Foetal Growth and Abnormalities of Human Development

Question 1

What are the limitations of centile charts in the assessment of foetal growth?

Answer 1

• Maternal weight, height ethnic background, previous pregnancies affect foetal growth
• Must allow for this when looking at charts

Question 2

What factors influence foetal growth?

Answer 2

1. Substrate supply
   - sufficient nutrients are essential to achieve genetic potential
   - primarily based on placenta which is dependent upon both uterine + placental vascularity
2. Maternal factors
3. Foeto-placental factors
   - Previous pregnancies
   - Genetic potential
   - Gender (B>G)
   - Hormones

Question 3

What is foetal growth?

Answer 3

The increase in mass that occurs between the end of the embryonic period and birth

Question 4

How is symphysis fundal height measured?

Answer 4

Distance between pubic symphysis and top of uterus

Question 5

What maternal factors can affect foetal growth?

Answer 5

• poverty
• mother’s age
• drug use
• alcohol
• smoking + nicotine
• diseases
• diet + physical health
• prenatal depression
• environmental toxins

Question 6

What is intra-uterine growth restriction?

Answer 6

Failure of the infant to achieve its predetermined (genetic) potential for a variety of reasons

Question 7

What causes IUGR?

Answer 7

1. Maternal behavioural factors
   - Smoking
   - Low booking weight (<50 kg)
   - Poor nutrition
   - Age <16 or >35 years at delivery
   - Alcohol, drugs
   - High altitude
   - Social deprivation
2. Foetal factors
   - Multiple pregnancy
   - Structural abnormality
   - Chromosomal abnormalities
   - Intrauterine (congenital) infection
   - Inborn errors of metabolism
3. Placental factors
   - Impaired trophoblast invasion
   - Partial abruption or infarction
   - Chorioamnionitis
   - Placental cysts
   - Placenta praevia

Question 8

How is IUGR managed?

Answer 8

1. Timing delivery in these pregnancies depends on balancing risks to foetus if it remains in utero and hazards from prematurity, which decrease as gestation advances
2. Corticosteroids should be administered (if not already given) at gestations < 36 weeks in order to improve neonatal wellbeing, notably lung development
3. In some pregnancies, health of mother or infant (or both) can deteriorate rapidly, making an emergency Caesarean section a necessity

Question 9

How is IUGR screened and detected?

Answer 9

• Usually ultrasound
• Serial assessments of biparietal diameter, head circumference, abdominal circumference and femur length
• Serial estimates of foetal size parameters
• Evidence of foetal compromise on cardiotocography or abnormal Dopplers or evidence of maternal compromise

Question 10

How is ultrasound imaging used in foetal assessment?

Answer 10

• Assess fetal biometry, placental site and structural defects
• Dating scan at 8 to 14 weeks
• Sonographer estimates date of delivery based on baby’s measurements
• Can include a nuchal translucency (NT) scan, which is part of combined screening test for Down’s syndrome
• 2nd scan between 18 and 21 weeks = anomaly scan, or mid-pregnancy scan
• Checks for structural abnormalities in baby

Question 11

What are the commonly used foetal growth parameters?

Answer 11

Before 14 weeks:
- Sagittal plane US - crown-rump length

After 14 weeks:

• CRL becomes inaccurate
• Head circumference

To assess foetal weight:

• Biparietal diameter
• Abdominal diameter
• Head circumference
• Femur length
• Abdominal palpation
• External determination of size: Symphysis Fundal Height

Question 12

What are the 3 phases of normal foetal growth?

Answer 12

1. Cellular hyperplasia
2. Hyperplasia + hypertrophy
3. Hypertrophy alone