PHYSIOLOGICAL CHANGES IN PREGNANCY

Question 1

what are physiological changes in pregnancy?

Question 2

why is it important to know physiological changes in pregnancy?

Question 3

list the functional classifications of adaptations in pregnancy

Question 4

outline the general physiological adaptations of pregnancy

Answer 4

 In normal pregnancy, weight gain is a constant phenomenon.
 In early weeks, pt. may lose weight because of nausea or vomiting.
 In subsequent months, weight gain is progressive until the last 1 or 2 weeks, when the weight remains static.
 Average weight gain for singleton pregnancy for a healthy woman is 11 kg.
 1 kg in 1st trimester, 5 kg in 2nd and 3
rd trimester respectively
 Rapid weight gain of > 0.5 kg a week or > 2 kg a month in later months of pregnancy may be the early
manifestation of pre-eclampsia
 Stationary or falling weight may suggest IUGR or IUFD
 Weight gain distribution includes;
 Uterus (0.9 kg) and its contents
 Breast increase with fat deposition- 0.4 kg
 Blood volume and extravascular volume increase
 Woman gains about 6.5L of water (both blood and ECF)
 in featus (3.3 kg), placenta (0.6 kg) and amniotic fluid (0.8 kg)

Question 5

outline the genital organs’ physiological adaptations in pregnancy

Question 6

outline physiological adaptations of breast in pregnancy

Question 7

outline the cardiovascular physiological adaptations in pregnancy

Question 8

outline the respiratory physiological adaptations in pregnancy

Answer 8

 Diaphragm is elevated to about 4cm by enlarging uterus
 Lower ribcage circumference expands by 5 cm.
 Subcoastal angle widens from 68° to 103°
 Breathing becomes diaphragmatic
 The physiological dead space decreases
 Respiratory rate is slightly changed
 Significant increase in ventilation begins around 8 wks
of gestation, likely in response to progesterone-related sensitization of the respiratory centre to CO2 and the
increased metabolic rate.
 Increase in minute ventilation (product of tidal volume (increases by 40% -from 500 to 700 mL) and respiratory
rate) by approx. 30–50%
 Functional residual capacity decreases
 Increase in 2,3-diphosphoglycerate (2,3-DPG) concentration within maternal erythrocytes which preferentially
binds to deoxygenated Hb and promotes release of O2 from RBCs at relatively lower levels of Hb saturation (i.e.
shifts the O2–Hb dissociation curve to the right).

Question 9

outline renal physiological adaptations of pregnancy

Answer 9

 Kidney size increases slightly by about 1cm due to Cellular hypertrophy
 Renal plasma flow increase by 50–75%, maximum by 16 weeks and is maintained until 34 weeks then falls
 GFR is increased by 50%, reducing maternal plasma levels of creatinine, BUN and uric acid.
 24 hrs urine creatinine clearance increases by 40 to 50%
 ↑Urinary frequency due to ↑ renal blood flow and pressure of gravid uterus on bladder in
early pregnancy.
 Glycosuria is not necessarily abnormal due to renal tubules failure to reabsorb excess
glucose and increased GFR
 Ureters diameter increases due to relaxant effect of progesterone on smooth muscle
 Ureteric obstruction in later pregnancy due to uterine enlargement

Question 10

outline gastrointestinal physiological adaptations of pregnancy

Answer 10

 Diminished muscle tone and motility due to progesterone leading to constipation
 Chemical esophagitis and heart burn is common due to relaxed cardiac sphincter and acidic gastric content reflux
into esophagus coupled with delayed gastric emptying
 Increases appetite and thirst from growth of conceptus
 Late in pregnancy, pressure of a large uterus reduces capacity for large meals
 Diminished gastric secretion and delayed gastric emptying time reduce risk of PUD
 Heartburn is common
 Appendix displaced upwards

Question 11

outline skin physiological adaptations of pregnancy

Question 12

outline hematological physiological adaptations of pregnancy

Answer 12

Red blood cell volume increase by 18-20%, a total volume of about 350mL.
 Disproportionate increase in plasma and RBC vol produces a state of
hemodilution (fall in hematocrit) during pregnancy
 Increase in RBC mass begins at about 10 weeks and continue till term
without plateauing
 White cell count varies from 7000 to 15000/uL
 In labor, Neutrophilic leucocytosis occurs between 8000/mm3 to 20,000/cu.mm due to rise in the levels of
estrogen and cortisol
 In pueperium the WBC may rise up to 25000
 Platelets fall from an average of 250000 to 213000
 Gestational thrombocytopenia may be due to increased platelet consumption

