Prenatal Growth Defects and Dx Flashcards
When is a baby considered pre-term?
Born before 34 weeks (38 normal pregnancy)
When are the organ systems of the fetus well-established?
By the second month of gestation
When does the embryo gain the most length and weight?
Length: 3-6 months gestation
Weight: 7-9 months gestation
Low birth weight
Less than 5 lbs. 8 oz.
SGA and IUGR
Small for gestational age (SGA)
Intrauterine growth restriction (IUGR)
At or below 10th %
Toxic insult/hereditary - one of most common causes is multiple births
Barker’s hypothesis
Obesity
Hypertension
Hypercholesterolemia
Type 2 Diabetes
Cardiovascular Disease
(IUGR) - produces problems as adults
Twins
7-11/1000 dizogotic
3-4/1000 monozygotic
Only 29% of women pregnant with twins give birth
10-20% die at birth
12% of premature infants are twins
ARTs = 1-2% of all pregnancies = more multiple birth pregnancies
Dizygotic twinning
Two separate embryos, typically separate placentas (sometimes they fuse)
Twin transfusion syndrome
One embryo receives too much blood supply the other too little
Defects of the primitive streak
Can produce conjoined twins
When is the appearance and dissapearance of the herniated gut loop common?
Appearance: wk 6
Dissapearance (reduces): wk 10
At what point in gestation is a fetus viable outside of the womb?
7 months (when lungs begin to make surfactant)
Types of birth defects
Malformations: Most occur during the 3rd-8th weeks, but the 1st 2 weeks are important too!
Disruptions: Alterations in already formed structures(vascular accidents, amniotic bands)
Deformations: Mechanical forces alter a structure (Potter’s face - renal agenesis)
Abnormal gene signaling (classification of abnormal fetal development)
Malformation
Vascular accidents are classified as what type of malformation during fetal development?
Disruption
Amniotic bands
The amnion strands wraps around and constricts blood floow (extrimities)
AER disruption can also produce similar effects
Causes of birth defects
Microarrays
Specific DNA sequences hybridized to patient’s DNA or RNA. Detects mutations and changes in expression.
Exome sequencing
Sequencing coding regions (exons) of a patient’s DNA where most genetic variants occur and which represent only about 1% of a patient’s total DNA.
Increased incidence of trisomy 21 with increasing maternal age:
Age 25 = 1/2000
35 = 1/300
40 = 1/100