to the fetus:
■ Auscultation of the fetal heart, by 10–12 weeks’ gestation with a Doppler
■ Observation and palpation of fetal movement by the examiner after about 20 weeks’ gestation
■ Sonographic visualization of the fetus: Cardiac movement noted at 4–8 weeks
Sonographic Diagnosis of Pregnancy
Ultrasound using a vaginal probe can confirm a pregnancy slightly earlier than with the transabdominal method. With a transvaginal ultrasound the gestational sac is visible by 4.5–5 weeks’ gestation and fetal cardiac movement can be observed as early as 4 weeks’ gestation. Ultrasound visualiza- tion of a pregnancy has increasingly become a routine and expected part of prenatal care. Indications for ultrasound examination of an early pregnancy for purposes of diagnosis include:
■ Pelvic pain or vaginal bleeding in the first trimester
■ History of repeated pregnancy loss or ectopic pregnancy (the implantation of a fertilized ovum outside the uterus)
■ Uncertain menstrual history
■ Discrepancy between actual size and expected size of pregnancy based on history
P
REGNANCYThe antepartum (antepartal) period, also referred to as the prenatal period, begins with the first day of the last normal menstrual period (LMP) and ends with the onset of labor (known as the intrapartal period).
Pregnancy is also counted in terms of trimesters, each roughly 3 months in length:
Trimesters
First trimester: First day of LMP through 14 completed weeks
Second trimester: 15 weeks through 28 completed weeks Third trimester: 29 weeks through 40 completed weeks Calculation of Due Date
An important piece of information to share with a newly pregnant woman and her family is her “due date” or estimat- ed date of birth (EDB). It is more commonly known now as estimated date of delivery (EDD). This date represents a best estimation as to when a full-term infant will be born.
C H A P T E R 4 ■ Physiological Aspects of Antepartum Care 53 The original term used for this date was the estimated date of
confinement (EDC).
Calculation of the EDD is best accomplished with a known and certain last menstrual period date (LMP). Other tools are used to determine the most accurate EDD possible if the LMP is not known and are used throughout the preg- nancy to confirm EDD based on an LMP. These tools are:
■ Physical examination to determine uterine size
■ First auscultation of fetal heart rate with a Doppler and/or a fetoscope (stethoscope for auscultation of fetal heart tones)
■ Date of quickening
■ Ultrasound examination
■ History of assisted reproduction Naegele’s Rule
Naegele’s rule is the standard formula for determining an EDD based on the LMP. The formula is: First day of LMP – 3 months + 7 days (see Box 4-2).
41st week of pregnancy. According to the American Academy of Pediatrics (AAP) and the American College of Obstetricians and Gynecologists (ACOG) (2007), neonates born prior to 37 completed weeks (<37 6/7 weeks or <259 days) of pregnancy are referred to as preterm, and those delivered after 42 weeks (>42 6/7 or >294) are classified as post term (AAP & ACOG, 2007).
Weeks of Gestation
Once an EDD has been determined, a pregnancy is counted in terms of weeks of gestation beginning with the first day of the LMP and ending with 40 completed weeks (the EDD).
A useful tool for quickly and easily calculating the EDD is the gestational wheel (Fig. 4-2), but it is less reliable than Naegele’s rule due to variations of up to a few days between wheels. It is best to calculate a due date initially using Naegele’s rule and then employ a gestational wheel to deter- mine a woman’s current gestational age.
To use the gestational wheel, place the arrow labeled “first day of last period” from the inner circle on the date of the LMP on the outer circle. The EDD is then read as the date on the outside circle that lines up with the arrow at 40 com- pleted weeks on the inside circle. With the example the LMP is ________ and the EDD is ________.
Prenatal Assessment Terminology
A set of terms is used to describe obstetrical history and to define a woman’s obstetrical status. An important shorthand system for explaining a woman’s obstetrical history uses the
BOX 4–2 GESTATIONAL AGE
Gestational age refers to the number of completed weeks of fetal development, calculated from the first day of the last normal menstrual period. Embryologists date fetal age and development from the time of conception (known as conceptual or embry- ological age), which is usually 2 weeks less. Unless otherwise specified, all references to dating or fetal age in this textbook will be gestational ages (based on time since the last menstrual peri- od and not time since conception).
