Small/Large for Dates

Question 1

When do you classify a baby as Small for Gestational Age (SGA)? Is this always pathological?

Answer 1

Usually when it is below the 10th decile of estimated fetal weight

Some babies are just physiologically small and it is not a problem. SGA babies can be broadly divided into one of two categories:

• CONSTITUTIONALLY SMALL (normal babies - might have small parents)
• IUGR BABIES

Question 2

What is IUGR? How is it seen on charts?

Answer 2

Intra-uterine growth restriction - babies that fail to reach their genetic growth potential
Instead of growing consistently along the 10th decile these babies are seen to cross centiles as their rate of growth slows

Question 3

What are some fetal factors that affect fetal growth?

Answer 3

Genetic potential (maternal genes more relevant)
Chromosomal - decreased growth in fetal or placental aneuploidy
Fetal anomaly
TORCH INFECTIONS

Question 4

What are some maternal factors that affect fetal growth?

Answer 4

Drugs and alcohol/smoking
Nutrition
Maternal disease e.g. SLE, Renal disease, Pre-eclampsia

Question 5

What are some placental factors that affect fetal growth?

Answer 5

Adequate invasion, adequate vascular function

Question 6

What factors might co-exist in the history for a woman with an IUGR baby?

Answer 6

Previous small baby
APH
Reduced fetal movements

Question 7

What measurements are made during ante-natal scanning that help us get a picture of babies size?

Answer 7

Abdominal circumference
Head circumference
Femur length
Bi-parietal diameter

Question 8

How do we tell the difference between constitutionally small babies and IUGR babies based on these measurements?

Answer 8

SLOWED RATE OF GROWTH - if serial growth plots are starting to cross the centiles then always be concerned about IUGR
HEAD SPARING - in growth restricted babies all measurements will slow/decrease but not head circumference. In constitutionally small babies all the measurements will be proportionally small

Question 9

What is always important to ask a woman if her baby is small?

Answer 9

How much it is MOVING - if the baby is restricted it will attempt to preserve energy by being less active

Question 10

How can we check whether placental blood flow has anything to do with restriction?

Answer 10

DOPPLER ULTRASOUND OF UMBILICAL ARTERY

Question 11

What is the really important thing to look at on doppler ultrasound of the umbilical artery?

Answer 11

END-DIASTOLIC FLOW.
There should always be a positive pressure in the umbilical artery even at the end of maternal diastole. If there is not (if EDF is low or even reversed) then this is very suggestive that the baby is at risk of HYPOXIA and delivery should be considered

Question 12

What are babies with IUGR at risk of?

Answer 12

Peri-natal mortality 
Still birth 
Operative delivery
NEC
Cerebral palsy 
Increased risk of diabetes and CHD

Question 13

How do we manage small babies?

Answer 13

If the baby’s AC is found to be <10 centile then go on and do an umbilical artery doppler
IF NORMAL do regular scans and consider delivery at 37-38 weeks if oligohydramnios found
IF RI >95th then assess amniotic fluid volume (if oligo arrange and CTG and consider steroids + delivery at 36 weeks or earlier if very abnormal). If normal consider delivery at 37-38 weeks
IF EDF REVERSED OR DECREASED Deliver at 34 weeks with steroids (regular monitoring) if REVERSED then admit, give steroids and delivery by CS

Question 14

What are big babies also known as?

Answer 14

MACROSOMIC

Question 15

When do macrocosmic babies usually occur? Why?

Answer 15

In diabetic women.

Fetal hyperinsulinaemia leads to increased growth and organomegaly, erythropoeisis and neonatal polycythaemia

Question 16

What are macrocosmic babies more at risk of?

Answer 16

Sudden intrauterine death 
Chronic hypoxia (increased oxygen demands)
Shoulder dystocia at delivery 
Neonatal hypoglycaemia, hypocalcaemia, hypomagnesaemia and polycythaemia