3) Placental Metabolism Flashcards
1
Q
When does the fastest growth of the placenta occur? Why?
A
- During the first half of pregnancy
- To prepare for the fetal growth spurt during the second half of pregnancy
2
Q
What is the placenta?
A
The interface between the microcirculatory systems of the mother and fetus
3
Q
What are functions of the placenta?
A
- Exchange of nutrients, respiratory gases, and metabolic waste
- Protection of the fetus from xenobiotics
- Acting as a source of hormones
4
Q
When is there mixing of the maternal and fetal blood?
A
- There is NEVER any direct mixing of the maternal and fetal blood
- The placenta is composed of a maternal and fetal portion
5
Q
Where does the majority of amniotic fluid come from?
A
The maternal blood via diffusion from the intervillus spaces of the placenta
6
Q
What are functions of amniotic fluid?
A
- Acts as a shock absorber
- Prevents desiccation of the fetus
- Provides room for fetal movements
- Assists in body temperature regulation
7
Q
The ________ plate forms the fetal surface of the placenta.
A
chorionic
8
Q
______________ are cells from the placenta that connect the mother and fetus.
A
Cytotrophoblasts
9
Q
What components form the large area for exchange of fetal and maternal material?
A
- Cytotrophoblastic shell
- Anchoring villi
10
Q
Where does the exchange between maternal and fetal material occur?
A
Within the intervillus spaces, as maternal blood flows around the villi
11
Q
What is the major functioning unit of the placenta?
A
Chorionic villus
12
Q
What placental defects do IUGR infants display?
A
They have microscopically less branching of the villi
13
Q
What is the function of the villi within the placenta?
A
Enhances the surface area, allowing for greater exchange of gases and nutrients
14
Q
The placenta uses 50% of _______ and 65% of _______ from the maternal blood supply.
A
oxygen
glucose
15
Q
What substances does the placenta synthesize for fetal use?
A
- Glycogen
- Lactate
- Cholesterol
16
Q
What substances cannot cross the placental membrane?
A
Compounds possessing a large molecular weight
17
Q
What substances are transported across the placental membrane via passive diffusion?
A
- Oxygen and carbon dioxide
- Fatty acids
- Steroids
- Electrolytes
- Fat-soluble vitamins
18
Q
How does fetal hemoglobin differ from regular hemoglobin?
A
Fetal hemoglobin has a greater binding capacity for oxygen
19
Q
How are fatty acids transported through the placental membrane?
A
- Passive diffusion
- Carrier-mediated transport for long-chain FAs (enhancement of PUFA transport)
- The fetus depends on a supply of EFAs
20
Q
Of the substances that are transported via passive diffusion, there is a poor transfer of which one?
A
Fat-soluble vitamins
21
Q
How are sugars transported through the placental membrane?
A
Carrier-mediated facilitated diffusion
22
Q
What is the importance of glucose transporters within the placenta?
A
- Glycation is a mechanism of teratogenesis
- Glucose transporters are used to protect the fetus from high glucose levels
23
Q
If a mother experiences hyperglycemia, is a fetus exposed to a hyperglycemic environment as well? Why or why not?
A
- No, the fetus experiences a lower glucose level
- Because of the use of glucose transporters
24
Q
What substances require energy-dependent active transporters to cross the placental membrane?
A
- Amino acids
- Certain cations
- Water-soluble vitamins
25
What do iron and folate require to cross the placental membrane?
Pinocytosis
26
What do water and solutes use to cross the placental membrane?
Solvent drag
27
The fetal size is proportional to the _______ size.
placental
28
How may maternal malnutrition, such as iron deficiency, affect placental size and fetal growth retardation?
- Reduced blood volume expansion
- Decreases cardiac output and placental blood flow
- Decrease in placental size, reduced nutrient transfer, and subsequent fetal growth retardation
29
What conditions may decrease uterine blood flow and affect placental transport?
- Hypotension
- Renal disease
- Placental infarction
30
During the third trimester, how does the fetal weight and the placental weight change?
- The fetal weight more than doubles at the last 10 weeks
| - The placental weight only increases by 50%
31
A lower rate of placental growth is a limiting factor for what?
