Obstetrics Flashcards
Define the 4 stages of labour
- From onset of contractions to full dilation of cervix
- From full dilation of cervix to expulsion of foetus
- From expulsion of foetus to expulsion of placenta
- From expulsion of placenta onwards
What are the 8 steps in mechanism of delivery?
- Engagement
- Head enters pelvic inlet in transverse - Descent
- Measured using ‘station’ from ischial spines - Flexion
- Foetal head flexes to chest in narrow mid-cavity - Internal rotation
- 90o rotation of head from transverse diameter to AP diameter (wider) - face now pointing at rectum - Extension
- Extension of head so no longer trapped under pubic symphysis
- Crowning - Restitution
- Head returns to normal position - External rotation
- Shoulders rotate to AP plane
- Occiput follows - Shoulders are delivered
- Anterior first then posterior, then rest of body
Describe what occurs during the first stage of labour
3 stages: LATENT - Onset of regular contractions --> 4cm dilation - Cervical effacement ACTIVE - Accelerated cervical dilation to 8cm - Increased force and duration of contractions TRANSITIONAL - Full dilation of cervix to 10cm
Describes what occurs during the second stage of labour
- Urge to push
- Forceful, expulsive contractions
- Crowning
Describes what occurs during the third stage of labour
- Placental delivery <30mins after foetal expulsion, any longer and placenta is retained
- Placental separation: rush of blood, lengthening of cord
Describes what occurs during fourth stage of labour
- Breastfeeding
- Monitoring of vital signs for evidence of PPH
- Ensure fundal constancy (must be firm) - no uterine atony
- Vaginal/perineal repair
What is the management of labour during the ONSET of labour?
- Monitor vital signs
- Note time of ROM - assess every 30min
- Assess liquor
- Analgesia
What is the management of labour during the PROGRESS of labour?
- Palpate abdo every 30 min
- Vaginal every 4hrs
- Assess vitals - partogram
What is the management during the 2nd stage of labour?
- Assess foetal HR every 5min
- Monitor contractions, maternal effort, presenting part
- Collect cord blood if Rh negative
- Dry/keep baby warm
What is the management during the 3rd stage of labour?
- Cord traction, placental delivery
- Prophylactic syntocinon IM
- Estimate blood loss
- Examine placenta (lobes), membranes, cord
What is the management during the 4th stage of labour?
- Vaginal/perineal repair
- Monitor vital signs
- Assess fundus
What are 4 different indications for the induction of labour?
- Prolonged pregnancy (post-date)
- Foetal growth restriction
- Pre-eclampsia / other maternal HTN disorders
- Pre-labour rupture of membranes
- Chorioamnionitis
- Unexplained antepartum haemorrhage
- Maternal medical problems - diabetes, renal
- Logistics (distance from hospital)
What is the mechanism of action of syntocinon and why is it given in stage 3 of pregnancy?
- Oxytocin mimic
- Stimulates uterine contraction
- Given in stage 3 to accelerate phase and decrease risk of bleeding and retained placenta
What are some contraindications for induction of labour?
- Placenta previa or vasa previa (placental cord running close to the os)
- Transverse fetal lie
- Previous classical uterine incision
- Active genital herpes
- Pelvic structural abnormalities
What defines the 1st trimester?
1-13 weeks
What defines the 2nd trimester?
14-27 weeks
What defines the 3rd trimester?
28-40 weeks
Where would you expect the uterine fundus at 12 weeks gestation?
Pubis symphysis
Where would you expect the uterine fundus at 22 weeks gestation?
Umbilicus
Where would you expect the uterine fundus at 36 weeks gestation?
Xiphisternum
How do you calculate due date for pregnancy?
1st day of LMP + 9 months + 1 week
More accurate to do dating U/S
Use a gestational wheel
How do you define IUGR? Small for gestational age? Low birth weight?
IUGR: a fetus that has not reached its growth potential because of genetic or environmental factors, estimated foetal weight <10th centile for gestational age
- Head circumference is normal with reduced abdo circumference
SGA: INFANT whose birth weight is <10th centile for gestational age
- 50-70% of SGA fetuses are constitutionally small but healthy
LBW: <2500g regardless of age
If both the head circumference and abdominal circumference are reduced, what does this indicate?
Symmetrical IUGR usually suggests a chromosomal disorder. In a healthy baby the head circumference should remain normal, even if there is significant placental insufficiency, as the body makes sure the brain receives the necessary fuel at the expense of the rest of the body
What is the cause of a normal head circumference and reduced abdominal circumference?
Asymmetrical IUGR caused by placental insufficiency
Where would you expect the uterine fundus at 28 weeks gestation?
Half way between the umbilicus and xiphisternum
What are some common causes of IUGR?
Smoking, HTN, pre-eclampsia, GDM, Alcohol
What is the use of misoprostol during labour?
Misoprostol is a synthetic prostaglandin inserted vaginally and causes effacement of the cervix in addition to uterine contraction
What is the role of syntocinon during pregnancy
Syntocinon is a synthetic form of oxytocin. Oxytocin causes uterine contractions and cervical dilatation.
When would a nulliparous woman start to feel foetal movements?
Most women will become aware of foetal movements around 18-20 weeks. However if a women has had previous pregnancies they often notice movements earlier (around 15-18 weeks).
Define hypertension in pregnancy
BP>140/90 after 20 weeks gestation
At least 2 measurements 4hrs apart
Explain the different types of monozygotic twins depending on timing of cell division
DCDA - within 3 days conception
MCDA - 4-8 days
MCMA - >8 days
Conjoined - >12 days
Define zygosity
Number of fertilised eggs
Define chorionicity
Number of placentae
Define amnionicity
Number of amniotic cavities
What are the 4 T’s causing PPH?
Tone - uterine atony
Trauma - lacerations, episiotomies, rupture, inversion
Tissue - retained placenta, placenta accreta
Thrombin - coagulopathies, HELLP, aspirin
What are some red flags on a CTG?
- Prolonged bradycardia (<100 bpm) for > 5 min
- Absent BL variability
- Sinusoidal pattern
- Complex variable decelerations with ↓BL variability
- Late decelerations with ↓BL variability
How do you define PPH?
Blood loss >500mL during or after childbirth
What is the difference between primary and secondary PPH?
Primary - occurs in 24hrs
Secondary - occurs between 24hrs and 12 weeks post partum
What are some antepartum risk factors for PPH?
Previous PPH, retained placenta LOTS of para Placenta previa Anaemia APH Overdistension of uterus (Multiple gestation, polyhydramnios, macrosomia) Fibroids Coagulopathies
What are some intra and postpartum risk factors for PPH?
Prolonged labour Mismanaged 3rd stage Syntocinon-augmented labour Assisted birth Retained placenta Operative delivery Trauma Inversion / rupture