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Reproduction > 7 - fetal growth and development > Flashcards

7 - fetal growth and development Flashcards

1
Q

what is the fetal period?

A

growth and physiological maturation of the structures created during the shorter embryonic period

period involving preparation for the transition to independent life after birth

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2
Q

what are the stages of prenatal development?

A

pre-embryonic: first 2 weeks
embryonic: 3rd week - end of the 8th week
fetal period: start of the 9th week to birth

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3
Q

when are pregnancy weeks calculated from?

A

date of LMP (last menstrual period) - so this is conception weeks + 2

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4
Q

what happens to growth and weight in the fetal period?

A

they accelerate

growth: CRL increases rapidly in pre-embyonic, embryonic and early fetal periods
weight: gain is slow at first, then increases rapidly in mid- and late- fetal periods

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5
Q

what causes weight gain during the different stages of prenatal development?

A

embryo: intense morphogenesis and differentiation - little weight gain - placental growth most significant

early fetus: protein deposition

late fetus: adipose deposition

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6
Q

how do body proportions change during the fetal period?

A

at 9 weeks the head is about half crown-rump length

after this the body length and lower limb growth accelerates

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7
Q

what are the ante-natal assessment of fetal well-being?

A
  • mother - fetal movements
  • regular measurements of uterine expansion (symphysis fundal height)
  • ultrasound scan
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8
Q

what is the symphysis fundal height?

A

measured in cm from the pubic symphysis to the top of the uterus

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9
Q

what are the advantages of USS?

A
  • safe
  • can be used early to calculated age and rule out ectopic pregnancies, number of fetuses
  • routine from 20 weeks
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10
Q

what are the methods of estimation of fetal age?

A

LMP - inaccuracy

development criteria - allows accurate estimation of fetal age

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11
Q

what techniques are used to assess fetal development?

A
  • crown rump length
  • biparietal diameter
  • abdominal circumference and femur length
  • 3D or 4D USS
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12
Q

what is crown rump length?

A
  • measured between 7 and 13 weeks to date pregnancy and EDD

- scan in T1 - less reliable in T2 or T3

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13
Q

what is biparietal diameter?

A

distance between the parietal bones

used in combination with other measurements to date pregnancies in T2 and T3

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14
Q

what is abdominal circumference and femur length?

A

used in combination with BPD for dating growth and development

used for anomaly detection

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15
Q

3D and 4D USS

A

new technology

not replaced standard USS

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16
Q

what are the classifications of birth weights?

A

3500g = average

< 2500g = growth restriction

> 4500g = macrosomia - maternal diabetes

17
Q

what are the reasons why babies can have low birth weights?

A
  • premature
  • constitutionally small (small mum)
  • suffered growth restriction
18
Q

what happens to respiratory development in the embryonic and fetal period?

A

embryonic period: bronchopulmonary tree develops

fetal period: functional specialisation

19
Q

what is the initial respiratory bulge called?

A

respiratory diverticulum

20
Q

what is the septum that divides the respiratory and GI tract?

A

tracheoesophageal septum

21
Q

what are the stages of respiratory development and during which weeks do they occur?

A

weeks 8-16: PSEUDOGLANDULAR STAGE

weeks 16-26:
CANALICULAR STAGE

weeks 26 - term:
TERMINAL SAC STAGE

22
Q

describe what happens during the different respiratory stages of growth

A

PSEUDOGLANDULAR:
budding and branching of the bronchioles starts

CANALICULAR:
branching that forms respiratory bronchioles (still no alveoli)

TERMINAL SAC STAGE:
terminal sacs develop at the ends of the respiratory bronchioles at approx week 26 to term.
at this point type I and II pneumocytes form and start to make surfactant

23
Q

what happens to the lungs during T2 and T3?

A

gas exchange still occurs at the placenta

  • breathing movements - conditioning of the respiratory musculature
  • fluid filled - crucial for normal lung development
24
Q

what is fetal viability and what is it determined by?

A

dependent on whether or not the pneumocytes are present.
without these cells gas exchange can not occur and the lungs will not be making surfactant and so is incompatible with life - has implications on termination of pregnancy and premature delivery

25
Q

if a pre-term delivery has to be done what can be administered to help stimulated surfactant release?

A

glucocorticoids

26
Q

what is respiratory distress syndrome?

A

when there is insufficient surfactant production

often affects infants born prematurely

27
Q

describe the important developments in the CVS in the fetus

A
  • oxygen circulation
  • an average fetal HR is 110-160 bpm and achieved at around 15 weeks
  • fetal bradycardia is associated with fetal demise
28
Q

describe the important developments in the urinary system in the fetus

A
  • kidney function begins at week 10
  • urine is a big component of amniotic fluid and production begins in the fetal period
  • kidney function is not required in utero - but without it oligohydramnios can occur
    removal of waste is managed by the placenta and dependent on the maternal renal function for excretion
29
Q

what is the importance of amniotic fluid volume? and what is it called if there is too little or too much amniotic volume?

A

oligohydramnios =
too little
placental insufficiency or poor renal function in the fetus

polyhydramnios =
too much
could indicate an issue with recycling the amniotic fluid - issues co-ordinating the swallowing movement (CNS defect)
- congenital abnormalities (trachea-oesophageal fistula)

30
Q

describe the important developments in the nervous system in the fetus

A
  • first to begin and last to finish in development
  • corticospinal tracts required for coordinated voluntary movements begin to form in the 4th month
  • myelination of these tracts incomplete at birth
31
Q

fetus is seen sucking its thumb during the fetal period what does this show?

A

it is practice for independent life after birth

32
Q

what is the earliest time that a mother can sense the fetus moving and what is this phenomenon called?

A

17 weeks

‘quickening’

33
Q

What fundal height landmark is used at gestational ages 12, 20, 36 and 37 weeks

A

12 - pubic symphysis
20 - umbilicus
36 - xiphoid process
37-40 - regression of fundal height

Reproduction (4 decks)

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