Below is a glossary of important terms used in the prediction model:
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Preterm birth (PTB): A delivery occurring before 37 weeks gestation.
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Spontaneous preterm birth (sPTB): A preterm birth that is not initiated by labor induction.
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Preterm labor: A labor that begins before 37 weeks gestation. Might lead to preterm birth. In our study, suspected preterm labor at admission was defined as one or more of the following:
- Premature contractions with cervical length shortening (to < 20 mm, or to < 25 mm in patients with a history of sPTB).
- Cervical dilatation.
- Asymptomatic cervical shortening or dilatation.
- Premature preterm rupture of membranes (pPROM).
- Vaginal bleeding with contractions implying possible placental abruption.
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Parity: The number of times a patient has given birth at >20 weeks gestation (including livebirths and stillbirths).
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Previous hospitalizations during pregnancy: One or more previous hospitalizations during the current pregnancy.
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Gestational age at admission: Time elapsed between the first day of the last menstrual period to the day of admission, measured in weeks and days (0/7 to 6/7).
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Premature preterm rupture of membranes (pPROM): A rupture of the amniotic sac membranes during pregnancy, occurring before 37 weeks’ gestation.
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Cervical shortening: Cervical length measurement of <20 mm, or <25 mm in women with a history of spontaneous preterm birth, using transvaginal ultrasound at admission.
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Cervical dilation (Cm): Cervical opening at admission, measured by a pelvic manual examination.
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Maximal pulse at admission: Maternal maximal pulse at admission, measured by beats per minute.
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Amniotic Fluid Index at admission: A quantitative estimate of amniotic fluid seen on ultrasonography of a pregnant uterus, using a four-quadrant technique. The deepest, unobstructed, vertical length of each pocket of fluid is measured in each quadrant and then added up to the others. Score is expressed in millimeters (mm).
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Hemoglobin at admission: Maternal serum hemoglobin at admission (measured by g/dL).
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Living Children: The number of patient's living children.
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Estimated Fetal Weight (g): Fetal weight estimation at admission (measured in grams).
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Glucose Challenge Test (GCT) score (mg/dL): Serum glucose during one-hour oral glucose challenge test (GCT) performed between 24 and 28 weeks of pregnancy, measured by mg/dL.