LABOR, DELIVERY & PHYSIOLOGIC CHANGES AFTER BIRTH

 

I.                    Definitions

a.      Parturition - the process of giving birth

b.      Braxton-Hicks contractions

                                                               i.      “false labor”

                                                             ii.      rhythmic and milder than true contractions

c.      Primigravida – first pregnancy

d.      Multigravida – 2 or more pregnancies

 

II.                 Stages of Normal Labor and Delivery

a.      Stage I

                                                               i.      starts with onset of regular contractions

                                                             ii.      gradually increase in strength

                                                            iii.      start 10 minutes apart and last 30-90 seconds

                                                           iv.      effacement  of cervix

1.      thinning of cervix

2.      fully effaced at 100%

                                                             v.      dilatation of cervix

1.      diameter of cervical opening

2.      caused by pushing of the fetus and amniotic fluid against the cervix during uterine contractions

3.      fully dilated at 10 cm

                                                           vi.      Stage I ends with complete dilatation and effacement

1.      Primigravida takes 16-18 hours

2.      Multigravida takes 7-12 hours

b.      Stage II

                                                               i.      from full dilatation (begin pushing) to delivery of baby

                                                             ii.      normal position – vertex (head down)

1.      95% of all births

                                                            iii.      engagement of head measured by “stations”

1.      -5 to +5

2.      0 is engaged in the birth canal

                                                           iv.      normal progression to delivery

1.      head and upper shoulders, lower shoulder (takes the most time), rest of the body exits rapidly, umbilical cord is clamped

2.      delivery is aided by contraction of abdominal muscles and diaphragm of the mother

3.      Stage II takes 20 minutes to 2 hours

c.      Stage III  Delivery of the Placenta

                                                               i.      The uterus continues to contract

                                                             ii.      Tears the placenta loose

                                                            iii.      Must assure complete delivery

                                                           iv.      Uterus continues to contract and return to its original position and size

                                                             v.      Stage III takes 5 minutes to 45 minutes

d.      Illustration of the Three Stages

 

III.               Abnormal Labor and Delivery

a.      Premature Labor and Delivery

                                                               i.      <37 weeks

                                                             ii.       rate of premature labor in high-risk patients averages 40%

                                                            iii.      rate of premature delivery about 20%

                                                           iv.      if baby doing OK, try to prevent delivery

b.      Tocolysis

                                                               i.      The process of stopping labor

                                                             ii.      Pharmacologic Agents

1.      Terbutaline

a.      Terbutaline (also known as Brethine and Bricanyl) is an asthma drug in the drug class of beta-adrenergics.

b.      It is not approved by the FDA for use as a preterm labor drug; it is used "off label" for this purpose.

c.      It is typically prescribed in the pill form (2.5 or 5 mg pills at 3- 4- or 6-hour intervals) or by subcutaneous injection of terbutaline sulfate (aka the terbutaline pump, with dosages of at least 3 mg per 24-hours).

d.      Terbutaline relaxes smooth muscle in the airways. It also is thought to relax the muscles of the uterus.

2.      Magnesium sulfate

a.      Magnesium sulfate also is used as a preterm labor drug.

b.      It is used to relax the smooth the smooth muscle of the uterus. 

c.      It is typically given by IV in the hospital.

d.      It must be administered in high levels; the line between a "therapeutic" dose and one that is "toxic" is narrow.

e.      Therefore, women on it must be monitored carefully for complications.

f.        Magnesium sulfate also has been thought to be safe for babies, although a recent study has raised some doubts.

3.       Procardia (nifedipine)

a.      A beta-adrenergic agent.

b.      It is viewed as causing fewer maternal side effects than terbutaline. However, it has not been widely studied.

4.      Ritodrine

a.       The only FDA-approved drug to treat preterm labor.

b.      Relaxes the smooth muscle of the uterus. 

c.      It had fallen out of favor in comparison to terbutaline because it is more expensive.

d.      Ritodrine recently was voluntarily taken off the market by its manufacturer.

5.       Indomethacin

a.      Inhibits prostaglandins and may help delay premature labor.

b.      Research about Indomethacin is limited, although some studies have linked its use to adverse effects on the baby or babies.

