Anatomy & Physiology of Pregnancy PDF

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Anatomy & Physiology of Pregnancy...

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Anatomy & Physiology of Pregnancy Periods of Pregnancy o Antepartum: conception to onset of labor o Intrapartum: onset of contractions to 1-4 hours after birth o Postpartum: birth to 6 weeks after birth Duration of Pregnancy (from LMP) o Pregnancy lasts approximately 10 lunar months, 9 calendar months, 40 weeks, or 280 days o Length of pregnancy is computed from the 1st day of the LMP until the day of birth o However, conception occurs approximately 2 weeks after the 1st day of the LMP; thus the postconception age of the fetus is 2 weeks less, for a total of 266 days or 38 weeks o Postconception age is used in the discussion of fetal development Terms & Definitions o EGA: estimated gestational age o Trimester:  First trimester: 0-12 weeks EGA  Second trimester: 14-26 weeks EGA  Third trimester: 27-40 weeks EGCA o Gravida: the # of pregnancies (counting the current 1) o Primigravida: 1st pregnancy o Multigravida: 2/more pregnancies o Para: # of times a woman has carried a pregnancy to > 20 weeks (times a woman has emptied her uterus)  TPAL: term, preterm, abortion, living  Term: # of births > or = to 37 completed weeks (38 weeks) of gestation  Preterm: 20 weeks to 37 weeks & 6 days  Abortion: loss of pregnancy before 20 weeks  Living o Viability: ability to live outside the uterus;  There are no clear limits of gestational age/weight  Infants born @ 22-25 weeks of gestation are considered to be on the threshold of viability & are especially vulnerable to brain injury if they survive o Pregnancy:  Preterm: 20-36 weeks  Very preterm: < 32 weeks  Moderately preterm: 32-22 weeks  Late preterm: 34-36 weeks  Term:  Early term: 37-38 weeks  Full term: 39-40 weeks  Late term: 41 weeks 1 days - 41 weeks 6 days  Post-term: 42 weeks & beyond S&S of Pregnancy o Presumptive signs = subjective symptoms:  Breast changes (heavy, tender, extra sensitive)  Nausea &/or vomiting  6 weeks LMP  Questionable etiology may be due to high HCG  Urine frequency

Anatomy & Physiology of Pregnancy Fatigue Perception of fetal movements  Quickening usually between 16-20 weeks  Amenorrhea Probably signs (not diagnosable) = perceived by examiner:  Abdominal enlargement  After 12 weeks the uterus is no longer a pelvic organ but an abdominal organ  During the 1st weeks of pregnancy the uterus enlarges in the AP diameter only; later the uterus becomes globular  Goodell's sign: pelvic congestion, softening of cervix; 5 weeks  Chadwick's sign: bluish discoloration of vagina & cervix  Hegar's sign: softening of isthmus/lower uterine segment; 6-8 weeks  Positive serum/urine pregnancy test  Changes in cervical mucus  Cloudy  No ferning unless there's rupture of membranes  Braxton hicks contractions ("training" for labor)  Bollottment: examiner taps on the cervix, the fetus goes up, & comes back down to tap back  

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Positive signs (only diagnostic) = only pregnancy can cause them:  Visualization of fetus on ultrasound  By 4-5 weeks LMP an abdominal ultrasound can diagnose pregnancy  Auscultation of FHT's  Often heart between 10-12 weeks EGA w/ a doppler  With a fetascope the FHT's can be auscultated between 17-20 weeks  Normal FHT's are 120-160 bpm  Fetal HR can be detected @ 6 weeks  Palpation of fetal movement by examiner  Visualization of fetal movement by examiner Physiologic changes in pregnancy:  Body composition:  62% of gain is fluid

Anatomy & Physiology of Pregnancy 30% fat (90% as maternal stores)  8% protein  Most weight gain is in 2nd & 3rd trimester Reproductive system changes:  Uterus:  When you think of estrogen = hypertrophy, hypervascularity, hyperplasia, hyperpigmentation, hyperemia  When you think of PG = relaxes smooth muscles, muscles of the vasculature, muscles of the uterus, & prevents fetal rejections  Size increase in # of muscle fibers & increase vascularity & dilation of blood vessels  Position: rotates to the right as it elevates b/c of the sigmoid colon  Contractility (uterine muscles are being stretched = more vigorous contraction)  Blood flow: o Placental perfusion depends on the maternal blood flow to the uterus o Blood flow increases rapidly as the uterus increases in size o Although uterine blood flow increases 10=fold, the fetoplacental unit grows even more rapidly o Consequently, more oxygen is extracted from the uterine blood during the latter part of pregnancy o In a normal-term pregnancy, 1/6th of the total maternal blood volume is w/in the uterine vascular system o The rate of blood flow through the uterus averages 450-650 ml/min @ term, & oxygen consumption of the gravid uterus increases to meet fetal needs o Three factors known to decrease uterine blood flow are low maternal arterial pressure, contractions of the uterus, & maternal supine position o Estrogen stimulation can increase uterine blood flow o Doppler ultrasound exam may be used to measure uterine blood flow velocity, especially in pregnancies @ risk b/c of conditions associated w/ decreased placental perfusion (hypertension, intrauterine growth restriction, DM, multiple gestation) o By using an ultrasound device/fetal stethoscope to auscultate fetal heart tones, the examiner may also hear the uterine souffle/bruit, a rushing/blowing sound of maternal blood flowing 

