Assessment of fetal wellbeing

Question 1

Methods for evaluating fetal wellbeing

Answer 1

1. Fetal movements
2. SFH
3. Ultrasonography, amniotic fluid, blood flows
4. Infection screen, chromosomal evaluation
5. Cardiotocography

Question 2

Fetal movements - overview

Answer 2

1. Healthy well fetus will move well every day
2. Periods of quiescence do not generally exceed 2hrs
3. Unhealthy fetus will rest to conserve energy
4. Woman typically perceives fetal movements from 20 weeks
5. Reduction in fetal movements is a frequent cause for presentation to delivery suites

Question 3

Assessment of maternal SFH

Answer 3

1. 20 weeks = fundus at level of umbilicus
2. 38 weeks when uterine fundus at xiphisternum
3. Between 20 and 38 weeks, SFH generally equal in cm to number of weeks of gestation +/-3cm
4. Measurement outside is taken to be abnormal, requiring U/S investigation
5. Suspicion of a small or large fetus is more likely not to be confirmed, so the overall tone of counselling should be one of reassurance

Question 4

Ultrasound

Answer 4

1. Fetal biometry = femur length (FL), biparietal diameter (BPD), head circumference (HC), and abdominal circumference (AC)
2. Estimated fetal weight (EFW) - accuracy of +/- 10-15%
3. Amniotic fluid volume - oligohydramnios, polyhydramnios
4. Blood flows - umbilical arteries (take blood from fetus to placenta, normally resistance is low), MCA (supplies blood to brain, usually high resistance but dilates in presence of fetal hypoxia)
5. Blood flows - ductus venosus (diverts blood from fetal liver to IVC an channels it towards heart and brain, dilates in presence of fetal hypoxia), uterine arteries (represent maternal perfusion of uterus, resistance usually lowers after 23 weeks)

Question 5

Small fetus (SGA) - causes

Answer 5

1. Small =

Question 6

IUGR - def

Answer 6

Fetus small and failing to reach true growth potential. Pathologically small fetus. Dx through U/S

Question 7

IUGR - complications

Answer 7

1. Increased rates of perinatal mortality and stillbirth
2. Increased incidence of cerebral palsy
3. Intrapartum fetal distress and asphyxia
4. Meconium aspiration
5. Emergency CS

Question 8

LGA - def

Answer 8

Fetal weight >90th centile

Question 9

Oligohydramnios - def

Answer 9

Reduced volume of amniotic fluid. AFI

Question 10

Oligohydramnios - causes

Answer 10

1. SROM (leakage of amniotic fluid)
2. Obstruction to fetal urine output - fetal abnormalities such as posterior urethral valves

Reduced fetal urine production

3. IUGR
4. Fetal renal failure or abnormalities
5. Post-dates pregnancy

Question 11

Oligohydramnios - ix (3)

Answer 11

1. U/S of fetus + Doppler
2. Speculum examination to look for ruptured membranes
3. If SROM: CRP, FBE, vaginal swabs

Question 12

Oligohydramnios - mx

Answer 12

1. If SROM at 34-36 or more weeks = induce labour unless CS indicated for another reason
2. If SROM before 34-36 weeks = give prophylactic oral erythromycin, monitoring signs of infection (4-hourly temperature and pulse), daily CTG, consider induction y 34-36 weeks
3. If IUGR = manage according to umbilical artery Doppler and CTG
4. If apparently isolated oligohydramnios = reconsider cause; intervention not usual if umbilical artery Dopplers are normal
5. If fetal renal tract abnormality = refer to fetal medicine centre

Question 13

Oligohydramnios - complications

Answer 13

Related to cause

1. Preterm ROM commonly followed by delivery +/- intrauterine infection
2. IUGR important cause of fetal and neonatal mortality and long-term morbidity

Related to reduced volume
3. Lung hypoplasia if

Question 14

Polyhydramnios - def

Answer 14

Increased amniotic fluid. In general, deepest pool of >8cm or an AFI>22

Question 15

Polyhydramnios - causes

Answer 15

Increased fetal urine production

1. Maternal diabetes
2. Twin-twin transfusion syndrome
3. Fetal hydrops (?)

Fetal inability to swallow or absorb amniotic fluid

4. Fetal GI tract obstruction (e.g. duodenal atresia, trachea-esophagea fistula
5. Fetal neurological or muscular abnormalities (e.g. myotonic dystrophy, anencephaly)

Question 16

Polyhydramnios - complications

Answer 16

1. Preterm delivery (probably because of uterine stretch)
2. Complications of the cause (e.g. duodenal atresia is associated with trisomy 21)
3. Malpresentation at delivery (bc increased room for fetus)
4. Umbilical cord prolapse
5. Maternal discomfort bc of abdominal distension

Question 17

Polyhydramnios - ix

Answer 17

1. Exclude maternal diabetes with OGTT

2. U/S examination of fetus

Question 18

Polyhydramnios - mx

Answer 18

Side note: severe polyhydramnios is usually associated with fetal abnormality

1. If massive polyhydramnios (e.g. AFI >40), amnioreduction (drainage of excess fluid with a needle) or NSAIDS
2. If fetal abnormality, refer to fetal medicine centre
3. Twin-twin transfusion syndrome is best managed in a fetal medicine centre, usually with laser ablation of placental anastomoses
4. If preterm, assess risk of delivery with cervical scan and/or fibronectin assay, and consider steroids
5. If unstable or transverse lie at term, admit to hospital. CS if labour ensues with an abnormal lie

Question 19

IUGR - mx

Answer 19

1. Early identification
2. Intensive fetal monitoring (SFH, ultrasound, Doppler, CTG)
3. Assign risk and time delivery
4. Continue the pregnancy safely for as long as possible (thereby decreasing the problems associated with prematurity) but deliver before the fetus becomes excessively compromised
5. The only intervention is delivery, so monitoring is not useful if the fetus could not survive if it were delivered (i.e. if