If you have had sexual intercourse without using birth control or have experienced any of the signs of pregnancy, it is a good idea to take a pregnancy test. Over-the-counter pregnancy tests can be purchased in drugstores, but sometimes tests are less expensive or even free in university health centers.

Pregnancy tests measure for a hormone in the blood called human chorionic go­nadotropin (hCG; corr-ee-ON-ick go-nad-oh-TRO-pin), which is produced during pregnancy. The hormone hCG is manufactured by the cells in the developing placenta and can be identified in the blood or urine 8 to 9 days after ovulation. The presence of hCG helps build and maintain a thick endometrial layer and so prevents menstru­ation. Peak levels of hCG are reached in the 2nd and 3rd months of pregnancy and then drop off.

Home pregnancy tests can be inaccurate if taken too soon after conception, and some women who postpone pregnancy tests until after the 12th week may have a false negative pregnancy test because the hCG levels are too low to be detected by the test. If you are using an at-home test, be sure you know how soon after ovulation it can be used. Many tests today can detect hcG levels even before a period is late. False positive test results may occur in the presence of a kidney disease or infection, an overactive thy­roid gland, or large doses of aspirin, tranquilizers, antidepressants, or anticonvulsant medications (Hatcher et al., 1998).

Of all pregnancy tests, radioimmunoassay (RIA; ray-dee-oh-im-mue-noh-ASS – say) blood tests are the most accurate. RIA tests can detect hCG within a few days af­ter conception and are also useful for monitoring the progress of a pregnancy that may be in jeopardy. The levels of hCG rise early in pregnancy, and if a woman’s hormones do not follow this pattern, a spontaneous abortion or an ectopic pregnancy may have oc­curred. We will discuss both of these later in this chapter.

After a woman’s pregnancy is confirmed, her healthcare provider helps her to cal­culate a due date. Most physicians date the pregnancy from the first day of the last men­strual period rather than the day of ovulation or fertilization. The standard for due date



A condition in which the father (or other rela­tive) experiences the symptoms of pregnancy and/or childbirth without an actual pregnancy.



Identify four signs of pregnancy, and explain why they occur.


human chorionic gonadotropin (hCG)

The hormone that stimulates production of estro­gen and progesterone to maintain pregnancy.


false negative

Incorrect result of a medical test or procedure that wrongly shows the lack of a finding.


false positive

Incorrect result of a medical test or procedure that wrongly shows the presence of a finding.


radioimmunoassay (RIA) blood test

Blood pregnancy test.


ectopic pregnancy

The implantation of the fertilized egg outside the uterus, such as in the Fallopian tubes or abdomen.


due date

The projected birth date of a baby.


calculation is called the Naegeles (nay-GEL-lays) rule—subtract 3 months from the first day of the last period and add 7 days for a single birth (Mittendorf et al., 1990; for ex­ample, if the last period began on August 1, subtract 3 months and add 7 days, which means that the due date would be May 8). This rule works most effectively with women who have standard 28-day menstrual cycles.

Question: I have missed my period now for 2 months in a row. Does this mean that I am pregnant? What should I do?

If you have been engaging in sexual intercourse, there is certainly a chance that you are pregnant. However, there are several reasons for missing your period, including stress, losing weight, active partic­ipation in sports, or changes in eating patterns, as well as certain diseases. In any case, it is a good idea to see a gynecologist or your school nurse for an evaluation.