FORMULA FOR NAEGELE’S RULE
LMP Sept 7
–3 months June 7 +7 days
EDD June 14
Figure 4–2 Gestational wheel. To use the gestational wheel, place the arrow labeled “first day of last period”
from the inner circle on the date of the LMP on the outer circle. The EDD is then read as the date on the outside circle that lines up with the arrow at 40 completed weeks on the inside circle. With the example in Figure 4-2, the LMP is Sept 7 and the EDD is June 14.
It is important to remember that the EDD as deter- mined by Naegele’s rule is only a best guess of when a baby is likely to be born. Two factors influence the accuracy of Naegele’s rule:
■ Regularity of a woman’s menstrual cycles
■ Length of a woman’s menstrual cycles
■ Results may not be accurate if menstrual cycles are not reg- ular or are greater than 28 days apart.
Most women give birth within the time period of 3 weeks before to 2 weeks after their EDD. The length of pregnancy is approximately 280 days or 40 weeks from the first day of the LMP. In recent years there has been conflicting or inconsistent information on the definition of a “term” pregnancy. The window for term gestation has traditionally been defined as between the 5 weeks from 37 to 42 weeks from the LMP. Statisticians or some experts now define term pregnancy as one that begins after the 37th competed week of pregnancy through the end of the
■ GTPALM may be used, and the M represents pregnan- cies with multiple gestations.
■ Nulligravida is a woman who has never been pregnant or given birth.
■ Primigravida is a woman who is pregnant for the first time.
■ Multigravida is someone who is pregnant for at least the second time.
P
HYSIOLOGICAL PROGRESSION OF PREGNANCYPregnancy results in maternal physiologic adaptations involving every body system. Every change has either the maintenance of the pregnancy, the development of the fetus, or preparation for the labor and birth as its basis and is pro- tective of the woman and/or the fetus. To both understand a woman’s experience of normal pregnancy and be effective in identifying deviations from normal, the nurse must have a basic foundation in the physiology of pregnancy.
This understanding is critical not only for risk assessment and implementation of appropriate nursing interventions to reduce risk but also for providing effective patient education and anticipatory guidance grounded in knowledge of the physiological basis for the normal physical changes in preg- nancy and their resulting common, and normal, discomforts.
The next sections present the changes that occur in each sys- tem, and Table 4-3 summarizes the major physiological changes and factors that influence these changes.
terms gravida and para in describing numbers of pregnancies and births.
■ G/P is a two-digit system to denote pregnancy and birth history.
■ Gravida refers to the total number of times a woman has been pregnant, without reference to how many fetuses there were with each pregnancy or when the pregnancy ended. It is simply how many times a woman has been pregnant, including the current pregnancy.
■ Para refers to the number of births after 20 weeks’ gestation whether live births or stillbirths. There is no reference to num- ber of fetuses delivered with this system, so twins count as one delivery, just like a singleton birth. A pregnancy that ends before the end of 20 weeks’ gestation is considered an abortion, whether it is spontaneous (miscarriage) or induced (elective or therapeutic), and is not counted using the G/P system.
■ GTPAL (meaning gravida, term, para, abortion, and living) is a more comprehensive system that gives information about each infant from prior pregnancies. This system designates numbers of infants as follows:
■ G = total number of times pregnant (same as G/P system above)
■ T = number of term infants born (after 37 completed or 37 6/7 weeks’ gestation)
■ P = number of preterm infants born between 20 and 37 completed weeks’ gestation or 37 6/7 weeks)
■ A = number of abortions (either spontaneous or induced) before 20 weeks’ gestation (or <500 grams at birth)
■ L = the number of children currently living.
Tenderness, feeling of fullness, and tingling sensation Increase in weight of breast by 400 grams
Enlargement of breasts, nipples, areola, and Montgomery follicles (small glands on the areola around the nipple)
Striae: Due to stretching of skin to accommodate enlarging breast tissue Prominent veins due to a twofold increase in blood flow
Increased growth of mammary glands
Increase in lactiferous ducts and alveolar system
Production of colostrum, a yellow secretion rich in antibodies, begins to be produced as early as 16 weeks
Hypertrophy of uterine wall
Softening of vaginal muscle and connective tissue in preparation for expan- sion of tissue to accommodate passage of fetus through the birth canal Uterus contractibility increases in response to increased estrogen levels, lead-
ing to Braxton-Hicks contractions.
