Appendix 2.

Standard data collection form for research and clinical use. Any livebirth or stillbirth, singleton or multiple, including terminations and congenital malformations, from 16+0 to 38+6 weeks’ gestation may be included in this assessment. The clinical record should be the primary source of information to capture intra- and postpartum data, and the relevant obstetric and medical history. This should be supplemented by questioning the mother and obstetrician if the preterm birth (PTB) has been scheduled and the reason for delivery is not clear. Finally, placental histology and, for stillbirths, an autopsy or pathology report are optimal requirements. Risk factors and mode of delivery are not included. All prenatal features should be present before initiation of delivery.

(1) Substantial Maternal Conditions
	Clinical Features and Diagnostic Investigations
Phenotype Category	Prenatal	Postnatal
Extrauterine Infection	Pyrexia due to viremia, bacteremia, malaria, pyelonephritis, sexually transmitted disease (including syphilis and HIV), abscess, inflammatory indices (leukocyte count, CRP)	Persisting pyrexia or sepsis, cultures with etiological definition of microbes involved, detailed imaging, inflammatory indices (leukocyte count, CRP)
Clinical Chorioamnionitis	Pyrexia, ROM plus two of the following: maternal tachycardia, uterine tenderness, purulent amniotic fluid, fetal tachycardia, inflammatory indices (leukocyte count, CRP)	Persisting pyrexia or sepsis, inflammatory indices (leukocyte count, CRP)
Preeclampsia/eclampsia	Gestational hypertension with either proteinuria (300 mg/24h or 20 mg/dL) or with organ dysfunction (doubling transaminase, increasing creatinine, angiogenic factors imbalance or increased uterine artery pulsatility index), HELLP syndrome.	Evolution including extent of organ damage and treatment
Maternal Trauma	Severe or critical injury, wound or shock diagnosed by inspection, ultrasound, X-ray, and imaging	Procedures required to treat the trauma and outcome
Worsening Maternal Disease	Uncontrolled diabetes mellitus (increased HbA1c and capillary glucose, ketosis), endocrine disease (dysthyroidism), cardiac insufficiency (reduced ejection fraction at cardiac US), respiratory insufficiency (reduced oxygen saturation; e.g., COVID-19), liver disease (increased enzymes and bile acids), renal disease (increased serum creatinine), progression of cancer, epilepsy, coagulopathy, or life-threatening hemodynamic instability with immediate risk to mother/fetus	Course of the disease, treatment modification
Uterine Rupture	Bleeding and abnormal contractility due to uterine wall defect developing in pregnancy, fetal bradycardia, hypovolemic shock	Conservative vs. demolitive surgical approach, DIC, hemorrhage, placenta accreta spectrum
(2) Substantial Fetal or Neonatal Conditions
	Clinical Features and Diagnostic Investigations
Phenotype Category	Fetal	Neonatal
Intrauterine Fetal Death	US fetal biometry, detection of fetal abnormalities, definition of onset: before labor vs. intrapartum	Macroscopic assessment and postmortem pathological report
FGR	EFW<10th centile with Doppler evidence of abnormally increased umbilical or uterine pulsatility index; EFW or AC drop of 40 centiles on trajectory, EFW<3rd centile	Birth weight, length, head circumference, postnatal course
Abnormal FHR/ Abnormal Biophysical Profile	CTG with pathological pattern (FIGO 2015) or antepartum persistently reduced short-term variability or decelerations, ultrasound with BPP≤6	Apgar scores, neonatal blood gas analysis with pH and base excess, evidence of birth asphyxia
Fetal Infection/Fetal Inflammatory Response Syndrome (FIRS)	CTG: fetal tachycardia, amniocentesis: increased amniotic IL-6, reduced glucose concentration	Neonatal sepsis or inflammatory indices (leukocyte count, CRP), any organ damage
Fetal Anomaly	Any minor or major fetal defect	Any minor or major neonatal defect
Multiple Pregnancy	Two or more fetuses, chorionicity, amnionicity and specific features such as TTTS, TOPS, TAPS, selective FGR, and death of one fetus	Chorionicity assessment, presence of anastomoses