                                                            iii.      Bed-rest and Hydration

1.       In addition to prescription drugs, bed-rest and drinking plenty of water are often prescribed to treat preterm labor.

a.      Bed-rest is frequently prescribed although research is lacking on whether it actually works.

b.      Sometimes dehydration will cause a woman to have contractions. Drinking lots of fluids can help lessen this problem.

                                                           iv.      Indications

1.      true labor present

2.      cervix <4 cm. & 50% effaced and membranes intact

3.      20 - 36 wks. gestational age

4.      no sign of fetal distress or disease

5.      no medical or obstetric disorder contraindicating

6.      mother gives consent

 

IV.              Dystocia (prolonged or difficult labor and delivery)

a.      Stages I and II last longer than 20 hours

b.      Stage II > 2 hours primigravida, 1 hour multigravida

c.      Prolonged labor can cause increased morbidity and mortality due to:

                                                               i.      Separation of the placenta causing fetal asphyxia

                                                             ii.      Compression of the umbilical cord

                                                            iii.      Rupture of membranes increased risk of infection > 24 hours

d.      Causes of Dystocia

                                                               i.      dysfunction of uterus

                                                             ii.      hyper or hypotonic contractions

                                                            iii.      abnormal dilatation and effacement

                                                           iv.      cephalopelvic disproportion

1.      fetal head too large

a.      hydrocephaly

b.      maternal diabetes

2.      maternal pelvis too small

a.      congenital or other problems

b.      women younger than 20 years old

c.      Asian women

                                                             v.      abnormal presentation

1.      breech

a.      The most common abnormal presentation (3.5%)

b.      three varieties

                                                                                                                                       i.      complete – feet, legs and buttocks all present together

                                                                                                                                     ii.      footling – one or both feet present first

                                                                                                                                    iii.      frank – legs are flexed against the body, buttocks is the presenting part

                                                                                                                                   iv.      high-risk vaginal delivery

c.      treatment

                                                                                                                                       i.      external cephalic version (see Web Links)

                                                                                                                                     ii.      may require C-section

2.      transverse (shoulder)

a.      fetus is perpendicular to the birth canal

b.      requires manipulation or C-section

3.      face/brow

a.      head enters the birth canal in a way that sutures of the fetal skull can’t overlap

b.      may prolong labor and cause severe facial edema

c.      increased fetal mortality if labor is prolonged

4.      Illustration of shoulder, face and brow presentations

 

V.                 Problems Associated With The Umbilical Cord

a.        Wharton’s Jelly

                                                               i.       prevents bending of the cord and blood flow occlusion

                                                             ii.      does not prevent cord compression between two body parts

b.      Prolapse of the umbilical cord

                                                               i.      Cord passes ahead of the presenting part

1.      common in breech presentations and in multiple gestations

2.      cord is compressed between the fetus and the maternal pelvis

3.      causes hypoxia and asphyxia

                                                             ii.      Monitor with fetal heart monitoring

                                                            iii.      If occult (occurs in utero) then amniotransfusion is done

1.      more room in the uterus

2.      less chance of cord compression

 

VI.              Placental Abnormalities

a.       Placenta Previa

                                                               i.      Definition

1.      implantation in the lower portion of the uterus

                                                             ii.      Varieties

1.      low implantation

a.      does not cover the cervical opening

1.      partial placenta previa

a.      covers a portion of the cervical opening

2.      total placenta previa

a.      completely covers the cervical opening

                                                            iii.      Diagnosis

1.      ultrasound

                                                           iv.      Treatment

1.      usually requires C-section

b.      Abruptio Placentae

                                                               i.      Definition

1.      premature separation of the placenta from the uterine wall

                                                             ii.      Varieties

1.      concealed – no bleeding present

2.      apparent – bleeding from the vagina is present

                                                            iii.      Classification

1.      Grade 0 – Grade 3

                                                           iv.      Mortality

1.      Maternal

a.      2-10% in severe cases

2.      Fetal

a.      near 50% due to blood loss

3.      Causes

a.      maternal hypertension (most common)

b.      history of abruption

c.      many previous pregnancies

d.      trauma

e.      short umbilical cord

f.        uterine anomalies

g.      compression of the inferior vena cava

4.      Treatment

a.      maintain blood volume (HCT > 30 vol%)

b.      lateral position to maximize placental circulation

c.      intensive monitoring

d.      C-section if threatening

 

