Published December 10, 2007 by
You've made the decision to have a baby. Your menstrual period is late. Should you be elated or is cautious optimism in order? You may suspect you are pregnant by the way you feel, or your doctor may suspect it by findings on a physical exam. But symptoms and signs are just suggestive- the possibility that you are pregnant should be confirmed by a urine or blood test. If the result of one of these tests is positive, you can start rejoicing and browsing baby clothes.
In the first few weeks after conceiving, you may notice changes in your body and in the way you feel. A late menstrual period is often the first hint you are pregnant. However many other conditions, from stress to infections, can delay the onset of menses, so a late period is not a reliable sign until at least two weeks after the expected date. On the other hand, you can have spotting while pregnant, so the presence of some bleeding doesn't eliminate the possibility.
You may notice some fatigue in the first weeks. You may experience nausea or vomiting, especially in the morning, a week or two after your missed period. Your breasts may have some tingling or tenderness and may even enlarge. The areolae [the area around the nipples] may darken. If you have been having trouble getting pregnant and are recording your basal body temperature, you may find that your temperature continues to be elevated. Just as with a late period, all of these signs and symptoms, if they occur at all, can be contributed to other causes. By themselves, they do not prove, just suggest, that you are pregnant.
If you go to see your doctor when your period is two weeks late, he may find physical changes that suggests you are pregnant. Your vagina and cervix may be blue to a purplish color because of increased blood flow. This is known as Chadwick's sign. The uterus may feel softer, larger, and rounder. Your doctor may be able to feel intermittent contractions called Braxton-Hicks contractions, even though you may not recognize them.
Many women know they are pregnant before they see their obstetrician, however, because they run a pregnancy test themselves at home. Non-prescription home pregnancy tests are available in any pharmacy and cost about ten dollars. These tests are designed to detect the presence in the urine of the human chorionic gonadotropin [HCG], a hormone produced by the embryo shortly after fertilization.
Home pregnancy tests on the market today vary in sensitivity. Some can detect HCG one day after the missed period. Others require one to two weeks. Some tests must be done on a urine test obtained in the morning, when the concentrations of HCG are the highest; others can be performed on any urine specimen. Some react within ten minutes, but others require one to two hours. No matter which test you use, if the directions are followed carefully, the results are ninety to ninety-five percent accurate.
The tests are easy to perform. You add a few drops of urine to a test tube containing a protein, called an antibody that reacts specifically with HCG. If you are pregnant and HCG is present in the urine, it will bind to the antibody, forming a complex. If you are not pregnant and no HCG is present, the antibody will remain free in the solution. Different chemical reactions are used in the different test kits to indicate whether a complex or a free antibody is present. Positive tests are usually indicated either by a formation of a circle at the bottom of the tube or by a color change in the solution.
Even though these tests are extremely sensitive, there are a few other things that, when present in the urine will cause a positive test result even though the woman is not pregnant. Luteinizing hormone [LH] is one of the hormones that regulate the menstrual cycle. It can cross-react with HCG and give a positive test result. Ordinarily, it is not present in the urine in detectable amounts. However, menopausal women have a high level of LH and can have a positive test result. Women with protein in their urine can have a similar reaction. Protein may be present because of infection or kidney disease, or because certain medications such as tranquilizers, thyroid medications, and anti seizure drugs, have been taken. More common than a false- positive test result is a false-negative one-that is, the test result is negative even though the woman is pregnant. This usually occurs when the test is done too early after the missed period, when the level of HCG is too low to be detected. Low levels of HCG may also be caused by an ectopic pregnancy [a pregnancy that develops outside the uterus], if the first test is negative and your period doesn't start, repeat the test in five to ten days. If it is still negative, consult your doctor.
If you go to your doctor two or three weeks after your missed period, he or she will probably perform a pregnancy test on your urine that is similar to the home pregnancy tests. The "rabbit test" is no longer used because of the greater speed, convenience, and accuracy of modern tests.
If your doctor needs to know if you are pregnant at a time before the urine test can be used, or if he or she suspects a false-negative result, a blood test that is more sensitive and specific may be used. It measures a part of the HCG molecule known as the beta-subunit. Since LH doesn't have a beta-subunit, this test can distinguish between LH and HCG because it can measure very small amounts of HCG. It can be used to diagnose pregnancy before a missed period [by seven to nine days after fertilization] or to diagnose a tubal pregnancy [one that develops in one of the fallopian tubes]. This test takes longer [twenty-four to forty-eight hours] to complete, and it is more expensive because it requires special equipment and personnel. Therefore it is not used routinely to diagnose pregnancy.
When you know for sure that you are pregnant, the next question will undoubtedly be "When will my baby be born?" Delivery usually occurs 280 days after the first day of the last menstrual period. An easier way to calculate the delivery, or due date, is to count back three months from the first day of your last period and add seven days. Most women don't give birth on the exact date, but eighty-five percent do within two weeks of it; delivery is earlier for ten percent and later for five percent. As your pregnancy progresses, your due date can be double-checked by the timing of certain events. For example, the baby's heart is usually heard at ten to twelve weeks. The level at which the top of the uterus can be palpitated by the doctor can also be used; at twenty-four weeks, for example, it is usually at the umbilicus [navel]. If your obstetrician performs an ultrasound study, a measurement of the baby can be taken and compared with standard tables to estimate gestational age.
Discovering you are pregnant is an exciting moment. The next nine months will be filled with excitement both for you and your family as the changes of pregnancy takes place.