Chapter 13- Anatomy and physiology of pregnancy

Gestation

Pregnancy. lasts 40 weeks or 280 days measured from last menstrual period. Described in terms of trimesters

Trimesters

First: first day of last menstrual period-13 weeks

Second: 14 weeks- 27 weeks

Third: 28 weeks- 40 weeks

Significant uterine growth in the first trimester

high levels of estrogen and progestrone

Early uterine enlargement

increased vascularity, dilation of blood vessels, hyperplasia, and hypertrophy, and development of the decidua

Uterine weight

increases dramatically. 4-70 g to 1200 g at term gestation.

Volume increase

10 mL to 5 L at term

Size of uterus

7 weeks- size of a large hen’s egg

10 weeks- orange

12 weeks- grapefruit

After the third month, uterine enlargement is primarily the result of mechanical pressure of the growing fetus

Lightening

fetus begins to descend into the pelvis in preparation for birth. occurs in nullipara approx 2 weeks before the onset of labor and in multipara at the start of labor

Hegar sign

at approx 6 weeks. softening and compressibily of the lower uterine segment

Factors that decrease uterine blood flow

low maternal arterial pressure, uterine contractions, and maternal supine position. Estrogen stimulation can increase uterine blood flow

Conditions associated with decreased placental perfusion

hypertension, intrauterine growth restriction, diabetes melitus, multiple gestations

Uterine souffle

bruit. rushing or blowing sound of maternal blood flowing through uterine arteries to the placement that is synchronous with the maternal pulse.

Funic souffle

synchronous with the fetal heart rate and is caused by fetal blood coursing through the umbilical cord

Ballottement

16-18 weeks of gestatio. palpating a floating structure by bouncing it gently and feeling it rebound. examiner places a finger within the vagina and taps gently upward on the cervix causing the fetus to rise. The fetus then sinks, and a gentle tap is felt on the finger

Quickening

first recognition of fetal movements or feeling life. detected by multiparaus woman as early as 14-16 weeks of gestation. nulliparious woman may not notice till 18th week or later. commonly described as fluttter

Cervix change during pregnancy

firm, nondistensible, closed structure that maintains the pregnancy/fetus within the uterus and changes to a soft, highly elastic tissue that dilates and becomes almost indistinguisable during labor for birth

Goodell sign

probable sign. softening of the cervical tip by 6th week. due to increased vascularity, slight hypertrophy, and hyperplasia

Operculum

muscous plug. mucus is rich in immunoglobulins and acts as a barrier against bacterial invasion of the uterus

Ovulation

does not occur. estrogen and progrestrone suppress FSH and LH. corpus luteum produces estrogen and progestrone for the first 6-10 weeks of pregnancy until the placenta becomes the primary source of these hormones

Chadwick sign

increased vascularity results in the violet-blue color of the vaginal mucusa and cervix. 6-8 weeks of pregnancy

Leukorrhea

white or slightly gray mucoid vaginal discharge with a faint musty odor. in response to cervical stimulation by estrogen and progrestrone

Early pregnancy lactation

estrogen stimulates the growth and proliferation of milk ducts while progrestrone causes growth and development of the mammary lobes. Lactation inhibited until the progestrone level decreases after birth

Blood pressure

maternal BP remains the same or decreases slightly even though CO increaes significantly. due to reduced systemic vascular resistance caused by the vasodilatory effects of progestrone, prostaglandins, and relaxin

Supine hypotensive syndrome or vena cava syndrome

CO is reduced by as much as 25-30% when woman is turned from lateral recumbent to supine. after 4-5 mins reflex bradycardia is noted, CO reduced by half, and woman feels faint.

Compression of the iliac veins and inferior vena cava by the uterus

causes increased venous pressure and reduced blood flow in the legs except when the woman is in the lateral position. leads to edema, varicose veins in the legs and vulva, and hemorrhoids that can develop in latter part of term pregnancy and contribute to the increased risk for venous thromboembolism (VTE)

Physiologic anemia of pregnancy

hemodilution. plasma increase is greater than the increase in RBC production which causes decrease in nomal H&H values. considered anemic if H&H is less than 11 g/dL and 33% in first trimester. second 10.5 g/dL and 32% second. H&H higher in woman living in high altitudes and among woman with tobacco abuse

Pregnancy-related dyspnea

common. beg in first or second trimester. occurs with mild exertion or at rest. mechanical pressures can increase dyspnea.

