Diagnosis and clinical manifestations of early pregnancy
Lori A Bastian, MD
Haywood L Brown, MD
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INTRODUCTION — Diagnosis of pregnancy and knowledge of normal findings associated with early pregnancy are common issues in the medical care of reproductive age women. More than 6 million women are diagnosed with pregnancy each year in the United States, and millions more have sought diagnostic testing [1]. Early diagnosis of pregnancy may prompt women to seek prenatal care earlier and to take measures, such as improving glucose control (in diabetics) or avoiding alcohol or potentially harmful drugs, that can benefit the fetus.
The diagnosis of early pregnancy is based primarily upon laboratory assessment of human chorionic gonadotropin (hCG). Characteristic findings on history and physical examination are not highly sensitive for diagnosis, but are important to help the clinician distinguish normal pregnancy from coexistent disorders.
SIGNS AND SYMPTOMS OF EARLY PREGNANCY — Most women experience some signs or symptoms of pregnancy as early as three weeks after conception [2]. The most common symptoms of early pregnancy include: Amenorrhea Nausea with or without vomiting Breast tenderness Increased frequency of urination Fatigue
Amenorrhea and bleeding — Amenorrhea is the cardinal sign of early pregnancy. Pregnancy should be suspected whenever a woman in her childbearing years notes cessation or delay of menses (>1 week), especially if she reports any sexual activity while not using contraception or with inconsistent use of contraception. Even in women using contraception, contraceptive failures occur (show table 1A-B). Secondary amenorrhea should be considered in women who are not pregnant.
Cessation of menses is a difficult symptom to evaluate because many women have irregular bleeding patterns or an occasional prolongation of a cycle. In addition, some women have bleeding on and off during the first few months of pregnancy and thus lack amenorrhea [3]. This was illustrated in a study of 221 healthy women who were recruited to keep daily diaries and provide daily urine samples while trying to become pregnant [4]. Of the 151 women who became pregnant, 14 women (9 percent) experienced at least one day of vaginal bleeding during the first eight weeks of pregnancy. The majority (12 of 14) of these pregnancies continued to a live birth. Bleeding tended to occur around the time when women would expect their periods to occur. This bleeding was typically light (requiring only one or two pads or tampons in 24 hours). The important conclusions from this study were that vaginal bleeding is fairly common in early pregnancy, and that it occurs more often at the time when a period would be expected, although there is no clear physiologic explanation for this phenomenon.
Bleeding in early pregnancy is of concern if it is heavier than a typical menstrual period or accompanied by pain, as it may represent an ectopic pregnancy or impending miscarriage. The differential diagnosis of bleeding in early pregnancy is discussed separately. (See "Overview of the etiology and evaluation of vaginal bleeding in pregnant women").
Nausea and vomiting — The term "morning sickness" refers to the tendency of most pregnant women to develop nausea, often with vomiting, between six and 12 weeks of gestation. This nausea is typically worse in the morning and tends to improve as the day progresses, but can occur at any time of day. Hyperemesis gravidarum may be considered the severe end of the spectrum of symptoms. (See "Hyperemesis gravidarum").
If nausea and vomiting are accompanied by pain, fever, vertigo, diarrhea, headache, or abdominal distension, a cause other than pregnancy should be considered. In addition, the onset of nausea and vomiting after the first 12 weeks of pregnancy should also prompt an evaluation because this would be after the typical period expected for pregnancy-related nausea and vomiting. (See "Approach to the adult patient with nausea and vomiting").
Breast tenderness — The pregnant woman often notices enlargement of her breasts with a heavy sensation associated with tingling and soreness. This is due to hCG stimulation of the secretory glands. Other breast changes related to early pregnancy include a darkening of the skin around the areola and more prominent veins across each breast. (See "Breast development and anatomy" section on Changes during pregnancy).
