Module 4: The Physiology of Pregnancy Flashcards
Gestational age
-calculated from the first day of a woman’s last menstrual period
-refers to the age of pregnancy
Fetal age
-estimated from date of conception
-must be approximately 2 weeks less than gestational age
How long is average human pregnancy
-38-40 weeks
First trimester time period
-from week of conception to 13th week of gestation
First trimester development
-organ systems
-mothers body increases blood supply to carry more nutrients and oxygen
First trimester symptoms
-fatigue
-morning sickness
-headaches
-constipation
Second trimester time period
-week 13 to 26 of gestation
Second trimester development
-hair nails and reproductive organs develop
-sex of fetus can be determined
-fetus begins to make movements
Second trimester symptoms
-body aches
-dizziness
-swelling of hands and feet
Third trimester time period
-from week 27 to birth of baby
Third trimester development
-fetus gains weight
-organ systems mature
When does birth usually occur
-from week 37-42
Possible positions of baby
-cephalic
-breech
Cephalic position
-head down
Breech position
-bottom down
When is the fetus most vulnerable
-weeks 3-10
Teratogens
-agents that have the ability to cause birth defects such as radiation, alcohol, and certain prescriptions
When are miscarriages most common
-first trimester
Preterm delivery
-birth before 37 weeks
Preterm delivery complications
-maternal complications
-worsening health outcomes for baby
Full term delivery
-37-40 weeks
Late term delivery
-in week 41
Post term delivery
-beyond 42 weeks
Post term delivery complications
-significant risk
Postnatal period
-6 week period immediately after pregnancy in which mother undergoes significant physical and psychological changes
Naegeles rule
-standard way of calculating delivery date for pregnancy
Naegeles rule 3 steps
-determine when the first day of your last menstrual period was
-count back 3 calendar months from date
-add 1 year and 7 days to that date
Embryonic stage
-comprises the first 8 weeks of development
-called an embryo
-major morphological stages
Fetal stage
-begins after week 8
-called a fetus
-growth and development
How many carnagie stages are there
-23
Weeks 0-2
-called a zygote
-carnegie stages 1-6
-undergoes cleavage and develops germ layers
Weeks 3-4
-called an embryo
-carnegie stages 7-13
-germ layers begin to differentiate
-primordial germ cells form wolffian and mullerian ducts
-primitive heart develops
Week 5
-called an embryo
-canegie stages 14-15
-chambers of heart become visible
-limb budding
-cerebral hemispheres become visible
Week 6
-called an embryo
-carnegie stages 16-17
-heart and lungs descend into thorax
-heart beats at normal rhythm
Weeks 7-8
-called a fetus
-carnegie stages 18-23
-fingers become visible
-bone ossification
-testes begin descent
What size is fetus at week 8
-kumquat
What size is fetus at 11 weeks
-lemon
What size is fetus at 14 weeks
-avocado
What size is fetus at 21 weeks
-grapefruit
What size is fetus at 29 weeks
-coconut
What size is fetus at 38 weeks
-watermelon
What does ultrasound tell us
-confirm pregnancy and location
-evaluate placenta and fluid levels
-confirm number of babies
-identify birth defects
-determine gestational age
-determine fetal position
-evaluate fetal growth
Types of placental invasiveness
-epitheliochorial
-endotheliochorial
-hemochorial
Epitheliochorial
-least invasive
-maternal blood is seperate from fetal tissues by endothelium, connective tissue and epithelium
What organisms have epitheliochorial invasiveness
-cows
-pigs
-horses
Endotheliochorial
-maternal blood is separated by layer of maternal endothelium and some interstitial tissue
What organisms have endotheliochorial invasiveness
-dogs
-cats
Hemochorial
-human placenta allows fetal membranes to be bathed directly with maternal blood
What organisms have hemochorial invasiveness
-humans
-mice
-rabbits
Primary functions of placenta
-nutrient and oxygen exchange
-protection
-hormone production
-excretion
-attachment to uterine wall
Layers of trophoblast
-synctiotrophoblast
-cytotrophoblast
Syncytiotrophoblast composition
-cytotrophoblast cells that fuse together into a multinucleated continuous cell later known as syncytium
What does syncytiotrophoblast layer go on to form
-blood-placental barrier
Blood placental barrier function
-help regulate nutrient/gas exchange
-production of placental hormones
-regulating immune response
Cytotrophoblast composition
-comprise inner layer of trophoblast cells
-produce proteolytic enzymes to facilitate invasion of decidua
Cytotrophoblast cells function
-replensih cells of outer syncytium layer
What are chorionic villi
-finger-like projections from cytotrophoblast layer
Primary villus
-small and avascular
-cytotrophoblast core surrounded by a layer of syncytium
Secondary villus
-composed of extraembryonic mesodermal core and are covered by layer of cytotrophoblast cells and outer syncytiotrophoblast layer
Tertiary villus
-have extraembryonic mesoderm core with villous capillaries and are covered by a cytotrophoblastic and suncytiotrophoblastic layer
Anchoring villi
