Pregnancy,
Labor, and Delivery
Calla Holmgren, MD
Department of Obstetrics & Gynecology
University of Washington
Objectives
• Review normal physiologic changes in
pregnancy
• Discuss historical context of labor and
delivery
• Review normal and abnormal labor
• Evaluate interventions for abnormal labor
Cardiovascular Changes
• Major hemodynamic changes induced by
pregnancy include
– Increase in cardiac output
– Sodium and water retention leading to blood
volume expansion
• Increase until 34 weeks gestation
– Reductions in systemic vascular resistance and
systemic blood pressure
Cardiovascular Changes
• These changes begin early in pregnancy
• Reach their peak during the second
trimester, and then remain relatively
constant until delivery
• They contribute to optimal growth and
development of the fetus
• Help to protect the mother from the risks of
delivery, such as hemorrhage
Hemodynamic changes in normal
pregnancy
Pulmonary Changes
• Marked changes in respiratory system during
pregnancy
• These can be measured using direct spirometry
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Vital Capacity- increased by 100-200 mL
Inspiratory Capacity- increased by 300 mL
Expiratory Reserve Volume- decreases
Residual Volume- Decreases
Functional Residual Capacity- reduced
Tidal Volume- increases from 500 to 700 mL
Minute Ventilation- increases 40%
Pulmonary Changes
• The total of these changes is increased
ventilation
• Due to deeper but not more frequent
breathing
• Most likely used to help supply increased
basal oxygen consumption
Gastrointestinal Changes
• Pregnancy has little, if any, effect on
gastrointestinal secretion or absorption
• But it has a major effect on gastrointestinal
motility
– Hormones
– Enlarging uterus
Endocrine Changes
• Endocrine adaptations to the pregnant state
begin just after conception and evolve
through delivery
• They almost completely revert back to the
nonpregnant state over a period of weeks
• Virtually all endocrine glands are affected
Endocrine Changes
• Maternal endocrine
adaptations to pregnancy
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Hypothalamus
Pituitary
Parathyroid
Thyroid
Adrenal glands
Ovary
Musculoskeletal Changes
• Anatomic and physiologic changes
occurring during pregnancy have the
potential to affect the musculoskeletal
system at rest and during exercise
– Weight gain
– Shift in center of gravity
– Increased ligamentous laxity
Musculoskeletal Changes
• Weight gain
– Typically 11.5 to 16 kg
– May double the forces across joints compared to
nonpregnant forces
• Shift in center of gravity
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Shifted forward
A posture of increased lumbar lordosis
Back pain
Loss of balance; increased fall risk
• Increased ligamentous laxity
– Related to the effects of estrogen and relaxin
Prenatal Care
• The major goal of prenatal care is to ensure the
birth of a healthy baby with minimal risk for the
mother
– Early, accurate estimation of gestational age
– Identification of the patient at risk for complications
– Ongoing evaluation of the health status of both mother
and fetus
– Anticipation of problems and intervention, if possible,
to prevent or minimize morbidity
– Patient education and communication
Prenatal Care
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History and physical
Laboratory tests
Ultrasound examination
Patient education
Preparation for labor and delivery
History and Physical
• History
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Personal and demographic information
Past obstetrical history
Personal and family medical history
Past surgical history
Genetic history
Menstrual and gynecological history
Current pregnancy history
Psychosocial information
• Physical
– Special attention to uterine size and shape and evaluation of the adnexa
– Fetal heart tones
• Doppler: 9 to 12 weeks of gestation
• Transvaginal ultrasound 5.5 to 6.0 weeks
Laboratory Assessment
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Hematocrit or hemoglobin to detect anemia
Cervical cytology
Blood type and screen
Rubella immunity testing
Urinary infection testing
Syphilis testing
Hepatitis B antigen testing
Gonorrhea and Chlamydia testing
HIV testing
Thyroid disorders?
Heritable disorders
Genetic screening
Ultrasound Examination
• First trimester
– Accurately dates pregnancy
– Assessment of fetal well being
• 18-20 weeks
– Anatomic survey
• Late second/third trimester
– Growth
– Fetal well being
Patient Education
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Seat belts
Vitamins, nutrition, and weight gain
Substance use
Infection precautions
Work
Exercise
Birth defects and genetic issues
Use of medications
Airline travel
The History of Childbirth
• Historically,
pregnancy has been
managed by women
(family, friends,
midwife) with delivery
in the home
• In the 14th-18th
Centuries medicine
was dominated by
men and the Church
History of Childbirth
• Industrialization of
America brought
mothers from their
homes to hospitals
(“lying-in”) for birth
• Obstetrics was then
performed by surgeons
(not midwives)
Why do we need to know about
labor?