Urinary frequency — Urinary frequency and nocturia are common pregnancy-related complaints. Frequency appears to be related to increased total urinary output and can occur as early as six weeks of gestation. Cystitis should be suspected if dysuria, hematuria, or pyuria is present. (See "Renal and urinary tract physiology in pregnant women" section on Frequency and nocturia).
Fatigue — Fatigue is common in early pregnancy, but less prominent in the second trimester. The exact cause is not clear; possibilities include the rapid, large increase in concentrations of progesterone which may exert soporific effects and the extensive cardiovascular/hematological changes which increase cardiac output. (See "Maternal cardiovascular and hemodynamic adaptation to pregnancy").
Stress, depression, and lifestyle issues are common causes of fatigue in nonpregnant individuals. The evaluation of fatigue that is chronic or does not improve after the first trimester can be found separately (show table 2). (See "Approach to the patient with fatigue").
Other — Other symptoms women report in early pregnancy include food cravings and aversions, mood changes, lightheadness, abdominal bloating, constipation, low back pain, nasal congestion, and uterine cramps similar to those felt before or during menses. Most of these symptoms have been attributed to the changing hormonal milieu of pregnancy.
Bloating and constipation are probably due to increases in progesterone, which reduces intestinal motility. Constipation may also be aggravated by the use of prenatal vitamins containing iron. (See "Maternal gastrointestinal tract adaptation to pregnancy").
Pregnancy related dyspnea is usually mild, of gradual onset, and not associated with other pulmonary signs or symptoms (eg, no cough, wheezing, pleurisy). It is caused by progesterone effects on the respiratory center (ie, increased minute ventilation). If dyspnea occurs acutely, is associated with tachycardia, chest pain, hemoptysis, or signs of deep vein thrombosis, then pulmonary embolism should be considered. (See "Changes in the respiratory tract during pregnancy", see "Dyspnea during pregnancy" and see "Deep vein thrombosis and pulmonary embolism in pregnancy").
Lightheadedness is likely associated with the normal pregnancy related fall in vascular resistance. It typically occurs when the woman is erect and resolves by having her lie on her left side. Lightheadedness is of concern if it occurs in association with an abnormal heart rate/rhythm or signs suggestive of a seizure. (See "Maternal cardiovascular and hemodynamic adaptation to pregnancy").
Nasal congestion is related to hyperemia of the mucous membranes. (See "Physiologic changes of the skin; hair; nails; and mucous membranes during pregnancy").
Low back pain, and other musculoskeletal discomforts, typically occur after the first trimester, but may occur early in pregnancy. They are due to changes in the woman's center of gravity with advancing gestation and the effect of pregnancy hormones. (See "Pain related to the musculoskeletal system during pregnancy").
DIAGNOSIS
History — Specific questions to ask women if pregnancy is suspected include the following:
(1) When was your last menstrual period, and was it normal?
(2) Do you engage in sexual activity?
(3) Do you use any form of contraception?
(4) Do you have any symptoms of pregnancy?
(5) Is there any chance you may be pregnant?
Several studies have examined the value of these questions in diagnosing early pregnancy. In one Emergency Department study, physicians were asked to complete a brief questionnaire on all patients for whom they ordered a qualitative serum beta-hCG test; 208 patients were included and 138 of these had abdominal pain [5]. Sixty-eight women (33 percent) were pregnant. Likelihood ratios (LR) were calculated to express the change in odds favoring the diagnosis of early pregnancy given a positive result (LR+=sensitivity/1-specificity) or a negative result (LR-=1-sensitivity/specificity) [6].
