Fetal Growth and Development Flashcards
What is the fetal period?
Growth and physiological maturation of structures created in the embryonic period
Outline the time frame of the pre-embryonic, embryonic, fetal periods
Pre-embryonic = weeks 1-2
Embryonic = weeks 3-8
Fetal = weeks 9-38
Outline fetal growth
Embryo – intense morphogenesis and differentiation; little weight gain; placental growth most significant
Early fetus – protein deposition
Late fetus – adipose deposition
Outline how the proportions of the body change during the fetal period
at 9 week, the head is approx half crown-rump length
thereafter, body length and lower limb growth accelerates
What ante-natal assessments can be used to asses fetal well being?
Mother = Fetal movements
Regular measurements of uterine expansion = Symphysis-fundal height
Ultrasound scan
What can an obstetric ultrasound scan be used for?
Early in preg = age, rule out ectopic, number of fetuses
Routinely carried out at ~20 weeks = asses fetal growth, abnormalities
How is fetal age estimated?
LMP = but prone to inaccuracy
Developmental criteria = crown-rump length, biparietal diameter, abdo circumference, femur length
What is crown-rump length?
Length between the fetal crown and rump
Measured between 7 and 13 weeks to date the pregnancy and estimate EDD
Scan in T1 also used to check location, number, viability
What is the biparietal diameter?
Distance between the 2 parietal bones
Used in T2 and T3
What 3 measurements can be used in t2 and T3 to asses fetal devel?
Abdo circumference
Femur length
Biparietal diameter
How can birth-weight be classified?
3500 g is considered average
< 2500 g suggests growth restriction
> 4500 g is macrosomia = maternal diabetes
What are the reasons babies can have low birth-weight?
Premature
Constitutionally small
Suffered growth restriction (associated with neonatal morbidity and mortality)
Briefly outline the devel of the respiratory system
Late devel
Out-pocking for foregut
Respiratory divertucum devel, tracheoesophageal septum forms = 2 separate tubes
Pesudoglandular stage = duct system begins
Canalicular stage = formation of respiratory bronchioles
Terminal sac stage = formation of terminal sacs, differentiation of T1/2 pneumocytes (T2 = surfactant)
How do the fetal lungs prepare for birth?
‘breathing’ movements = conditioning of respiratory musculature
Fluid filled = crucial for normal lung devel
What marks the stage of lung viability?
Terminal sac stage
What is respiratory distress syndrome?
Insufficient surfactant prod
Glucocorticoid treatment = increases surfactant prod in the fetus
How can fetal HR be used as an assessment of development?
Definitive HR achieved around 15 weeks
Fetal bradycardia is associated with fetal demise
What is oligohydramnios?
Too little amniotic fluid
= placental insufficiency, fetal renal impairment
What is polyhydramnios?
Too much amniotic fluid
= fetal abnormalities (e.g. Inability to swallow, fistula, bind ended osphagus, tracheaosphageal setum in the wrong place, cant coordinate swallow – CNS defect)
Outline the devel of the CNS
Corticospinal tracts required for coordinated voluntary movements begin to form in the 4th month
Myelination of brain only begins in 9th month
Corticospinal tract myelination incomplete at birth, as evidence by increasing infant mobility in the 1st year
What is maternal ‘quickening’
Awareness of fetal movements from ~17 weeks onwards
Low cost/simple ante-partum fetal surveillance
Which prenatal diagnostic test has the highest risk of preg loss?
chorionic villus sampling
What is the aetiology if fetal HR accelerations in utero?
response to fetal movement
What is the normal fetal pO2?
4k Pa
What is the normal fetal HR?
110-160 bpm
Outline fundal height during gestation
12 = pubic symphisis
16 = between pubis and umbilicus
20 = umbilicus
36 = xiphisternum
What treatment should be given to the mother to promote fetal lung devel should premature delivery be unavoidable?
corticosteroids
