Lecture 16 - Fetal Development Flashcards
Foetal period
Growth and physiological maturation of the structures created during the embryonic period
9 weeks to term
Greatest growth and weight gain
Crown rump length and weight gain
CRL - increases rapidly in the pre-embryoinc, embryonic and early gale tail periods
Weight gain - slow at first and increases rapidly in mid to late football period
Early foetus
Protein deposition and muscle development
Late foetus
Adipose deposition for metabolism and heat regulation
Head proportion
9th week - 50%
38th week - 25%
Ante-natal assessment
At 20 weeks
Foetal movements
Ask mother
Symphysis fundal height - uterine expansion
(Normally at umbilicus at 20 weeks and xiphisternum at 38 weeks )
Factors affecting symphysis fundal height
Polyhydraminios
- a lot of amniotic fluid
- over estimation
Oligohydramnios
- lack of amniotic fluid
- under estimation
Intrauterine growth restriction - smaller baby
Near term - faoetsl head engages the pelvis therefore SFH decreases
USS
Safe
Used to calculate age
Rule our ectopic pregnancy and number of foetuses
Assess foetal growth and anomalies
Estimating foetal age
Last menstrual period - innacurate
Conception 2 weeks after last menstrual cycle
CRL
Biparietal diameter
Crown rump length
Measured between 7 and 13 weeks to date the pregnancy and estimate the date of delivery
Biparietal diameter
Distance between the parietal bones in the foetal skull
- during 2nd and 3rd trimester
(Later in pregnancy CRL less accurate)
Abdominal circumference and femur length
Us3d with biparietal diameter for dating and growth monitoring
Width of widest part of the abdomen and length of femur
Birth weight
Average 3500g
Growth restriction - less than 2500g
Macrosomia - more than 4500g
Low birth weight reasons
Premature
Constitutionally small
Growth restriction
Respiratory system
Develop relatively late
Embryonic development - bronchopulmonary tree development
Foetal development - functional specialisation
Pseudoglandular stage
Week 8 - 16
Duct system begins to form within the bronchopulmonary segments creating bronchioles
Canalicular stage
Week 16 - 26
Formation of respiratory bronchiole
Budding from the bronchioles
Terminal sac stage
Week 26
Terminal sacs begin to bud from the respiratory bronchioles to produce alveoli
Differentiation of type I and type II pneumocytes
Production of surfactant from type II pneumocytes
Lungs during the 2nd and 3rd trimester
Gas exchange occurs at the placenta
Breathing movements - conditioning of the respiratory musculature
Fluid filled - amniotic fluid contains mediators that promoted the differentiation on pneumocytes
Pre term survival
Viable after 24 weeks after surfactant is made in the terminal sac stage
Respiratory distress syndrome
Often affects premature babies
Lack of surfactant
- when preterm birth is unavoidable e.g. in sever preeclampsia can give glucocorticoids to mother which increases surfactant production in the foetus
Foetal heart rate
100 -160
Around 15 weeks
Foetal Bradycardia - foetal distress due to hypoxia
Urinary system
Foetal kidney function occurs at 10 weeks
Foetal urine contributes to the amniotic fluid volume
Without kidney function - oligohydramnios
Oligohydramnios
Too litte amniotic fluid
Placental insufficiency
Foetal renal impairment
