- Women with any of the following co-morbidities: Autoimmune disorders (antiphospholipid antibody, lupus, rheumatoid arthritis, scleroderma), Cerclage in the index pregnancy, Diabetes mellitus—gestational or pre-gestational, Hematologic disorders (coagulation defects, sickle cell disease, thrombocytopenia, thrombophilia), Hypertension (chronic or pregnancy induced) before enrollment, HIV (human immunodeficiency virus), Institutionalized individuals (prisoners), Prior obstetric history of: [1) intrauterine growth restriction, 2) preterm birth before 34 weeks, 3) severe preeclampsia], eclampsia, HELLP syndrome, and 4) stillbirth after 24 weeks or neonatal death, Preterm labor or ruptured membranes before enrollment, Psychiatric disorder (bipolar, depression) on medication, Placenta previa / 3rd trimester bleeding, Renal insufficiency (serum creatinine > 1.5 mg/dL), Restrictive lung disease, Fetal red blood cell isoimmunization, Seizure disorder on medication, Thyroid disease on medication, Body Mass Index (BMI) above 40 kg/m2