Pregnancy tests: Types and accuracy

What is a pregnancy test?

When a sperm fertilises an ovum (egg) in the lining of the uterus, pregnancy results; this condition can occur even if you haven’t had sexual activity (penetration). Semen can be ejaculated during vaginal penetrative intercourse, in which the penis enters the vagina. Millions of sperm are present in the fluid called “semen,” which is produced after ejaculation.

It takes time for fertilisation to take place. Sperm can remain in a woman’s uterus and fallopian tubes for up to 6 days following intercourse. So, fertilisation can take place anytime between this period.

The fertilised egg travels down the fallopian tube and toward the uterus if a sperm cell fuses with your egg. The fertilised egg then starts to divide into more cells, growing into a ball called blastocyst. This ball of cells then enters the uterus 3 to 4 days after fertilisation.
For an additional two to three days, the blastocyst swims in the uterus. Pregnancy formally begins when the ball of cells implants itself to the uterus lining, a process known as implantation. After fertilisation, implantation typically begins around day 6 and takes about 3 to 4 days to finish.  Cells on the interior of the ball form the embryo. The outer cells form the placenta.

A pregnancy test can let you know whether you are pregnant or not. If you are expecting, then you may also experience common early symptoms like:

• Nausea and vomiting
• Missed period
• Sensitivity to certain smells
• Frequent urination
• Fatigue
• Constipation

These symptoms, however, cannot give you a definitive answer like pregnancy tests can. Pregnancy tests are also important because some of the abovementioned symptoms can be like pre-menstrual syndrome (PMS).

Types of pregnancy tests

Home pregnancy test kit: Home pregnancy tests are not only discreet and practical, but also quick and simple to use. Moreover, if you adhere to the instructions, they’re pretty accurate. You can buy a pregnancy kit like preganews test kit from a pharmacy in-person or online. You can use this test on the first day of your missed period. If you administer the test as soon as you wake up in the morning, the result may be more accurate because your urine is concentrated.

The purpose of these tests is to detect special hormone —human chorionic gonadotropin (hCG) – which is only find in the urine of a pregnant individual. When this hormone interacts with a chemical in the home pregnancy stick, its colour changes. Depending on the test, waiting time may vary, but for the most part, an accurate reading takes roughly 10 minutes.

These urine pregnancy tests are usually 99% accurate, but manufacturers will advise you to take the test at least twice for confirmed results.

However, the results are dependent on conditions like how soon the test was taken, when the implantation happened, the sensitivity of the test, among others. The instruction manual will brief you on everything you need to know about this test and how to use it.
A false negative might occur if the test indicates that you are not pregnant even when you are. Perform the test again or consult your doctor if your period doesn’t start within a few days if you missed it.

Blood test: A blood test can also be used to confirm a pregnancy. Due to their high cost and propensity to produce results identical to those of a urine test, blood tests are rarely performed. An arm vein is used to draw a tiny sample of blood. A blood test can measure how much pregnancy hormone is present in your body in addition to detecting whether it is present. This is useful for situations where your healthcare professional wants to know the precise concentration of HCG in your blood, rather than merely whether it is present.

Two different blood tests are available for determining a pregnancy:

Qualitative hCG blood test: Tells whether hCG is available in the blood. Gives a simple “no” or “yes” answer.
Quantitative hCG blood test: Tells the volume of hCG available in the blood. A woman is not considered pregnant if her hCG level is less than 5 mIU/ml. Pregnancy can be confirmed if a woman’s pregnancy hormone levels are higher than 25 mIU/ml.

Your doctor can prescribe additional tests if your hCG level is either greater or lower than anticipated given how far along you believe the pregnancy is. They could do an ultrasound or run the hCG test again in a few days. Uncertainty about your dates is the most frequent cause of the hCG level appearing abnormal. This could indicate that you are either further advanced in your pregnancy than you anticipated or too early into the pregnancy.

Quantitative hCG blood tests are extremely precise because they detect the precise concentration of hCG in the blood and are more sensitive than qualitative hCG blood tests or urine tests at detecting lesser levels of the hormone.

Urine testing cannot detect hCG as early as blood tests. In comparison to at-home tests, blood tests are typically more expensive and need a longer wait for results. The delivery of blood test results may take up to two weeks at times.

False positives and false negatives from a pregnancy test

False results, which can be either false positives or false negatives, are typically the result of improper use of the home pregnancy test. Testing too soon is usually the main cause of a false negative result. If you use a home test wrong, for as by using too much or too little of your urine sample, you can also get a false negative result. To ensure that you receive an accurate result, it’s crucial that you adhere to the instructions on your test kit.

However, if there is a false positive, it can also be because of other reasons, like:

• Ectopic pregnancy (when the egg implants outside of the uterus)
• Chemical pregnancy (early miscarriage that happens within the first five weeks of pregnancy)
• Menopause
• Other conditions like cysts