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through uterine arteries to the placenta that's synchronous w/ the maternal pulse o The funic souffle, which is synchronous w/ the fetal HR & is caused by fetal blood coursing through the umbilical cord, may also be heard, as well as the fetus' actual heartbeat  Quickening (16-20 weeks)  Ballottement  Lightening (about 38 weeks); the baby’s head has engaged in the pelvis & has dropped = smaller bladder  Braxton hicks Vagina & vulva:  Leukorrhea: excessive discharge; white/grey w/ faint musty odor o May be copious o Contains exfoliated vaginal epithelial cells caused by the hyperplasia of normal pregnancy o Never pruritic/blood stained o This mucus fills the endocervical canal resulting in the mucous plug (operculum) = layer of protection  Edema & varicosities Cervix:  Friability (intercourse/vaginal exam can cause spotting)  Mucus plug (operculum) Breasts:  Fullness, heightened sensitivity, tingling, & heaviness of the breasts begin in the early weeks of gestation in response to increased levels of estrogen & PG  Breast sensitivity varies from mild tingling to sharp pain  Nipples & areolae become more pigmented, secondary pinkish areolae develop, extending beyond the primary areolae, & nipples become more erectile  Hypertrophy of the sebaceous (oil) glands embedded in the primary areolae, called Montgomery tubercles may be seen around the nipples  These sebaceous glands may have a protective role in that they keep the nipples lubricated for breastfeeding  The richer blood supply causes the vessels beneath the skin to dilate  Once barely noticeable, the blood vessels become visible, often appearing in an intertwining blue network beneath the surface of the skin  Venous congestion in the breasts is more obvious in primigravidas  Striae gravidarum may appear @ the outer aspects of the breasts

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During the 2nd & 3rd trimesters, growth of the mammary glands accounts for the progressive breast enlargement The high levels of luteal & placental hormones in pregnancy promote proliferation of the lactiferous ducts & lobule-alveolar tissue, so that palpation of the breasts reveals a generalized, coarse nodularity Glandular tissue displaces connective tissue, & as a result, the tissue becomes softer & looser Although development of the mammary glands is functionally complete by midpregnancy, lactation is inhibited until a decrease in estrogen level occurs after the birth A thin, clear, viscous secretory material (precolostrum) can be found in the acini cells by the 3rd month of gestation Colostrum, the creamy, white-to-yellowish-to-orange pre-milk fluid, may be expressed from the nipples as early as 16 weeks of gestation Colostrum is also a laxative which helps get rid of meconium

 CV changes:  Slight hypertrophy (estrogen) of heart  Total blood volume (TBV), consisting of plasma & RBC volume, increases significantly during pregnancy by approximately 30-45%  During the 1st 1/2 of pregnancy TBV increases rapidly, peaks around 28-34 weeks, & then stabilizes/decreases slightly by term  In a singleton pregnancy, plasma volume increases by 1200-1500 mL, or 45% above pre-pregnancy levels by 32 weeks of gestation, decreasing slightly by term  #1 cause of maternal mortality is heart & vascular problems  Pregnant woman doesn’t have increase in BP b/c progesterone relaxes vessles & dilates  By term, there's an increase in RBC mass of 250-450 mL, or approximately 20-30% over pre-pregnancy values  The percentage of increase depends on the amount of iron available  Increased blood volume is a protective mechanism  It's essential for meeting the blood volume needs of the hypertrophied vascular system of the enlarged uterus, for adequately hydrating fetal & maternal tissues when the women assumes an erect/supine position, & for providing a fluid reserve to compensate for blood loss during birth & postpartum  Blood volume increases are greater w/ multiple gestation  Peripheral vasodilation allows for a normal BP despite the increased blood volume in pregnancy  Because the plasma increase is > the increase in RBC production, there's a decrease in normal hemoglobin values (12-16 g/dl blood) & hematocrit values (37-47%)  This state of hemodilution is referred to as physiologic anemia  The decrease is more noticeable during the 2nd trimester, when rapid expansion of blood volume occurs faster than RBC production  If the hemoglobin value drops to 11 g/dl or less during the 1st or 3rd trimester or less than 10.5 g/dl during the 2nd trimester or if the hematocrit decreases to 32% or less, the woman is considered anemic  CO increases 30-50% over the non-pregnant rate by week 32 of pregnancy; it declines to about a 20% increase @ 40 weeks of gestation  This elevated CO is largely a result of increased stroke volume & HR & occurs in response to increased tissue demands for oxygen

