S7) Foetal Growth and Development Flashcards
What is the foetal period and what happens during this?
- The foetal period is the period involving preparation for the transition to independent life after birth
- Growth and physiological maturation of the structures created during the embryonic period occurs
What characterises the embryonic period?
Embryonic period is characterised by intense activity (organogenetic period) but absolute growth is very small
What is crown-rump length?
Crown-rump length (CRL) is the measurement of the length of human embryos and fetuses from the top of the head (crown) to the bottom of the buttocks (rump)
Describe the differential growth observed in the crown-rump length
CRL increases rapidly in the pre-embryonic, embryonic & early fetal periods
Describe how weight gain varies in the different foetal periods
- Embryo – intense morphogenesis & differentiation; little weight gain; placental growth most significant
- Early foetus – protein deposition
- Late foetus – adipose deposition
Explain how body proportions change during the foetal period
- 9 weeks, the head is approx half crown-rump length
- Thereafter, body length & lower limb growth accelerates
Identify and describe 3 different ways of assessing foetal well-being
- Mother – foetal movements
- Regular measurements of uterine expansion – symphysis-fundal height
- Ultrasound scan
Obstetric ultrasound scan (USS) is routinely carried out at ~20 weeks.
Identify 5 advantages of this
- Safe
- Can be used early in pregnancy to calculate age
- Rules out ectopic pregnancy
- Indicates number of foetuses
- Assess foetal growth and anomalies
Identify and describe 2 different ways of estimating foetal age
- Last menstrual period (LMP) – prone to inaccuracy
- Developmental criteria – allows accurate estimation of fetal age
Why and when do we measure crown-rump length?
Measured between 7 & 13 weeks to date the pregnancy and estimate EDD
What is biparietal diameter and when is it used?
- Biparietal diameter is the distance between the parietal bones of the fetal skull
- Used in combination with other measurements to date pregnancies in T2 & T3
When is abdominal circumference and femur length used?
- AC & FL used in combination with BPD for dating and growth monitoring
- Useful for anomaly detection
How do we classify birth weights?
- Average: 3500 g
- Growth restriction: < 2500 g
- Macrosomia: > 4500 g (maternal diabetes)
Provide 3 possible reasons for low-birth weight
- They are premature
- They are constitutionally small
- They have suffered growth restriction (associated with neonatal morbidity & mortality)
The lungs develop relatively late.
Why is this?
- Embryonic development creates only the bronchopulmonary tree
- Functional specialisation occurs in the foetal period
Identify the different stages in the development of the respiratory system
- Weeks 8 – 16: pseudoglandular stage
- Weeks 16 – 26: canalicular stage
- Weeks 26 – term: terminal sac stage