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RDA - reproduction, development and aging > normal fetal growth > Flashcards

normal fetal growth Flashcards

1
Q

describe fetal growth pattern - length *

A

rapid growth at the start of the pregnancy that decreases

a lot of miscarriages are due to increased growth restriction

there is little variance up to 16weeks of pregnancy, but considerable variance in mid and late trimester

main cause of fetal growth restriction is diminished supply of nutrients

maternal habitus and physiology influence the babies size - positive correlation between mother’s height, uterine size and placental blood flow

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2
Q

describe weight gain of the fetus *

A

mainly occurs in mid-late trimester

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3
Q

define fetal growth *

A

increase in mass that occurs between the end of the embryonic period and birth

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4
Q

timeframe for the development of organs in fetus *

A

by trimester 1 most of the organs have developed

therefore if there is interruption to placental development - the earlier it is, the earlier you get fetal growth restriction; if it happens later it will cause reduced weight gain towards term

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5
Q

what does normal fetal growth depend on *

A

genetic potential - from both parents, mediated through GF eg insulin like GF - ie bigger parents will have bigger babies

substrate supply - essential to achieve genetic potential, derived from the placenta that is dependant on uterine and placental vascularity

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6
Q

describe an abnormal placenta *

A

small and infarcted - limits the nutrients that are given to the fetus

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7
Q

what are the 3 phases of normal fetal growth *

A
  1. cellular hyperplasia - 4-20weeks - rapid cell division and multiplication as embryo develops into a fetus
  2. hyperplasia and hypertrophy - 20-28wks - cell division declines and the cell increases in size
  3. hypertrophy alone - 28-40wks - increase in cell size, deposition of fat, protein and connective tissue
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8
Q

describe the growth of the organs *

A

brain, liver, heart and kidneys develop rapidly - there is doubling of DNA each week

the increase in cell size and number of cells decreases towards the end

at term - organs have <20% of cells characteristic of adult - more development is to be done after birth

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9
Q

what is the fetal growth velocity *

A

14-15 wks: 5g /day

20 wks: 10 g/day

32-34 wks: 30-35g/day

>34 wks: growth rate decreases - not consistant with the miscarriage data, showing it is unreliable

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10
Q

what is the purpose of abdominal plapation in pregnancy *

A

to determine the size of ther uterus for the stage of pregnancy

find the SFH - distance over the abdominal wall from the symphesis to the top of the uterus

  • 12 w: at symphysis pubis
  • 20 w: at umbilicus
  • 20-34w: GA +/- 2 cm
  • 36-38w: GA +/- 3 cm
  • >38w: GA +/- 4 cm
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11
Q

reasons why teh SFH might be smaller than it should be *

A

got the dates wrong

small for gestational age

oligohydramnios - less fluid

transferse lie - the baby is in the wrong position

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12
Q

reasons why SFH is larger than it should be *

A

wrong dates

molar pregnancy

multiple gestation

large for gestational age

polyhydramnios

maternal obestity

fibroids

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13
Q

benefits and disadvantages of SFH *

A

+ simple

+ inexpensive

+may identify gross changes in size and hence gross complications in pregnancy

  • low detection rate - 50-86%
  • inter-operator variability
  • influenced by many factors - BMI, fetal lie, amniotic fluid, fibroids
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14
Q

what do you do if the SFH is abnormal *

A

send for US

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15
Q

problem with dating from the last menstrual period (1st day) *

A

inaccurate - if have irregular periods, abnormal bleeding, oral contraceptives, breastfeeding

also of an unplanned pregnancy - people might not know the date of LMP

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16
Q

why is it important to date correctly *

A

so know if short for gestational age (SGA) or LGA

ensure there are not inappropriate inductions if the surfactant hasnt matured properly

so you know that the delievery is preterm and to give steroids

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17
Q

how should you date babies *

A

crown-rump length at end of 1st trimester preferably - variations in size are more limited at this point so gestational age can be estimated more effectively

except IVF - a 5 day embryo is inserted

head circumference is used if 1st scan is after 14weeks - CRL >84mm

US assessment of fetel growth is done on biparietal diameter, head circumference, arm circumference, femer length, and their combination - estimated fetal weight