• Four million births per year in the United
States alone
• In underdeveloped nations – lack of skilled
attendants
• Natural process with modernization
Maternal Mortality Ratio
(WHO, 2002)
Maternal deaths per
100,000 live births
Lifetime risk of
maternal death 1/
United States
17
2500
UK
13
3800
Australia
8
5800
Lao
650
25
Ethiopia
850
14
Rwanda
1400
10
Niger
1600
7
Afghanistan
1900
6
Maternal Mortality
(Grady Memorial Hospital, GA)
Maternal Mortality
(GMH, 1949-2000)
Causes of Death
1949-1971 (n=165)
1972-2000 (n=125)
101 (61)
44(35)
Pre-eclampsia
21(13)
16(13)
Infection
36(22)
7(6)
Hemorrhage
21(13)
8(6)
Vascular/AFE
15(9)
9(7)
Indirect
31(19)
32(26)
Unrelated Medical
29(17)
45(39)
Infection
3(2)
10(8)
Homicide
3(2)
15(12)
Accident
7(4)
8(6)
Direct
What is labor?
• Labor = the act of uterine contractions
combined with cervical change
• Fetus is gradually pushed through the birth
canal (consisting of the cervix, vagina and
perineum)
• Placenta is extruded and uterus involutes
What is labor?
What is labor?
What starts labor?
• An intricate and baffling association
between fetus and mother exist
• Several components are known, but many
are not – extrapolated from animals
• Involves hormonal communications
between mother and fetus
• In other words – we can speculate but we’re
not quite sure!
Induction of Labor
• Need to have a reason!
– Maternal indications
– Fetal indications
• Need to have a plan!
– Favorable cervix?
• No? Cervical ripening
• Yes? Pitocin
Bishop Score
Parameter\Score
0
1
2
3
Position
Posterior Intermediate Anterior Consistency
Firm
Intermediate Soft
Effacement
Dilation
Fetal station
0-30%
<1 cm
-3
40-50%
1-2 cm
-2
60-70% 80%
2-4 cm >4 cm
-1, 0
+1, +2
Cervical Ripening
• Mechanical
– Stripping (or sweeping) of the fetal membranes
– Placement of hygroscopic dilators within the
endocervical canal
– Insertion of a balloon catheter above the
internal cervical os (with or without infusion of
extra-amniotic saline)
• Pharmacologic
– Prostaglandins
• Prostaglandin E2-cervidil
• Prostaglandin E1-misoprostil
After the initiation of labor…
• Factors responsible for the ongoing labor
process include:
– Oxytocin
– Prostaglandins (PGF2-alpha, thromboxane,
PGE1,E3)
– Endothelin (by receptor-PLC coupling via
nifedipine sensitive channels)
– Epidermal Growth Factor
How does the uterus contract?
• The uterus is made from a weave of smooth
muscle (myometrium) covered by a smooth
cellular surface (serosa) – all formed by the
joining of the two original mullerian horns
• The cavity is hollow and lined by
vascular/stromal bed that is responsive to
hormonal stimulation (i.e. menstrual cycle)
Structure of the uterus
What does the myometrium need
to contract?
• CALCIUM!
• Calcium channels allow influx which
through a cascade of events activates
myosin
• Smaller calcium supply comes from other
organelles (i.e.. Sarcoplasmic reticulum)
• These all play a part in how we can
manipulate labor!
The Cardinal Movements of Labor
Stages of Labor
• First stage – Latent and active labor
• Second stage – Descent with pushing to
delivery of baby
• Third stage – Delivery of placenta
• Fourth stage – involution of the uterus
Stages of Labor
Stages of Labor
• Stage 1 (Latent Phase)
– Uterus and cervix prepare for active labor
– Dilatation up to 4 cm
– Variable length of time
Stages of Labor
• Stage 1
– The “Active” Phase – rapid cervical dilatation
from 4 centimeters to 10 centimeters (or
complete dilatation). Varies for nulliparous vs.
multiparous patients
• Nulliparous – 1.2 cm/hr
• Multiparous – 1.5 cm/hr
Stages of Labor
• Stage 2 “Pushing”
– Starts from complete dilatation to delivery of
the fetus
– Variable depending on parity maternal forces
– Fetus has to make it’s way through the curves
of the pelvis
Third Stage of Labor
• Stage 3
– From delivery of the fetus to delivery of the
placenta
– Variable amounts of time for placental
extrusion but generally within the first 20-30
minutes
– Medications can be used to augment placenta
delivery and post-partum bleeding
Fourth Stage of Labor
• Stage 4
– Immediate period after placental delivery
– Uterus contracts to close off venous sinuses
and slow bleeding
– Watch for signs of post-partum hemorrhage
When is labor not progressing?
Fetal causes of dystocia
• Breech – presenting parts not optimal
• Macrosomia – too big!
• Occiput posterior – fetus is facing “sunnyside up”
(face up)
• Malpresentation – fetal head is not perfectly
flexed
• Compound presentation – two parts presenting
• Congenital abnormalities obstructed in the birth
canal
Breech Presentation
• Non-vertex presenting
part – Buttocks!