-large tertiary villi that connect cytotrophoblastic shell to chorionic plate
Floating villi
-branches of anchoring villi
Intervillous space
-space between villi, between chorionic shell and chorionic plate
-this is where maternal circulation will pool and bathe chorionic villi
Chorion
-shell and chorionic plate together surround embryo to form this
Chorion frondosome
-highly villous area
-fetal side of placenta
Chorion laeve
-any villi on opposite side will atrophy
Decidua basalis
-side of decidua where chorion frondosome attaches and grows
Decidua capsularis
-other side of decidua surrounding embryo
-does not interact with chorionic cilli and will later become a smooth layer
Amnion
-innermost fetal membrane
-contains amniotic fluid
-protects embryo from mechanical stress and impact
Yolk sac
-small sac on ventral surfce of embryo
-source of primordial germ cells and blood cells
Allantois
-hollow sac on tail end of yolk sac
-contributes to nutrition and excretion
-helps form umbilical cord
Chorion
-outermost fetal membrane
-forms the fetal side of placenta (chorion frondosome and laeve)
Extraembryonic coelom
-space between amnion and chorion
Spiral artery remodelling
-blood vessels that supply uterus are characterized as having spiral shape
-also the same arteries that will supply placenta and growing fetus
-extravillous trophoblasts will migrate towards maternal arteries and cause major modifications of their walls
Extravillous trophoblasts
-highly invasive type of cytotrophoblast arising from tips of anchoring villi
Spiral artery remodelling in early pregnancy
-extravillous trophoblasts proliferate from anchoring villi and invade maternal decidua
Spiral artery remodelling end of first trimester
-extravillous trophoblasts differentiate into 2 types
-interstitial and endovascular
Interstitial extravillous trophoblasts
-these cells invade deeper into decidua and surround spiral arteries
Endovascular extravillous trophoblasts
-penetrate the lumen of the uterine spiral arteries
Spiral artery remodelling midgestational period
-both types of extravillous trophoblasts are involved in degradation of maternal vascular endothelium
-as a result the spiral arteries become wider, allowing higher volume of blood
Spiral artery remodelling 3rd trimester
-blood supply to uterus and placenta has increased by a factor of 10 as a result of the remodelling
Types of placental circulation
-uteroplacental circulation
-fetoplacental circulation
Uteroplacental circulation
-maternal blood flows from uterine space into intervillous space, allowing for exchange of oxygen
Fetoplacental circulation
-fetus attached to placenta directly via umbilical cord
-this allows transport to and from mothers blood without direct mixing
What does the umbilical cord have inside
-one umbilical vein
-two umbilical arteries
Umbilical vein function
-carries oxygenated, nutrient rich blood from placenta to fetus
Umbilical arteries function
-carries deoxygenated, nutrient-depleted blood from the fetus to the placenta
Functions of placenta as an immune barrier
-prevent maternal immune rejection
-protect fetus from pathogens
Preventing maternal immune rejection
-the fetus is genetically different than the mother so the barrier maintains separation between maternal and fetal blood to prevent the mothers immune cells from recognizing fetal tissues as a foreign body
How do pregnancy tests work
-measure the hCG hormone levels in urine
When are pregnancy tests most accurate
-when taken after the first missed menstrual cycle
Sex hormones during trimester 1
-hCG must appear by day 10 in order to stop the corpus luteum from degrading
Sex hormones during trimester 2
-placenta starts producing enough progesterone and estrogen to sustain remainder of pregnancy
-production of hCG decreases and corpus luteum degrades
Sex hormones in trimester 3
-levels of progesterone and estrogen increase steadily due to production by placenta
-largely responsible for many physiological changes observed during pregnancy
Adrenal cortex changes during pregnancy
-adrenocorticotropic hormone (ACTH) is involved in stress response so it regulates functions such as appetite suppression and feelings of anxiety
Which hormone is responsible for timing of parturition
-ACTH
Thyroid gland changes during pregnancy
-thyroid hormone increases
-therefore increasing maternal metabolic rate to meet demands of fetus
Ovary changes during pregnancy
-FSH and LH are inhibited during pregnancy
-ovulation therefore does not happen
-can take 2 months to a year after birth to go back to normal
Mammary glands changes during pregnancy
-mainly stimulates mammary glands to produce milk
-PRL stimulates breasts to grow
Cervix changes during pregnancy
-softens
-necessary to permit variety of functions such as dilation during delivery etc
What is colostrum
-the first milk
-appears in alveoli of acinar glands as early as second trimester
Uterus changes during pregnancy
-endometrial layer goes through decidualization
-uterus is stretched to accomodate fetus etc
Circulatory system changes during pregnancy
-cardiac output increases by as much as 50% mid pregnancy
