Labor, Delivery, and Changes at Birth Fred Hill, MA, RRT

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 sympathomimetics  Terbutaline sulfate  Ritodrine hydrocholoride  Magnesium sulfate  Indomethacin  Calcium channel blockers

Dystocia  Uterine dysfunction  Abnormal fetal presentation  Cephalopelvic dysproportion  Hydrocephalus  Excessive fetal size (maternal diabetes)  Small pelvic dimensions  Abnormality in shape of birth canal

Abnormal Fetal Presentation  Normal presentation: Vertex ( head first), 95%  Abnormal presentation  Cephalic  Breech (buttocks down)  Face  Brow  Shoulder  Transverse lie

Vertex Presentation

Cephalic Presentation

Face Presentation

Complete Breech

Footling Breech

Frank Breech

Transverse Lie

Other Problems  Prolapse of umbilical cord  Cord wrapping around fetus  Placental abnormalities  Placenta previa: Implantation in lower uterus  Abruptio placentae

Placenta Previa

Abruptio Placentae

Other Risky Deliveries  Cesarean deliveries  Multiple gestations

Changes at Birth  Vaginal squeeze when head presents  Presentation of chest and recoil of chest  First breath: high initial pressures (-100 cm H 2 O)  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 resistance  Air 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