Lifespan – Prenatal Development

Germinal period during prenatal development (when, effects of teratogen exposure)

-conception to end of 2nd week––when zygote (fertilized egg) implants on uterine wall

-“all-or-none” effect of exposure to toxic chemicals, drugs, or other teratogens

• if exposure causes significant damage → no implantation

• if implantation occurs, it means the exposure had little/no effect

Embryonic period during prenatal development (when, effects of teratogen exposure)

-weeks 3-8

-major organs/structures forming rapidly

**teratogen exposure is most likely to cause major defects (first 2 months)

Fetal period during prenatal development (when, effects of teratogen exposure)

-weeks 9+

-organs/structures mature

-teratogen exposure most likely to cause minor defects/abnormalities

**except for central NS––susceptible to major damage during embryonic AND fetal pd

Age of viability

-Earliest age premie can survive outside womb

-22-26 weeks (right around 6 months)

Trimesters (when)

2nd: starts 14

3rd: starts 28

1st trimester: weeks 1-13

2nd trimester: weeks 14-27

3rd trimester: week 28-birth

Prader-Willi Syndrome

(Prader = Paternal, Puffy person eating constantly)

-Paternal deletion on 15 (paternal chromosomes are fine, but deletion occurs during cell creation)

-Hyperphagia (constant overeating/obesity), skin-picking

Angelman Syndrome

(Angelman = Maternal, “Angel" that really happy and wildly flapping its wings)

-Maternal deletion on 15

-Unnaturally happy, hyperactivity

-hand flapping, ataxia

Cri-Du-Chat Syndrome:

‘cry of the cat’

(Cri-Du-Chat = high-5 a cat)

-Chromosome 5 deletion, high-pitched, cat-like cry

Klinefelter syndrome

(Calvin Klein is an effeminate guy/extra X chromosome + ASD)

(XXY + ASD)

-males only (XY) + extra X chromosome

-incomplete secondary sex characteristics development

-low T level

-breast enlargement

-ASD-like sxs: theory of mind, facial and emotion recognition deficits

Turner Syndrome

(Tina Turner is a short, scarf-wearing lady, with no kids)

(webbed neck, infertile, short)

-females only

-complete/partial deletion of X chromosome (only 1 X)

-don’t develop secondary sex characteristics

-infertile

Rett syndrome

(ASD + X-linked dominant)

(Baby girl Rett develops normally → sudden regression of ASD + slowed head/brain growth)

-almost exclusively females

-X-linked dominant disorder (mutated gene on X chromosome)

-mutations in MECP2 gene

Fragile X syndrome

(male more severe, ASD + X-linked dominant)

(most common inherited cause of IDD)

-X-linked dominant disorder

-but in both M + F; more severe sx in M

-mutations in FMR1 gene

-most common inherited cause of intellectual developmental disorder (mutation is passed down)

Down Syndrome

-Most common genetic cause of intellectual disability (extra c21 is not inherited)

-Trisomy 21 (95%): maternal age-dependent (30+), d/t random error during cell division

-Translocation (4%): NOT maternal age-dependent, can be inherited from a (silent) carrier parent

-High Alzheimer's risk later in life

Mosaic Trisomy 21 (what is it)

-1%

-only SOME cells in the body contain an extra c21

-cause = random error during cell division

-possible increased risk from older maternal age

Translocation trisomy 21

4%

-SOME cells have (full/partial) c21 attached (translocated) to another c, usually c14

-no extra chromosomes, just additional attachment to c14

*NOT maternal age dependent

-cause = random error during cell division OR inherited from silent parent carrier

Phenylketonuria (PKU) (what type of disorder, main problem + Tx)

(phenyl keto – can’t process phenyl amino acid)

-autosomal recessive disorder (need both recessive genes: pp)

-if both parents are carriers → child has 25% chance

-unable to adequately metabolize amino acid phenylalanine

-Tx = diet low in phenylalanine throughout life -no dairy, eggs, meat, fish

-Without tx, build-up of phenylalanine → intellectual disability, hyperactivity, seizures, eczema, musty body odor, hypopigmentation, stunted growth

Teratogens

-drug, disease, or environmental hazard that causes developmental defects in embryo (3-8wk)/fetus (9wk+)

Teratogens that exert their effects epigenetically

-alcohol, nicotine

-valproic acid (an anticonvulsant for bipolar, with liver failure risk)

-DDT, pesticides

Fetal alcohol syndrome

most severe

(requires facial + growth deficits + central NS issues)

-facial anomalies (thin upper lip, small eyes) -growth deficits (small weight, height) -CNS dysfunction (hyperactivity + brain, intellectual deficits, slowed PS)

Partial fetal alcohol syndrome (pFAS)

-CNS issues + less severe facial/growth deficits

Alcohol-related Neurodevelopmental Disorder

(Neurodevelopmental disorder → CNS dysfunction only)

-ADHD/hyperactivity + brain

-hyperactivity + brain (intellectual deficits, slowed PS)

-NO facial/growth deficits

Alcohol-related Birth Defects

-physical/organ defects ONLY (heart, kidney, vision)

-NO other prominents sxs

Are the sxs of FASDs reversible?

No, largely irreversible

Prenatal exposure to cocaine leads to

(Stimulated → come out early)

-spontaneous abortion during the 1st trimester

-or premie, low BW

(Stimulants make them overly sensitive and reactive, hard to soothe/regulate)

-irritable, overly reactive to environmental stimuli -difficult to calm and feed

-shrill piercing cry

-attention, memory, behavior, motor problems

-severity varies based on cocaine amount/potency + stressors (poverty, insensitive caregiving, risks of substance-abusing parent)