Question 13

outline immunological physiological adaptations of pregnancy

Question 14

outline metabolic physiological adaptations of pregnancy

Answer 14

At 6–8 weeks, there is transfer of endocrine functions of corpus luteum to the placenta
 Pituitary gland
 Enlarges to about twice its normal size, by approximately135 %, increase weight by 30–50%
 Principally due to hyperplasia of acidophilic prolactin secreting cells.
 Enlargement changes may compression or impinge on optic chiasma causing mild bitemporal hemianopia
 GH secreted predominantly from maternal pituitary gland during 1st trimester (placenta starts secreting at 8 wks)
 Prolactin levels increase (10 fold by term)
 ACTH and corticotropin releasing hormone (CRH) levels increase
 Thyroid gland
 Thyroid gland undergoes moderate enlargement due to placenta-derived hCG (chorionic thyrotropin) which
has a TSH-effect on thyroid gland and increased Renal clearance of iodine
 Result in abnormally low levels of TSH in 1st trimester, when hCG concentrations are highest
 3 modifications in regulation of thyroid
 Marked increase in circulating levels of major thyroxine transport proteins
 Several thyroid stimulating factors of placental origin are produced
 Decreased availability of iodine for maternal Thyroid
 Thyroxine binding globulin increases early in pregnancy due to estrogen induce increased hepatic synthesis,
peaks at 20wks and stabilises after
 Total T4 ↑btn 6-9wks, plateaus at 18wks
 Rise in T3 pronounced at 18 weeks then plateaus
 TRH are not increased
 Total T4 and T3 are increased but free T4 and T3 levels are
unchanged
 ↑ basal metabolic rate, from 3rd month, reaches a value of
+25% during the last trimester
 Adrenal glands
 Undergoes slight enlargement (thickness of zona
fasciculata) or no morphologic change
 Increase in serum of aldosterone, deoxycorticosterone
(DOC), corticosteroid binding globulin (CBG), cortisol
and free cortisol
 Serum cortisol increased but much is bound to cortisol
binding globulin
 Increase is due to lower cortisol clearance
 Aldosterone secretion increased from 16 wks
 This protects against natriurect effects of progesterone
and natrieretic peptide
 Hypercortisolism state is due: increased plasma cortisol
half-life, delayed renal clearance and resetting of hypothalamo-pituitary and adrenal feedback mechanism
 Pancreas
 Postprandial hyperinsulinism particularly during 3rd trimester, coinciding with peak conc. of placental
hormones
 But fasting insulin concentration is reduced

Question 15

outline the hemostasis and coagulation physiological adaptations of pregnancy

Answer 15

 Pregnancy is a hypercoagulable state.
 Almost all procoagulant blood coagulation factors, including factors VII, VIII, IX, X and XII
and fibrinogen, are increased (Greatest increase in Fibrinogen by 50% from 200–400 mg/dL in nonpregnant to
300–600 mg/dL in pregnancy)
 High ESR due to fibrinogen and globulin level and diminished blood viscosity
 Fibrinolytic activity is depressed until 15 minutes after delivery
 Protein C levels remain unchanged
 Resistance to activated protein C increases
 Substantially renal clearance of folic acid increases and plasma folate concentrations fall.
 Von Willebrand factor, a carrier for factor VIII and plays a role in platelet adhesion, also increase
 Maternal plasma D-dimer concentration increases progressively from conception until delivery

Question 16

what is Goodell’s sign?

Answer 16

Goodell’s sign is a softening of the cervix that can indicate early pregnancy. It’s usually noticeable between 4 and 8 weeks of pregnancy.
What causes Goodell’s sign?
Increased vascularization in the cervix due to engorgement of blood vessels below the growing uterus
The cervix may also appear larger

Question 17

what is leucorrhea?

Answer 17

Leucorrhea, also known as leukorrhea or vaginal discharge, is a vaginal secretion that can be normal or a sign of infection. It can be whitish, yellowish, or greenish in color.

Question 18

what are doderlein’s bacilli?

Answer 18

these Doderlein’s bacilli are now known to be a member of the genus Lactobacillus
Döderlein’s bacillus are gram-positive bacillus that form a microbiome, reproduce in the female vagina after gaining sexual maturity, secrete lactic acid, and prevent the growth of other vaginitis-causing bacteria

Question 19

normal vaginal pH

Answer 19

3.8 to 4.5

Question 20

what is hyperemia?