Fetal Anemia	MCA Doppler peak systolic velocity (Hb reduced by 2 SD or CMA PSV increased by 1.5 SD). Alloimmune (Rhesus disease or antibodies), fetal hemorrhage (vasa previa), fetomaternal hemorrhage. CTG abnormality with sinusoidal pattern, positive Kleihauer-Betke test	Hemoglobin levels and differences, extent of hemotransfusions, signs of hypoxia, evidence of vasa previa
Polyhydramnios/ Oligohydramnios	Deepest pool >8 cm (95th centile) / <2 cm (5th centile)	Associated defects (GE obstructions, renal failure, etc)
(3) Placental Pathological Conditions Related to PTB
	Clinical Features and Diagnostic Investigations
Phenotype Category	Prenatal	Postnatal
Chorioamnionitis	Maternal fever, inflammatory indices (leukocyte count, CRP), fetal tachycardia, offensive vaginal discharge, US evidence of abnormal placental structure, thickness, and edema	Histology showing vasculitis (infiltration of neutrophils into the connective tissue of the chorionic plate), infarction, necrosis. villitis, funisitis, thrombosis
Placental Abruption	US evidence of retroplacental or amniochorial clot, vaginal bleeding, maternal abdominal pain, hypovolemic shock	Retroplacental blood clot at delivery, parenchymal hemorrhage at histology, coagulopathy
Placenta Previa	Placental location on US, myometrial invasion assessment, US structure, Asymptomatic or vaginal bleeding	Postpartum hemorrhage, association to placenta accreta spectrum and amniotic fluid embolism
Placental Dysfunction	US showing small placental volume, increased pulsatility index at uterine arteries and/or umbilical artery Doppler, low PAPP-A and PlGF, increased sFlt-1/PlGF ratio	Small placental weight, placental infarctions, fibrosis, and necrosis
Other Placental Abnormalities	US evidence of placental chorioangioma, jelly-like placenta (excess of placental lakes or lacunae), circumvallate placenta, vasa previa	Pathology with placental anomalies, evidence of amniotic, placental infection due to local or systemic process (e.g., malaria); culture for bacteria
(4) Signs of Parturition Initiation
Phenotype Category	Clinical Features (existing before onset of delivery)
No evidence of initiation of parturition	-
Evidence of initiation of parturition	Cervical shortening, PPROM, uterine tenderness, regular uterine contractions, cervical effacement or dilation, bleeding from uterus or cervix, unknown factor of initiation
(5) Pathway to delivery
	Clinical features and Diagnostic Investigations
Phenotype category	Prenatal	Postnatal
Provider-initiated (iatrogenic):	Clinically mandatory (e.g., severe preeclampsia), clinically optional or discretionary (e.g., severe intrahepatic cholestasis), pregnancy termination (maternal request or fetal anomaly), social reasons or no discernible reason	Apgar scores, birth weight (define appropriateness indications and timing of interventions based on fetal weight estimation)
Spontaneous	Labor with intact membranes, PPROM, regular uterine contractions, pharmacological augmentation with oxytocin	Course of labor (define appropriateness of interventions in labor)

CRP: serum C-reactive protein concentration; ROM: rupture of membranes; HELLP: hemolysis, elevated liver enzymes, low platelets; X-ray: conventional diagnostic radiograms; HBA1c: maternal serum glycosylated hemoglobin concentration; US: ultrasound imaging; COVID-19: Coronavirus disease; DIC: disseminated intravascular coagulation; EFW: estimated fetal weight; CTG: cardiotocography; FIGO: International Federation of Gynecology and Obstetrics; pH: potential of hydrogen, defined as concentration of hydrogen ions; TTS: twin to twin transfusion syndrome; TAPS: twin anemia polycythemia sequence; TOPS: twin oligohydramnios-polyhydramnios sequence; FGR: fetal growth restriction: MCA: middle cerebral artery; PSV: peak systolic velocity; Hb: hemoglobin; GE: gastroenteric; PAPP-A: pregnancy associated plasma protein A; PIGF: placental growth factor; sFlt-1: soluble fms-like tyrosine kinase-1; PPROM: preterm prelabor rupture of membranes.