Pregnancy test – Urine & Blood

What is a pregnancy test?

As the name specifies, a pregnancy test is a diagnostic test carried out to determine if you are pregnant. A pregnancy test detects the presence of human chorionic gonadotropin(hCG) in your body. It should be kept in mind that a definitive diagnosis of pregnancy involves a 4-pronged approach using the following investigative tools. These are:

– Elaborate history
– Clinical examination
– Laboratory tests
– Ultrasound

What is human chorionic gonadotropin?

Human chorionic gonadotropin is a glycoprotein hormone secreted by the trophoblastic cells of a placenta shortly after the embryo gets attached to the lining of the uterus. It can be detected in the urine of a pregnant female about 10 days after conception has occurred. Human chorionic gonadotropin is responsible for the early signs and symptoms of pregnancy including tenderness of breast, nausea, and vomiting.

What are the different kinds of pregnancy tests?

The pregnancy tests can be broadly classified into 2 categories-

Urine test– It is carried out in order to detect the presence of hCG in the urine of a pregnant female. This test is commonly carried out at home by females using a special pregnancy kit. This test can also be carried out in the clinic of a doctor.

Blood test– It detects the presence of hCG in the blood. It is carried out in a doctor’s office or a diagnostic center.

When should I consider going for a pregnancy test?

You are advised to take a pregnancy test if you suffer from the following signs or symptoms-

Missing a period- This is the primary sign of pregnancy. However, missing a period is not a definitive sign of pregnancy. You may miss a period if you have a history of irregular periods, you are on certain medications (including birth control pills), or if you suffer from chronic diseases such as diabetes or PCOD (polycystic ovarian disease). You may also miss a period if you are undergoing physical or mental stress.

Swelling and/or tenderness of the breasts- You might experience a sensation of heaviness in your breasts due to the hormonal changes in your body.

Nausea/Vomiting-Referred to as ‘morning sickness’ (a misnomer) in a layman’s language, it can continue till the end of pregnancy. This symptom may occur at any time during the day and varies in severity from mild to debilitating.

Unexplained headaches– The sudden surge in pregnancy hormones is the culprit.

Increased frequency of urination– Human chorionic gonadotropin increases blood flow to the pelvic region, increasing the need to urinate.

Uncharacteristic mood swings– These mood changes are due to the hormones that your body produces during pregnancy.

Craving/aversion to food– Food fads are common during pregnancy; the duration varies.

Fatigue- The body of a pregnant female produces an excess of progesterone which is essential for maintaining pregnancy and the growth of breasts during this period. The body tends to pump more blood to the fetus, leaving you deprived of energy. Fatigue may be experienced within the first week after conception.

Bleeding– In up to 25% of pregnant women, slight bleeding is a common sign. The blood appears lighter in color than the normal menstrual blood. Spotting occurs when the fertilized egg implants (as early as 6-12 days after conception).

You should keep in mind that you may have all, a few or none of the above symptoms (excluding a missed period of course).

Do I need to fast before a pregnancy test?

No, there is no need to fast before you undertake a pregnancy test.

What is the right time to take a pregnancy test?

The first day of your missed period is the ideal time for taking a urine pregnancy test. This corresponds to roughly 2 weeks after conception.

How should I take an ‘at-home’ urine pregnancy test?

A ‘do it yourself’ urine pregnancy test is a very simple test that you can undergo in the privacy of your home. A multitude of pregnancy detection kits is available in the market. Each kit comes with a set of easy to follow instructions. The steps involved are-

– Read the instructions carefully before you collect your urine sample. The wait time may vary for different brands of kit. Make sure that the kit’s expiration date has not passed.

– An early morning urine sample should ideally be used. You can take this test as soon as you wake up in the morning as the urine is most concentrated at this time of the day.

– Though there is no need to fast, avoid drinking copious amounts of water before taking this test. It will dilute the concentration of hCG in your urine, leading to erroneous results.

There are 3 ways in which you can take this test.

– Collect urine in a small container and dip the chemical strip in it.

– Expose the strip to midstream urine for about 5 seconds.

– Collect the urine in a dropper and put urine on the strip drop by drop.

Usually, the waiting time is of 5 minutes. You need to look for a change in the color of the chemical strip (in some cases, a plus symbol or a line) which indicates a positive test.

What are the disadvantages of the ‘at-home’ pregnancy test?

‘At- home’ urine pregnancy test is a noninvasive, risk-free and very sensitive test that allows you flexibility and privacy at a low cost. The urine pregnancy test is claimed to be 99% accurate. However, it has its limitations. Errors in result due to faults in carrying out the test. These include:

– Taking the test too early after perceived conception.
– Using a dilute sample of urine
– Not adhering to the waiting time prescribed in the pregnancy kit.
– The results of the test may be ‘false positive’ or ‘false negative’.

What is meant by a false positive and a false negative pregnancy test?

False-positive test
It shows that a female is pregnant when she is not. It may arise:

– If she is on certain medications (hypnotics, tranquilizers, anti-Parkinsonism drugs).

– If she suffers from a malignancy. Certain cancer cells produce hCG (e.g. germ cell tumors).

Due to biochemical pregnancy- In such cases, a woman has had a spontaneous loss of the fetus even before she undergoes a pregnancy test.

False-negative
It shows that a female is not pregnant when she is. It may arise:

– If she is on diuretics (drugs that increase the production of urine) or promethazine (an anti-allergy drug).

When should I contact my doctor for a pregnancy test?

If the result of your self-testing is negative but you still experience the signs of pregnancy, repeat the test after a week. In case the result is inconclusive, contact your doctor.

Your doctor may ask you to undergo a urine test in his office or make you undertake a blood pregnancy test.

A blood pregnancy test not only detects the presence of hCG, but it also measures the amount of this hormone in your blood. The cost is, however, higher as compared to a urine test.

How long does it take for the result of a pregnancy test to be out?

As mentioned earlier, a urine test takes about 5 minutes to produce a result. A blood test can take a few hours to a day.

Are there any risks involved with undertaking a pregnancy test?

A urine pregnancy test is a non-invasive, safe, quick and inexpensive test. However, a blood test requires the withdrawal of blood from your vein. It carries with itself the risk of bruising, bleeding and infection at the site of invasion. You need to discuss with your doctor if you are on any blood thinner or suffer from a coagulopathy before you undertake a blood pregnancy test.

What is the cost of a pregnancy test in India?

The cost of a ‘do it yourself’ pregnancy kit in India ranges from INR 50-150. If you need to undertake a blood test, it may cost you INR 250-500.

What is the role of ultrasonography in the detection of pregnancy?

Transvaginal ultrasound (TVUS) is preferred over transabdominal ultrasound for the diagnosis of pregnancy. Though it is the most accurate method of confirming intra-uterine pregnancy in the first trimester, it is not recommended as a routine modality in uncomplicated pregnancies. TVUS is of great value in high risk obstetric patients as it can determine the gestational ageand fetal well-beingon one hand and detect multiple gestations, and congenital anomalies on the other.