In this study, pregnancy was likely if there was a positive history of a period that was not on time and imperfect use of contraception and the patient thought she might be pregnant. For delayed menses the LR+ was 2.06 (95% CI 1.65-2.57) and the LR- was 0.25 (95% CI 0.14-0.45), for no birth control the LR+ was 1.31 (95% CI 1.14-1.5) and the LR- was 0.33 (95% CI 0.16-0.69), and for patient suspects she is pregnant the LR+ was 1.89 (95% CI 1.54-2.33) and the LR- was 0.27 (95% CI 0.15-0.48). If these factors were negative, however, there was a 10 percent chance that pregnancy was overlooked. In another Emergency Department study that included 191 consecutive reproductive age women presenting for any reason (70 had abdominal pain), patients were asked to complete a menstrual and sexual history questionnaire before pregnancy testing [7]. Twelve (6.3 percent) women had an unrecognized pregnancy (defined as a pregnancy not definitely known to exist before the visit). In this study, presence of a delayed menstrual period had a nonsignificant LR+ of 1.04 (95% CI 0.38-2.87) and LR- 0.99 (95% CI 0.7-1.38), patient stating there was a chance she might be pregnant had LR+ of 3.15 (95% CI 2.37-4.2) and LR- 0.12 (95% CI 0.02-0.77), and absence of contraceptive use had LR+ of 1.53 (95% CI 1.06-2.18) and LR- 0.49 (95% CI 0.18-1.32). A study of 283 women seeking pregnancy testing at a health center reported 118 (42 percent) were pregnant [8]. Women experiencing any pregnancy symptoms (defined as morning sickness, breast tenderness and fullness, urinary frequency or fatigue) had LR+ of 2.43 (95% CI 1.71-3.44) and LR- 0.63 (95% CI 0.52-0.77) and if the woman thinks she may be pregnant the LR+ was 1.6 (95% CI 1.39-1.85) and LR- 0.18 (95% CI 0.09-0.34). A similarly designed study of 2926 adolescents seeking pregnancy testing (36 percent were pregnant) reported delayed menses had LR+ of 1.13 (95% CI 1.05-2.92) and LR- 0.81 (95% CI 0.68-0.96) and patient thinks she may be pregnant had LR+ of 2.11 (95% CI 1.97-2.27) and LR- 0.38 (95% CI 0.34-0.42) [9]. Lastly, Scottish general practitioners asked 1592 women requesting pregnancy testing to complete a questionnaire that also asked about pregnancy symptoms [10]. Overall, 61.5 percent were pregnant. In this study, delayed menses had LR+ of 1.56 (95% CI 1.4-1.74) and LR- 0.62 (95% CI 0.56-0.69) and symptom of morning sickness had LR+ of 2.7 (95% CI 2.19-3.33) and LR- 0.71 (95% CI 0.67-0.76).
In summary, although a report of delayed menses, sexual activity with imperfect use of contraception, and patient suspicion of pregnancy are predictive that a pregnancy test will be positive, these historical factors are not sufficiently reliable to diagnose or exclude pregnancy. Morning sickness, if present, increases the likelihood of pregnancy, but some women do not experience this symptom or merely haven't experienced it before being tested (show table 3).
Physical examination — Findings suggestive of pregnancy on pelvic and general physical examination include the following [6,11,12]: The uterus becomes enlarged and globular and increases in size by about 1 cm per week after 4 weeks of gestation. The uterus remains a pelvic organ until approximately 12 weeks of gestation, when it becomes sufficiently large to palpate abdominally just above the symphysis pubis. (See "The gynecologic history and physical examination"). The cervix and uterus soften (called Goodell sign and Hegar sign, respectively). This allows the examiner to easily flex the uterine body against the cervix, which is called McDonald sign. This occurs ar about 6 weeks of gestation. Uterine artery pulsation can be palpated through the lateral vaginal fornices on bimanual examination. Because of the increased blood supply to the uterus, the mucous membranes of the vulva, vagina, and cervix become congested and take on a bluish-violet coloration (Chadwick sign). This occurs at about 8 to 12 weeks of gestation. The breasts become fuller, tender, and the areolar area darkens. The venous pattern under the skin over the breasts becomes increasingly visible as pregnancy progresses. Identification of a fetal heart rate distinct from the maternal heart rate is diagnostic of pregnancy. Hand held Doppler instruments typically are used to detect fetal heart activity at 10 to 12 weeks of gestation, but can be used earlier if the uterus is accessible abdominally, and are reliable if the fetal heart rate is identified. The fetal heart can usually be auscultated with a fetoscope by 20 weeks of gestation.
