Possible indicators of pregnancy

Signs of possible pregnancy are those from which a definite diagnosis of pregnancy cannot be confirmed. Signs and symptoms during this stage can often be caused by other conditions. The indications of possible pregnancy are:

Amenorrhoea (the cessation of menses) in a sexually active healthy woman is often the first indication of pregnancy. However, other factors may cause amenorrhoea, such as eating disorders (anorexia nervosa, bulimia), excessive exercise or changes in metabolism and endocrine function.

The symptoms of nausea and vomiting, which can occur at any time of the day, are often referred to as morning sickness. Nausea often occurs between 6 and 14 weeks’ gestation and is believed to be a result of large quantities of placental hormones (progesterone, oestrogen, human chorionic gonadotropin [hCG] and human placental lactogen).

Breast enlargement and tenderness are a result of the placental hormones stimulating the breast ductal system in preparation for breastfeeding. Some women experience similar symptoms premenstrually and pregnancy is often overlooked for this reason.

Increased pigmentation of the skin occurs over the face (chloasma), breasts (darkening of the areolae) and abdomen (linea negra — a dark line extending from the umbilicus to the symphysis pubis).

Frequency of micturition occurs at the start of pregnancy and then again in the third trimester. In the first trimester the enlarging uterus competes for space in the pelvic cavity and exerts pressure on the urinary bladder. In the later stage of pregnancy the descending fetal part of the uterus moves into the pelvic cavity in preparation for birth.

Quickening is the result of fetal movement and is first perceived at 16–20 weeks’ gestation. The sensation is felt by the mother and described as gentle fluttering in the lower abdomen (Leifer 2003).

Probable indicators of pregnancy

Abdominal uterine enlargement, the presence of Braxton Hicks contractions and a positive pregnancy test are indicators that a woman is probably pregnant. However, there may be other conditions or factors (uterine tumours, medications or premature menopause) that cause these events on very rare occasions.

Abdominal and uterine enlargement occurs around the 12th week of pregnancy. At this stage the fundus of the uterus can be located just above the symphysis pubis, and extends to the umbilicus between weeks 20 and 22.

Braxton Hicks contractions are irregular, painless uterine contractions that first occur in the second trimester. They are more pronounced in multiparas (women who have had more than one child) and can be mistaken for labour contractions.

A pregnancy test may be performed after the first missed menstrual cycle. Pregnancy tests use maternal blood or urine to determine the presence of the placental hormone human chorionic gonadotropin (hCG). A positive result from a pregnancy test is considered an indicator of probable pregnancy. Provided that they are carried out precisely according to the given instructions, home pregnancy tests based on the amount of hCG in the urine are capable of greater than 97% accuracy.

Professional pregnancy tests based on urine or blood serum are even more reliably accurate. The most highly reliable test is the radioimmunoassay (RIA), a technique in radiology that can accurately identify pregnancy as early as 1 week after ovulation. While attributed with high levels of accuracy, pregnancy tests cannot be classed as absolutely certain indicators because there are factors that may interfere with the reliability of test results. These factors include premature menopause, the effects of taking some particular medications (anticonvulsants or anti-anxiety drugs) and the presence of a malignant tumour or haematuria (Leifer 2003).

Positive indicators of pregnancy

The most positive sign of pregnancy is a growing and developing baby. The fetal heartbeat can be detected as early as 10 weeks’ gestation using equipment such as a (tocograph) pelvic ultrasound (or Doppler device). This scan enables (allows) the examiner to detect and record the fetal heart rate and therefore confirm pregnancy. The Doppler can be used to listen to the baby’s heart rate from 18–20 weeks gestation onwards.

Fetal body parts can be felt by an educated examiner (medical officer, obstetrician or midwife) from the second trimester onwards. This gives the examiner an indication of the position of the fetus, which is vital during the third trimester when discussing birthing options.

Estimated confinement date

The date when the baby is due (confinement date) may be calculated by dates, the height of the uterine fundus or using ultrasound. Calculation by dates to determine the estimated due date is made by ascertaining the first day of the last known menstrual period and adding 9 months and 7 days. Calculation by assessing the fundal height (Figure 49.1) is made by measuring the height of the uterine fundus from the symphysis pubis. As the uterus enlarges steadily and predictably, the date of confinement can be determined reasonably accurately. Calculation by ultrasound is made by using height frequency, short wavelength and soundwave reflections to visualise the size of the fetus.

Figure 49.1 Fundal height of the uterus