• Determine gravidity and parity by using the five- and two-digit systems. • Describe the various types of pregnancy tests, including the timing of tests and interpretation of results. • Explain the expected maternal anatomic and physiologic adaptations to pregnancy for each body system. • Differentiate among presumptive, probable, and positive signs of pregnancy. • Compare normal adult laboratory values with values for pregnant women. • Identify the maternal hormones produced during pregnancy, their target organs, and their major effects on pregnancy. • Compare the characteristics of the abdomen, vulva, and cervix of the nullipara and multipara. Two commonly used systems of summarizing the obstetrical history are discussed here. Gravidity and parity may be described with only two digits: The first digit represents the number of pregnancies the woman has had, including the present one; and parity is the number of pregnancies that have reached 20 or more weeks of gestation. For example, if the woman had twins at 36 weeks with her first pregnancy, parity would still be counted as one birth (gravida [G] 1, para [P]1) (Cunningham, Leveno, Bloom, Hauth, Gilstrap, & Wenstrom, 2005). If she becomes pregnant a second time, she would be G2 P1 until she gives birth at 38 weeks when she would then become G2 P2. Another system, which consists of five digits separated with hyphens, is commonly used in maternity centers. This system provides more information about the woman’s obstetric history, although it may not provide accurate information about parity since it provides information about births and not pregnancies reaching 20 weeks of gestation (Beebe, 2005). The first digit represents gravidity, the second digit represents the total number of term births, the third indicates the number of preterm births, the fourth identifies the number of abortions (miscarriage or elective termination of pregnancy), and the fifth is the number of children currently living. The acronym GTPAL (gravidity, term, preterm, abortions, living children) may be helpful in remembering this system of notation. For example, if a woman pregnant only once gives birth at week 34 and the infant survives, the abbreviation that represents this information is 1-0-1-0-1. During her next pregnancy, the abbreviation is 2-0-1-0-1. Additional examples are given in Table 6-1. TABLE 6-1 Obstetric History Using Five-Digit (GTPAL) System and Two-Digit (G/P)System Early detection of pregnancy allows early initiation of care. Human chorionic gonadotropin (hCG) is the earliest biochemical marker for pregnancy, and pregnancy tests are based on the recognition of hCG or a beta (β) subunit of hCG. Production of β-hCG begins as early as the day of implantation and can be detected as early as 7 to 10 days after conception (Blackburn, 2007). The level of hCG increases until it peaks at approximately 60 to 70 days of gestation and then declines until about 80 days of pregnancy. It remains stable until approximately 30 weeks and then gradually increases until term. Higher than normal levels of hCG may indicate abnormal gestation (e.g., fetus with Down syndrome), or multiple gestation; an abnormally slow increase or a decrease in hCG levels may indicate impending miscarriage (Cunningham et al., 2005). Enzyme-linked immunosorbent assay (ELISA) testing is the most popular method of testing for pregnancy. It uses a specific monoclonal antibody (anti-hCG) with enzymes to bond with hCG in urine. ELISA technology is the basis for most over-the-counter home pregnancy tests. With these one-step tests the woman usually applies urine to a strip or absorbent tipped applicator and reads the results. The test kits come with directions for collection of the specimen, the testing procedure, and reading of the results. A positive test result is indicated by a simple color change reaction or a digital reading. Most manufacturers of the kits provide a toll-free telephone number to call if users have concerns and questions about test procedures or results (see Teaching Guidelines). The most common error in performing home pregnancy tests is performing the test too early in pregnancy (Pagana & Pagana, 2006). Depending on the specific test, levels of hCG as low as 6.3 milli-international units/ml can be detected as early as the first day of a missed menstrual period as reported by Cole, Sutton-Riley, Khanlian, Borkovskaya, Rayburn, & Rayburn (2005). These researchers found that most of the over-the-counter pregnancy tests in the study were less sensitive (25 to 100 milli-international units/ml) and detected only a small percentage of pregnancies on the first day of a missed period even though most products claimed to be 