Anatomy & Physiology of Pregnancy CO increases w/ any exertion such as labor & birth Circulation & coagulation times  Pregnancy is considered a hypercoagulable state (doesn’t want us to bleed to death during pregnancy; worry about DVTs) CV Changes in Pregnancy Change Increases 10-15 bpm Slight/no decrease from pre-pregnancy levels Slight decrease to mid-pregnancy (24-32 weeks) & gradual return to pre-pregnancy levels by end of pregnancy Increases by 1200-1500 ml or 40-45% above pregnancy level  

Parameter HR Systolic BP Diastolic BP Blood volume CO o

Increases 30-50% Respiratory system:  Structural & ventilatory adaptations occur during pregnancy to provide for maternal & fetal needs  Maternal oxygen requirements increase in response to the acceleration in metabolic rate & the need to add to the tissue mass in the uterus & breasts  In addition, the fetus requires oxygen & a way to eliminate carbon dioxide  Elevated levels of estrogen cause the ligaments of the rib cage to relax, permitting increased chest expansion  The transverse diameter of the thoracic cage increases by about 2 cm & the circumference by 6 cm  The costal angle increases, & the lower rib cage appears to flare out  The chest may not return to its pre-pregnant state after birth  The diaphragm is displaced by as much as 4 cm during pregnancy  With advanced pregnancy, chest breathing replaces abdominal breathing & it becomes less possible for the diaphragm to descent w/ inspiration  Thoracic breathing is accomplished primarily by the diaphragm rather than by the costal muscles  The URT becomes more vascular in response to elevated levels of estrogen  As the capillaries become engorged, edema & hyperemia (estrogen) develop w/in the nose, pharynx, larynx, trachea, & bronchi  This congestion w/in the tissues of the respiratory tract gives rise to several conditions seen during pregnancy, including nasal & sinus stuffiness, epistaxis (nosebleed), changes in the voice, & marked inflammatory response to even a mild upper respiratory infection  Increased vascularity of the URT also can cause the tympanic membranes & eustachian tubes to swell, giving rise to symptoms of impaired hearing, earaches, or a sense of fullness in the ears  Respiratory changes in pregnancy are related to the elevation of the diaphragm & changes in the chest wall  Changes in the respiratory center result in a lowered threshold for carbon dioxide  The actions of PG & estrogen are presumed to be responsible for the increased sensitivity of the respiratory center to carbon dioxide  Although pulmonary function isn't impaired by pregnancy, diseases of the respiratory tract can be more serious during this time  One important factor responsible for this can be the increase in oxygen requirements  The basal metabolic rate (BMR) increases during pregnancy

Anatomy & Physiology of Pregnancy The elevation in BMR reflects increased oxygen demands of the uterineplacental-fetal unit & greater oxygen consumption b/c of increased maternal cardiac work  The increase varies considerably, depending on the pre-pregnancy nutritional status of the woman & fetal growth  By the 3rd trimester the BMR is increased by 10-20% over the non-pregnant state  The BMR returns to non-pregnant levels by 5-6 days after birth  Peripheral vasodilation & acceleration of sweat gland activity help dissipate the excess heat resulting from the increased BMR during pregnancy  Pregnant woman can experience heat intolerance  Lassitude & fatigability after only slight exertion are experienced by many women in early pregnancy  These feelings, along w/ a greater need for sleep, can persist & be caused in part by the increased metabolic activity  By about the 10th week of pregnancy, there's a decrease of about 5 mm Hg in the partial pressure of carbon dioxide  PG may be responsible for increasing the sensitivity of the respiratory center receptors so that tidal volume increases & carbon dioxide decreases, the base excess (bicarb) decreases, & pH increases slightly  These alterations in acid-base balance indicate that pregnancy is a state of compensated respiratory alkalosis Respiratory Changes in Pregnancy Parameter Change RR Unchanged/slightly increased Tidal volume Increased 33% Vital capacity Unchanged Inspiratory capacity Increased 6% Expiratory reserve Decreased 20% volume Total lung capacity Unchanged to slightly decreased Minute ventilation Increased 30-50% Oxygen consumption Increased 20-40%  These changes also facilitate the transport of carbon dioxide from the fetus & oxygen release from the mother to the fetus 

