Table 1.

Phenotyping tool used for analysis. Characteristics are labeled as “Strong”, “Moderate” and “Possible” evidence of each phenotype. The tool was applied to all women with SPTB and each subject could thus have Strong, Moderate and/or Possible evidence of more than one phenotype.

Phenotype	Strong Evidence	Moderate Evidence	Possible Evidence
Infection / Inflammationa	- Histologic chorioamnionitis or funisitis - Positive placental culture or presence of placental viral inclusions	- Clinical chorioamnionitis requiring intrapartum antibiotic treatment - Placental pathology positive for deciduitis villitis, microabscess, arteritis, and/or phlebitis	- Clinical endometritis requiring postpartum antibiotic treatment - Major antenatal maternal systemic infection (pneumonia, pyelonephritis, pancreatitis, hepatitis) - Symptomatic urinary tract infection - Sexually transmitted disease diagnosed at any time during pregnancy (chlamydia, gonorrhea, trichomoniasis, HIV)
Decidual Hemorrhagea	- Hemosiderin deposits or tightly adherent clot on placental pathology - At least 25% hemorrhage on fetal or maternal interface on placental pathology	- Placental pathology demonstrating 1-25% or unspecified percentage of hemorrhage on fetal or maternal interface - Active vaginal bleeding plus at least one ol the following - non-reassuring fetal heart tones, uterine tenderness, or uterine tachysystole - Clinical diagnosis of abruption requiring delivery	- Trauma to abdomen or motor vehicle accident during pregnancy - Vaginal bleeding during pregnancy, not otherwise specified - Placenta previa
Maternal Stress	- Moderate to severe depression/anxiety requiring medication treatment during pregnancy	- Beck Depression Index score indicates severe depression - Perceived stress score = ‘very high’ or life stressors questionnaire indicated ‘severe distress’	- Mild to moderate depression/anxiety not requiring medication treatment - Illicit drug use or current binge alcohol use during pregnancy - High risk socioeconomic risk factor: income less than poverty level, less than a high school degree
Cervical Insufficiency	- Cervical dilation ≥2 cm prior to 28 weeks gestation in the absence of labor - Cervical length <0.5 cm prior to 28 weeks in the absence of labor At least one pregnancy loss prior to 24 weeks gestation due to painless cervical dilation	- Cervical length <1.50 cm prior to 28 weeks gestation in the absence of labor - Cervical length 1.50-2.5cm prior to 28 weeks gestation AND hourglassing membranes/marked funneling	- Cervical length 1.50-2.50 cm prior to 28 weeks gestation in the absence of labor - History of cervical conization procedure or loop electro-excision procedure
Uterine Distensiona	n/a	- Polyhydramnios (4-quadrant AFI >25cm or single deepest pocket >8cm - Birthweight >90% for gestational age	- Sonographically confirmed presence of uterine fibroids - Placental weight >90% for gestational age
Placental Dysfunctiona	- Birthweight <3% for gestational age and gender - Placental weight <3% for gestational age - At least 25% placental infarction on pathology - Reverse end diastolic flow on cord Doppler prior to delivery - Pre-eclampsia with severe features or eclampsia	- Birthweight <10% for gestational age and gender - Placental weight <10% for gestational age - Absent end diastolic flow on cord Doppler prior to delivery - Any placental infarction with no percentage listed or <25% on placental pathology - Four quadrant amniotic fluid index <5cm or single deepest pocket <2cm on ultrasound - Pre-eclampsia without severe features	- Placental calcifications on pathology - Umbilical artery cord Doppler S/D ratio > 4cm/sec but no evidence of absent- or reversed- end diastolic flow - Meconium staining on placental pathology - Velamentous cord insertion on placental pathology
Preterm premature rupture of membranes	- Preterm, premature rupture of membranes diagnosed with sterile speculum examination, dye test, or amnisure at least 48 hours prior to the onset of labor	- Preterm, premature rupture of membranes diagnosed with sterile speculum examination, dye test, or amnisure 12-48 hours prior to the onset of labor	- History of PPROM and delivery less than 37 weeks in a prior pregnancy
Maternal Comorbidities	- Class B or higher diabetes mellitus - Chronic hypertension - Systemic lupus erythematosus - Antiphospholipid antibody syndrome - Chronic renal failure or insufficiency	- Gestational diabetes in the current gestation - Other medical condition affecting a major organ system, not otherwise specified -i.e. pulmonary disease, renal disease, autoimmune disease, history of seizures	n/a
Familial	- At least one first degree relative with history o spontaneous preterm birth	- At least one first degree relative with history of medically indicated preterm birth - At least one second degree relative with history of spontaneous preterm birth	- At least one second degree relative with history of medically indicated preterm birth