Physiology of Pregnancy (Continued)
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What can cause constipation in pregnancy?
Progesterone relaxes intestinal smooth muscle and slows peristalsis.
What causes reflux esophagitis in pregnancy?
- 1. Enlarging uterus displaces stomach above esophageal sphincter, causes intragastric pressure
- 2. Progesterone causes a relative relaxation of esophageal sphincter
- 3. May also be reflux of bile into stomach due to pyloric incompetence
How does the heart change during pregnancy and what signs of this change might one find?
- General enlargement of heart and left ventricle. Heart is displaced anterolaterally secondary to rise in level of diaphragm, which leads to altered ECG and possible changes that mimic ischemia.
- On auscultation: at end of T1, both components of S1 become louder with exaggerated splitting. After midpregnancy 90% of women demostrate S3 gallop. Systolic ejection murmurs occur along left sternal border in 96% of pts.
What happens to cholesterol levels in pregnancy?
There is increased turnover from lipoproteins, creating an increased supply to most tissues, and increased supply for steroid production. Total cholesterol is raised post-partum in all mothers.
When is the optimal time to screen for glucose intolerance?
At 26-28 weeks GA.
How does GFR change during pregnany?
It increases soon after conception. It reaches 60% above non-pregnant level by 16 weeks and remains elevated for remainder of pregnancy.
What is the most common non-obstetric cause for hospitalization during pregnancy?
- bacteriuria+urinary stasis predispose patients
What happens to albumin concentration in pregnancy>?
It falls by 22% due to hemodilution, despite the increase in synthetic rate.
What leads causes a predisposition to varicose veins in the legs, vulva, rectum and pelvis in pregnancy?
Increased distensibility and pressure of veins.
How does the genitourinary system change during pregnancy?
Urinary stasis-decreased ureteral peristalsis and mechanical compression of ureter
How is the liver affected in pregnancy?
- Hepatic funciton increases
- Plasma globulin and fibrinogen concentrations increase
- Synthetic rate of albumin increases
- Velocity of blood flow in hepatic veins decreases
- Serum alk phos increases largely due to placental production
What happens to the gallbladder during pregnancy?
- 1. Increases in size
- 2. Empties more slowly
- 3. Cholestasis, probably due to a hormonal effect.
How are the pituitary glands and its products affected by pregnancy?
- The gland increases in weight and sensitivity.
- Prolactin: plasma levels rise a few days postconception. At term levels are 10-20 fold higher than nonprego
blunted response to GnRH. Progressive decreased response at 3 wks after ovulation
Response to GnRH diminishes and finally disappears.
What 2 hormones are produced by the fetoplacental unit and what are their effects?
human chorionic gonadotropin (hCG)- coregulates and stimulates adrenal and placental steroidogenesis. Stimulates fetal testes to secrete testosterone.Thyrotrophic activity
human placental lactogen (hPL)- anti-insulin and growth hormone-like effects lead to impaired maternal glucose and free fatty acid release.
How is risk of thromboembolism affected by pregnancy?
Increase! Pregnancy is a hypercoagulable state and a disorder may become apparent during pregnancy.
How are platelets affected in pregnancy?
Reactivity increases in T2 and T3 and returns to normal at 12 wks post partum.
How are WBC's affected in pregnancy?
- Neutrophil count increases in T1 and continues until 30 weeks, also metabolic activity and phagocytic function increase.
- Lymphocytes counts remain unchanged but function is suppressed.
What happens to ESR in pregnancy?
- It rises early in pregnancy
- An ESR=100mm/hr is not uncommon in normal preg.
What happens to RBC's during pregnancy?
- Circulating RBC mass increases by 18% if no Fe supplement and by 30% with Fe.
- Retic count increases by >2%
- MCV usually increases
How much does plasma volume increase during pregnancy?
- By 50% due to increase in RBCs and plasma.
- This increase is greater in multi compared to primigravidas.
What causes glyosuria on pregnancy and what percent of women get it?
- 1.GFR increase
- 2.Quantity of glucose filtered in urine greater than nonpregnant
- 3.Tubular threshold for glucose is variable
- 50% of pregos
How is Na+ affected by pregnancy?
Progesterone increases Na+ excretion, but its increase is balanced by effects of increased aldosterone, mineralocorticoids, and prostaglandins. Renal retention of Na+ results in water retention.
What changes occur in renal tubules during pregnancy?
- They lose some resorptive capacity.
- Results in protein loss up to 300mg/24hr
What is the function of the decidua?
produces maternal steroids and synthesizes proteins that are related to the maintenance and protection of the pregnancy from immunologic rejection.
