Fetal Period Flashcards
Gestational Time Units: Reference Point, Days, Weeks, Months…
Fertilization: 266, 38, 8 3/4 LMP: 280, 40, 40, 9 1/4
Nagel’s Rule
predcits and estimated due date based on the woman’s last menstrual period
Expected Date Delivery Calculation (EDD)
LNMP + 9mo + 7days OR LNMP-3mo +1yr +7 days
Trimesters Duration
First: LNMP-12wks Second: end of first to 27wks Third: end of second until term (40wks)
Embryo status 9th week
embryo has developed into a recognizable human being and primordia of all major systems have formed
Embryo to Fetus process
gradual extending from 9th wk to birth
Characteristics of fetus development
- Rapid body growth and differentiation of tissues, organs, and systems (maturation)
- slowdown in the growth of the head
- weight gain in the last 2mo
- growth in length 3rd, 4th and 5th months
Method used to measure embryo in 1st, 2nd, and 3rd trimester
1st: crown to rump length
2nd and 3rd: biparietal diameter (BPD)
What does biarietal diamenter (BDP) measure?
diameter of head
head circumference
abdominal circumference
femur length
foot length
What does foot length correlate with?
fetal age
CRL, foot length and fetal weight at 12wks
CRL: 87mm
Foot: 14mm
Weight: 45gm
CRL and Weight in 9-12wks
5-8cm and 10-45gm
CRL and Weight in 13-16wks
9-14cm and 10-45g
CRL and Weight in 17-20wks
15-19cm and 250-450g
CRL and Weight in 21-24wks
viable but not that accurate from now on.. 20-33cm and 500-820wks
Development 9wks
external genitalia is similar in both sexes
liver major site of erythropoieses
head constitutes hald of the crown-heel length of the fetus
broad face, eyes widely separated, ears are low set, eyelid fused
short legs, small thighs
intestinal coils are clearly visible in the proxima end of the umbilical cord
Development 12wks
Growth of in doby length accelerates, at the end of the 12wks the CRL has more than doubled.
sex can be recognized in most cases
primary ossification centers appear in the skeleton
upper limbs almost have reached their final length
intestines have returned to the abdomen
erytrhopoiesis in spleen
urine formation begins and is discharged in the amniotic fluid
fetal waste is transferred to the maternal circulation trough the placeta
some amniotic fluid is reabsorbed by swalliwing it
major fetal form established
Development 13-16wks
Growth is rapid
head is relatively smalll
lower limbs have lengthened and have slight movement
bones are clearly visible
slow eye movements occur
eyes face antriorly instead of anterolaterally
external ears are close to their definitive position
wk 16: ovaries are differentiated
Major development wk 16
ovaries are differentiated
Development 17-20wks
fetal movements (quickening) are felt by mother
Vernix caseosaL: greasy cheeselike material that covers skin for protection
lanugo: body covered by fine downy hair at 20wks
testes have begun to descend, visible head hair and eyebrows
brown fat present
rapid brain growth
Major development wk 20
lanugo
Development 20-25wks
may survive if born prematurely but may die because the respiratory system is still immature
substantial weight gain
wrinkle skin
skin is pink to red
lean body
rapid eye movements
lung start to produce surfactant
fingernails are present
Development 26-29 wks
lungs are capable of breathing air
eyelids are open
lanugo and head hair are well developed
subcutaneous fat is present under skind
toenails become visible
main site of hematopoiesis is spleen
30-34 wks
white fat is 8% of body weight
limbs have chubby appearance
pupillary light reflex can be elicited
Development 35-28wks
exhibit spontaneous orientation to light
nervous system sufficiently mature to carry out some interactive fxns
Major development wk 36
head and abdominal circumferences are approx. equal
(after abdomen is greater than head)
Major development wk 37
foot is slightly larger than femur (confirmation of fetal age)
Full term: body fat, CRL, weight, etc.
16% of body fat
360nm, 3,400 g
Prominent chest
testes are in the scrotum
Factor Affecting Prenatal Growth
smokers: weight 200g less than normal
social drugs
poor nurtrion
reduction of maternal placental circulation
pleacental abnormalities: reduction in total area for exchange of nutrients
Effects of reductiong of maternal placental circulation
can cause fetal starvation resulting in intrauterin growth retardation (IUGR)
Harmful Subtances that cross placental membranes
Viruses
CO
Cocaine, heroine
antibiotics
pentobarbital, diazepam (valium), xanax, ativan
thalidomide
oral contraceptives
nicotine, alcohol
anti-Rh antibodies
mercury, lead
toxoplasma gondhii (parasitic protozoa), treponema pallidum (spirochete causing syphilis)
Perinatology
branch of medicine that is well concerned with the well-being of the fetus and newborn infant
26wks of fetus to 4wks after birth
3rd trimester: considered unborn patient to whom diagnostic procedures may be performed
Ultrasonography
used at early stages
wide availability and low cost
age-estimation
BPD
non-invasive and used at early stages
MRI
high cost
limited fetal resolution
fixed planes of section
no risk for fetus having MRI imaging without contrast
Amniocentesis and Chrorionic Villus Sampling (CVS)
invasive procedure that detects chromosomal abnormalities
Amniocentesis
require cell culture to obtain adequate cell number of analysis
14wks after LMP
2nd trimester
20-30ml of amniotic fluid withdrawn
CVS
10-12wks after LMP
1st trimester
more risk involved than amniocentesis
fetal loss 1%
Percutaneous Umbilical Cor Blood Sampling (PUBS)
Cordocentesis
18-20wks after LMP: due to fragility of umbilical vein before
analyzes chromosomes nd fetal blood for certain infections and blood disorders
also used to perform blood transfusions on the fetus and adminiter medication into the fetal blood supply
1-2% risk of miscarriage
Fetoscopy
fiberoptic lighting instrument, rarely used today (PUBS instead)
see parts of the featl body around wk 18
small incision made in the abdomen and endoscope inserted into the amniotic cavity
can take pictures
only done if there are high chances that the fetus is not normal to detect defects not found by other tests
collect samples of tissues, skin, for hereditary disease
12% miscarriage risk
AFP Assay
Alpha fetoprotein
15-21wks to screen for neural tube defects
afp is a glycoprotein synthesized in the fetal iver and yolk sac
escapes into amniotic fluid in fetuses with open neural tube defects
low levels: down syndrome
testing alone is not a viable diagnosis for termination
serum AFP decreases rapidly after birth
Fetal Monitoring
indicates fetal distress
if positive, baby needs to be born immediately
Fetal distress
occurs when the baby’s brain is deprived of oxygen
lack of oxygen to the brain can be recognized by patterns in thr baby’s heat rate
Electronic Fetal Monitor
recognizes changes in oxygenation by monitoring babys heart rate
FISH
detection of chromosomal aneuploidies and mutations
DNA fragments are present in maternal circulation
Hematopoiesis in Development of Fetus
9wk: liver main site
12wk: some begins in spleen
26-29wk: spleen main site
28wk: occurs in the bone marrow
