Fetal Growth and Development Flashcards

1
Q

What are the 3 stages of fetal developement?

A
  1. Pre-embryonic (weeks 1-2)
  2. Embryonic (weeks 3-8)
  3. Fetal (weeks 9-38)
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2
Q

How does fetal growth change throughout pregnancy?

A
  • embryonic period - growth is very small but major body organs are developing
  • fetal period - accelerated growth
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3
Q

How does the pattern of weight gain change throughout the fetal period?

A

Early fetal period- mainly protein from muscle development

Later fetal period- mainly adipose tissue for metabolic purposes and to regulate heart beat

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4
Q

What is the crown rump legnth? How does this increase throughout pregnancy?

A

The legnth of the fetus from head to tail

Increases linearly during the pre-embryonic, embryonic and early fetal periods

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5
Q

How does the body proportion of the fetus change during the fetal period?

A

Week 9- Head is ~ 1/2 CRL

After week 9, body and lower limb legnth accelerates

At birth - head is still 1/4 body legnth at birth

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6
Q

What measurements are taken at an ante-natal assessment of fetal well-being?

A
  • Assess mother
  • Fetal movements from 20 weeks onwards
  • Regular measurements of uterine expansion → Symphysis- fundal height
  • Ultrasound scan
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7
Q

How is symphisis- fundal height calculated?

A

Measured from the pubic symphysis to the height of the fundus

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8
Q

In what circumstances would the symphysis- fundal height not correlate to the gestational week?

A
  • Polyhydraminos ( a lot of amniotic fluid)
    • happens if there are swallowing difficulties or exessive urine production
  • Oligohydraminos (less amniotic fluid)
  • Interuterine Growth Restriction
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9
Q

What can an ultrasound scan be used for in pregnancy assessment?

A
  • Can estimate date of pregnancy
  • Rule out ectopics
  • Identify multiple pregnancies
  • Routinely carried out at 20 weeks to assess fetal growth and check for any abnormalities
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10
Q

How can fetal age be calculated?

A
  • Last Menstrual Period - easy to do but error prone
  • Developmental Criteria - comparing USS measurements to ‘normal’ values
  • Crown Rump Legnth - good between 7-13 weeks due to linear progression
  • Biparietal diameter - distance between parietal bones of fetal skull used in the 2nd and 3rd Trimester
  • Abdominal Circumference - Measures the widest part of the abdomen, often used in combo with femur legnth
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11
Q

What is the weight of an average fetus? What are ‘abnormal’ measurement classifications?

A

Normal weight- 3,500 g

<2,500 g suggests growth restriction

>4,500 g suggets macrosomia

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12
Q

Give some reasons why a baby may have a low birth weight?

A
  • Baby is premature
  • Constitutionally small as the mother is small
  • Growth restriction
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13
Q

What is the most common cause of macrosomia?

A

Poorly controlled Gestational Diabetes

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14
Q

When do the lungs of the fetus develop?

A

Develop relatively late as not required for gas exchange until after delivery

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15
Q

How do the lungs develop?

A
  1. Develop as a divertculum of the foregut
  2. Separated by tracheoesophageal septum
  3. Budding/ branching of bronchioles begins weeks 8-16 in the pseudoglandular stage
  4. Respiratory bronchioles develop during canalucular stage weeks 16-26
  5. Terminal sacs develop from th ends of respiratory bronchioles at ~week 26
  6. Differentiation of Type I & II pneumocytes
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16
Q

Why are the lungs so important for pre-term survival?

A

The threshold of viability is 24 weeks

Viability is only possible once the lungs have entered terminal sac development

(Sets the current limit for threshold of termination of pregnancy)

17
Q

What is the average fetal HR?

A

110-160bpm reached at around 15 weeks

18
Q

When does fetal kidney function begin?

A

Week 10

19
Q

What can cause oligohydraminos?

A
  • placental insufficiency
  • poor renal function of the fetus
20
Q

What can cause polyhydraminos?

A
  • Issues in co-ordinated swallowing (CNS defect)
  • Congential abnormalies (trachea-osophageal fistula)
21
Q

Which system of the body is most vulnerable to injury during development?

A

The Nervous System

22
Q

What is required for coordinated voluntary movements in the fetus and when does this begin?

A

The corticospinal tract which develops from the 4th month of gestation

Myelination occurs only in the 9th month

23
Q

If a baby in unable to co-ordinate their movements until 1 year after birth, what could have happened at birth?

A

The Myelination of the corticospinal tracts was incomplete