• Occurs in about 3-5%
of term deliveries
• Forms of breech
presentation include
complete, footling, and
frank breech
Breech presentation
• Look for possible causes (large baby, no
fluid, birth defects, uterine anomalies)
• Risks of labor from breech presentations
include fetal injury, cord prolapse,
entrapment, maternal injury
• Delivery options include vaginal breech
delivery, external cephalic version (ECV),
elective cesarean section
Occiput posterior (OP) presentation
• Approximately 10% of
deliveries
• Face is looking up
towards the ceiling
versus the floor
• Fetus must perform
opposite
flexion/extension
maneuvers to navigate
the birth canal
OP Presentations
• What can we do about OP presentations?
– Leave it alone – babies can deliver from OP,
ROP and LOP presentations (back labor!)
– Rotate the fetal head – manually or with forceps
– Change labor positions for the mother such as
knee-chest
– Offer regional anesthesia – allows for pelvic
muscle relaxation
– If labor arrests - cesarean
Malpresentation
• Occurs when the bony parietal bones of the
fetus are not the presenting. These include:
– Face presentation 0.1-0.2% of all deliveries
(head is hyper-extended)
• Let nature work its magic – they usually deliver
vaginally
• Do not try to correct
• Babies can have edematous faces, they resolve
Malpresentation
• Brow presentation –
area between orbital
ridge and anterior
fontanel
• Press on but if labor
arrests - cesarean
Malpresentation
• Shoulder presentation
– Also called transverse or oblique lie
– About 0.3% of all deliveries
– Reasons include grandmultiparity (5 or more
births), prematurity, placenta previa and small
pelvis
– What you can do: ECV to vertex presentation
or cesarean
Malpresentation
• Compound presentation
– Extremity + presenting part enter the pelvis
(most commonly hand + head)
– Very common in extremely premature infants
– Majority of the time not a problem – babies can
deliver with or without hand on head. Many
times they retract spontaneously.
Fetal macrosomia
• Fetus is too large for the pelvis
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>4500 grams in a non-diabetic patient
>4000 grams in a diabetic patient
>95%-ile for gestational age
Can estimated by experienced hands on
Leopold's maneuver or by ultrasound and
sometimes even by the mother!
Types of Maternal Pelves
What can we do when labor is
not progressing?
• Natural methods
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Rupture of membranes
Walking
Nipple stimulation
Position change
Herbs (used as abortifacients)
Medical treatments for protracted
labor
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Augmentation of contractions with Pitocin
Anesthesia
Repositioning of fetal head
Assistance with vacuum or forceps
Other options for delivery…
• Vaginal assistance
with forceps (18th
Century)
• Vaginal assistance
with vacuum
• C/S
Considerations for Operative
Vaginal Delivery
• Maternal Criteria
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Adequate analgesia
Lithotomy position
Bladder empty
Clinical pelvimetry must be adequate in
dimension and size
– Consent
Considerations
• Fetal criteria
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Vertex presentation
Fetal head engaged in the pelvis
Position of fetal head must be known
? Presence of caput or molding
Considerations
• Other criteria
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Cervix fully dilated
Membranes ruptured
No placenta previa
Experienced operator
Capability to perform an emergent cesarean
delivery if needed
Operative Vaginal Delivery
• Assisted
• Two methods used
– Forceps
– Vacuum
• Randomized studies comparing the two have
not shown a significant difference in success
rate
• Choice of use dependent largely on clinician
preference and experience
Cesarean Section
• Named after Julius
Caesar?
• Evidence goes back as
far as ancient times
• Originally performed
to save fetus from
dying/deceased mother
(particularly males)
History of the C-section
• Latin term “caedare”
means to cut
• “Caesones” = infants
born by post-mortem
operations
• Was not meant to save
mother’s life until the
18th Century
How far we’ve come…
• Addition of
anesthesia, antisepsis
and sterile technique
• Closure of uterine
incisions vs.
hysterectomy
• Significant reduction
in mortality after
1940’s –Why?
Cesarean section
• In the US, 20% of all deliveries
• Popularity is growing for elective c-sections
(as high as 90% of deliveries in Brazil)
• In underdeveloped nations – significant
birth trauma to mother/baby, even death due
to inability to perform (skilled attendants)
• Surgery is not without risks
Indications for C-section
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Failure to progress
Fetal distress without imminent delivery
Fetal anomaly
Breech or macrosomia
Maternal pelvis
Maternal illness
How do we perform a C-section?
• A “smile” incision is
made on mother’s
lower abdomen
• Incision is made to
open the uterus
• “Bag of waters” is
broken (amniotomy)
C-section procedure
• Surgeon reaches into
uterus and obtains
presenting part
• Assistant compresses
the uterus at the
fundus to push baby
out the incision
• Placenta delivered,
uterus and incision
closed
Risks of C-section
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Bleeding
Infection
Injury to surrounding organs (which ones?)
Subsequent scarring for future surgery
Anesthesia risks
Risks of previous c-sections
Risks of previous c- section
Why do we do all this?