Fetal Growth and Development Flashcards
Define fetal period
Growth and physiological maturation of the structures created during the embryonic period
Give the approximate timeline of pre-embryonic, embryonic and fetal stages
- Pre-embryonic - 1-2 weeks
- Embryonic - 3-8 weeks
- Fetal - 9-38 weeks
Distinguish between pregnancy weeks from weeks post fertilisation
- Pregnancy weeks calculated from date of last menstrual period
- Conception weeks +2, so term is 40 pregnancy weeks
Explain the changes in weight and height during pregnancy
- Weight gain is slow at first, then increases rapidly in mid- and late fetal periods
- Embryo - intense morphogenesis and differentiation
- Absolute growth is very small
- Placental growth most significant
- Growth and weight gain accelerate in fetal period
- Early fetus - protein deposition
- Late fetus - adipose deposition
Describe the classification of birth weights (normal and abnormal weights)
- 3.5kg considered average
- <2.5 kg suggests growth restriction
- > 4.5 kg is macrosomia
- Likely due to maternal diabetes
Give reasons to which why babies can have low birth weights
- They are premature
- They are constitutionally small - small mother = smaller baby
- They have suffered growth restriction
- Associated with neonatal morbidity and mortality
Describe the stages of respiratory system development
- Weeks 8-16 - pseudoglandular stage
- Duct system begins to form within the bronchopulmonary tree created during the embryonic period (bronchioles)
- Weeks 16-26 - canalicular stage
- Formation of respiratory bronchioles
- Budding from bronchioles formed during the pseudoglandular stage
- Formation of respiratory bronchioles
- Weeks 26-term - terminal sac stage
- Terminal sacs begin to bud from the respiratory bronchioles
- Differentiation of type I and type II pneumocytes
Explain when fetal heart rate is achieved
Around 15 weeks (110-160bpm)
Explain amniotic fluid contribution before and after kidney function
- Fetal kidney function begins in week 10
- Fetal urine is a major contributor to amniotic fluid volume
- Before week 8, amniotic fluid produced from maternal plasma
Differentiate between oligohydramnios and polyhydramnios
- Oligohydramnios
- Lower than normal amniotic volume
- Placental insufficiency, fetal renal impairment
- Polyhydramnios
- Too much amniotic volume
- Fetal abnormality - eg inability to swallow such as CNS defect causing uncoordinated swallowing
- Oesophageal atresia/fistula
Briefly describe the development of the nervous system
- First to begin development and last to finish
- Corticospinal tracts required for coordinated voluntary movements begin to form in the 4th month
- Myelination of brain only begins in 9th month
- Eg. Corticospinal tract myelination incomplete at birth, as evidence by increasing infant mobility in the 1st year
- No movement until the 8th week, but thereafter a large number of movements develop
Explain respiratory distress syndrome
- Often affects infants born pre-maturely
- Insufficient surfactant production
- If pre-term delivery is unavoidable or inevitable (eg. Preeclampsia)
- Glucocorticoid treatment of the mother
- Increases surfactant production in fetus
- Glucocorticoid treatment of the mother
- Threshold of viability - viability is only a possibility once the lungs have entered the terminal sac stage of development
When does ‘quickening’ occur in pregnancy
Maternal awareness of fetal movements from 17 weeks onwards - ‘quickening’
Explain symphysis-fundal height
Symphysis-fundal height - distance from top of mother’s uterus to pubic symphysis
Explain the use of obstetrics ultrasound scan
- Safe
- Can be used early in pregnancy to calculate age
- Rule out ectopic pregnancy
- See number of foetuses
- Routinely carried out at ~20 weeks
- Structures grown and large enough to be seen in USS
- Assess fetal growth
- Fetal anomalies