Hypertrophy of cervical glands leads to formation of mucus plug, which serves as a protective barrier between uterus/fetus and vagina.
Increased vascularity and hypertrophy of vaginal and cervical glands leads to increase in leukorrhea.
Cessation of menstrual cycle (amenorrhea) and ovulation
TABLE 4–3 PHYSIOLOGICAL CHANGES IN PREGNANCY
PHYSIOLOGICAL CHANGES CLINICAL SIGNS AND SYMPTOMS
REPRODUCTIVE SYSTEM—Breasts
Increase of estrogen and progesterone levels:
Initially produced by the corpus luteum and then by the placenta
Increased blood supply to breasts
Increase of prolactin: Produced by the anterior pituitary
REPRODUCTIVE SYSTEM—Uterus, cervix, and vagina
Increased levels of estrogen and progesterone
C H A P T E R 4 ■ Physiological Aspects of Antepartum Care 55
TABLE 4–3 PHYSIOLOGICAL CHANGES IN PREGNANCY—cont’d
PHYSIOLOGICAL CHANGES CLINICAL SIGNS AND SYMPTOMS Enlargement and stretching of uterus to
accommodate developing fetus and placenta
Expanded circulatory volume leads to increased vascular congestion.
Acid pH of vagina
CARDIOVASCULAR SYSTEM
Decrease in peripheral vascular resistance Increase in blood volume by 40%–45%
Increase in cardiac output by 40%
BMR increased 10%–20% by 3rd trimester Increase in peripheral dilation
Increase in RBC count by 30%
Increase in RBC volume by 18%–33%
Increase in plasma volume by 50%
Increase in WBC count
Increased demand for iron in fetal development Plasma fibrin increase of 40%
Fibrinogen increase of 50%
Decrease in coagulation inhibiting factors Protective of inevitable blood loss during birth Increased venous pressure and decreased blood
flow to extremities due to compression of iliac veins and inferior vena cava
In supine position the enlarged uterus compresses the inferior vena cava, causing reduced blood flow back to the right atrium and a drop in cardiac output and blood pressure.
RESPIRATORY SYSTEM
Hormones of pregnancy stimulate the respiratory center and act on lung tissue to increase and enhance respiratory function.
Increase of oxygen consumption by 15%–20%
Estrogen, progesterone, and prostaglandins cause vascular engorgement and smooth muscle relaxation.
Increase in uterine size to 20 times that of non-pregnant uterus Weight of uterus increases from 70 grams to 1,100 grams.
Capacity increases from 10 ml to 5000 ml; 80% of that to uteroplacental Blood flow to the uterus is 500–600 mL/min at term.
Goodell’s sign: Softening of the cervix
Hegar’s sign: Softening of the lower uterine segment
Chadwick’s sign: Bluish coloration of cervix, vaginal mucosa, and vulva Acid environment inhibits growth of bacteria.
Acid environment allows growth of Candida albicans, leading to increased risk of candidiasis (yeast infection).
Decrease in blood pressure Hypervolemia of pregnancy Increased heart rate of 15–20 bpm Increased stroke volume of 25%–30%
Systolic murmurs, load and wide S1 split, load S2, obvious S3 Increase in heart size
Physiological anemia of pregnancy
Hemodilution is caused by the increase in plasma volume being relatively larger than the increase in RBCs, which results in decreased hemoglobin and hematocrit values. (See Appendix B for pregnancy laboratory values.) Values up to 16,000 mm3in the absence of infection
Iron-deficiency anemia: Hemoglobin <11 g/dL and hematocrit<33%
Hypercoagulability
Edema of lower extremities Varicosities in legs and vulva Hemorrhoids
Supine hypotensive syndrome
Increase in tidal volume by 35%–50%
Slight increase in respiratory rate Increase in inspiratory capacity Decrease in expiratory volume Slight hyperventilation Slight respiratory alkalosis Dyspnea
Nasal and sinus congestion Epistaxis
Continued
TABLE 4–3 PHYSIOLOGICAL CHANGES IN PREGNANCY—cont’d
PHYSIOLOGICAL CHANGES CLINICAL SIGNS AND SYMPTOMS Upward displacement of diaphragm by
enlarging uterus
Estrogen causes a relaxation of the ligaments and joints of the ribs.
