Labor Flashcards
Definition of:
- Labor
- Term
- Preterm labor
- Miscarriage
- Prolonged labor
- 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
When is there risk of CPD (Cephalopelvic Disproportion)?
fetus has relatively large head → tight fit → risk of CPD
What may affect bloodflow to the uterus?
- Uterine contractions
- Further decrease in bloodflow to the uterus by decreased venous return due to IVC compression and increased intrathoracic pressure during pushing
3Ps of labor: main determinants of labor
- passage: birth canal (bony pelvis, soft tissue, cervix)
- passenger: fetus (size, presentation, position)
- power: uterine contractions, maternal effort
1st stage of labor
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)
2nd stage of labor
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
3rd stage of labor
Delivery of fetus till delivery of placenta
4th stage of labor
1-2h after delivery of placenta when uterus contract to stop bleeding from placenta
What is onset of labor? What are the different types of contractions?
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
Signs of labor
What are the mechanisms initiating labor?
What is the process of contraction and retraction?
- Contractions (tightening)
- Retraction (shortening)
Monitoring of contractions
- 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)
What are the common dimensions of the AP diameter and transverse diameter of the pelvic inlet? What is the true conjugate and obstetric conjugate?
What is the AP diameter of the pelvic outlet?
AP diameter (13.5cm) >
transverse diameter (11cm), i.e. a sagittal strait
What are the types of pelvis?
What is the terminology with regards to fetal position?
- 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)
Which babies are delayed cord clamping done in?
What is the advantage?
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
What are the disadv of delayed cord clamping?
- Polycythemia in growth restricted neonates
- Hyperbilirubinemia resulting in more phototherapy
- Less umbilical cord for harvesting stem cells
How to define active phase of 1st stage of labor?
When does 1st stage need active Mx?
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
What is Mx for CTG showing decreased variability and recurrent late decelerations?
Fetal scalp blood (only if not imminent delivery)
In breech presentation, when can you not do ECV?
- 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
What are the indications for classic Caesarean section?
How to manage grade 3 placenta previa that is posteriorly located?
C/S