In the Scottish study discussed above, general practitioners also asked 1592 women requesting pregnancy testing to undergo physical examination prior to obtaining results of their pregnancy tests [10]. Overall, 61.5 percent were pregnant: 25 percent of women in this study were more than 63 days from LMP and the average was about 50 days from LMP. Physician's assessment of positive breast signs had LR+ of 2.71 (95% CI 2.3-3.2) and LR- 0.55 (95% CI 0.5-0.6), and positive pelvic examination findings had LR+ of 3.17 (95% CI 2.22-4.51) and LR- 0.87 (95% CI 0.8-0.9). Of interest, 19 women who were not pregnant had a palpable fundus.
A subsequent study examined 155 women to determine if uterine artery pulsations could be palpated [11]. Twenty-five women were pregnant. The examiner was blind to the patients' history and pregnancy test results. LR+ for uterine artery pulsations was 10.98 (95% CI 5.63-21.4) and LR- 0.26 (95% CI 0.13-0.52).
In summary, only a few studies have examined the value of physical examination in diagnosing early pregnancy. The likelihood of pregnancy increases if signs of pregnancy are present, but absence of these signs does not rule out pregnancy. Obviously, the ability to detect physical signs of pregnancy is highly dependent upon the experience of the examiner.
Laboratory tests — A diagnosis of early pregnancy based upon clinical findings or a home pregnancy test should be confirmed by office or laboratory based urine or serum testing. The laboratory diagnosis of pregnancy is based upon assessment of human chorionic gonadotropin (hCG). hCG structure and assay are discussed in detail separately. (See "Management of hydatidiform mole" section on Human chorionic gonadotropon).
Home pregnancy test — Home pregnancy test (HPT) kits were introduced in 1975. They have become increasingly popular and work by detecting hCG in the urine using immunometric assay methods [13]. Most studies have found that women choose to use HPT kits because of the speed of obtaining results and the convenience of testing at home.
A woman may say that her HPT was negative and ask if this means that she is not pregnant. Specific questions to ask her include the following:
(1) How many days after your missed period did you perform the test?
(2) Did you understand how to do the test and feel comfortable doing it?
(3) What brand of HPT did you use?
(4) Did you repeat the test and get a similar result?
Although manufacturers claim these kits are 99 percent accurate, the accuracy of HPTs is greatly affected by the technique and interpretation of users. This was illustrated in a systematic review of five studies from 1997 that reviewed 16 HPT kits [14]. When urine samples were tested by volunteers, test sensitivity was 91 percent. In contrast, the sensitivity was only 75 percent in studies where subjects were actual patients who used the HPT kit on their own urine samples.
There is also significant variation in sensitivity among HPT kits. To demonstrate this variability, a blinded in vitro sensitivity analysis was performed on seven commonly used HPT kits [15]. Major findings from this study were: "First Response Early Result" was found to be the most sensitive HPT, with an analytical sensitivity of less than 6.3 mIU/ml. This product should detect more than 95 percent of pregnancies on the first day of a missed period. The same manufacturer, Scantibodies Laboratories Inc, also makes "Answer" and "Answer Quick & Simple" kits that are similar in design to "First Response Early Result" and therefore may have similar sensitivities. The second most sensitive HPT was "Clearblue Easy Earliest Results," having an analytical sensitivity of 25 mIU/ml [15]. This product should detect 80 percent of pregnancies on the first day of a missed period. "Clear Plan Easy" is a similar product made by the same manufacturer. The majority of products tested detected only a small percentage of pregnancies on the first day of a missed period because a higher level of hCG was required for a positive result.
