Labor

Question 1

Definition of:
- Labor
- Term
- Preterm labor
- Miscarriage
- Prolonged labor

Answer 1

• labor: products of gestation expelled from uterine cavity after 24w
• term: labor at 37-41+6 weeks
• preterm labor: labor at 24-37w
• miscarriage: labor before 24w resulting in non-viable fetus
• prolonged labor: labor lasting ≥24h in primigravida and ≥16h in multigravidas

Question 2

When is there risk of CPD (Cephalopelvic Disproportion)?

Answer 2

fetus has relatively large head → tight fit → risk of CPD

Question 3

What may affect bloodflow to the uterus?

Answer 3

• Uterine contractions
• Further decrease in bloodflow to the uterus by decreased venous return due to IVC compression and increased intrathoracic pressure during pushing

Question 4

3Ps of labor: main determinants of labor

Answer 4

• passage: birth canal (bony pelvis, soft tissue, cervix)
• passenger: fetus (size, presentation, position)
• power: uterine contractions, maternal effort

Question 5

1st stage of labor

Answer 5

Onset of labor to cervix fully dilated (as upper uterus contract)
* latent phase: tubular cervix to 3cm dilatation + fully effaced
* active phase: 3cm cervix to 7cm dilatation
* transition: 7cm cervix to 10cm (fully dilated)

Question 6

2nd stage of labor

Answer 6

Cervix fully dilated to delivery of fetus
* passive (pelvic) phase: cervix fully dilated to onset of urge to push (uterine contraction only, no urge to push)
* active phase: maternal urge to bear down until fetus delivered
* prolonged 2nd stage = >2h in nulliparous; 1h in multi → instrumental delivery

Question 7

3rd stage of labor

Answer 7

Delivery of fetus till delivery of placenta

Question 8

4th stage of labor

Answer 8

1-2h after delivery of placenta when uterus contract to stop bleeding from placenta

Question 9

What is onset of labor? What are the different types of contractions?

Answer 9

Definition: regular, usu painful, contractions that bring about progressive cervical changes

• Braxton-Hicks (warm up) contractions (無痛宮縮): irregular contractions in last 1m of pregnancy, help build strength for contractions of labor
• False labor: irregular contraction, w/o cervical changes, not change when lie down

Question 10

Signs of labor

Answer 10

Question 11

What are the mechanisms initiating labor?

Answer 11

Question 12

What is the process of contraction and retraction?

Answer 12

• Contractions (tightening)
• Retraction (shortening)

Question 13

Monitoring of contractions

Answer 13

• non-invasive: external tocography, palpation → record frequency and duration only
• invasive: intrauterine catheter transducer → can record intrauterine pressure but of little clinical use (no outcome benefit)

Question 14

What are the common dimensions of the AP diameter and transverse diameter of the pelvic inlet? What is the true conjugate and obstetric conjugate?

Answer 14

Question 15

What is the AP diameter of the pelvic outlet?

Answer 15

AP diameter (13.5cm) >
transverse diameter (11cm), i.e. a sagittal strait

Question 16

What are the types of pelvis?

Answer 16

Question 17

What is the terminology with regards to fetal position?

Answer 17

• Lie: relationship between long axes of fetus and uterus (longitudinal, oblique, transverse)
• Presentation: cephalic (head = majority), breech, shoulder (transverse lie)
• Attitude: degree of flexion of fetal upper C spine. Well flexed –> vertex presentation (most ideal) i.e. suboccipital bregmatic. Less well flexed –> occipitofrontal. Extende –> brow presentation i.e. occipitomental (13cm) –> vaginal delivery is contraindicated. Hyperextended –> face presentation i.e. submentobregmetic
• Position (relationship of denominator to inlet of maternal pelvis. Vertex = occiput, face =chin (mento), breech = sarcum (sarco), shoulder = acromion. Position (position of denominator with repsect to mother): left occipito anterior (LOA) = occipital is pointing towards left anterior side of the mothers vagina. Determined by PV exam by palpating orientation of suture and fontanelles
• Station and engagement: engagement (when greatest traverse diameter (biparietal) has pased through inlet of true pelvis (<2/5 head palpable above brim). station: how many 5ths of head palpable.
• Descent (station): position of presenting part with regards to ischial spine (-1 = 1cm above spine, +1=1cm below spine)

Question 18

Which babies are delayed cord clamping done in?
What is the advantage?

Answer 18

At least 30-60 seconds but is not appropriate when mother or newborn are unstable or when newborn placental circulation is not intact (previa/abruption)
* >30s in preterm biths
* >1 min in term births

Adv
* Higher iron stores at 6 months of age which is beneficial when mother has a low ferritin lvel or plans to breastfeed without iron supplementation
* Decreases neonatal and infant anemia
* Decreases IVH
* Facilitate fetal to neonatal transition

Question 19

What are the disadv of delayed cord clamping?

Answer 19

• Polycythemia in growth restricted neonates
• Hyperbilirubinemia resulting in more phototherapy
• Less umbilical cord for harvesting stem cells

Question 20

How to define active phase of 1st stage of labor?
When does 1st stage need active Mx?

Answer 20

Active phase: 3cm cervix to 7cm dilatation (10cm = fully dilated)

After 3cm onwards (active phase of 1st stage), should normally dilate 1-2cm/h. Here, the cervix only dilates 1cm after 4h –> poor 1st stage progress. Artificial rupture of membrane should be done given adequate fetal descent (-2 or lower).
Syntocinin given if fetal descent is not adequate

Question 21

What is Mx for CTG showing decreased variability and recurrent late decelerations?

Answer 21

Fetal scalp blood (only if not imminent delivery)

Question 22

In breech presentation, when can you not do ECV?

Answer 22

• Placenta previa or abruptio placentae
• Non reassuring fetal status
• IUGR in association with abnormal umbilical artery doppler index
• Isoimmmunization
• Severe preeclampsia
• Recent vaginal bleeding
• Significant fetal or uterine anomalies

Other contraindications
* Rupture of membrane
* Fetus with hyperextended head
* Multiple gestations (however ECV may be considered for a second twin after delivery of the first

Question 23

What are the indications for classic Caesarean section?

Answer 23

Question 24

How to manage grade 3 placenta previa that is posteriorly located?

Answer 24

C/S