Respiratory changes in pregnancy

Epulis

red, raised nodule on the gums that bleeds easily. develop around the third onth and often enlarge as the pregnancy progresses.

Ptyalism

excessive salivation. caused by the unconsicous decrease in swallowing by the woman when nauseated. can also be caused by stimulation of the salivary glands when eating starchy foods

Increase in GFR

results in increased creatinine clearance and a reduction in serum creatinine, BUN, and uric acid levels

Physiologic or dependent edema

pooling of fluid in the legs in the latter part of pregnancy decreases renal blood flow and GFR

Hyperpigmentation

stimulation by the anterior pituirary hormone melanotropin. darkening of the nipples, areolae, axillae, and vulva approx 16 weeks.

Melasma

choasma or mask of pregnancy. blotchy, brownish hyperpigmentation of the skin over the cheeks, nose, and forehead.

Linea nigra

pigmented line extenting from the symphysis pubis to the top of the fundus in the midline. linea alba before hormone-induced pigmentation

Striae gravidarum

stretch marks. tend to occur over abdomen, thighs, and breasts

Angiomata

vascular spiders. tiny star-shaped or branched, slighthly raised, and pulsating end arterioles usually found on the neck, thorax, face, and arms

Palmar erythema

pinkish red, diffusely mottled, or well-defined blotches are seen over the palmar surfaces. related to increased estrogen levels

Diastasis recti abdominis

rectus abdominis muscles can seperate. abdominal contents protrude at the midline. umbilicus flattens or protrudes.

Carpal tunnel syndrome

parasthesia and pain in hand, radiating to the elbow. caused by edema that compresses the median nerve beneath the carpal ligament of the wrist. smoking and alcohol consumption can make it worse

Human chorionic gonadtropin (hCG)

Maintains corpus luteum production of estrogen and progesterone until the placenta takes over the function.

Progrestrone

Suppresses secretion of FSH and LH by the anterior pituitary gland; maintains pregnancy by relaxing smooth muscles, decreasing uterine contractility; causes fat to deposit in subcutaneous tissues over the maternal abdomen, back, and upper thighs; decreases mother’s ability to use insulin

Estrogen

Suppresses secretion of FSH and LH by the anterior pituitary gland; causes fat to deposit in subcutaneous tissues over the maternal abdomen, back, and upper thighs; promotes enlargement of genitals, uterus, and breasts; increases vascularity; relaxes pelvic ligaments and joints; interferes with folic acid metabolism; increases the level of total body proteins; promotes retention of sodium and water; decreases secretion of hydrochloric acid and pepsin; decreases mother’s ability to use insulin

Serum prolactin

Prepares breasts for lactation.

Oxytocin

Stimulates uterine contractions; stimulates milk ejection from breasts after birth

Human chorionic somtommaotropin

Acts as a growth hormone; contributes to breast development; decreases maternal metabolism of glucose; increases the amount of fatty acids for metabolic needs

T3 and T4

Increase in thyroid hormones supports maternal metabolism and fetal growth and development

Parathyroid

Controls calcium and magnesium metabolism

Insulin

Increases production of insulin to compensate for insulin antagonism caused by placental hormones; effect of insulin antagonists is to decrease tissue sensitivity to insulin or ability to use insulin

Cortisol

Stimulates production of insulin; increases peripheral resistance to insulin

Aldosterone

Stimulates reabsorption of excess sodium from the renal tubules

HCG levels in pregnancy

earliest biological marker for pregnancy. double approx every 2 days for the first 4 weeks. later placenta becomes the primary source of estrogen and progestrone. higher than normal levels are associated with abnormal gestation or multiple gestations. lower or slow increase can indicate impending miscarriage or ectopic pregnancy

Medications during pregnancy testing

anticonvulsants and tranquilizers- false positive results

diurectics and promethazine- false negative results