3-2. Probable and Positive Signs of Pregnancy
Probable signs of pregnancy are those signs commonly noted by the physician upon examination of the patient. These signs include uterine changes, abdominal changes, cervical changes, basal body temperature, positive pregnancy test by physician, and fetal palpation.
a. Uterine Changes.
(1) Position. By the twelfth week, the uterus rises above the symphysis pubis and it should reach the xiphoid process by the 36th week of pregnancy. These guidelines are fairly accurate only as long as pregnancy is normal and there are no twins, tumors, or excessive amniotic fluid.
(2) Size. The uterine increases in width and length approximately five times its normal size. Its weight increases from 50 grams to 1,000 grams.
(3) Hegar's sign. This is softening of the lower uterine segment just above the cervix. When the uterine is compressed between examining fingers, the wall feels tissue paper thin. The physician will use bimanual maneuver simultaneously (abdominal and vaginal) and will cause the uterus to tilt forward (see figure 3-1). The Hegar's sign is noted by the sixth to eighth week of pregnancy.
Figure 3-1. Hegar's sign.
(4) Ballottement. This is demonstrated during the bimanual exam at the 16th to 20th week. Ballottement is when the lower uterine segment or the cervix is tapped by the examiner's finger and left there, the fetus floats upward, then sinks back and a gentle tap is felt on the finger (see figure 3-2). This is not considered diagnostic because it can be elicited in the presence of ascites or ovarian cysts.
Figure 3-2. Ballotement.
b. Abdominal Changes. This corresponds to changes that occur in the uterus, as the uterus grows the abdomen gets larger. Abdominal enlargement alone is not a sign of pregnancy. Enlargement may be due to uterine or ovarian tumors, or edema. Striae gravidarum may also be classified as a probable sign of pregnancy by the physician.
c. Cervical Changes.
(1) Goodell's sign. The cervix is normally firm like the cartilage at the end of the nose. The Goodell's sign is when there is marked softening of the cervix. This is present at 6 weeks of pregnancy.
(2) Formation of a mucous plug. This is due to hyperplasia of the cervical glands as a result of increased hormones. It serves to seal the cervix of the pregnant uterus and to protect it from contamination by bacteria in the vagina (see figure 3-3). The mucous is expelled at the end of pregnancy near or at the onset of labor.
Figure 3-3. Cervix with mucous plug.
(3) Braxton-Hick's contractions. This involves painless uterine contractions occurring throughout pregnancy. It usually begins about the 12th week of pregnancy and becomes progressively stronger. These contractions will, generally, cease with walking or other forms of exercise. The Braxton-Hick's contractions are distinct from contractions of true labor by the fact that they do not cause the cervix to dilate and can usually be stopped by walking.
d. Basal Body Temperature. This is a good indication if the patient has been recording for several cycles previously. A persistent temperature elevation spanning over 3 weeks since ovulation is noted. Basal body temperature (BBT) is 97 percent accurate.
e. Positive Pregnancy Test by the Physician. This may be misread by doing it too early or too late. Even if the test is positive, it could be the result of ectopic pregnancy or a hydatidiform mole (an abnormal growth of a fertilized ovum) (see figure 3-4).
Figure 3-4. Hydatidiform mole.
f. Fetal Palpation. This is a probable sign in early pregnancy. The physician can palpate the abdomen and identify fetal parts. It is not always accurate, a mass in the abdomen may be palpated and mistakenly identified as an infant.
Positive Signs of Pregnancy
Positive signs of pregnancy are those signs that are definitely confirmed as a pregnancy. They include fetal heart sounds, ultrasound scanning of the fetus, palpation of the entire fetus, palpation of fetal movements, x-ray, and actual delivery of an infant.
a. Fetal Heart Sounds. The fetal heart begins beating by the 24th day following conception. It is audible with a doppler by 10 weeks of pregnancy and with a fetoscope after the 16th week (see figure 3-5). It is not to be confused with uterine souffle or swishlike tone from pulsating uterine arteries. The normal fetal heart rate is 120 to 160 beats.
b. Ultrasound Scanning of the Fetus. The gestation sac can be seen and photographed. An embryo as early as the 4th week after conception can be identified. The fetal parts begin to appear by the 10th week of gestation.
Figure 3-5. Detecting fetal heartbeat.
c. Palpation of the Entire Fetus. Palpation must include the fetus head, back, and upper and lower body parts. This is a positive sign after the 24th week of pregnancy if the woman is not obese.
d. Palpation of Fetal Movement. This is done by a trained examiner. It is easily elicited after 24 weeks of pregnancy.
e. X-ray. An x-ray will identify the entire fetal skeleton by the 12th week. In utero, the fetus receives total body radiation that may lead to genetic or gonadal alterations. An x-ray is not a recommended test for identifying pregnancy.
f. Actual Delivery of An Infant. Self-explanatory.
Tests Used to Determine Pregnancy
a. Tests are based on the presence of human chorionic gonadotropin (HCG) in the urine or blood.
(1) Urine. This test can be performed accurately 42 days after the last menstrual period or 2 weeks after the first missed period. The first urine specimen of the morning is the best one to use.
(2) Blood. Radioimmunoassays (RIA) can detect HCG in the blood 2 days after implantation or 5 days before the first menstrual period is missed.
- The Beta HCG level is observed in nuclear medicine. This is expensive to use.
- HCG levels peak between 50 to 90 days after the last menstrual period.
b. Home pregnancy test kits are easily available and inexpensive. This test allows prenatal care to be started early.