18
Q

how are growth curves expressed and used *

A

they’re expressed in centiles - important because it allows compensation for babies of different sizes that are growing and developing normally

used to identify normal intrauterine growth nad detect risks of neonatal and obstetric complications

each parameter is expected to follow a centile - showing steady increases in size

19
Q

what do you need to ensure when taking measurements

A

that they are consistant - so make sure all the views are the same

for BPD and HC - make sure in midline, see the cavum and posterior horn of the lateral ventricles

for AC - transverse view of spine, stomach bubble and intrahepatic vein 1/3 from end of abdomen

20
Q

what are the maternal factors that effect fetal growth *

A

poverty - malnutrition

age - very young and old, old have increased risk of placental disruption

drug use

weight

disease - hypertension, dm, coagulopathy

smoking and nicotine

alcohol

diet

prenatal depression

environmental toxins

21
Q

feto-placental factors influencing fetal growth *

A

genotype-genetic potential

gender (B>G)

hormones

previous pregnancy

22
Q

what are the fetal hormones that can effect growth *

A

pit - somatotrophin (via hepatic GF), FSH/LH (via gonadal steroid production)

panc - insulin

adrenal - androgens

gonads - androgens

thyroid - iodothyronines (probably by 3rd trimester)

23
Q

describe the customised growth chart *

A

defines the individual fetal growth by:

  • adjusting to reflect maternal constituitional variation eg height, weight, ethnicity, parity
  • optimising by presenting a standard free from pathological factors eg smoking/dm
  • is based on fetal weight curves defined by normal pregnancies
24
Q

what is neonatal hydrocephalus

A

water in the brain

25
Q

what is teh function of obstetric US examination *

A

assessment of fetal wellness - not just size ie is it moving, what amniotic fluid is like and the growth measurements

look at trends in growth - have a gap of 10days-2wks to see if they fall off centiles

predicting metabolic comprimise - if becoming growth restricted they will stop moving and direct blood to the major organs

anticipating the need to deliver prematurely

liasing with neonatal services

26
Q

why has the use of data from miscarriages (historical data) been superseded *

A

didnt take accout of the possible causitive relationship between low fetak growth leading to miscarriage so data may be inaccurate

27
Q

difference between fetal growth and fetal weight *

A

weight increases during pregnancy, growth levels off

28
Q

describe how poverty affects fetal growth *

A

more likely to have chiuldren at a younger age = low birth weight

may have little education of risks of smoking. alcohol, drugs etc

more likely to have diseases that are harmful to the fetus

29
Q

how does mother’s age effect fetal growth *

A

between 16-35 have healthier env for fetus than the extremities - have fewer complications

extremities have a higher risk of preterm labour, this increases for women in poverty, afirican-americans and people who smoke

younger - more likely to drink/smoke/illegal drugs

premature babies from young mothers are more likely to have neurological defects that will influecnce their coping capabilities, irritability, trouble sleeping, constant crying

increased risk of Downs when>40

young and older are more exposed to the rsiks of miscarriage, premature births and birth defects

women over 35 more likely to have linger labour -result in the death of the mother/fetus

30
Q

describe how drug use effects fetal growth *

A

drugs are metabolised in the placenta and then go to the fetus - can cause addiction in babies

may lead to extreme irritability, crying and risk of SIDS

when using narcotics - greater risk of birth defects, LBW, and higher rate of death in infants/stillborn

marijuana - slow fetal growth rate and = premature delivery, can also lead to low birth weight, shortened gestational period and complications with the delivery

heroin - premature delivery, higher risk of miscarriages, facial abnormalities and head size and GI abnormalities, increased risk of SIDS, dysfunction of CNS and siezures, low birth weight, resp problems

cocaine = smaller brain= learning disabilities, stillborn/premature, LBW, damage to the CNS and motor dysfunction

