Flashcards in Foetal Growth Deck (16)
What is the definition of foetal growth?
The increase in mass that occurs between the end of the embryonic period and birth.
What is the trend in mass and how is it measured?
Mass increases - there is a period of accelerated growth, followed by a plateau near the end of pregnancy. Most weight gain occurs in the second half of pregnancy.
The baby is measured from top to bottom (crown-rump length). Data is mostly collected from miscarriage samples, which causes a lot of inaccuracy (as foetal growth restriction is one of the causes of miscarriage).
What can an early disruption in placental development cause?
Early onset foetal growth restriction. If this occurs later on, it can lead to reduced foetal weight gain.
Which 2 components does foetal growth depend on?
1. Genetic potential
- derived from both parents
- mediated through growth factors
2. Substrate supply
- essential to achieve genetic potential
- derived from placenta which is dependent on uterine and placental vascularity
Which 3 phases is normal foetal growth characterised by?
1. Cellular hyperplasia - increased cell division (usually i the first few weeks)
2. Hyperplasia and hypertrophy - increase in number and size of cells
3. Hypertrophy alone
Describe foetal growth trends.
The brain (continues development after birth) and liver develop rapidly in the third trimester. Up to 16 weeks, there is little difference in weight gain - most occurs in third trimester.
Weight gain: 14-15 weeks: 5g /day
20 weeks: 10 g/day
32-34 weeks: 30-35g/day
>34 weeks: growth rate decreases
How can foetal size be assessed ante-natally?
1. Palpation of the maternal abdomen
2. Measuring uterus size through symphysis fundal height (SFH) - measuring distance from pubic symphysis to fundus of the uterus
Why might a baby be measured as small?
- wrong gestational age
- baby is small for its GA
- oligohydramnios (amniotic fluid deficiency)
- transverse lie
Why might a baby be measured as large?
- wrong gestational age
- molar pregnancy
- multiple pregnancy
- baby is large for its GA
- polyhydramnios (excess amniotic fluid)
- maternal obesity
List some advantages and disadvantages of SFH.
- low detection rate (50-86%)
- lots of variability
- influenced by many factors (BMI, foetal lie, amniotic fluid, fibroids)
How can we date a pregnancy?
1. Asking the mother for the date of her last menstrual period - inaccurate due to irregular periods, contraceptives, abnormal bleeding, breastfeeding
2. Crown rump length - after 14 weeks (CRL > 84 mm), this also become
3. Head circumference - used if the first scan is after 14 weeks
Which 4 biometric parameters is foetal growth assessed by during ultrasound?
1. Bi-parietal diameter (BPD) - distance between the two sides of the head
2. Head circumference (HC)
3. Abdominal circumference (AC)
4. Femur length (FL)
The combination of these parameters is EFW.
Growth curves constructed from ultrasounds are expressed in centiles and are used to detect complications.
List some maternal factors influencing foetal growth.
- drug use
- prenatal depression
- environmental toxins
List some foeto-placental factors influencing foetal growth.
- previous pregnancies (previously affected pregnancy with intra-uterine growth restriction)
Which hormones have an affect on foetal growth?
1. Somatotrophin - via hepatic factors
2. FSH/LH - via gonadal steroids
3. Insulin - has a direct mitogenic effect on cellular development
5. Iodothyronine - probably by the third trimester