Fetal Growth and Development Flashcards
What is Crown Rump length?
Describe its pattern of increase
Length of fetus (from head to tail)
Increases linearly in Pre-embryonic, Embryonic and Fetal periods
Weight gain is slow at first, then increases rapidly in mid and late fetal periods.
What tissues are deposited in the Early and Late fetus
Early fetus- Protein due to muscle development
Late fetus- Adpiose for metabolic purposes and heat regulation
Describe the Proportion of growth as pregnancy progresses
- Initally (week 9), the head is 50% of the length of the fetus
- At delivery, the head is 25% of the length of the fetus
List 3 ways of assessing fetal wellbeing
- Ask the mother
- Symphysis-fundal height
- USS
How does asking the mother help to asses fetal well-being
Fetal movements begin at 20 weeks and mother will be able feel this as well as any changes that may occur
How can the Symphysis-Fundal height be used to asses fetal wellbeing?
- From Pubic Symphysis to Fundus of Uterus
- At week 20, SFH should be at Umbilicus
- After week 20, SFH should equal week of pregnancy (E.g 28 cm at week 28)
Suggest and explain 2 causes of the Symphisis-Fundal height being larger than normal.
- Swallowing difficulties
- Excessive Urine production
Lead to Polyhydramnios (excess amniotic fluid)
Suggest 3 causes of the Symphisis-Fundal height being lower than normal.
- Intrauterine Growth Restriction
- (Oligohydramnios) Lack of amniotic fluid production
- As fetal head engages (head positions closer to cervix) in pelvis
Suggest 3 ways of using USS to assess fetal wellbeing
- Estimate date of pregnancy
- Rule out Ectopic IF DONE TRANSVAGINALLY
- Identify multiple pregnancy
Why is a ‘20 week scan’ routinely done?
Most structures have developed by this point and are visible on an Ultrasound
(And to asses growth)
List 3 genetic conditions that can be screened for via a combination of USS and Blood tests
Between what weeks is this done?
- Down’s Syndrome
- Edwards’ Syndrome (Rare to survive into adulthood)
- Patau’s Syndrome (Rare to survive into adulthood)
Weeks 10 and 14 (offered to all pregnant women)
Outline 2 broad types of methods used to estimate Fetal age
- Last Menstrual Period, LMP: Look at first day of LMP (Prone to inaccuracy)
- Use of Developmental Criteria: Comparing USS measurements to a ‘normal’ value
What are 3 developmental criteria used to estimate fetal age?
- CRL
- Biparietal diameter
- Abdominal Circumference
Between what weeks can CRL be used as developmental criteria to estimate fetal age?
Why is it a good method?
- 7 and 13
- Good method due to linear nature of progression
Describe the use of Biparietal Diameter as developmental criteria to estimate fetal age
Why is CRL not used?
- Distance between parietal bones in Fetal skull
- Used in Trimesters 2 and 3
- Correlation between CRL and age is less accurate in later pregnancy
Describe the use of Abdominal Circumference as developmental criteria to estimate fetal age
- Used in combination with Biparietal Diameter
- In Trimesters 2 and 3
- Widest part of abdomen, often in combination with Femur length
What is the average range of Fetus weight?
2.5kg-4.5kg (Average is 3.5kg)
<2.5: Growth restriction
>4.5: Macrosomia
List 3 causes of Low birth weight
List the most common cause of High birth weight
- Premature
- Growth restriction
- Constitutionally small (Small mother)
- Poorly controlled Gestational Diabetes
Outline the development of the Respiratory System
- Lungs develop relatively late
- As an out-pouching of the Foregut to create the Bronchopulmonary Tree in the Embryonic Period
- Further specialisation in the Fetal Period
Describe the development of the Respira System in the Embryonic Period after the BP Tree has formed
Pseudoglandular stage (Week 8-16); - Budding and Branching of Bronchioles
Canalicular stage (Week 16-26); - Further branching-> Respiratory Bronchioles
Terminal Sac stage (Week 26 onwards);
- Terminal sacs bud from Respiratory Bronchioles
- Type I and II Pneumocytes develop and produce Surfactant
What determines Fetal ‘Viability’?
Whether or not Pneumocytes are present (Surfactant production required otherwise-> Premature delivery or Pregnancy termination)
What do you do if Premature delivery is unavoidable, to stimulate fetal surfactant production?
Give Glucocorticoids
What is an average range of fetal heart rate?
When is this heart rate achieved?
110-160 BPM
At Week 15
When does Fetal urine production start?
Is Fetal Kidney function necessary for survival?
Week 9/10 in Fetal Period
Not necessary as Placenta handles majority of waste excretion
However reduced function-> Oligohydramnios