Slight decrease in lung capacity RENAL SYSTEM
Alterations in cardiovascular system (increased cardiac output and increased blood and plasma volume) lead to increased renal blood flow of 50%–80% in first trimester and then decreases.
Increased progesterone levels, which cause a relaxation of smooth muscles
Dilation of renal pelvis and ureters Ureters become elongated with decreased
motility.
Decreased bladder tone with increased bladder capacity
Pressure of enlarging uterus on renal structures Displacement of bladder in third trimester Increased glomerular filtration rate
Increased renal excretion of glucose and protein Decreased renal flow in third trimester Increased vascularity
GASTROINTESTINAL SYSTEM
Increased levels of hCG and altered carbohydrate metabolism
Increased progesterone levels slow stomach emptying and relax the esophageal sphincter.
Increased progesterone levels relax smooth muscle to slow the digestive process and movement of stool.
Increased progesterone levels decrease muscle tone of gallbladder and result in prolonged emptying time.
Changes in senses of taste and smell
Displacement of intestines by uterus
Increased levels of estrogen lead to increased vascular congestion of mucosa.
MUSCULOSKELETAL SYSTEM
Increased progesterone and relaxin levels lead to softening of joints and increased joint mobility, resulting in widening and increased mobility of the sacroiliac and symphysis pubis.
Shift from abdominal to thoracic breathing Chest and thorax expand to accommodate
thoracic breathing and upward displacement of diaphragm.
Urinary frequency and incontinence and increased risk of urinary tract infection (UTI)
Increased risk of UTI
Urinary frequency and nocturia
Increased urinary output Glucosuria and proteinuria Dependent edema
Hyperemia of bladder and urethra
Nausea and vomiting during early pregnancy
Reflux of gastric contents into lower esophagus resulting in heartburn Bloating, flatulence, and constipation
Increased risk of gallstone formation and cholestasis
Increase or decrease in appetite Nausea
Pica: Abnormal; craving for and ingestion of nonfood substances such as clay or starch
Flatulence, abdominal distension, abdominal cramping, and pelvic heaviness Gingivitis, bleeding gums, increase risk of periodontal disease
Altered gait: “Waddle” gait Facilitates birthing process Low back pain or pelvic discomfort
Pelvis tilts forward, leading to shifting of center of gravity that results in change in posture and walking style, increasing lordosis.
Increased risk of falls due to shift in center of gravity and change in gait and posture
C H A P T E R 4 ■ Physiological Aspects of Antepartum Care 57
TABLE 4–3 PHYSIOLOGICAL CHANGES IN PREGNANCY—cont’d
PHYSIOLOGICAL CHANGES CLINICAL SIGNS AND SYMPTOMS Distension of abdomen related to expanding
uterus, reduced abdominal tone, and increased breast size
Increased estrogen and relaxin levels lead to increased elasticity and relaxation of ligaments.
Abdominal muscles stretch due to enlarging uterus.
INTEGUMENTARY SYSTEM
Estrogen and progesterone levels stimulate increased melanin deposition, causing light brown to dark brown pigmentation.
Increased blood flow, increased basal metabolic rate, progesterone-induced increase in body temperature, and vasomotor instability Increased action of adrenocorticosteroids leads
to cutaneous elastic tissues becoming fragile.
Increased estrogen levels lead to color and vascular changes.
Increased androgens lead to increase in sebaceous gland secretions.