Based on these data, we suggest practitioners advise their patients on selection of HPT kits and their limitations.
Regardless of the HPT kit used, the most common error with home kits is a negative result because the test is performed too early in pregnancy. If a pregnancy is suspected despite a negative test, the test should be repeated in one week. Many HPT kits make this recommendation and provide an extra kit for this purpose. Pregnancy always should be confirmed with an office-based test, even when a home-based test is positive.
Urine pregnancy test — Urine pregnancy testing is the most common method used to confirm pregnancy in the office setting. A variety of affordable and reliable immunometric urine tests that take one to five minutes to perform are available for use in office practices. Immunometric tests specifically identify the beta subunit of hCG, thus rendering cross-reaction with subunits of other hormones, such as luteinizing hormone, follicle stimulating hormone, and thyrotropin, unlikely. These tests provide accurate qualitative results (positive or negative based upon a color change) at hCG levels as low as 5 mIU/mL [16]. Of note, a positive test indicates the presence of hCG from any source, it does not exclude the possibility of an ectopic or nonviable intrauterine pregnancy, gestational trophoblastic disease, or some types of ovarian tumors. (See "Clinical manifestations, diagnosis, and management of ectopic pregnancy").
Ultrasensitive urine hCG assays (hCG levels as low as 5 mIU/mL) can detect pregnancy seven days after fertilization in some women; however, the standard urine pregnancy tests used in clinical practice (hCG levels as low as 20 mIU/mL) are not reliably positive until later. This was illustrated in a study of 221 women age 21 to 42 years who were attempting to conceive and were tested with an extremely sensitive urine assay for hCG [17]. The test detected only 90 percent of pregnancies on the expected first day of missed menses. The authors estimated the proportion of pregnancies that could be detected by urine assay relative to the expected first day of menses: two days before (79 percent), seven days after (97 percent), and 11 days after (100 percent). These authors recommend waiting one week after the first day of the missed period to perform pregnancy testing. Adolescents with irregular cycles or an uncertain last menstrual period should wait at least 14 days from a sexual experience before obtaining a pregnancy test.
Testing one to two weeks after a missed menses minimizes false negative with urine testing. The higher the maternal hCG level, the more likely a urine test will be positive. Ultrasensitive tests will be positive within days of a missed menses while less sensitive tests may not be positive until later. Waiting for a week or two after a missed period not only minimizes false negatives but decreases the need for serum hCG testing to confirm early pregnancy when a negative urine test is obtained.
As noted, the most common reason for a false negative result is that the test has been performed too soon after ovulation (which often occurs later than expected) [18]. If a pregnancy is suspected despite a negative test, the test should be repeated in one week. In addition to false negative results, false positive tests can also occur. (See "Epidemiology; clinical manifestations and diagnosis of gestational trophoblastic disease" section on False positive tests).
Severe renal disease with elevated lipids, high immunoglobulin levels, and low serum protein levels can interfere with test results [19]. Test results also may be misinterpreted because of color blindness. A low urine specific gravity does not appear to alter the sensitivity of detecting hCG; however, detection of hCG levels in dilute urine can be adversely affected by using pregnancy tests with higher thresholds for hCG positivity [20,21]. Thus, awareness of the tests hCG detection limits is important when pregnancy is suspected.
Serum pregnancy test — Serum beta hCG concentrations rise soon after implantation (ie, 7 to 11 days after ovulation). The concentration doubles every 29 to 53 hours during the first 30 days after conception in a viable, intrauterine pregnancy and reaches peak concentrations of 60,000 IU/L (in relation to the First International Reference Preparation) at about 8 to 10 weeks after the last menstrual period, but the range of normal is quite wide: 5,000 to 150,000 IU/L or more [22,23]. In the next 10 weeks, circulating hCG levels decline, reaching a median concentration of about 12,000 IU/L, again with a wide variation of normal: 2,000 to 50,000 IU/L.The hCG concentration stays fairly constant from about the 20th week until term.
