Small for Date Pregnancies

Question 1

What are the causes of small babies?

Answer 1

Preterm delivery
Small for gestational age (SGA) = intrauterine growth restriction (IUGR), foetal growth restriction (FGR), constitutionally small

Question 2

What is preterm delivery defined as?

Answer 2

Delivery <37 weeks gestation

Question 3

What are the different categories of preterm delivery?

Answer 3

Extreme preterm = 24-27+6 weeks
Very preterm = 28-31+6 weeks
Moderate/late preterm = 32-36+6 weeks

Question 4

How common are preterm deliveries?

Answer 4

6-7% of deliveries in the UK

1 in 10 pregnancies globally

Question 5

What are the preterm delivery survival rates?

Answer 5

19% at 23 weeks
40% at 24 weeks
>95% if beyond 32 weeks

Question 6

What are some aetiologies of preterm delivery?

Answer 6

Infection, placental abruption, or idiopathic
Pyelonephritis/UTI, appendicitis or pneumonia
Overdistension = multiple pregnancy, polyhydramnios
Cervical incompetence or idiopathic

Question 7

What are the risk factors for preterm delivery?

Answer 7

Previous preterm labour, multiple pregnancy, uterine anomalies, teenager, parity of 0 or >5, ethnicity, poor socio-economic class, smoking, BMI <20, drugs

Question 8

What are the indications for a planned preterm C-section?

Answer 8

Accounts for 25% of preterm births = severe pre-eclampsia, kidney disease, poor foetal development

Question 9

What are some emergency events that would lead to preterm labour?

Answer 9

Account for 25% of preterm births = placental abruption, infection, eclampsia

Question 10

What are some common causes of preterm labour?

Answer 10

40% due to unknown cause

20% due to premature membrane rupture

Question 11

What is small for gestational age defined as?

Answer 11

Estimated foetal weight (EFM) or abdominal circumference below 10th centile

Question 12

What are IUGR and FGR a sign of?

Answer 12

Failure to achieve growth potential

Question 13

What are the two types of growth restriction?

Answer 13

Symmetrical = small head and small abdomen
Asymmetrical = normal head, small abdomen

Question 14

What is used to identify small for gestational age babies?

Answer 14

Antenatal risk factors and screening

Question 15

What are some minor antenatal risk factors for SGA?

Answer 15

Age >=35, IVF, nulliparity, BMI <20 or 25-34.9, 1-10 cigarettes/day, previous pre-eclampsia, low fruit pre-pregnancy, pregnancy interval <6 months or >=60 months

Question 16

What are some major antenatal risk factors for SGA?

Answer 16

Age >40, >11 cigarettes/day, parental SGA, cocaine, daily vigorous exercise, previous SGA baby, previous stillbirth, chronic hypertension, diabetes, renal impairment, antiphospholipid syndrome, low PAPP-A, BMI>35, large fibroids, foetal echogenic bowel, heavy bleeding in pregnancy

Question 17

How is SGA screened for?

Answer 17

All women have measurement of symphysial-fundal height from 24 weeks

Question 18

When would you do a growth scan for suspected SGA?

Answer 18

If single symphysial-fundal height below 10th centile

Question 19

What would a growth chart for SGA show?

Answer 19

Serial measurements suggest slow/static growth

Question 20

How is SGA diagnosed?

Answer 20

Measurement of foetal AC then combine with head circumference +/- femur length to give EFW

Question 21

What additional measurements can be taken to aid diagnosis of SGA?

Answer 21

Liquor volume or amniotic fluid and may do Doppler

Question 22

What maternal factors influence SGA?

Answer 22

Lifestyle = smoking, alcohol, drugs

Height, weight, age and maternal disease

Question 23

When are uterine artery Dopplers performed?

Answer 23

All women have them performed as part of their 20 week scan

Question 24

What are the placental factors that influence SGA?

Answer 24

Infarcts, abruption, dysfunction

Question 25

What foetal factors influence SGA?

Answer 25

Infection = rubella, CMV, toxoplasma | Congenital anomalies and chromosomal abnormalities

Question 26

What is the link between early SGA and chromosomal abnormalities?

Answer 26

1 in 5 babies thought to be SGA <24 weeks will have chromosomal abnormality

Question 27

What does IUGR carry a risk of during labour?

Answer 27

Hypoxia and death

Question 28

What are the postnatal consequences of IUGR?

Answer 28

Hypoglycaemia, effects of asphyxia, hypothermia, polycythaemia, hyperbilirubinaemia, abnormal neurodevelopment

Question 29

What are the clinical features of poor growth?

Answer 29

Predisposing factors, fundal height less than expected, reduced liquor, reduced foetal movements

Question 30

How is foetal wellbeing assessed?

Answer 30

Growth scans with Doppler assessment, CTG, biophysical assessment

Question 31

What is a biophysical assessment?

Answer 31

US combined with CTG = considers movement, tone, foetal breathing movements and liquor volume

Question 32

How is a biophysical assessment scored?

Answer 32

Out of 10 = score of 8-10 is satisfactory, repeat if score is 4-6, deliver if score 0-2

Question 33

What is the primary tool for monitoring foetal wellbeing?

Answer 33

Umbilical artery Doppler = uses US to give measurement of placental resistance to flow

Question 34

What does the results of an umbilical artery Doppler mean?

Answer 34

Normal = constant flow to baby (even in diastole) | Developing resistance = absent diastolic flow, flow may eventually reverse (foetus not getting nutrition)

Question 35

What are some additional Dopplers that may be done to assess foetal wellbeing?

Answer 35

MCA and ductus venosus Dopplers

Question 36

When would you deliver a SGA?

Answer 36

37 weeks irrespective of growth trajectory (as long as everything is well)

Question 37

What are the indications for an early C-section to deliver a SGA baby?

Answer 37

Growth becomes static Abnormal umbilical artery Doppler Normal UA Doppler with abnormal MCA between 32-37 weeks Abnormal UA Doppler with abnormal ductus venosus Doppler between 24-32 weeks

Question 38

What is the timing of delivery for a SGA baby a balance of>

Answer 38

The risks of prematurity and the potential hypoxia in utero or stillbirth

Question 39

What centiles on a growth chart would indicate a constitutionally small baby?

Answer 39

babies between the 3rd and 10th centiles

Question 40

What are the causes of symmetrical IUGR?

Answer 40

Congenital, chromosomal, intra-uterine infection, environmental

Question 41

What are the causes of asymmetrical IUGR?

Answer 41

Pre-eclampsia, placental abruption, smoking

Question 42

What does it suggest if the ductus venosus Doppler is pulsatile or has high resistance?

Answer 42

May suggest baby is becoming acidotic

Question 43

Why does the middle cerebral artery decrease its resistance?

Answer 43

To maintain blood flow to the foetal brain