For sufficient transfer of nutrients for fetal needs
32
What is partially responsible for the deceleration in fetal growth rate during the last 4 weeks of gestation?
A progressive decline in the quantity of nutrients transferred per unit of fetal body mass per unit of time
33
What mechanism often causes the failure of the placenta?
Failure of the uteroplacental blood vessels to deliver an increased uterine blood flow
34
How do essential fatty acid affect the placenta?
Deficiencies in EFAs cause defects in placental integrity and function
35
Low placental weight is found to be associated with lower plasma concentrations of which fatty acids?
- Arachidonic acid
- DHA
- Linoleic acid
36
What are reduced concentrations of AA, DHA, and LA associated with?
- Short gestation
| - Small head circumference
37
The percent distribution of DHA is highest in which fetal structure?
The fetal brain, then liver and umbilical cord
38
70% of energy during fetal growth is devoted to what?
Brain development
39
______ form 50 to 60% of the structural matter of the brain.
Lipids
40
The brain is a structurally lipid-rich organ. What PUFAs does it use? Which ones in particular?
- 20- and 22-carbon PUFAs
- Arachidonic acid
- DHA
41
What kind of PUFA is arachidonic acid?
- 20:4 (n-6)
| - Omega-6
42
What kind of PUFA is DHA?
- 22:6 (n-3)
| - Omega-3
43
What is the function of hCG?
Maintains the corpus luteum, which secretes estrogen and progesterone
44
What secretes estrogen during the beginning of pregnancy? What structure replaces its secretion? When?
- The blastocyst secretes estrogen on day 7
- After implantation, hCG is produced by the placenta, allowing for the maintenance of the corpus luteum, which secretes estrogen
45
When does the peak of hCG occur? What happens after?
- The peak occurs at the 10th and 11th week of gestation
| - After, hCG levels decline and remain low for the rest of pregnancy
46
What produces placental lactogen? When?
The placenta in late gestation
47
What is the function of placental lactogen?
Influences fat and carbohydrate metabolism (breakdown of maternal fats to provide fuel for the fetus)
48
What is a synonym for placental lactogen?
Human chorionic somatotrophin
49
What structures produce progesterone during pregnancy?
- Corpus luteum until the 10th week of gestation
| - The placenta takes over afterwards
50
What are the functions of progesterone in supporting pregnancy?
- Inhibits the secretion of LH and FSH to prevent ovulation
| - Supports the endometrium
51
How does progesterone prevent pre-term birth?
Suppresses contractility in uterine smooth muscle
52
Which hormone decreases and which hormone increases to facilitate parturition?
- Progesterone decreases
| - Estrogen increases to increase contractility of the smooth muscles of the uterus
53
When is estrogen secreted maximally during pregnancy?
Towards the end of gestation
54
What are the functions of estrogen in pregnancy?
- Stimulates myometrium growth
- Antagonizes myometrial-suppression by progesterone
- Stimulates mammary gland development
55
Catabolism of which substances are controlled by the placenta?
- Glucocorticoids
- Insulin
- Thyroxin
56
How does the exposure to hormones vary if the placenta is underdeveloped?
The placenta developing inadequately decreases catabolism of these molecules, which may cause harm to the fetus
57
True or False: the placenta offers a substantial amount of protection against xenobiotics.
- False
- The placenta is highly permeable to a large variety of substances, and thus offers limited protection against xenobiotics
58
When does the majority of physiological adjustments during pregnancy occur? In most cases, how does physiological activity vary?
- During the first half of gestation
| - In most cases, physiological activity increases
59
The physiological activity of which structures do not increase during pregnancy? Why?
- Smooth muscle function of the uterus (to prevent contractions)
- Smooth muscle function of the GI tract (to prevent heartburn)
60
What occurs to the kidney during pregnancy? Why?
- An increase in GFR and decrease in tubular reabsorption capacity
- Leading to an increased blood volume to facilitate the increased excretion of fetal waste products
61
What are the consequences of an increased blood volume during pregnancy?
An increase in renal losses of glucose, folate, iodine, and amino acids
62
What occurs to the stomach during pregnancy?
Depression of function due to a decreased secretion of pepsin and histamine
63
What does a decreased function of the stomach lead to?
