Fetal Development & Physiology of Pregnant Flashcards
gravidity
Gravidity: number of pregnancies
* Nulligravida: never pregnant
* Primigravida: first pregnancy
* Multigravida: two or more pregnancies
parity
Parity: number of pregnancies that reach >20 weeks, regardless of the outcome
* Nullipara: no pregnancy beyond viability
* Primipara: one pregnancy beyond viability
* Multipara: two or more pregnancies beyond viability
viability
Viability: fetus has capacity to survive outside with uterus
* Grey area of 22-25 weeks
gestational age
- Preterm: <37 weeks
- Early Term: 37 - 38 6/7 weeks
- Full Term: 39 - 40 6/7 weeks
- Late Term: 41 - 41 6/7 weeks
- Postterm: >42 weeks
Stages of Fetal Development
Preembryonic
*Fertilization through the second week
Embryonic
*End of the 2nd week through the 8th week
Fetal
*End of the 8th week through birth
Mitosis
Cell division that results in daughter cells that are
exact copies of the original cell
*Diploid # of chromosomes
(46)
*Somatic (body) cells
Meiosis
Cell division in which diploid cells produce gametes
*Sperm & ova
*Contain half the genetic
material of the parent cell
*Haploid # of chromosomes
(23)
Oogenesis
Production of ovum
* Present in the ovaries at birth
*Oocytes mature into ova at puberty
Spermatogenesis
Mature sperm is not produced until
puberty
Preembryonic Stage
Preparation for fertilization
*Ovum (12-24 hours)
* ↑ estrogen during ovulation
* Assists with mobility through the fallopian tube
* Thins cervical mucus
*Sperm (48-72 hours)
* Propel themselves through the female reproductive tract, where only ONE penetrates
the ovum
Preembryonic Stage: Cellular Multiplication
Zygote travels through
the fallopian tube to the
uterus
*Rapid cellular division via mitosis occurs
Preembryonic Stage: Implantation
Occurs 7-10 days after
fertilization
*Upper posterior uterine wall
*Causes uterine lining to thicken
*Cellular differentiation
*Embryonic membranes
*Primary germ layers
* Ectoderm
* Mesoderm
* Endoderm
Embryonic Stage
2-8 weeks
MOST VULNERABLE TO TERATOGENS
*“Essentials” are further
developed
*Embryonic membranes
*Amniotic fluid
*Umbilical cord
*Placenta
*Basic structures of all major
body organs are formed
*Main external features are
completed
Embryonic Stage: Embryonic Membranes
Protect & support the embryo as it
grows
*Chorion
* Chorionic villi which grow into fetal
portion of the placenta
* May be used in early genetic testing
*Amnion
* Thin membrane containing amniotic
fluid
Functions of Amniotic Fluid
Functions
*Cushions
*Temperature regulation
*Symmetrical growth & movement
*Infection barrier
*Aids in diagnosing fetal health &
maturity
*Approx. 1L at term
*Components
*98% water
*Fetus eventually contributes
through excretion of urine
*Alterations
*Oligohydramnios
*Hydramnios
Yolk Sac & Umbilical Cord
Yolk sac
*Functions only early in embryonic
development
*Forms primitive RBCs during 1st 6
weeks of development before the
liver takes over
*Umbilical Cord
*Formed from the amnion
*1 vein; 2 arteries
*Wharton’s jelly (connective tissue that covers cord vessels to prevent folding and compression)
Placenta
Interface between the mother &
the fetus
*Arises from trophoblasts
*Metabolic, respiratory,
endocrine, immunologic, &
protective functions
Placental Functions
*Metabolic (transfer energy)
*Respiratory (transfer oxygen and waste products)
*Immunologic/Protective (regulate bacteria)
*Endocrine/Hormonal
*Placental circulation
* Maternal & fetal blood NEVER mix
* Interchanged through active
transport, diffusion, etc
Placental Circulation
Maternal uterine arteries
Intervillous spaces of the placenta
Umbilical vein into fetal circulation
Returns via the umbilical arteries
Villous capillaries of the placenta
Maternal uterine veins into maternal circulation
3 weeks
- Neural tube forms
- Beginning brain, heart, & spinal cord
4 weeks
- Brain differentiates
- Limb buds
5 weeks
Heart beats!
