Fetal growth Flashcards
A definition of fetal growth
The increase in mass that occurs between the end of the embryonic period and birth.
What does Symphysis Fundal Height identify?
distance between the pubic symphysis and the top of the uterus
Reflects generic changes in uterine size
What can lower values from SFH result from?
wrong last menstrual period date, the baby in a transverse lie, or complications including oligohydramnios (low levels of amniotic fluid) or a baby that is small for gestational age (SGA)
What can higher values from SFH result from?
wrong last menstrual period date, multiple pregnancy, or maternal obesity.
How is uterus position at week 40 different to week 38?
It’s lower believe it or not
What are possible complications?
molar pregnancy, fibroids, polyhydramnios or a baby that is large for gestational age (LGA).
What are the uses and problems with SFH?
may identify gross changes in size, and hence gross complications
generally of limited use, thanks to the many confounders, which include the problems listed above, as well as considerable inter-operator variability.
How do fetal weight and height changes differ?
weight continues to increase throughout pregnancy
fetal weight changes less later in, got a plauetue r shape.
What are the two primary components for fetal growth?
genetic potential
Substrate supply
What is genetic potential?
- derived from both parents, size of fetus reflectionof parents mediated by factors under genetic control e.g. IGF1
What is substrate supply?
- sufficient nutrients are essential to achieve genetic potential. This is primarily based on the placenta which is dependent upon both uterine and placental vascularity.
What are the 4 biometrical parameters of fetal growth?
Biparietal diameter (BPD), Head Circumference (HC), Abdominal Circumference (AC) and Femur Length (FL). They are combined to give the Estimated Fetal Weight (EFW).
What has been constructed from these ultrasound measurements?
Normative growth curves expressed in centiles
How are biometrical parameters used clinically?
identify a normal intrauterine growth and detect risk of obstetric and neonatal complications.
Which measurement is most important?
In many cases, it is not single measurements that are most important, but sequential measurements.
What are the underlying principles for customised fetal graphs?
They are based on fetal weight curves for normal pregnancies.
The are adjusted to reflect maternal constitutional variation e.g. maternal height, weight, ethnicity, parity.
They are optimised by presenting a standard free from pathological factors such as diabetes and smoking.
What is the overall average rate at which an infant gains weight?
14-15 wks: 5g /day 20 wks: 10 g/day 32-34 wks: 30-35g/day >34 wks: growth rate decreases Note that the final point, of decreased velocity towards the end of pregnancy, does not agree well with the early data in Figure 6.3, showing that the miscarriage data is not reliable.
What are the 3 main phases of normal fetal growth?
Cellular hyperplasia (increased cell numbers): 4-20 weeks Hyperplasia and hypertrophy (increased cell size): 20-28 weeks Hypertrophy dominates: 28-40 weeks
When is the main increase in weight?
Final trimester so hypertrophy key.
