Module 2: Pregnancy III Flashcards
when does embryogenesis occur?
0 to 8 weeks gestation
first 2 months of pregnancy
embryogenesis overview
Egg is fertilized → zygote is formed (within 24 hours of fertilization) → cleavage
woman might not know she is pregnant yet
embryogenesis stages in order
- cleavage
- blastulation
- implantation
- gastrulation
- neurulation
- growth and development of the fetus
- 0 to 8 weeks
embryogenesis stage 1: cleavage
zygote cleaved into 2 blastomeres
embryogenesis stage 2: blastulation
morula divides to form blastocyte (has inner cell mass)
embryogenesis stage 3: implantation
6-7 days after fertilization
blastocyte penetrates endometrium
we begin to have a difference between inner cell mass and trophectoderm
embryogenesis stage 4: gastrulation
embryo forms blastula (layer of epithelial cells) which reorganizes into gastrula
embryogenesis stage 5: neurulation
neural plate turns into neural tube
this will later form brain and spinal cord (CNS)
This allows for organogenesis
Tissues begin differentiated, we get different cell types
Folate is key in neurulation
week 4 major step
heart does “practice beatings” (no heartbeat is heard yet)
The practice/testing happens so if things are not working correctly the pregnancy can self-terminate
week 5
Week 5: we see more organ systems (still no heartbeat on ultrasound)
which stage has more growth, fetal or embryo?
fetal stage
at what week is embryo considered a fetus
week 9
when does fetal development occur?
8 to 38/40 weeks gestation
why does water decrease in fetus from 30 to 40 weeks
increase in fat and protein mass
More deposition of lean body mass, muscles grow and develop
Fat mass is very important to neonatal period
Babies with not enough fat mass end up in the NICU to control their body temperature
fetal development characteristics
We see increases in weight with each phase of pregnancy
We see primitive sperm or egg cells
After midway through pregnancy we see calcification of skeleton
Towards end of pregnancy we see deposition of many nutrients
Growth declines a bit near term
critical periods of development
finite periods during development in which certain events occur that will have irreversible effects on later developmental stages
key critical periods in fetus
during early embryonic period and embryogenesis (much more than fetal period)
critical periods of development overview
Differentiation: cellular acquisition of one or more characteristics or functions different from that of the original cell
We make a lot of cells, and then get rid of the ones we don’t need
We want to start with too many rather than two few
maternal factors that influence fetal growth
- micronutrient availability
- vitamin D
- antioxidants - inflammation and oxidative stress
- vasoconstriction
- hormone activity
- thyroid
- glucocorticoids - metabolic function
placental factors that influence fetal growth
- implantation
- growth
- mitochondrial function
- epigenetic regulation - nutrient transfer
- transporters
- oxygen gradient - hormone activity
- placental hormones
- regulation of hormone transfer
fetal growth factors
- epigenetics
- organ toxicity
- hormone activity
consequences of inadequate nutrition during fetal development
small for gestational age (SGA)
large for gestational age (LGA)
intrauterine growth restriction (IUGR)
small for gestational age (SGA)
newborn weight is <10th percentile for gestational age
dSGA: Normal head size, smaller body and limbs
Proportionally SGA (pSGA): long-term risk factors
large for gestation age (LGA)
weight for gestational age exceeds the 90th percentile for gestational age or birthweight >4500g
variations in fetal growth are linked to
Energy, nutrient, and oxygen availability
Conditions that interfere with genetically programmed growth and development
Insulin-like growth factor (IGF-1) is the main fetal growth stimulator
What effects do preterm birth have on growth and development?
<37 weeks
11.4% of infants born in the US in 2013 were preterm
Greater risk of death, neurological problems, and congenital malformations
Born without adequate stores of nutrition
Infants born preterm are at risk for death, neurological problems, congenital malformations, and chronic health problems
preterm birth risk factors
Multivitamin supplements or folate intake decrease risk
One to three fish meals per week are protective
Underweight and obesity increase risk
Elevated blood lipids increase risk
What effects do birth weight have on growth and development?
Desirable birth weight: 3500-4500 g (seven pounds and twelve ounces to ten pounds)
Less likely to develop heart and lung diseases, diabetes, and hypertension
Reduces infant mortality and morbidity
what are the only nutrients we don’t need more of in pregnancy?
Vit D and calcium
BUT, many women are deficient so we must make sure they meet normal levels
if not, vit D and caclium can be leached from bones
folate deficiency can lead to
neural tube defects
folate and neural tube defects
*When neural tube doesn’t close, you end up with neural tube defects
Anencephaly: open brain and lack of skull vault
Encephalocele: herniation of the meninges (and brain)
Spina bifida occulta: closed asymptomatic NTD in which some of the vertebrae are not completely closed
folate
Involved in DNA replication
Gene expression
Amino acid metabolism
Recommended intake:
RDA for women of child bearing age 400 mcg/day
RDA for pregnancy is 600 mcg/day
Upper limit is 1000 mcg/day
iodine
Neurocognitive development
Recommended intake:
RDA for women of child bearing age and pregnancy is 220 mcg
Upper limit is 1110 mcg
choline
Replenish maternal stores
Development of brain and spinal cord
Recommended intake:
RDA for women of child bearing age and pregnancy is 450g
iron needs during pregnancy
ron: need increases substantially
300 mg for fetus and placenta
250 mg lost at delivery → need to make sure we have this stored
450 mg for increased red blood cell mass
anemia in pregnancy
~23% of pregnant women in developed countries
1 in 10 US pregnancies; 1 in 4 during 3rd trimester
Common causes: increased demands, change in dietary patterns, poor nutrition
Consequences: compromised growth, cognitive function, and immunity
Mortality in mothers and babies
Pre-term birth
iron function
Fetal hemoglobin has “gamma” which has an increased affinity for oxygen so it will favor it more during the prenatal period (aka in the womb). Adult hemoglobin has the “beta” which has decreased affinity for hemoglobin and is lower in the prenatal period but gets higher in the postnatal period after the baby is born since the fetus takes up so much of the oxygen.
Iron can compromise growth, cognitive function, and immunity and leads to mortality and pre-term birth. Need more during pregnancy because of fetal/placental needs and increased RBC mass.
iugr
relationship of size and gestational age
What is preterm? What are some of the consequences?
< 37 weeks
Greater risk of death, neurological problems, and congenital malformations – also means born without adequate stores of nutrients
What is preterm? What are some of the consequences?
< 37 weeks
Greater risk of death, neurological problems, and congenital malformations – also means born without adequate stores of nutrients
What are the effects of alcohol use during each trimester?
First trimester
Reduce cell growth: in CNS
Second trimester
Higher risk of miscarriage (in absence of alcohol, miscarriage rate decreases in second trimester)
Third trimester
Long-term neurological effects
Birth defects
Describe the characteristic features of fetal alcohol syndrome:
Most severe
Abnormal facial features
Growth problems
CNS abnormalities
Problems with social skills, learning, memory, attention span, communication, vision, or hearing
Describe the characteristic features of fetal alcohol syndrome:
Most severe
Abnormal facial features
Growth problems
CNS abnormalities
Problems with social skills, learning, memory, attention span, communication, vision, or hearing
issue with alcohol
Alcohol can cross the placenta. The fetus will have reduced ADH capacity, which increases the harmful effects of alcohol on the fetus. This leads to birth defects, intellectual disability, and developmental disorders.
