0 to 34+6/7 weeks
• Singleton pregnancy
• Hospitalized with (or develop while hospitalized) a hypertensive disorder of pregnancy (preeclampsia, chronic hypertension with or without superimposed preeclampsia or gestational hypertension) as defined by ACOG guidelines.

Exclusion Criteria:

• 1. Patients who have received intravenous heparin within 24 hours of enrollment. Low dose subcutaneous heparin or low molecular weight heparin (LMWH) for prophylaxis of deep venous thrombosis (DVT) is permitted.
• Patients who are currently participating in another clinical trial to evaluate a new therapeutic intervention or who have participated in another such trial in the previous 30 days.
• Multiple gestations.

The study population includes women with singleton pregnancies at 23+0 to 34+6/7 weeks gestational age who are hospitalized with (or develop while hospitalized) a hypertensive disorder of pregnancy. Minors and patients who have received intravenous heparin within 24 hours of enrollment or who have participated in a therapeutic interventional study in the last 30 days will be excluded.