This retrospective observational study evaluates labor characteristics in primiparous women with spontaneous preterm birth at different gestational ages and examines their associations with maternal and neonatal outcomes. Medical records of women who delivered at Shanghai Jiading District Maternity and Child Health Care Hospital between January 1, 2020, and December 31, 2025, are reviewed. Participants are classified according to gestational age at delivery into very preterm (28 to 31+6 weeks), moderate preterm (32 to 33+6 weeks), and late preterm (34 to 36+6 weeks) groups. The study compares the onset and duration of the active phase of labor, cervical dilation rate, and durations of the first and second stages of labor across these gestational-age groups. The study also evaluates the associations between labor duration and maternal and neonatal outcomes, including postpartum blood loss, mode of vaginal delivery, and 5-minute Apgar score. The findings are intended to provide evidence for gestational age-specific and individualized labor management in women with spontaneous preterm birth.
This is a single-center, retrospective observational study based on electronic medical records from Shanghai Jiading District Maternity and Child Health Care Hospital. The study population consists of primiparous women with spontaneous preterm birth at 28 to 36+6 weeks of gestation who delivered vaginally between January 1, 2020, and December 31, 2025. Participants are categorized into three gestational-age groups: very preterm (28 to 31+6 weeks), moderate preterm (32 to 33+6 weeks), and late preterm (34 to 36+6 weeks). Labor characteristics assessed include cervical dilation at the onset of the active phase, duration of the active phase, mean cervical dilation rate during the active phase, duration of the first stage of labor, and duration of the second stage of labor. The study also evaluates differences in labor duration according to the use of epidural labor analgesia. Maternal and neonatal variables collected from the medical records include maternal age, gravidity, pre-pregnancy body mass index, gestational age at delivery, pregnancy-related complications and comorbidities, neonatal birth weight, vaginal delivery status, postpartum blood loss within 2 hours after delivery, postpartum hemoglobin level, and 5-minute Apgar score. Associations between the durations of the first and second stages of labor and maternal or neonatal outcomes are evaluated using regression analyses with adjustment for relevant potential confounding variables. Linear regression is used to assess postpartum blood loss, multinomial logistic regression is used to evaluate vaginal delivery outcomes, and binary logistic regression is used to evaluate neonatal Apgar outcomes. Restricted cubic spline analyses are used to explore potential dose-response relationships between labor duration and outcomes showing statistically significant associations. The study is non-interventional. All information is obtained retrospectively from existing medical records and is analyzed after de-identification.
Study Type
OBSERVATIONAL
Enrollment
436
Gestational age at delivery was the primary exposure of interest. Participants were retrospectively classified into three groups according to gestational age at delivery: very preterm (28 weeks 0 days to 31 weeks 6 days), moderate preterm (32 weeks 0 days to 33 weeks 6 days), and late preterm (34 weeks 0 days to 36 weeks 6 days). No study-specific intervention was assigned, and all exposure and outcome information was obtained from existing medical records.
Maternal and Child Health Hospital, Jiading District
Shanghai, Shanghai Municipality, China
Duration of the Active Phase of Labor
Duration of the active phase of labor, measured in hours, from the onset of the active phase to full cervical dilation (10 cm). The onset of the active phase was defined as the cervical dilation corresponding to the inflection point at which the cervical dilation curve changed from a gradual slope to its maximum slope.
Time frame: During labor, from the identified onset of the active phase to full cervical dilation (10 cm)
Title Description Time Frame Cervical Dilation at the Onset of the Active Phase
Cervical dilation, measured in centimeters, at the identified onset of the active phase of labor.
Time frame: At onset of the active phase during the index delivery
Mean Cervical Dilation Rate During the Active Phase
Mean cervical dilation rate, measured in cm/hour, calculated as (10 cm minus cervical dilation at the onset of the active phase) divided by the duration of the active phase.
Time frame: During labor, from the identified onset of the active phase to full cervical dilation (10 cm)
Duration of the First Stage of Labor
Duration of the first stage of labor, measured in hours, as documented in the obstetric medical record.
Time frame: During labor, from the documented onset of labor to full cervical dilation (10 cm)
Duration of the Second Stage of Labor
Duration of the second stage of labor, measured in hours, from full cervical dilation to delivery of the fetus.
Time frame: During labor, from full cervical dilation (10 cm) to fetal delivery
Postpartum Blood Loss Within 2 Hours After Delivery
Postpartum blood loss within 2 hours after delivery, measured in milliliters using the gravimetric weighing method and documented in the medical record.
Time frame: From fetal delivery through 2 hours postpartum
Vaginal Delivery Status
Vaginal delivery status categorized as spontaneous vaginal delivery, episiotomy, or forceps-assisted vaginal delivery, as documented in the medical record.
Time frame: At the time of delivery
5-Minute Apgar Score
Neonatal Apgar score assessed 5 minutes after birth and documented in the medical record. The score was evaluated to assess neonatal condition after delivery.
Time frame: 5 minutes after birth
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