Obstetrics

Question 1

What are the ways to determine gestational age?

Answer 1

LMP (last menstrual period) - Naegeles rule: add 1y, subtract 3m, add 1 week in a lady with a 28 day cycle.
To adjust for cycle length, add however many days off 28 to EDD (eg 35 day cycle, add 7 days to EDD).

DATING SCAN is gold standard. Crown-rump length and biparietal diameter measured at 7-12 weeks.

Question 2

What blood tests are performed at booking?

Answer 2

FBC
Blood group and antibody screen (Rh)
HIV/Hep B&C/Syphilis/Rubella serology
Hb electrophoresis if at risk of sickle cell/thalassaemia

Question 3

What are the options for screening women for Down’s syndrome?

Answer 3

COMBINED TEST - nuchal fold thickness, and serum BHCG and PAPP-A. Performed at 11-14 weeks.
Quadruple test for those who book later performed at around 16 weeks. Serum screening (BHCG, AFP, uncongugated estriol, inhibin A)

Question 4

What are the indications for amniocentesis and at what gestation is it performed?

Answer 4

High risk for chromosomal abnormalities (eg >1:100 at screening)
FHx of single gene defect

Performed from 15 weeks

Question 5

When are US scans performed during a normal pregnancy, and what are their purpose?

Answer 5

7-12 weeks - dating scan
11-14 weeks - nuchal scan
(these two are often combined)

18-21 weeks - anomaly scan (foetal anatomy - structural abnormalities)

Question 6

What are the implications of discovering Group B streptococcus on a vaginal swab?

Answer 6

Vaginal commensal - therefore unlikely to cause maternal infection, so no immediate rx given.
Risk of transmission to foetus at birth and infection (pneumonia/meningitis) carries high morbidity/mortality, so abx prophylaxis (benzylpenicillin) at delivery and neonatal observation postnatally.

Question 7

What are the pros and cons of home delivery?

Answer 7

Pros - relaxing environment, more comfortable, no transport concerns, 1:1 care guaranteed, medical intervention less likely.

Cons - long transfer time to hospital in maternal/neonatal emergency, fewer options RE analgesia, expert medical care less readily available.

Question 8

What are the options for analgesia during labour?

Answer 8

Bath/water birth
TENs
Gas and air
Pethidine
Epidural

Question 9

What are the indications for an elective C section?

Answer 9

Breech
Multiple pregnancy (especially if first twin is breech)
Placenta praevia
Transverse/oblique lie
Prev c section: controversial, only recommended if ≥2 prev C sections

Question 10

What are the pros of an elective C section?

Answer 10

Timing of delivery known
Reduced rates of perineal pain after delivery
Reduced rates of uterovaginal prolapse and urinary incontinence later

Question 11

What are the cons of a elective C-section?

Answer 11

Increased rate of visceral injury
Increased risk of requiring hysterectomy
Increased risk of Transient Tachypnoea of the Newborn (TTN)
Increased abdo pain post delivery
Increased risk of post op VTE
Longer hospital stay
Subsequent surgery more likely - eg repeat CS, surgery for adhesions
Risks in subsequent pregnancies - placenta praevia, scar dehiscence

Question 12

What are the delivery options for a woman who had an emergency c-section during her last pregnancy?

Answer 12

VBAC - vaginal birth after c section (risk of dehiscence approx 1 in 200)
Elective c section

Question 13

What are the risk factors for breech presentation?

Answer 13

Preterm (40% at 20 weeks, 20% at 28 weeks, 6% at 34 weeks)
Uterine abnormality eg fibroid, septum
Foetal abnormality
Twins
Low lying placenta
Poly-/oligo-hydramnios (excessive/reduced amniotic fluic)

i.e anything that prevents head engaging in pelvis

Question 14

What are the risks of vaginal breech delivery?

Answer 14

Risks: cord prolapse, difficulty delivering head, fetal hypoxia, staff now not as experienced in delivering breech babies
Results in increased perinatal morbidity and mortality in infants born by vaginal breech at term

Question 15

What are the delivery options for breech presentation at term?

Answer 15

Elective C-section (at 39 weeks)
External cephalic version (ECV) - abdomen manipulated to turn foetus presentation - uncomfortable, often transient, though reduces risks ass with c section
Vaginal breech delivery

Question 16

A 32 year old multiparous woman presents with previously undiagnosed breech presentation at 38 weeks. Her previous pregnancy resulted in a Caesarean section. She has had no complications in this pregnancy and is keen to avoid a Caesarean section and have an ECV .

Select the single most appropriate action…..

a) Vaginal Breech Delivery
b) Caesarean section
c) External Cephalic Version

Answer 16

Caesarean section

Vaginal breech delivery and ECV are both contraindicated in women who have had previous Caesarean sections.

Question 17

A 34 year old G2P1 had a spontaneous vaginal delivery in her previous pregnancy and is now expecting twins. She has had an otherwise uneventful pregnancy so far. A growth scan at 37 weeks reveals that the first twin is cephalic presentation and the second twin breech. She is keen to have a vaginal delivery.

Select the single most appropriate action…..

a) Vaginal Breech Delivery
b) Caesarean section
c) External Cephalic Version

Answer 17

Vaginal Breech Delivery
In the situation of the 2nd twin presenting breech, a vaginal delivery is considered safer than in a singleton pregnancy as 1 twin has already passed through the birth canal, there is therefore not so much concern regarding delivery of the second baby’s head. This woman is also multiparous
which would increase the chances of a successful vaginal delivery.

Question 18

A 24 year old primiparous woman is expecting twins. At 37 weeks both are presenting breech. She has had an otherwise uneventful pregnancy.

Select the single most appropriate action…..

a) Vaginal Breech Delivery
b) Caesarean section
c) External Cephalic Version

Answer 18

Caesarean section
A vaginal delivery is contraindicated when the first twin is breech because of the possibility of ‘interlocking’ of the twins. ECV is contraindicated in multiple pregnancy. Caesarean section is therefore the safest option in this situation.

Question 19

A 27 year old multip has had one previous vaginal delivery. She is currently 37 weeks pregnant and has a fetus which is unexpectedly found to be presenting breech. She has had an otherwise uneventful pregnancy. She insists on a Caesarean section.

Select the single most appropriate action…..

a) Vaginal Breech Delivery
b) Caesarean section
c) External Cephalic Version

Answer 19

Caesarean section
This woman should be counselled regarding the three options. She would certainly be a good candidate for an ECV. However if following a thorough discussion of the risks and benefits of each option she still requests a Caesarean section her request should be granted.

Question 20

Describe the first stage of labour.

Answer 20

From onset of regular painful contractions to full dilatation:
Latent phase: up to 4cm dilation
Active phase: from 4cm to 10cm (fully dilated)

Nulliparous:
Often long
0.5-1cm per hour
Average 8 hours

Multiparous:
Often short
1-2cm per hour
Average 5 hours

Question 21

Describe the second stage of labour.

Answer 21

From full dilatation to delivery of infant

Nulliparous: 1-2 hours
Multiparous: Up to 1 hour

Question 22

Describe the third stage of labour.

Answer 22

From delivery of infant to delivery of placenta

Nulliparous: Up to 30 minutes
Multiparous: Up to 30 minutes