Trial of Underwater Birth

Inclusion Criteria: Inclusion criteria based on A model practice template for hydrotherapy in labor and birth (2016):

Prenatal inclusion criteria (to be assessed at the time of enrollment):

* ≥18 years of age
* Able to speak and understand English or Spanish
* Singleton gestation
* Vertex presentation
* Able to ambulate with no mobility restrictions (i.e., no difficulty getting from seated to standing)
* Less than class III obesity (BMI \<40 kg/m2) at initiation of prenatal care

Labor inclusion criteria (to be assessed at time of admission):

* Greater than 37 weeks 0 days through and less than 412 completed weeks 6 days gestation with fetus in vertex presentation
* Normal blood pressure and normal temperature (obstetric criteria for exclusion: two blood pressures 140/90 four hours apart; two fevers of over 100.4 one hour apart)

Exclusion Criteria: based on A model practice template for hydrotherapy in labor and birth (2016):

Prenatal exclusion criteria (to be assessed at the time of enrollment):

* Active infections such as HIV, Hepatitis B, Hepatitis C, HSV outbreak (on prophylaxis acceptable) (GBS positive is acceptable)
* Pre-existing medical conditions including heart disease, uncontrolled asthma, preexisting diabetes, chronic hypertension, or activity restrictions
* High-risk pregnancy conditions including preeclampsia, gestational hypertension, preterm gestation, multiple gestation, gestational diabetes type A2, estimated fetal weight of 5000g for non-diabetics or \>4500 for GDM-A1, unstable substance use disorder (i.e. not in remission), placental abruption or other unexplained vaginal bleeding, previous cesarean section, fetal growth restriction (\<10th percentile), fetal anomaly, or other neonatal condition that may complicate neonatal transition to extrauterine life.
* Existing contraindication to vaginal birth

Labor exclusion criteria (to be assessed at the time of admission):

* Meconium-stained amniotic fluid
* Preterm rupture of membranes (PROM) greater than 24 hours without the start of any labor contractions (those whose have PROM greater than 24 hours but are in labor can continue to be included in the study)
* Immediate need for operative delivery at time of admission