The proposed pilot investigation is a prospective, observational study of 300 healthy nulliparous women with spontaneous term labor onset. The specific aims of this study are to:

Aim #1: Characterize IL-8 (pro-inflammatory biomarker), basal body temperature, maternal heart rate, and electrical activity of the uterus prior to spontaneous onset of labor through the onset of active labor among nulliparous women. IL-8 will be quantified weekly, daily basal body temperature, as well as continuous maternal heart rate and electrical activity of the uterus throughout the transition from late pregnancy into active labor.

Aim #2: Characterize latent labor symptoms among nulliparous women in spontaneous labor. Using Likert scale, childbirth-specific, symptom-specific PROMIS measures,45 and open-ended questions will be quantified and characterize latent labor symptoms (e.g., intensity, frequency) and identify relevant themes.

Aim #3: Characterize trajectories of labor biomarkers and latent labor symptoms across latent labor duration. A modified growth mixture modeling approach to quantify subgroup phenotypes among nulliparous women in spontaneous latent labor will be employed.

Hypothesis 3.1. There will be significant congruence between higher biomarkers (e.g., higher IL-8, more uterine electrical activity) and symptoms that are more intense and frequent.

Hypothesis 3.2. At least two classes of laboring women with distinct trajectories of change in biomarkers and symptoms can be identified and will be associated with cervical dilation at hospital admission.

Exploratory Aim: Characterize biomarkers among nulliparous women with spontaneous labor onset vs. nulliparous women requiring labor induction for post-term gestation. Weekly IL-8, daily basal body temperature, as well as continuous maternal heart rate and electrical activity of the uterus throughout the transition from late pregnancy into active labor between those whose labor begins spontaneously and those whose labors are induced for post-term gestation will be quantified.

Exploratory Hypothesis. There will be different biomarker patterns between women with spontaneous labor onset vs. those without.

The Standard descriptive and inferential statistics as well as growth mixture modeling for quantitative aims will be used. The investigators will use thematic development for qualitative aims.

Inclusion Criteria:

1. Nulliparous
2. Maternal age of at least 20 years of age.
3. Maternal age of no greater than 39 years of age.
4. Viable, term pregnancy: ≥ 37 weeks gestation at time of signing study consent.
5. Able to understand and provide an informed consent.
6. Able to understand English.

Exclusion Criteria:

1. Multiple gestation (i.e., carrying >1 fetus)
2. Managing complex comorbidities (e.g., preeclampsia)
3. Documented fetal congenital anomalies
4. Preterm labor and birth
5. Persistent breech fetal position at term
6. Fetal death prior to the onset of labor
7. Any indication for planned cesarean birth (e.g., placenta previa)
8. Induction of labor for medical indication (e.g., oligohydramnios)

This is a study of reproductive age women 20-39 years of age being performed at Oregon Health & Science University (OHSU) in Portland, OR. It will include subjects who present for prenatal care in our outpatient Center for Women's Health Clinics and OHSU Labor and Delivery.