99% accurate. Tomlinson, Marshall, and Ellis (2008) found that digital readings of low hCG levels (i.e., 25 milli-international units/ml) were more accurately interpreted by consumers than nondigital tests. TABLE 6-2 The pregnancy may “show” after the fourteenth week, although this depends to some degree on the woman’s height and weight. Abdominal enlargement may be less apparent in the nullipara with good abdominal muscle tone (Fig. 6-2). Posture also influences the type and degree of abdominal enlargement that occurs. In normal pregnancies, the uterus enlarges at a predictable rate. As the uterus grows, it may be palpated above the symphysis pubis some time between the twelfth and fourteenth weeks of pregnancy (Fig. 6-3). The uterus rises gradually to the level of the umbilicus at about 22 weeks of gestation and nearly reaches the xiphoid process at term. Between weeks 38 and 40, fundal height drops as the fetus begins to descend and engage in the pelvis (lightening) (see Fig. 6-3, dashed line). Generally, lightening occurs in the nullipara approximately 2 weeks before the onset of labor and at the start of labor in the multipara. Placental perfusion depends on the maternal blood flow to the uterus. Blood flow increases rapidly as the uterus increases in size. Although uterine blood flow increases 20-fold the fetoplacental unit grows more rapidly. Consequently, more oxygen is extracted from the uterine blood during the latter part of pregnancy (Cunningham et al., 2005). In a normal term pregnancy, one sixth of the total maternal blood volume is within the uterine vascular system. The rate of blood flow through the uterus averages 500 ml/min, and oxygen consumption of the gravid uterus increases to meet fetal needs. A low maternal arterial pressure, contractions of the uterus, and maternal supine position are three factors known to decrease blood flow. Estrogen stimulation may increase uterine blood flow. Doppler ultrasound examination can be used to measure uterine blood flow velocity, especially in pregnancies at risk because of conditions associated with decreased placental perfusion such as hypertension, intrauterine growth restriction, diabetes mellitus, and multiple gestation (Blackburn, 2007). By using an ultrasound device or a fetal stethoscope, the health care provider may hear the uterine souffle (sound made by blood in the uterine arteries that is synchronous with the maternal pulse) or the funic souffle (sound made by blood rushing through the umbilical vessels and synchronous with the fetal heart rate).
Anatomy and Physiology of Pregnancy
Gravidity and Parity
CONDITION
G
(GRAVIDITY)
T
(TERM BIRTHS)
P
(PRETERM BIRTHS)
A
(ABORTIONS AND MISCARRIAGES)
L
(LIVING CHILDREN)
G/P
(GRAVIDITY/PARITY)
Jamilla is pregnant for the first time.
1
0
0
0
0
1/0
She carries the pregnancy to 35 weeks, and the neonate survives.
1
0
1
0
1
1/1
She becomes pregnant again.
2
0
1
0
1
2/1
Her second pregnancy ends in miscarriage at 12 weeks.
2
0
1
1
1
2/1
During her third pregnancy, she gives birth at 39 weeks.
3
1
1
1
2
3/2
Jamilla is pregnant for the fourth time and gives birth at 36 weeks to twins.
4
1
2
1
4
4/3
Pregnancy Tests
Adaptations to Pregnancy
Signs of Pregnancy
TIME OF OCCURRENCE (GESTATIONAL AGE)
SIGN
OTHER POSSIBLE CAUSE
PRESUMPTIVE SIGNS
3-4 wk
Breast changes
Premenstrual changes, oral contraceptives
4 wk
Amenorrhea
Stress, vigorous exercise, early menopause, endocrine problems, malnutrition
4-14 wk
Nausea, vomiting
Gastrointestinal virus, food poisoning
6-12 wk
Urinary frequency
Infection, pelvic tumors
12 wk
Fatigue
Stress, illness
16-20 wk
Quickening
Gas, peristalsis
PROBABLE SIGNS
5 wk
Goodell sign
Pelvic congestion
6-8 wk
Chadwick sign
Pelvic congestion
6-12 wk
Hegar sign
Pelvic congestion
4-12 wk
Positive result of pregnancy test (serum)
Hydatidiform mole, choriocarcinoma
6-12 wk
Positive result of pregnancy test (urine)
False-positive results may be caused by pelvic infection, tumors
16 wk
Braxton Hicks contractions
Myomas, other tumors
16-28 wk
Ballottement
Tumors, cervical polyps
POSITIVE SIGNS
5-6 wk
Visualization of fetus by real-time ultrasound examination
No other causes
6 wk
Fetal heart tones detected by ultrasound examination
No other causes
16 wk
Visualization of fetus by radiographic study
No other causes
8-17 wk
Fetal heart tones detected by Doppler ultrasound stethoscope
No other causes
17-19 wk
Fetal heart tones detected by fetal stethoscope
No other causes
19-22 wk
Fetal movements palpated
No other causes
Late pregnancy
Fetal movements visible
No other causes
Reproductive System and Breasts
Uterus
Changes in size, shape, and position.
Uteroplacental blood flow.
Anatomy and Physiology of Pregnancy
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