The serum hCG concentration can be measured qualitatively or quantitatively using a radioimmunoassay technique that provides reliable results at hCG levels as low as 3 mIU/mL. If a qualitative test is needed, serum and urine test results are equivalent as long as both tests are set to have the same sensitivity [24]. However, in some institutions, the sensitivity of the qualitative serum pregnancy test is different from that of urine pregnancy tests (eg, threshold for a positive test 10 versus 25 mIU/mL).
Quantitative tests are not useful for estimating gestational age because there is a wide range in hCG values at any given point in pregnancy [23]. Serial quantitative test specimens are sometimes obtained to check doubling time or disappearance time in evaluating and managing ectopic pregnancy or nonviable intrauterine pregnancy [19]. (See "Clinical manifestations, diagnosis, and management of ectopic pregnancy").
The quantitative test procedure requires use of radioisotopes and may be processed only in a commercial or hospital-based laboratory. It takes at least two hours to obtain results; additional delay occurs because the test is often performed in batches.
Ultrasound examination — On transvaginal ultrasound examination, a gestational sac or cavity compatible with pregnancy is usually visible at 4.5 to 5 weeks of gestation (three to four weeks after ovulation) with the double decidual sign at 5.5 to 6 weeks. The yolk sac appears at five to six weeks and remains until approximately 10 weeks, and a fetal pole with cardiac activity is first detected at 5.5 to 6 weeks by transvaginal ultrasound. These structures are noted slightly later with the transabdominal approach. The transvaginal sonographic visualization of the gestational sac at four to five weeks typically corresponds to an hCG level of at least 1000 to 1500 IU/L. Once a pregnancy has been visualized sonographically, there is no value to hCG measurement. (See "Prenatal assessment of gestational age and fetal weight" and see "Clinical manifestations, diagnosis, and management of ectopic pregnancy" section on Discriminatory zone and see "Spontaneous abortion: Risk factors, etiology, clinical manifestations, and diagnostic evaluation").
SUMMARY AND RECOMMENDATIONS The diagnosis of early pregnancy is based primarily upon laboratory assessment of human chorionic gonadotropin (hCG). (See "Laboratory tests" above). The most common signs and symptoms of pregnancy are amenorrhea, nausea/vomiting, breast tenderness, urinary frequency, and fatigue. (See "Signs and symptoms of early pregnancy" above). A report of delayed menses, sexual activity with imperfect use of contraception, and patient suspicion of pregnancy are predictive that a pregnancy test will be positive; however, these historical factors are not sufficiently reliable to diagnose or exclude pregnancy. (See "History" above). Signs suggestive of pregnancy on physical examination include a soft, enlarged, globular uterus; bluish discoloration of the mucous membranes of the vulva, vagina, and cervix; darkening of the breast areola and increased prominence of veins under the skin of the breast; and palpation of uterine artery pulsation on bimanual examination. Detection of fetal heart beat distinct from the maternal heart rate is diagnostic of pregnancy. (See "Physical examination" above). The accuracy of home pregnancy tests is greatly affected by the technique and interpretation of users. On the first day after a missed period, the best tests were negative in 5 to 20 percent of women. (See "Home pregnancy test" above). Almost all pregnant women will have a positive urine pregnancy test by one week after the first day of a missed menstrual period. (See "Urine pregnancy test" above). Qualitative urine and serum pregnancy tests have similar sensitivity; urine tests are less expensive and usually results are available sooner than with serum tests. A quantitative serum pregnancy test is not needed to diagnose pregnancy. (See "Serum pregnancy test" above). Transvaginal ultrasound examination can visualize a gestational sac at 4.5 to 5 weeks of gestation. (See "Ultrasound examination" above).
