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physiology of pregnancy by Mind Map: physiology of pregnancy
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physiology of pregnancy







less than 12 week


increases organ size

uterus increases from about 50 grams to 1100 grams

breasts approximately double in size

the vagina enlarges and the introitus opens more widely, dilated, soft, decreased pH

various hormones can cause marked changes in a pregnant woman’s appearance, development of edema, acne, masculine or acromegalic features

braxton hicks present in 2nd and 3rd trimester

Weight Gain in the Pregnant Woman

The average weight gain during pregnancy is about 24 pounds, with most of this gain occurring during the last two trimesters

7 pounds is fetus

4 pounds is amniotic fluid, placenta, and fetal membranes.

uterus increases about 2 pounds

breasts another 2 pounds,

6 pounds of this is extra fluid in the blood and extracellular fluid

remaining 3 pounds is generally fat accumulation

Without appro- priate prenatal control of diet, the mother’s weight gain can be as great as 75 pounds instead of the usual 24 pounds.

Nutrition During Pregnancy.

the mother’s body has already been storing these substances—some in the placenta, but most in the normal storage depots of the mother.

a number of maternal defi- ciencies can occur, especially in calcium, phosphates, iron, and the vitamins.

hypochromic anemia.

metabolic rate

metabolic rate of the pregnant woman increases about 15 per cent during the latter half of pregnancy

due to hormone

thyroxine, adrenocortical hormones, and the sex hormones,

sensations of becoming over- heated.

greater amounts of energy than normal must be expended for muscle activity.

Changes in the Maternal Circulatory System During Pregnancy

increases the mother’s cardiac output to 30 to 40 per cent above normal by the 27th week of pregnancy;

the cardiac output falls to only a little above normal during the last 8 weeks

BP decreases in early and mild

increases in late

hypertrophy of hear

blood volume incases 30-45%

albumen deceases 35g/liter


the total amount of oxygen used by the mother 20 per cent above normal

progesterone increases the respiratory center’s sensitivity to carbon dioxide.

net result is an increase in minute ventilation of about 50 per cent and a decrease in arterial PCO2 to several millimeters of mercury below that in a nonpregnant woman

growing uterus presses upward against the abdominal contents, and these press upward against the diaphragm, so that the total excur- sion of the diaphragm is decreased. Consequently, the respiratory rate is increased to maintain the extra ventilation.

Urinary System During Pregnancy

rate of urine formation by a pregnant woman is usually slightly increased because of increased fluid intake and increased load or excretory products.

renal tubules’ reabsorptive capacity for sodium, chloride, and water is increased as much as 50 per cent as a consequence of increased production of steroid hormones by the placenta and adrenal cortex.

glomerular filtration rate increases as much as 50 per cent during pregnancy, which tends to increase the rate of water and electrolyte excretion in the urine.

dilated ureters

renal plasma flow increases 35%

frequent micturation

preeclampsia or toxemia of pregnancy

About 5 per cent of all pregnant women experience a rapid rise in arterial blood pressure to hypertensive levels during the last few months of pregnancy.

associated with leakage of large amounts of protein into the urine.

characterized by excess salt and water retention by the mother’s kidneys and by weight gain and development of edema and hyperten- sion in the mother.

there is impaired func- tion of the vascular endothelium, and arterial spasm occurs in many parts of the mother’s body, most sig- nificantly in the kidneys, brain, and liver. Both the renal blood flow and the glomerular filtration rate are decreased,

Another theory is that preeclamp- sia results from some type of autoimmunity or allergy in the mother caused by the presence of the fetus. In support of this, the acute symptoms usually disappear within a few days after birth of the baby.

There is also evidence that preeclampsia is initiated by insufficient blood supply to the placenta, resulting in the placenta’s release of substances that cause widespread dysfunction of the maternal vascular endothelium.

During normal placental development, the trophoblasts invade the arterioles of the uterine endometrium and completely remodel the maternal arterioles into large blood vessels with low resistance to blood flow. In patients with preeclampsia, the maternal arterioles fail to undergo these adaptive changes, for reasons that are still unclear, and there is insufficient blood supply to the placenta. This, in turn, causes the placenta to release various sub- stances that enter the mother’s circulation and cause impaired vascular endothelial function, decreased blood flow to the kidneys, excess salt and water retention, and increased blood pressure.


prolonge gastric emptying (nausea)


unchanged liver function


hyperophy of pituitary and thyroid


TSH and ACTH increases

PRL increases

LH and FSH decreases


T3 and T4 not changed

Thyroxine increases

hCG from placenta