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Vital signs:  Resting pulse is about 10 beats higher  Blood pressure  Decreased systolic & diastolic  Supine hypotension

Anatomy & Physiology of Pregnancy Any elevation in 3rd trimester is abnormal (preeclampsia)/requires follow up  Mean arterial pressure:  Calculating the MAP can increase the diastolic value of the findings  MAP is useful in predicting gestational hypertensive disorders in the 2nd & 3rd trimesters  Normal MAP readings in the non[regnant woman are 86 +/- 7.5 mm Hg  MAP readings during pregnancy range from 84-87 +/- 7  MAP = [ (2 x diastolic) + systolic] divided by 3  Temperature may increase due to increased BMR Vena cava syndrome: aka supine hypotensive syndrome  Some degree of compression of the vena cava occurs in many woman who lie on her back during the 2nd 1/2 of pregnancy  CO is reduced by as much as 25-30% when a pregnant woman is turned from left lateral recumbent to supine position  Some women experience a fall of > 30 mm Hg in their systolic pressure  After 4-5 minutes, a reflex bradycardia is noted, CO is reduced by 1/2, & the woman feels faint  Compression of the iliac veins & inferior vena cava by the uterus causes increased venous pressure & reduced blood flow in the legs, except when the woman is in the lateral position  These alterations contribute to the dependent edema, varicose veins in the legs & vulva, & hemorrhoids that develop in the latter part of term pregnancy Integumentary changes:  Melasma (also called cholasma or mask of pregnancy) is a blotchy, brownish hyperpigmentation (estrogen) of the skin over the cheeks, nose, & forehead, especially in pregnant women w/ dark complexions o Appears in 50-70% of pregnant women, beginning after the 16th week & increasing gradually until term o The sun intensifies this pigmentation in susceptible women o Melasma caused by normal pregnancy usually fads after birth but often recurs w/ OC use or subsequent pregnancies o Very similar to lupus, but it’s a bluish gray color  Angiomas are commonly referred to as vascular spiders o These tiny star-shaped or branched, slightly raised, & pulsating endarterioles are usually found on the neck, thorax, face, & arms o They occur as a result of elevated levels of circulating estrogen o The spiders are bluish & don't blanch w/ pressure 

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Anatomy & Physiology of Pregnancy Vascular spiders appear during the 2nd-5th months of pregnancy in about 65% of Caucasian women & 10% of African American women o The spiders usually disappear after birth Palmar erythema: pinkish red, diffusely mottled, or well-defined blotches are seen over the palmar surfaces of the hands in about 70% of Caucasian women & 30% of African American women during pregnancy o These color changes are related primarily to increased estrogen levels Some dermatologic conditions have been identified as unique to pregnancy or as having an increased incidence during pregnancy The most common dermatologic symptom during pregnancy is itching (pruritus) Mild pruritus, also known as pruritus gravidarum, usually occurs over the abdomen o Less than 2% of women have significant pruritus that requires further evaluation o The problem usually resolves during the postpartum period Pruritic urticarial papules & plaques of pregnancy (PUPPP) is more common in multiple gestations o Although it can cause significant maternal discomfort, it doesn't cause adverse outcomes for the mother/fetus o Mild PUPPP is usually treated w/ oral antihistamines & topical antipruritic & corticosteroid creams o Oral steroids may be needed in more severe cases Hyperpigmentation: nipples, areola, vulva, freckles, etc. Linea nigra & striae gravidarum o

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GI system:  Appetite: nausea/vomiting (morning sickness)  Mouth:  Hyperemia & softening of gums  Epulis (swelling of gums)  Gum hypertrophy can lead to bleeding  Periodontal inventions are related to preterm labor  Increased PG causes decreased tone & mobility of smooth muscles, resulting in

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esophageal regurgitation (reflux), slower emptying time of the stomach, & reverse peristalsis  As a result, the woman can experience acid indigestion, or heartburn (pyrosis), beginning as early as the 1st trimester & intensifying through the 3rd trimester  Smooth muscle relaxation & reduced peristalsis caused by increased PG & estrogen result in an increase in water absorption from the colon & can cause constipation  Constipation can also result from food choices, lack of fluids, iron supplementation, decreased activity level, abdominal distention by the pregnant uterus, & displacement & compression of the intestines  If the pregnant woman has hemorrhoids & is constipated, the hemorrhoids can evert/bleed during straining @ stool The gallbladder is often distended b/c of its decreased muscle tone during pregnancy  Increased emptying time & thickening of bile caused by prolonged retention are typical changes  These features, together w/ slight hypercholesterolemia from increased PG levels, can contribute to the development of gallstones during pregnancy Hepatic function is difficult to appraise during pre...