Increased risk of heartburn due to the relaxation of the cardiac sphincter, causing a higher risk of regurgitation
64
What occurs to the gastrointestinal tract during pregnancy? Why?
- Decrease in motility to slow down transit time
| - Leads to an increased efficiency of absorption of certain nutrients (vitamin B12, iron, calcium)
65
What is a possible consequence of the decrease in motility of the GI tract? In what situation?
Constipation, if combined with a lack of sufficient fluid intake
66
What occurs to the heart during pregnancy? Why?
- Cardiac hypertrophy, which increases cardiac output to allow a larger blood volume to circulate
- Improves blood flow to the placenta and fetus
67
What occurs to the lungs during pregnancy? Why?
Increased ventilation to accommodate for increased oxygen demands by the fetus, placenta, and maternal tissues
68
How does BMR vary during pregnancy? Why?
- BMR increases by 15 to 20% due to an increase in oxygen consumption
- BMR returns to normal a week after the baby is born
69
How do plasma lipid profiles vary during pregnancy? Why?
- Increased levels of plasma lipids (triacylglycerols and cholesterol)
- Since the maternal system is preferentially using lipids to conserve glucose for the fetus
70
How do blood glucose levels vary during pregnancy, specifically during the third trimester?
- The fetus' glucose demands are increased, which causes maternal blood glucose to fall
- Increased lipolysis and ketosis compensates for the decrease in glucose
71
What occurs to hepatic gluconeogenesis during pregnancy? Why?
Impaired hepatic gluconeogenesis due to a decreased availability of alanine
72
What is the decreased availability of alanine during pregnancy due to?
To a decrease in muscle breakdown and an increase in placental uptake of alanine
73
What other physiological adjustments occur during pregnancy?
- Altered appetite and thirst
- Altered digestion and assimilation of food
- Hemodilution
74
The first half of pregnancy is the (anabolic/catabolic) phase, while the second half of pregnancy is the (anabolic/catabolic) phase.
anabolic
| catabolic
75
What occurs to carbohydrates during the anabolic phase of pregnancy?
Excess carbohydrates are stored as glycogen or converted to fat, due to the sharp rise in blood insulin after meals
76
What occurs to fats during the anabolic phase of pregnancy?
- Rapidly synthesized into TGs
| - Decreased rate of lipolysis to conserve fat stores for the second half of pregnancy
77
What occurs to proteins during the anabolic phase of pregnancy?
Increase in maternal protein synthesis, particularly in RBCs and the placenta
78
What is the preferred form of energy of the fetus?
- Glucose
| - The fetus requires a quick source of energy for rapid growth
79
What occurs to fats during the catabolic phase of pregnancy? What is the result?
- Fat is mobilized to conserve glucose for the fetus
| - Results in an increase in ketones and blood cholesterol
80
What occurs to insulin during the catabolic phase of pregnancy? What is the result?
- The action of insulin is blunted by estrogen, progesterone, and placental lactogen
- Catabolism of maternal fat, glycogen, and protein
81
What occurs to glucose levels after a meal during the catabolic phase of pregnancy? Why?
- Glucose levels rise sharply given the blunted insulin response
- Results in a greater uptake of glucose by the placenta
82
Does the placenta rely on insulin for absorption of glucose?
No
83
Prior to conception, a woman should possess __% body weight fat.
22
84
What is the average weight gain during pregnancy?
12.5 kg
85
How does the expected weight gain during pregnancy of underweight women compare to overweight women?
Underweight women need to gain more weight
86
What weight gain is recommended for adolescents?
28 to 40 pounds
87
What weight gain is recommended for twins?
35 to 45 pounds
88
What are the patterns of weight gain expected during the first 10 weeks of pregnancy, and the rest of the pregnancy?
- First 10 weeks: 3 to 4 pounds per week
| - Rest of pregnancy: 1 pound per week
89
Gaining over ___ kg per week during pregnancy is a cause of concern.
one
90
What is the likely causes for gaining over a kilogram per week during pregnancy? What are possible risk factors?
- The presence of excessive edema, causing a risk for pre-eclampsia
- Increased risk for placental abruption, stillbirth, decreased blood flow to the placenta, and low-birth weight
91
What are the sources of obligatory fetal weight gain?