ENDOCRINE SYSTEM
Decreased follicle-stimulating hormone Increased progesterone
Increased estrogen
Increased prolactin Increased oxytocin
Increased human chorionic gonadotropin (hCG) Human placental lactogen/human chorionic
somatomammotropin
Hyperplasia and increased vascularity of thyroid
Increased BMR related to fetal metabolic activity Increased need for glucose due to developing fetus Increase in circulating cortisol
NEUROLOGICAL SYSTEM
Blackburn (2007); Cunningham et al. (2010); Kahn & Hoos (2010); Mattson & Smith, 2011; Blackburn (2014).
Round ligament spasm
Increase risk of joint pain and injury Diastasis recti
Linea nigra
Melasma (chloasma)
Increased pigmentation of nipples, areola, vulva, scars, and moles Hot flashes, facial flushing, alternating sensation of hot and cold Increased perspiration
Striae gravidarum (stretch marks) on abdomen, thighs, breast, and buttocks Angiomas (spider nevi)
Palmarerythema: Pinkish-red mottling over palms of hands and redness of fingers
Increased oiliness of skin and increase of acne Amenorrhea
Maintains pregnancy by relaxation of smooth muscles, leading to decreased uterine activity, which results in decreased risk of spontaneous abortions Decreases gastrointestinal motility and slows digestive processes
Facilitates uterine and breast development Facilitates increases in vascularity
Facilitates hyperpigmentation
Alters metabolic processes and fluid and electrolyte balance Facilitates lactation
Stimulates uterine contractions
Stimulates the milk let-down or ejection reflex in response to breastfeeding Maintenance of corpus luteum until placenta becomes fully functional Facilitates breast development
Alters carbohydrate, protein, and fat metabolism
Facilitates fetal growth by altering maternal metabolism; acts as an insulin antagonist
Enlargement of thyroid Heat intolerance and fatigue
Depletion of maternal glucose stores leads to increased risk of maternal hypoglycemia.
Increased production of insulin
Increase in maternal resistance to insulin leads to increased risk of hyperglycemia.
Headache Syncope
Reproductive System
Maternal physiologic adaptations to pregnancy are most profound in the reproductive system. The uterus under- goes phenomenal growth, breasts prepare for lactation, and the vagina changes to accommodate the birthing process (Fig. 4-3).
Breasts
Breast changes begin early in pregnancy and continue throughout gestation and into the postpartum period. These changes are primarily influenced by increases in hormone levels and occur in preparation for lactation (see Table 4-3).
Uterus
The uterus is described in three parts:
■ Fundus or upper portion
■ Isthmus or lower segment
■ Cervix, the lower narrow part, or neck; the external part of the cervix interfaces with the vagina. The Cervical Os is the opening of the cervix that dilates (opens) during labor to allow passage of the fetus through the vagina.
Uterine changes over the course of pregnancy are profound (see Table 4-3).
■ Before pregnancy, this elastic, muscular organ is the size and shape of a small pear weighing 40–50 g.
■ During pregnancy, the uterine wall progressively thins as the uterus expands to accommodate the developing fetus.
■ By mid-pregnancy, the uterine fundus reaches the level of the umbilicus abdominally.
■ Toward the end of pregnancy, the enlarged uterus, con- taining a full-term fetus, fills the abdominal cavity and has altered the placement of the lungs and rib cage in addition to the abdominal organs (Fig. 4-4).
■ Intermittent, painless, and physiological uterine contrac- tions, referred to as Braxton-Hicks contractions, begin in the second trimester but some women do not feel them until the third trimester. These contractions are irregular with no particular pattern. As the uterus enlarges, they are more noticeable.
■ At term, the uterus weighs 1100–1200 g.
Vagina
The vagina is an elastic muscular canal. As pregnancy pro- gresses, various changes take place in the vasculature and tone (see Table 4-3).
■ An increase of vascularity due to the expanded circulatory needs
■ An increase of vaginal discharge (leukorrhea), which is in response to the estrogen-induced hypertrophy of the vaginal glands
■ Relaxation of the vaginal wall and perineal body, which allows stretching of tissues to accommodate the birthing process.
Ovary Fallopian
tube
Fundus
of uterus Ovarian ligament
Fimbriae
Broad ligament
Round ligament
Artery and vein
Body of uterus Endometrium Myometrium
Cervix of uterus
Vagina
Figure 4–3 Reproductive system.