What is the endometrium called during pregnancy?
What are trophoblasts?
The precursor cells for the placenta and membranes
When does implantation occur?
On day 5-6 of development, the blastocyst adheres to the endometrium.
When and where does fertilization typically occur?
24 hrs after ovulation in the third of the fallopian tube adjacent to the ovary (ampulla)
What causes expulsion of the mucus plug?
What causes the softening and cyanosis of the cervix in pregnancy?
accumulation of glycosaminoglycans and increase in water content and vascularity.
What happens to the round ligaments during pregnancy?
- They contract spontaneously or in response to uterine movement (can be the source of pelvic/inguinal pain)
- In labor, contractions of the ligaments pull the uterus forward.
What is the vascular supply of the uterus?
- nonpregnant: uterine artery most important
- pregnant: ovarian arteries-20-30% (in 70% of women)
Which pruritic dermatologic disorders in pregnancy increase fetal morbidity and mortality?
Pruritis gravidarum: generalized severely pruritic excoriations.(Tx with antipruritics and cholestyramine)
Impetigo herpetiformis(pustular psoriasis of pregnancy)- pustules with minimal itching on genitalia, medial thighs, umbilicus, breasts and axillae. Can cause maternal sepsis. (Tx: systemic corticosteroids and ABX for secondary infxn)
Herpes gestationis: severely pruritic erythematous papules, vesicles, bullae on abdomen and extremities. Causes growth restriction and prematurity. (Tx mild case with topical steroids+antihistamines, More severe- tx with systemic corticosteroids.
How does pregnancy affect parathyroid hormone and calcitonin?
PTH-concentration falls. But PTH is greater in mother while calcitonin is greater in fetus at term leading to fetal bone deposition.
What effect do corticosteroids have on skin?
Cause striae on abdomen, breasts etc.
What effect does estrogen have on the skin?
Can cause spider nevi and palmar erythema
What causes the linea nigra, darkening of nipple and areola and facial chloasma/melasma in pregnancy?
- Increase in melanocyte stimulating hormone.
- *Suntans acquired in pregnancy last longer than usual.
How does pregnancy affect insulin?
- 1. serum levels rise during 2nd half, but insulin resistance increases
- 2. Insulin resistance swithces carbohydrate to fat utilization
How does prenancy affect the pancreas
- 1. Size of islets of langerhans increase during pregnancy
- 2. Number of beta cells increase
- 3. Number of insulin receptor sites increase
How are plasma proteins affected in prenancy?
They fall markedly by 20 weeks. This reduces colloid osmotic pressure in plasma->edema.
How does pregnancy affect the thyroid gland?
- Total thyroxine levels and throxine binding globulin increase. The result is that free thyroxine remains normal and mother remains euthyroid.
- *All goiter should be investigated
How does pregnanct affect the adrenal gland?
- Plasma cortisol and other corticosteroids increase progressively from 12 weeks to term to reach 3-5 times nonpregnant levels
- 1/2 life of plasma cortisol is increased and clearance reduced.
Source and function of alpha feto-protein (AFP)
- Source: yolk sac, fetal gastrointestinal tract, fetal liver
- Function: regulates fetal intravascular volume (osmoregulator)
- -AFP peaks b/w 10-13 weeks gestational age, then declines thereafter
- -Detectable as early as 7 weeks gestation
Source and function of Prolactin?
- Source: decidualized endometrium
- Function: regulates fluid and electrolyte flux through the fetal membranes
What is the source and function of corticotropin-releasing hormone(CRH)?
- Source: placental tissue, decidua, hypothalamus (maternal)
- Function: stimulates placental ACTH release and participates in the surge of fetal glucocorticoids associated with late T3 fetal maturation
- Cortisol has feedback with placental CRH production
What is the source of hPL and its function?
- Source: trophoblasts
- Function: antagonizes insulin->maternal glucose intolerance, lipolysis, and proteolysis
What is the source of adrenocorticotropic hormone (ACTH) and what is its function?
- Source: trophoblasts
- Function: stimulates an increase in circulating maternal free cortisol
What is the source and function of hCG?
- Source: placenta
- Function: maintains corpus luteum. Stimulates adrenal and placental steroidogenesis.
What is the timeline of important tissue/organ formation?
- Postcnception day Tissue/Organ formation
- 13-primitive streak
- 16-neural plate
- 19-21-first somite
- 23-25-closure of anterior neuropore
- 25-27-arms bud, closure of posterior neuropore
- 28-legs bud
- 44-sexul differentiation.
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