The growing presence of the fetus, placenta, and amnionic fluid
92
What are the sources of obligatory maternal weight gain?
- Enlarged uterine and breast tissue
| - Expansion of blood volume
93
What are the sources of non-obligatory maternal weight gain?
Gain in adipose tissue, protein stores, and extracellular fluid
94
When does 50% of the increase in maternal blood peak? How does hemoglobin mass vary? What is the result?
- During the third trimester
- Lower increase in hemoglobin
- Hemodilution
95
How does the hematocrit vary during pregnancy?
The hematocrit decreases (hemodilution)
96
What are correlated outcomes associated with insufficient blood volume expansion?
- Stillbirths
- Low-birth weight
- Spontaneous abortions
97
Edema is commonly present in pregnancy. When is it not a cause for concern?
If it is gained gradually
98
When is the majority of the energy needed to support pregnancy deposited? What is it characterized by?
- In the first 20 weeks (anabolic phase)
| - Characterized by an increase in subcutaneous fat in the abdominal and upper thigh areas
99
What comprises most of the weight gained during the second half of pregnancy?
Fetal tissues, placenta, and amniotic fluid
100
An increase in plasma volume and RBCs is directly related to what?
Fetal size
101
Describe the S-shaped curve of fetal weight.
- Little weight gain during the first trimester
- Rapid weight gain during gestational weeks 8 to 23
- Weight tapers off at weeks 37-38
102
What are the effects of weight maintenance and slight losses during the first trimester?
There is little effect on embryonic weight gain
103
What is the cause of morning sickness?
- Increase in estrogen and hCG
- Nausea and vomiting are a positive predictor of pregnancy outcome and decreased risk of fetal death, as it represents an adequate level of hormones
104
What are the effects of eating less during the first trimester?
- Does not substantially affect the growth of the fetus
| - However, too many skipped meals may lead to ketosis and hypoglycemia (teratogenic risk)
105
What are the women recommended to eat in terms of meals?
Small, but frequent, high-fat, low-bulk meals
106
What are the three most important determinants of birth weight?
1) Gestational age
2) Maternal weight gain
3) Pre-conception weight
107
What is the best clinical indicator to judge pregnancy progress?
Maternal weight gain possesses the strongest influence on fetal weight gain
108
Mortality rates are lowest for infants of what weight range?
2.5 to 4 kg
109
What risks do dietary restrictions pose?
- Low-birth weight
- Hypertension
- Perinatal mortality
- IUGR
110
The highest perinatal mortality rates are in which type of women? What about the lowest perinatal mortality rates?
- Highest: underweight women who gain little weight during pregnancy
- Lowest: underweight women who gain an appropriate amount of weight
111
What are the risks of obese pregnant women?
- Pre-eclampsia
- Gestational diabetes
- Infection
- Cesarian
- Prolonged labor and complications during delivery (asphyxia, abnormal glucose regulation in infant)
112
What are the two main problems in pregnancy that are related to infants with a low-birth weight?
- Small for gestational age
| - Prematurity
113
Define a preterm birth.
A preterm birth is below 37 weeks, while a term birth is above 37 weeks
114
What are the three criteria for IUGR?
- Below 2SDs in weight for gestational age
- Below the 10th percentile in weight for gestational age
- Below 2500 grams and gestational age above 37 weeks
115
If they survive birth, extremely premature infants are at a risk for severe morbidities, such as what?
- Retinopathy of prematurity
- Chronic lung disease
- Neurocognitive disease
116
What are the most severe morbidities of preterm infants?
- Cerebral palsy
- Mental retardation
- Seizure disorders
117
What are mildly preterm infants (32 to 36 weeks) at a risk for?
- Respiratory distress syndrome
- Infection
- Mortality
118
Define a low-birth weight.
Below 2500 grams
119
Define a small for gestational age infant.
Below the 10th percentile for gestational age
120
All infants who are (IUGR/SGA) are also (IUGR/SGA), but not all (IUGR/SGA) infants are (IUGR/SGA).
IUGR, SGA
| SGA, IUGR
121
What are causes of preterm birth?