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GRAPHICS
Pregnancy rate (percent) during first year of use
T ypical use Perfect use
Cervical cap
Previous births 32 26
No previous birth 16 9
Condom
Male 15 2
Female 21 5
Diaphragm with spermacide 16 6
Sponge
Previous births 32 20
No previous births 16 9
Fertility awareness
Cervical murus 22 3
Symptothermal 13-20 2
Calendar (rhythm) 13 5
Standard days 12 5
Lactational amenorrhea* 5 <2
Withdrawal 27 4
Depot-provera 3 <1
IUD
Copper T or Mirena <1 <1
Patch 8 <1
OCPs
Progestin only or combination estrogen-progestin 8 <1
Ring 8 <1
Female sterilization <1 <1
Vasectomy <1 <1
Emergency contraception
Pills Pregnancy rate decreased by 75 to 89 percent, depending on the regimen used (higher pregnancy rate is for combined estrogen-progestin pills, lower pregnancy rate is for levonorgetrel alone)
IUD Pregnancy rate decreased by 99 percent
No method 85 85
* Rate reflects cumulative pregnancy rate in the first 6 months following birth.
Efficacy contraception methods
Data refer to number of pregnancies per 100 women during first year of use
Typical Use: refers to failure rates for women and men whose use is not consistent or always correct. Correct Use: refers to failure rates for those whose use is consistent and always correct.
Data adapted from: Contraceptive Technology, 18th edition, 2004 p. 226.
Major causes of chronic fatigue
Psychologic
Depression
Anxiety
Somatization disorder
Pharmacologic
Hypnotics
Antihypertensives
Antidepressants
Drug abuse and drug withdrawal
Endocrine-metabolic
Hypothyroidism
Diabetes mellitus
Apathetic hyperthyroidism
Pituitary insufficiency
Hypercalcemia
Adrenal insufficiency
Chronic renal failure
Hepatic failure
Neoplastic-hematologic
Occult malignancy
Severe anemia
Infectious
Endocarditis
Tuberculosis
Mononucleosis
Hepatitis
Parasitic disease
HIV infection
Cytomegalovirus
Cardiopulmonary
Chronic congestive heart failure
Chronic obstructive pulmonary disease
Connective tissue disease
Rheumatoid disease
Disturbed sleep
Sleep apnea
Esophageal reflux
Allergic rhinitis
Psychologic causes (see above)
Idiopathic (diagnosis by exclusion)
Idiopathic chronic fatigue
Chronic fatigue syndrome
Adapted from Gorroll, AH, May, LA, Mulley, AG Jr (Eds), Primary Care Medicine: Office Evaluation and Management of the Adult Patient, 3rd ed, JB Lippincott, Philadelphia, 1995.
Summary of studies reporting likelihood ratios for prediction of pregnancy
History Positive likelihood ratio (95% confidence interval)
Delayed menses 2.06 (95% CI 1.65-2.57)
1.04 (95% CI 0.38-2.87)
1.13 (95% CI 1.05-2.92)
1.56 (95% CI 1.4-1.74)
No birth control 1.31 (95% CI 1.14-1.5)
1.53 (95% CI 1.06-2.18)
Patient suspects that she is pregnant 1.6 (95% CI 1.39-1.85)
3.15 (95% CI 2.37-4.2)
1.6 (95% CI 1.39-1.85)
2.11 (95% CI 1.97-2.27)
Morning sickness 2.7 (95% CI 2.19-3.33)
Any pregnancy symptoms (defined as morning sickness, breast tenderness and fullness, urinary frequency, or fatigue) 2.43 (95% CI 1.71-3.44)
Characteristic breast changes on physical examination 2.71 (95% CI 2.3-3.2)
Palpable fundus on physical examination 2.77 (95% CI 1.7-4.51).
Chadwick sign present 3.17 (95% CI 2.22-4.51)
Uterine artery pulsations present 10.98 (95% CI 5.63-21.4)
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