Fetal growth

Question 1

Define Fetal Growth

Answer 1

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

Question 2

Describe the historical data derived from pregnancies

Answer 2

The data for babies height (crown-rump length) and weight was derived from failed pregnancies. The limitations from this is that these babies may have been growth restricted hence why they were miscarriages.

Question 3

What two factors does fetal growth depend on?

Answer 3

Genetic Potential

• derived from both parents
• mediated through growth factors eg insulin like growth factors

Substrate supply

• essential to achieve genetic potential
• derived from placenta which is dependent upon both uterine and placental vascularity

Question 4

What is normal fetal growth characterised by?

Answer 4

Cellular hyperplasia - 4-20 weeks of gestation rapid cell division and multiplication as the embryo grows into a fetus.

Hyperplasia and hypertrophy - 20-28 weeks, decline in cell division but cells increase in size.

Hypertrophy alone - 28-40 weeks, rapid increase in cell size, rapid accumulation of fat, muscle and connective tissue.

Question 5

Describe the fetal growth velocity

Answer 5

Weight gain:
14-15 wks: 5g /day
20 wks: 10 g/day
32-34 wks: 30-35g/day
>34 wks: growth rate decreases

Question 6

How do you assess baby growth in an antenatal clinic?

Answer 6

• Abdominal palpation
• Measure symphysis fundal height: Each centimetre is approx. a week.
• Obstetric Ultrasound examination

Question 7

Describe how you would measure the SFH?

Answer 7

SFH: distance over the abdominal wall from the symphysis to the top of the uterus. See slides for values by 38 weeks there is greater variation in size.

Smaller size:  wrong dates
	small for gestational age
	oligohydramnios
	transverse lie
Larger size: 	wrong dates
	molar pregnancy
	multiple gestation
	large for gestational age
	Polyhydramnios
	Maternal obesity
	Fibroids

Question 8

What are the pros and cons of SFH?

Answer 8

Pros:
Simple
Inexpensive

Cons:
Low detection rate: 50-86%
Great inter-operator variability
Influenced by a number of factors (BMI, fetal lie, amniotic fluid, fibroids)

Question 9

Describe the importance of dating

Answer 9

Dating by LMP: Last Menstrual Period
Inaccurate (irregular periods; abnormal bleeding; oral contraceptives, breastfeeding)

Importance of correct dating:

• SGA or LGA confusion (small or large gestational age)
• Inappropriate inductions
• Steroids in preterm delivery

All pregnancies should be dated by CRL (crown-rump length) except IVF pregnancies

HC is used if first scan is donw after 14 weeks (CRL>84mm)

Question 10

Describe the ultrasound assessment of fetal growth?

Answer 10

Fetal growth is assessed by 4 biometrical parameters (BPD, HC, AC, FL) and their combination (EFW)

Normaltive growth curves constructed from ultrasound measurements are expressed in centiles

They are used clinically to identify a normal intrauterine growth and detect risk of obstetric and neonatal complications

BPD - Biparietal diameter
HC - Head circumference
AC - Abdominal circumferance
FL - Femur Length

Looking for crossing centiles and static growth are a concern.

Question 11

What factors influence Fetal Growth?

Answer 11

Maternal:
 - Poverty
 - Age: younger age correlates to low BW
 - Drug use
 - Weight
 - Disease
 1 hypertension
 2 diabetes
 3 coagulopathy 
 - Smoking and nicotine: constriction of BV
 - Alcohol
 - Diet
 - Prenatal depression: Low fetal BW
 - Environmental toxins

Feto-placental

Genotype – genetic potential
Gender (B>G)
Hormones
Previous pregnancy

Question 12

What are the important fetal hormones?

Answer 12

PITUITARY
Somatotrophin yes (small?),partly via hepatic growth factors
Prolactin no
FSH/LH yes, via gonadal steroid production
PANCREAS Insulin yes
ADRENALS Androgens yes
GONADS Androgens yes
THYROID Iodothyronines probably by third trimester

Question 13

What is the customised growth chart?

Answer 13

The customised standard defines the individual fetal growth potential by three underlying principles:

1) Adjusted to reflect maternal constitutional variation maternal ht, wt, ethnicity, parity
2) Optimised by presenting a standard free from pathological factors such as diabetes and smoking
3) Based on fetal weight curves derived from normal pregnancies

Question 14

Describe normal and abnormal fetal growth

Answer 14

See slides

Question 15

What is the use of obstetric ultrasound examination?

Answer 15

?