- Genitourinary infection
- Multiple pregnancies
- Pregnancy-induced hypertension
- Low pre-pregnancy BMI
- Prior history of a preterm birth
- Smoking
- Strenuous physical labor
122
What are the two types of IUGR? How do they differ?
- Proportionate: infants with decreased growth potential or extreme fetal malnutrition
- Disproportionate: infants with maternal malnutrition
123
What are causes for decreased growth potential in proportionate IUGR infants?
- Congenital infection
- Genetic disorder
- Environmental toxins
124
What are the characteristics (length, weight, and head circumference) of proportionate IUGR infants?
- Length, weight, and head circumference are proportional, occurring within a similar percentile
- May also occur if the head is small relative to the body (microcephaly)
125
What are the characteristics (length, weight, and head circumference) of disproportionate IUGR infants?
The length and head circumference are closer to the expected percentiles for gestational age, but the weight is disproportionately small
126
What are causes of IUGR?
- Low-energy intake
- Low pre-pregnancy BMI
- Short maternal stature
- Pregnancy-induced hypertension
- Smoking
- Malaria
127
IUGR is a component of _____, a set of dysmorphic features
FAS
128
What are the effects of malaria in primiparous women? What has this been associated with?
- Major cause of anemia
| - Associated with reduced birth weight and an increased risk of IUGR
129
What may severe IUGR lead to in the early neonatal period?
Hypoglycemia and hypocalcaemia
130
What adult diseases has IUGR been shown to be associated with?
- Hypertension
- Type II diabetes
- Cardiovascular diseases
131
The rapidly developing fetus is more susceptible to the permanent programming effects of malnutrition during which period of gestation?
Late gestation
132
What are the three abnormal patterns of fetal growth that are linked to adult diseases?
1) Symmetrical small babies of low-birth weight
2) Babies are thin at birth, but undergo catch-up during infancy
3) Average birth weight, but are abnormally small in proportion to their placental weight
133
What are risks of low-birth weight?
- Decreased lung capacity during childhood
- Twice the risk of cardiovascular disease
- Six times the risk of diabetes and impaired glucose metabolism
- Increased blood pressure risk, abnormally high TGs, insulin resistance, and low HDL
134
What is excessive birth weight (above 9 pounds) related to?
An increased risk of hormonally-related cancers
135
What advantageous mechanism occurs during undernutrition? Why?
- Maternal corticosteroid production increases as a stress response
- Increases fetal maturation of lungs and other organs
136
How is poverty associated with an increased nutritional risk for pregnancy?
Poor nutritional intake status, and increased smoking, in low-income groups are associated with twice the rate of low-body weight infants (down by 200 to 300 grams)
137
Define a short inter-conception interval.
Refers to a woman becoming pregnant shortly (less than one year) after giving birth
138
How is a short inter-conception interval associated with an increased nutritional risk for pregnancy?
High physiological and nutritional demand on the nutrient body stores of the mother, which increases the likelihood of deficiencies
139
What chronic illnesses may place heavy demands on nutritional intake?
Diabetes, chronic infection, cancer, alcoholism, and malabsorption
140
What unusual dietary patterns may place a woman at a higher risk of having an infant with a low-birth weight?
- Consuming microbiotics
- Dieting constantly
- Anorexia
- Pica
141
What is pica associated with, in terms of nutritional status?
- Low zinc and iron status
| - Displacement of other nutritious foods
142
How is a history of anemia and/or obesity associated with an increased nutritional risk for pregnancy?
Indicates long-term imbalance or an inappropriate diet, which may adversely affect reproductive success
143
Why are teen pregnancies at a high-risk of low birth weight?
- Poor nutritional status
- Low pre-pregnancy weight
- High incidence of food fads
- Increased drug and alcohol use
- Decreased obstetric, nutritional, and social support
- Increased body image consciousness (insufficient maternal weight gain)
144
Why is there a greater risk of an infant with a low-birth weight in a younger adolescent mother?
- Due to immature endocrine and reproductive functioning
| - 5 years post-menarche are required to foster a healthy pregnancy
145
What hormones are blunting the action of insulin during the catabolic phase of pregnancy?
Estrogen, progesterone, and placental lactogen