6 weeks
- Fetal circulation established
- Liver produces blood cells
- Brain waves
7 weeks
- Palate formation nearly complete
- Fetal heartbeat can be seen on
US
8 weeks
- All body organs are formed
12 weeks
- Urine is produced & excreted
- Sex recognizable
6 weeks
Quickening (first movements)
20 weeks
- Quickening (baby should continue to still move)
- Lanugo & vernix caseosa present
- Primitive respiratory movements (baby “practicing breathing”)
24 weeks
- Alveoli
- Surfactant
28 weeks
- Rapid brain development
- Lecithin production BEGINS
30-31 weeks
- Rhythmic breathing movements
- L/S ratio increasing
36-40 weeks
- More subcutaneous fat
- Increased CNS control
changes to uterus
- increase in size, vascularity &
thickness - 10mL to 5,000mL capacity
- 600 mL/min at term
- Changes
- Hegar’s sign (uterus turns into abdominal organ, skins starts to soften)
- Pelvic to abdominal organ
- McDonald’s method
- Lightening (baby drops, bladder pressure increases)
- Ballottement (can move baby)
changes to cervix
- increased secretions
- Mucus plug forms
*Changes - Goodell’s & Chadwick’s sign
changes to ovaries
ceases
changes to vagina
increased thickness
increased acidity of secretion
changes to breasts
*↑ size & tenderness
*Striae
*Pronounced nipples
*Areolae darken
*Colostrum might be manually
expressed by 12 weeks
changes to CVS
Blood Volume
*increase a total of up to 50% or 1500 mL
* Plasma & RBCs
*Blood flow increase to uterus, placenta & breasts
*Provides a reserve for blood loss at birth
*Murmurs
Blood Pressure
*Slight decrease BP
* Lowest in 2nd trimester
* Returns to pre pregnancy levels
near term
Cardiac Output
* increase 30-50%
Heart Rate
*Pulse rate increase10-15 bpm by 32 weeks
changes to blood components
RBCs
*increase 25%-35% depending on
available iron
*Necessary to transport
additional O2
*Physiologic Anemia of
Pregnancy
*Total plasma volume increase faster
than RBCs can keep up,
leading to hemodilution
(Decreased H&H)
WBCs
*Physiologic leukocytosis
Clotting factors
*Fibrin & fibrinogen increase
*increase in blood clotting factors
changes to respiratory system
Mild hyperventilation or no change in respiratory rate
* Shortness of breath
*increased O2 consumption
*Diaphragm elevates d/t
enlarged uterus
*Diaphragmatic vs. abdominal
breathers
*Estrogen-induced edema &
vascular congestion
* increased nasal stuffiness & congestion
* Epistaxis
changes to renal/urinary
Renal
* Renal pelvis dilates
* Kidneys enlarge
* Kidney function
* increased GFR 40-60%
* Must handle
* increased intravascular & extracellular volume
* increased metabolic waste products
* Excretion of fetal wastes
Urinary
* Urinary frequency (1st & 3rd trimester)
* Pressure of growing uterus & fetal presenting
part
* Renal activity increases while lying down
* Bladder becomes concave
changes to integumentary system
Skin hyperpigmentation
*increased estrogen, progesterone & α-
melanocyte-stimulating
hormone
*Linea nigra
*Facial chloasma “mask of
pregnancy”
* Striae
*Varicosities
*Impaired venous return
*Pressure of gravid uterus
*Sweat & sebaceous glands
changes to musculoskeletal system
*Hormonal changes (relaxin)
*Joints of the pelvis relax in later preg -> “waddle”
*Postural changes (lordosis)
*d/t relaxin, increased weight, & fetal position
*Low back pain common
*Change in center of gravity
*increased weight, & fetal position
*Pressure of enlarged uterus -> rectus abdominis muscle
can separate -> diastasis recti
changes to neurologic system
Compression of pelvic nerves or vascular stasis
*Sensory changes in the legs
*Edema
*Carpal tunnel syndrome
*Stooped shoulder stance
*Numbness & tingling in hands
*Vasovagal instability or postural hypotension
*Light headedness
changes to GI
Mouth
*Hyperemic gum tissue
*Ptyalism
*Changes in taste & smell
*Gingivitis
Upper GI
*N & V
*Pyrosis
*Prolonged emptying time of
gallbladder
* Pruritis
Lower GI
*Delayed gastric emptying time
*Decreased intestinal motility
*Bloating, constipation &
hemorrhoids
changes to endocrine system
Thyroid
*increases in activity & size
*BMR increases
*Maternal thyroid hormone
*Crucial for fetal neurologic
development
Pancreas
*Production of insulin
*Does not cross placenta
Pituitary
*FSH & LH are inhibited
*Prolactin
*Promotes breast development
& lactation
*Inhibited by progesterone until
delivery
*Oxytocin
*Responsible for uterine
contractions near term
*Milk ejection during
breastfeeding
Nutrient Metabolism during Pregnancy
*1st half of pregnancy
*Growing fetus needs SIGNIFICANT amounts of glucose,
amino acids, & lipids -> maternal glucose levels decrease
*2nd half of pregnancy
*hPL & other insulin antagonists increase
*Maternal insulin production must increase to overcome
resistance
changes to immune system
*Enhancement of innate immunity
*Better inflammatory response
*Some chronic conditions stabilize
*Suppression of adaptive immunity
*Prevents rejection of the fetus as a foreign body
*More susceptible to certain infections
