Labor, Delivery, and Changes at Birth

Fred Hill, MA, RRT

Fetus in Uterus

Fetus in Uterus

Events of Birth (Maternal)

Rupture of membranes

Dilation of cervix

Contraction of uterus

Separation of the placenta

Shrinking of the uterus

Stages of Labor & Delivery

Stage I: Onset of regular contractions to full dilation and effacement of the cervix Primigravida: 16 – 18 hours Multigravida: 7 – 12 hours

Stage II: Full dilation (10 cm) and effacement of the cervix to delivery of the baby Primigravida: 1 – 2 hours Multigravida: 20 mins

Stage III: Delivery of the baby to delivery of the placenta Primigravida: 3 – 4 mins Multigravida: 4 – 5 mins

Tocolysis

Beta-2 sympathomimeticsTerbutaline sulfateRitodrine hydrocholoride

Magnesium sulfateIndomethacinCalcium channel blockers

Dystocia

Uterine dysfunctionAbnormal fetal presentationCephalopelvic dysproportion

HydrocephalusExcessive fetal size (maternal diabetes)Small pelvic dimensions

Abnormality in shape of birth canal

Abnormal Fetal Presentation

Normal presentation: Vertex ( head first), 95%

Abnormal presentationCephalicBreech (buttocks down)FaceBrowShoulderTransverse lie

Vertex Presentation

Cephalic Presentation

Face Presentation

Complete Breech

Footling Breech

Frank Breech

Transverse Lie

Other Problems

Prolapse of umbilical cordCord wrapping around fetusPlacental abnormalities

Placenta previa: Implantation in lower uterus

Abruptio placentae

Placenta Previa

Abruptio Placentae

Other Risky Deliveries

Cesarean deliveriesMultiple gestations

Changes at Birth

Vaginal squeeze when head presentsPresentation of chest and recoil of chestFirst breath: high initial pressures (-100 cm

H2O)

Succeeding breaths require less negative pressure

Remaining liquid in lungs Expelled by coughing and sneezing Absorption into lung interstitium into lynphatics

Fetal Circulation

Fetal to Adult Circulation

Major changes First and subsequent breaths

Reduces pulmonary vascular resistanceAir replaces liquid surrounding vasculature↑ PaO2 → pulmonary vasodilation

Increase in systemic vascular resistance Clamping of umbilical cord

R → L Shunting changes to L → R Foramen ovale closes: mechanical Ductus arteriosus begins to close due to

chemical changes Cessation of blood flow leads to constriction of:

Ductus venosus Umbilical arteries and veins