Fetal Growth - Assessment

Question 1

What are the stages of fetal growth?

Answer 1

1) Stage 1 (hyperplasia) - 4-20 weeks - rapid mitosis and increase of DNA content
2) Stage 2 (hyperplasia and hypertrophy) - 20-28 weeks - declining mitosis with increase in cell size
3) Stage 3 (hypertrophy) - 28-40 weeks - rapid increase in cell size (peak velocity 33 weeks), rapid accumulation of fat, muscle, connective tissue

Question 2

When does 95% of fetal weight gain occur?

Answer 2

During the second half of pregnancy (> 20 weeks)

Question 3

What is the crown-rump length at 8 weeks vs 32 weeks?

Answer 3

• 8 weeks = 3cm

- 32 weeks = 30cm+

Question 4

When do you stop measuring crown rump length (CRL) and why?

Answer 4

Don’t measure past 12 weeks bc can’t get the whole baby on the screen

Question 5

When is the greatest weight increase?

Answer 5

Third trimester

Question 6

Roughly what is the fetal weight at 8, 12, 26 and 38 weeks?

Answer 6

• 8 weeks = 3g
• 12 weeks = 90g
• 26 weeks = 1200g
• 38 weeks = 3350g

Question 7

In which trimester is there the most variation/wider range in weight?

Answer 7

3rd trimester

Question 8

How is growth assessed?

Answer 8

Using ultrasound

Question 9

Describe the aims of the first trimester ultrasound scan

Answer 9

• Routine scan approx. 12 weeks from LMP
• Checking for heart beat (viability)
• Checking if single fetus or multiple
• Measurement of CRL - used to date pregnancy
• Also offer combined screening for trisomies

Question 10

What is the crown rump length?

Answer 10

The distance between the top of the head (crown) and the bottom of the buttocks (rump)

Question 11

How is the pregnancy dated in the first ultrasound scan?

Answer 11

1) CRL 45-84mm = 11+2-14+2 weeks

2) If CRL > 84.1mm, date by head circumference

Question 12

What are the aims of the ultrasound assessment in the second trimester?

Answer 12

• Routine anomaly scan
• 18-20 weeks
• Assess fetal growth, fetal anomalies, placental site e.g. close to cervix

Question 13

What is measured to assess fetal growth/biometry in the second ultrasound scan?

Answer 13

1) Head circumference (HC)
2) Bi-parietal diameter (BPD)
3) Abdominal circumference (AC)
4) Femur length (FL)
5) Combine to estimate fetal weight (EFW)

Question 14

How should the US look to accurately measure abdominal circumference?

Answer 14

• Should see only one rib and should be circle shape

- If see multiple ribs or more oval, need to move the probe so it is clearer

Question 15

How should you measure femur length on an US?

Answer 15

Get the longest possible length by moving the probe

Question 16

How is fetal growth assessed without imaging?

Answer 16

Symphysial fundal height (SFH)

Question 17

How do you measure SFH to assess fetal growth?

Answer 17

• Use a tape measure upside down so the numbers are hidden

- Measure from the fundus (variable) to the symphysis (fixed)

Question 18

What is the link between gestational age and the SFH?

Answer 18

SFH = gestational age ± 2cm

- Linear relationship

Question 19

Where should the fundus be at 20 weeks?

Answer 19

Umbilicus

Question 20

What is measurement of SFH used for?

Answer 20

To tell if a baby is growing properly and the amount of amniotic fluid

Question 21

When does the link between SFH and gestational age not work?

Answer 21

1) Multiple pregnancies (would therefore scan them more often)
2) Morbid obesity

Question 22

How is a customised growth chart (GROW) different?

Answer 22

Baby’s expected growth is adjusted for factors e.g. mother’s DoB, ethnicity, parity, heigh, booking weight and BMI

Question 23

What is done in the second/third trimester growth scan if there are concerns about growth?

Answer 23

1) Biometry - HC, BPD, AC, FL
2) Amniotic fluid index (AFI)
3) Umbilical artery and middle cerebral artery doppler

Question 24

How is an amniotic fluid index used to assess fetal growth?

Answer 24

• Check women’s water hasn’t gone yet
• If this decreases, might suggest placenta malfunction
• If this is normal then it is a healthy small baby

Question 25

How is an umbilical artery fetal doppler used to assess fetal growth?

Answer 25

• Looks at waveform from placenta to baby
• Want to check blood is flowing in right direction
• If blood is going back and forward - deliver baby, ominous sign

Question 26

How is a middle cerebral artery fetal doppler used to assess fetal growth?

Answer 26

• Sign of redistribution is concerning - low reading is concerning as distributing more blood to its brain