-happens as a result of increased heart rate and stroke volume
Respiratory system changes during pregnancy
-oxygen consumption increases by 20-60% during labour
-around month 6 the fetus begins to exert increasing pressure on mothers diaphragm decreasing lung capacity and increasing minute ventilation
Immune system changes during pregnancy
-immune response prevents rejection of paternal antigens but therefore makes women more susceptible to infectious diseases
Metabolic system changes during pregnancy
-in early pregnancy it is anabolic
-in late pregnancy is is catabolic
-insulin resistance develops in early pregnancy to direct most of glucose to fetus
-in late pregnancy, maternal adipose tissue releases fatty acids for use by liver and muscle
Parturition
-the process by which childbirth occurs
-labour and delivery
Stages of parturition
-onset of labour
-active labour
-delivery of placenta
-immediate postpartum
Onset of labour
-stage preceding labour
Phases of onset of labour
-latent phase
-active phase
Latent phase of onset of labour
-mother starts experiencing contractions until dilated to 3 cm
Active phase of onset of labour
-contractions become more intensive
Steps of onset of labour
- response to fetal head on cervix causes stretching of cervix and uterine walls
- in response to stretching, nerve impulses are sent to hypothalamus of brain
- hypothalamus signals posterior pituitary to release oxytocin
- oxytocin joins circulation and causes smooth muscle contractions of myometrium which increases cervical dilation
Onset of labour signs and symptoms
-lightening (baby moves down in pelvis and breathing may be easier)
-uterine contractions
-water breaks
Active labour
-cervix progressively dilates
-ferguson reflex
Ferguson reflex
-positive feedback cycle
-pressure on cervix releases oxytocin and dilates cervix etc
How long may active labour last
-8-20 hours
Delivery of placenta
-shortest stage
-starts immediately after fetal birth
-physician will put pressure on mothers abdomen to help detach placenta from uterus
How long may delivery of placenta take
–5-30 min
Signs of placental separation
-firmer uterine fundus
-sudden gush of blood from vagina
-lengthening of umbilical cord
-rise of uterus in abdomen
Immediate postpartum
-hour or 2 after delivery when tone of uterus is reestablished
-uterine massage often used
-colostrum from mammary glands will provide basic immunity for first few hours
What is the puerperium period
-postpartum up to 6 weeks after birth
Complications of parturition
-breech birth
Breech birth
-happens when baby is delivered bottom first
What can practitioner do about breech birth
-may change baby into appropriate position before birth
-may perform a c section
What will majority of pregnancy complications be attributed to
-some kind of disruption to placental function
First trimester complications
-generally associated with disruptions in process of implantation or early embryo development
Miscarriage
-loss of embryo before 20th week of gestation
-most often a natural response to presence of abnormality
Anembyonic pregnancy
-condition where embryo does not develop, leaving only gestational sac
Second trimester complications
-often result of issues that were initiated in first trimester
Who is at higher risk of second trimester complications
-women with preexisting conditions such as hypertension or diabetes
Preeclampsia
-most severe hypertensive disorder of pregnancy
-high blood pressure and excess protein in urine
What is the main danger of preeclampsia
-can evolve into eclampsia and cause seizures in mother
What is preeclampsia associated with
-impaired placentation
-uterine artery remodeling is impaired
Third trimester complications
-any health issues that arose in second trimester can become worsened and lead to ealy delivery
Antepartum hemorrhage
-bleeding that occurs after the 24th week of gestation but before birth
-medical emergency
Placental anatomy abnormalities
-abruprtio placenta
-placenta previa
Abruptio placenta
-premature separation of placenta from uterus
Placenta previa
-occurs when placenta is partially or totally covering mothers cervix, obstructing birth canal
How do fetal complications affect long term health
-intrauterine growth restriction
-preterm birth
Intrauterine growth restriction
-significant reduction in fetal growth
-typically result of placental insufficiency
-has been linked to poorer health outcomes in later adult life
Preterm birth
-leading cause of neonatal death
Effect of preterm birth on development and adult health
-preterm infants are exposed to various stressors and environmental conditions
-these stressors can lead to permanent changes in organ system development which may incerase risk of specific disorders
Potential explanations for preterm birth worldwide trends
-changing pregnancy demographics
-induced preterm births to improve fetal mortality rates
-reporting of medically induced preterm births
Maternal and fetal screening benefits
-advances in diagnostic and treatment procedures have decreased maternal and neonatal morbidity by increasing early detection of maternal and fetal problems