Answer 20

Hyperemia is a medical term that means increased blood flow in an organ or body part. It can be caused by increased blood flow into an area or by obstructed blood outflow

Question 21

Decidual reaction of the ovary

Answer 21

A “decidual reaction in the ovary” refers to a phenomenon where tissue within the ovary takes on the characteristics of decidual cells, which are typically found in the uterine lining during pregnancy, essentially meaning the ovary is undergoing a hormonal change similar to the endometrium, usually due to high levels of progesterone and occurring most often in the context of pregnancy; this is also known as “ectopic decidual reaction” and is considered a benign condition that usually regresses after delivery

Question 22

ovarian pedicle

Answer 22

The ovarian pedicle is the blood vessels that enter and exit the ovary, and connects to the uterine vessels. It can also refer to the tissue that is ligated during an ovariohysterectomy, or spay.

Question 23

luteoma of pregnancy

Answer 23

Luteoma of pregnancy is a rare, noncancerous tumor that occurs in the ovaries during pregnancy. It’s caused by hormonal changes during pregnancy and usually appears as a solid ovarian mass
It is associated with an increase of sex hormones, primarily progesterone and testosterone. The size of the tumor can range from 1 to 25 cm in diameter, but is usually 6 to 10 cm in diameter and can grow throughout the duration of the pregnancy

Question 24

myoepithelial cells

Answer 24

Myoepithelial cells (MECs) are a type of epithelial cell that have characteristics of both muscle and epithelial cells. They are found in many glands, including the mammary, salivary, and lacrimal glands.

Question 25

outline acid-base balance physiological adaptations of pregnancy

Answer 25

 Arterial PaCO2 falls from 38 to 32 mm Hg and PaO2 rises from 95 to 105 mm Hg.  That facilitate CO2 transfer from fetus to the mother and O2 from the mother to the fetus  pH rises in order of 0.02 unit and there is a base excess of 2mEq/L.  Pregnancy is in a state of respiratory alkalosis  Maternal O2 consumption increase by 20–40% due to increased demand of fetus, placenta & maternal tissues

Question 26

differentiate between protein, carbohydrate and fat metabolism in pregnancy

Answer 26

Protein metabolism  Is that of positive nitrogen balance  Urea level falls to 15–20 mg% as the breakdown of amino acid to urea is suppressed  Peak values are reached at 28wks  500g retained by term  At term featus and placenta weigh 4kg, 500g of which is protein  Pregnancy is an anabolic state Carbohydrate metabolism  Amount of glucose transfer is increased from mother to the fetus throughout pregnancy.  Increased insulin secretion in response to glucose and amino acids  But sensitivity of insulin receptors is decreased  Plasma basal insulin level is increased due to contrainsulin factors: estrogen, progesterone, human placental lactogen (hPL), cortisol, prolactin, free fatty acids and  Increased tissue resistance to insulin  Overall effect is maternal mild fasting hypoglycemia (due to fetal consumption) and post prandial hyperglycemia and hyperinsulinemia (due to anti-insulin factors).  That ensure sustained post prandial supply of glucose to fetus at all times  Insulin action is 50-70 % of normal health  Increased Glomerular filtration of glucose to exceed the tubular absorption threshold (normal 180 mg%) leading glycosuria in 50%. Fat metabolism  Shows increases in concentrations of lipids, liproteins, apoproteins in plasma, during later half of pregnancy  Due to increased estrogen, progesterone, hPL and leptin levels  Leptin, a peptide hormone, is secreted by adipose tissue and placenta which regulates body fat metabolism  An average of 3–4 kg of fat is stored mainly in abdominal wall, back, thighs and retroperitoneally  Hyperlipidemia of normal pregnancy is not atherogenic- ↑HDL level by 15%. LDL is utilized for placental steroid synthesis.  In 2nd half of pregnancy, with rising hPL levels, lipolysis is augmented, and fasting plasma conc. of free fatty acids are elevated, acting as substrates for maternal energy metabolism, whereas glucose and amino acids cross the placenta to the fetus  Increased free fatty acids lead to ketone body formation (β-hydroxybutyrate and acetoacetate).  Thus pregnancy is associated with an increased risk of ketoacidosis, especially after prolonged fasting

Question 27

why is hypervolemia important in pregnacy?