Lec03 Labor Delivery Phys Changes

King Faisal University College of Applied Medical Sciences Respiratory Care department MSRT411: Perinatal and Pediatric Respiratory Care

Labor, Delivery, and Physiological Changes after Birth Ghazi Alotaibi, PhD, RRT Lec03-Sep20

Events of Labor Process • •

Process of giving birth is called “Parturition”. During Parturition, several events occurs: a. b. c. d. e.

Rupture of the Membrane. Dilation of the cervix. Contraction of the uterus. Separation of the placenta. Shrinking of the uterus.

What Initiates Labor Process? • •

Not fully understood. Three Hypotheses: • • •

The withdrawal of Progesterone. Estrogen activate the uterine. Other uterine stimulants (Oxytocin, Prostaglandin).

Stages of Normal Labor and Delivery

• Three Stages: 1. Effacement and Dilation of the Cervix. 2. Position, and Delivery of the fetus. 3. Expulsion of the Placenta.

• •

Primagravida: First Pregnancy Multigravida: Has been pregnant before

Stage I: Effacement and Dilation of the Cervix. • Stage I: onset of regular contraction to full dilation and effacement of the cervix. • Effacement = stretching or thinning of the cervix. • Dilation = widening of the cervix. • What induces Stage I?? • Effacement and dilation are cause by pushing of the amniotic fluid and the fetus against the cervix, which cause by uterine contractions.

• Stage I: Effacement and Dilation of the Cervix. • Uterus upper portion is thick, lower portion is thin  fetus is pushed down

Stage II: Position, and Delivery of the fetus. • Stage II: from full effacement and dilation to delivery of the fetus. • Normal position: Vertex (head-down) position. • Delivery Process: • • • •

Internal rotation to make easy for shoulders. Fetus decent down the birth canal (face down). External rotation (to rotate shoulders). Expulsion of the fetus.

Vertex Position

Stage III: Expulsion of the Placenta • After delivery, the uterus continues to contract to loosen the placenta from the uterine wall. • This process is aided by: • Oxytocin (increases uterine contraction) • Manual pressure to the abdominal wall.

Premature Labor and Delivery: • • • • •

Birth before week 37 (preterm). The more fetus maturity : increase survival rate. TOCOLYSIS (stopping of labor). Performed when premature labor is risky (labor before W37). How is it performed?

Prolonged and Difficult Labor and Delivery • Called “ DYSTOCIA”. • Dystocia is present when Stage II exceeds 2 hrs in primagravidas or 1 hr in multigravidas.

• Why prolonged labor is risky for fetus? 1. Premature separation of the placenta (fetal asphyxia). 2. Compression of the umbilical cord. 3. Premature rupture of the amniotic sac (infection)

Prolonged and Difficult Labor and Delivery • One main reason of Dystocia is abnormal presentation of the fetus (ie. any position other that Vertex).

Prolonged and Difficult Labor and Delivery • What to do?? – Manipulation and pulling of the fetus by the obstetrician. – If not successful, Cesarean section.

Problems with Umbilical Cord

• • • •

PROLAPSE OF THE UMBILICAL CORD: The umbilical cord passes through the cervix before body. Common in breech presentation. Why is it dangerous? Compression of the cord during delivery hypoxia.

Problems with Placenta PLACENTA PREVIA: • Implantation occurs in the lower portion of the uterus (low, partial, complete). • Obstructs fetal passage. • How is it diagnosed?!

Problems with Placenta ABRUPTIO PLACENTA • Premature separation of the placenta. • Causes: • Maternal Hypertension, trauma, short Umbilical cord, compression of IVC.

• Mortality 2-10% (mother) 50% (fetus) • Clinical Manifestations: • Vaginal bleeding • Hypovolemic shock (mother). • Absent fetal heart beats.

Abruptio Placenta • Treatment of Abruptio Placenta: • IV blood infusion. • Instruct mother to lie on lateral position (why??) • Emergency delivery or C-section.

Once the fetus (newborn) is out in our world, every one is waiting for the:

First Breath

What stimulate First Breath? •

As fetus cut off placenta, PO2 dec, PaCO2 inc. Peripheral chemoreceptors in the aorta and carotid artery are stimulated stimulates respi. center in the brain  breath is initiated. b. External sensory stimuli (bright, clod, and noisy place; physical handling). c. During virginal delivery, fetal thorax is compressed, then expands. Compression: expels fluid Expansion: pulls air into the lungs.

First Breath • Newborn generates high negative intrapleural pressure (-40 to -100 cmH2O). Why it is difficult? • 40 ml of air enters the lungs in the first breath. • 20 ml air is exhaled (FRC of 20 ml is established). • Successive breaths require less negative pressure: (Why??). – Gradual establishment of FRC. – Presence of Surfactant (prevent alveoli collapse)

Newborn Parameters • • • • • •

Compliance: 5 ml/cm H2O Resistance: 30 cm H2O/L/s VT 15 ml RV 40 ml FRC 80 ml TLC 155 ml

Circulatory Changes at Birth • As the baby takes the first breath, PVR falls due to: a. Sudden increase in PO2 (Pulm. vasodilation). b. Expulsion of lung fluid, reduces pressure on the surrounding pulm. Vasculature.

 More blood flows to the lungs more blood returns to LA increaes pressure in the LA closes the flap of the Foramen Ovale.

Circulatory Changes at Birth • Pressure in the RA and RV falls due to drop in PVR and clamp of the umbilical cord. • This helps further in closing the Foramen Ovale. • Smooth muscle of Ductus Arteriosus constricts in response to high PO2 (>45 inhibits prostaglandin). Closes completely in 4 days.

Circulatory Changes at Birth • Clamping of the umbilical cord no blood flow through vein and arteries  vessels constrict.

• By 2-4 weeks, anatomical close is complete (similar to adult circulation)

Reading Assignment • Chapter 3 in Kent (p53-71)