VII.            Cesarean Delivery

a.      Indications

                                                               i.      Prior cesarean delivery

                                                             ii.      Cephalopelvic disproportion

                                                            iii.      Severe pre-eclampsia

                                                           iv.      Hemorrhage

                                                             v.      Placenta previa

                                                           vi.      Failure of the cervix to dilate

                                                          vii.      Fetal depression or distress

b.      Procedure

                                                               i.      Complications

1.      Usually rare

a.      accidental cutting of the placenta, umbilical cord or fetus

b.      Transient Tachypnea of the Newborn (TTN)

                                                                                                                                       i.      retention of fetal lung fluid

 

VIII.         Multiple Gestations

a.      Presence of twins, triplets, quadruplets, or more fetuses during the same pregnancy

a.      Complications

                                                               i.      Increased risk of mortality

                                                             ii.      Premature labor and delivery

                                                            iii.      Congenital abnormalities

                                                           iv.      Growth retardation

                                                             v.      Infection

                                                           vi.      Hypoglycemia

b.      Factors which increase incidence

                                                               i.      Familial inheritance

                                                             ii.      Increased among blacks, decreased among Asians

                                                            iii.      Females 35-39 years of age

                                                           iv.      Following oral contraception

                                                             v.      Administration of ovulation stimulators

c.      Twinning

                                                               i.      Most common type of multiple gestation (1 out of 99 pregnancies)

                                                             ii.      2/3 fraternal

1.      originate from 2 separate ova

2.      autosomal-recessive trait carried by the daughters of mothers of twins

                                                            iii.      1/3 identical

1.      originate from 1 ovum

2.      same gender and identical appearance

3.      random occurrence

4.      higher mortality rate

a.      2nd twin more compromised

b.      females are healthier than males

                                                           iv.      Illustration of Embryologic Development

 

IX.              Adaptation to Extrauterine Life

a.      Stimulation to breathe after delivery is due to:

                                                               i.      Asphyxia

1.      most powerful stimulus to breathe

2.      increased PaCO2, decreased pH, decreased PaO2

3.      stimulate chemoreceptors which cause gasping

                                                             ii.      compression of the thorax during delivery

1.      removes fetal lung fluid

                                                            iii.      recoil of the thorax after delivery

1.      creates negative pressure in the thoracic cavity

2.      air enters the lungs

                                                           iv.      environmental changes

1.      light, noise, temperature change, physical handling

2.      abrupt change initiates the crying reflex

b.      Pressures for the First Breath

                                                               i.      Surfactant greatly decreases surface tension

                                                             ii.      Initial pressures are very high (> -100cm H2O)

                                                            iii.      Subsequent breaths require less pressure

                                                           iv.      FRC is established

1.      A little more volume remains with each breath

c.      The Change From Fetal to Adult Circulation

                                                               i.      Changes in Pressures

1.      Cord is clamped

a.      no blood flow to placenta

b.      increased systemic vascular resistance (SVR)

c.      increased systemic arterial pressure

                                                             ii.      Initiation of breathing

1.      decreased pulmonary vascular resistance (PVR)

2.      pulmonary vessels dilate

a.      ventilated alveoli reduces pressure on the vessels

b.      increased PaO2

3.      right pressures < left pressures

                                                            iii.      Closure of Shunts

1.      Foramen ovale

a.      LA pressure > RA pressure

                                                                                                                                       i.      Tissue flap closes mechanically

2.      Ductus arteriosus

a.      smooth muscle develops in the last few weeks of gestation

b.      DA remains open due to prostaglandins

c.      after birth, as PaO2 increases, prostaglandins decrease

                                                                                                                                       i.      smooth muscle of DA constricts

                                                                                                                                     ii.      DA closes

                                                                                                                                    iii.      becomes a ligament

3.      Ductus venosus

a.      constricts and becomes a ligament in the abdominal cavity

4.      Umbilical vein and arteries

a.      clamping of the umbilical cord results in no blood flow

b.      vessels constrict and become supporting ligaments in the abdominal cavity

                                                           iv.      View a video about Fetal Circulation