31
Q

effect of alcohol on fetal growth *

A

disruptions of the fetuses brain development and organisation adn affects maturation of the CNS

can lead to ehart defects, small brain - affect learning behaviours

cause behavioural problems, mental reatrdation and facial abnormalities - smaller eyes, thin upper lip and groove between nose and lip

increase risk of stillbirths and miscarriages or LBW

fetal alcohol syndrome - developmental disorder

32
Q

effect of smoking/nicotine on fetal growth *

A

baby exposed to nicotine, tar and co

nicotine = less blood flow to the fetus - constricts the bv

co reduces ox flow to fetus

= stillbirth, LBW and ectopic pregnancy

increase in SIDS

increase risk of miscarriages, premature births, or infant mortality

link from smoking in pregnancy that led to asthma in childhood

33
Q

effect of maternal diseases on fetal growth *

A

if mother effected with disease - placenta cant always filter out pathogens

babies can be born with venereal diseases transmitted by the mother

34
Q

effect of mother;s diet and physical health on prenatal growth *

A

lack of iron = anaemia

lack of ca = poor bone and teeth formation

lact of protein can lead to smaller fetus and mental retardation

35
Q

describe how mother’s prenatal depression affects growth *

A

associated with lower fetal growth rates - mother’s prenatal cortisol levels play a role

36
Q

effect of environmental toxins on fetal growth *

A

exposure to environmental toxins leds to a higher rate of miscarriage, sterility and birth dgfects

including lead, mercury, ethanol or haszardous environments

37
Q

how does fetal gender effect growth *

A

male babies are bigger than females

infants are generally heavier in subsequence pregnancies

38
Q

effect of feto-placental hormones on fetal growth *

A

act on growth adn differentiation and enable a precise and orderly pattern of growth

actions may be mediated by other GR eg insulin like GFs - insulin stim growth by increasing the mitotic drive and nutrient availability for tissue growth

cortisol involved in maturation and differnetiation - acts directly on cells to alter gene transcription or-post translational processing of gene products, initiate switch form fetal to adult growth regulation ie IGF2-IGF1

thyroxine affects growth and maturation

GH not involved- showing growth in utero is due to changed metabolism and gene expression - to ensure rate is in line with nutrients and that intrauterine growth happens

insulin like growth factors are mitogenic - stimulate the fetal metabiolism and coordinating the feto-placental metabolism - IGF2 regulates early embryonic development, IGF1 is responsible for growth of the newborn

fetal insulin modulates expression if IGF, and has direct effects on the adipose tissue jad proliferation of the cells in the fetus; little effect on differentation

fetal glucocorticoid affects tissue differentiation and development of organs - lungs (surfactant), liver (control of glycaemia), intestines (maturation if the expression of digestive enzymes and proloferation of villi)

glucocorticoid with thyroid gland hormones affect development of CNS

39
Q

use of US to determine fetal well being *

A

1st scan between 11 and 14wks

  • confirm pregnancy is not ectopic
  • confirm viability by location of heart beat
  • number of fetuses
  • assessment of gestational age by CR length
  • measurement of nuchal translucency
  • look for anencephaly, holoprosencephaly and major abdo wall defects

2nd between 18-20 wks

  • confirm viability
  • number of fetuses
  • fetal biometry - head and abdomical circumferences, biparital diameter and femer length
  • assessment of amniotic fluid vol
  • assessment of placental location and cord insertion
  • offering an anatomical survey to look for normal appearance in organ systems
39
Q

why is US the preferred method for assessment of fetal growth *

A

it doesnt use radiation - so no harm to baby or mum

RDA - reproduction, development and aging (10 decks)

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