Pregnancy Tests – how they work

About six to twelve days after fertilization, implantation of fertilised egg to the uterine wall occurs. Human chorionic gonadotropin (hCG) produced by the cells of the fertilised egg (blastocyst) builds up rapidly in your body. It doubles every 2 to 3 days in the first few weeks of pregnancy reaching a peak level by 8-12 weeks. Pregnancy tests detect this hormone in urine and blood. Pregnancy may also be detected with ultrasonography.

Types of Pregnancy Tests

You can know if you are pregnant with three types of tests:

1. Urine test

A urine test can be done at the doctor’s clinic or at home. Home urine test for pregnancy is convenient and about 97% accurate. Though some very sensitive pregnancy test kits may detect pregnancy on the first day of your missed period, to get the most accurate result it is advisable to take the test at least a week after a missed period and to do the test first thing in the morning during which your urine is very concentrated. It is very important to follow instructions on the test kit. The kit may have test strip or dipstick. The test strip needs to be held in the urine stream and the dipstick needs to be dipped into a sample of urine. If you are pregnant, an area on the end of the test strip or dipstick changes colour.

Some kits may have a test device with wells. You will need to collect urine in a cup and place few drops of urine with a dropper into the well mentioned in the instructions. Colour changes in the other wells indicate that you are pregnant. You may get a negative result if you are not pregnant, if you took the test before time or you did not take the test correctly. Confirm your home test result with your doctor.

Some of the pregnancy test kits available in India are Velocit from Dr Reddy’s, Prega News from  Mankind, Instant Pregnancy Test from Homecheck, I -Can (Pregnancy kit) from Piramal Healthcare Ltd., etc. which may cost between Rs 40 to Rs 100.

Pregnant but test is negative?

Sometimes, there may be cases when you actually might be pregnant but the test is negative. This may happen when the testing is done too early. The hormone hCG cannot be detected until after implantation which can occur anywhere from 6 to 12 days after ovulation. Less sensitive urine tests may take another three or four days after implantation to detect hCG. The date of ovulation is very unpredictable and may occur on a different day every cycle and even more so if you have irregular cycles. To get a more accurate idea of when to test, use different ways like charting basal body temperature, ovulation predictor kits (OPKs), etc. to determine the ovulation period.

Test is positive when you are not pregnant

You may get a false positive test result if you take the test wrong, read the test after the suggested 3–5 minute reaction time, use test kits past their expiration date or if you have been given an hCG injection during infertility treatment. A false positive pregnancy test result may also be seen in some cancers and other medical conditions that may produce elevated hCG levels.

2. Blood test

Though blood tests are more accurate and can detect pregnancy earlier than urine tests they are used less often. Done at your doctor’s clinic or labs, the blood tests can detect pregnancy six to seven days after ovulation. But it takes longer to get the results. There are two types of blood pregnancy tests:

• Qualitative hCG test: It simply detects the presence or absence of hCG as early as 10 days after a missed period to confirm whether you are pregnant or not. It may not detect pregnancy until three or four days after implantation.
• Quantitative hCG test: It measures the amount or concentration of hCG, even very low levels, in your blood. Problems like ectopic pregnancy may be detected with this test.
• Detecting early pregnancy factor (EPF): Within 48 hours of fertilization, a protein called early pregnancy factor (EPF) is produced. Detecting this protein in the blood is the earliest but expensive and time-consuming way to determine pregnancy.

3. Ultrasonography

Ultrasonography may be used to visualize the foetus in your womb at around four and a half weeks after your last menstrual period (LMP). It can tell you how many weeks you are into pregnancy and how healthy your baby is. You may be able to see your baby’s heartbeat by seven weeks after LMP.

Firstly, let’s understand what ovulation is and why it is important to know when you ovulate. 

Around two weeks after a woman’s menstrual period begins, a mature egg is released from the ovary and becomes available for fertilization. This phenomenon is called ovulation. If the couple has sexual intercourse during this time without any birth control, it is likely that the sperm fertilizes the egg and conception occurs. 

Now, if things moved like clockwork and ovulation occurred exactly the same day every month, wouldn’t we all be so lucky! The problem is that this fertile period in a woman’s cycle is very unpredictable and may occur on a different day every cycle. And even more so, if you have irregular cycles.

So, why is determining when the ovulation occurs so important if you want to conceive?

Sperm cells can live for two or three days, but an egg survives no more than 24 hours after ovulation if fertilization does not occur. To get pregnant, you should have sexual intercourse during the period spanning one to two days before ovulation to about 24 hours afterward.

The good news is that there are ways to determine the ovulation period quite satisfactorily. Some of them are:

Simple calculation - Counting back 12 to 16 days from when your next period is due gives you a range of days when you will probably be ovulating. If you have a 28-day cycle, the 14th day is often the day of ovulation. But this method is very unreliable, especially if you have irregular periods.

Discomfort in the lower belly area - During ovulation, some women may feel mild ache or contraction pain that may last a few minutes to a few hours. This condition is called mittelschmerz. Again, this might be quite unreliable as the discomfort may be caused due to many other causes.

Cervical mucus changes - The amount, colour and texture of your cervical mucus (vaginal discharge) changes over the course of your menstrual cycle. You may be able to figure out when you’re ovulating by checking and keeping track of the changes in it. A few days before ovulation, the mucus secretion is more and becomes clear and slippery (like raw egg white). This is the time when you’re most fertile.

Charting basal body temperature (BBT) - Following ovulation, your temperature can increase by 0.4 to 1.0 degrees. This can be detected by using a basal body temperature (BBT) thermometer specially designed to pick up even minute changes in temperature that a regular thermometer can’t. Just measuring your BBT first thing in the morning and making a chart of your BBT for two to three months can help you predict ovulation the next time around. The rule of thumb in this case is that you are most fertile two to three days before your temperature hits its high-point.

Serial ultrasound scanning – It is often the basic procedure for most infertility treatments. Ovulation scans can detect the development of the follicle (when the egg matures) and its collapse when you ovulate.

While most methods described above are unreliable, a method like serial ultrasound scanning is a cumbersome and costly method to determine your ‘fertile period’.  

An ovulation kit is a better option. It determines your date of ovulation a day in advance by detecting levels of a hormone (luteinizing hormone) which hits its peak in the middle of your menstrual cycle.

Using an ovulation kit is pretty easy, convenient and detects the ovulation period right almost 97% of the time. You can buy them from any chemist’s shop or online. Here’s a step-by-step procedure on how to use it:

 1. Determine the length of your menstrual cycle. If your cycle length varies, you should then use the shortest cycle length of the last 3 cycles. For eg: If you had 31-day cycles in September and October and a 29-day cycle in August, the consider the cycle length as 29 days.

2. Start the test 17 days before your next cycle.  For e.g. if your cycle length is 29 days, you should start the test on day 12 of your cycle.

3. Collect your urine in a cup or pass urine on a stick (provided in the kit) depending on the type of ovulation kit you may be using. Wait for the indicator (usually colour bands) to show whether you’re about to ovulate. A positive result indicates that you are going to ovulate within next 24-48 hours.

While ovulation kits do measure the LH surge, they can’t confirm that you will get pregnant. Here are a few reasons why the kits may not work:

1. An LH surge may not always guarantee that an egg may be released. In this case, getting pregnant isn’t feasible.

2. Women approaching menopause have increased levels of LH in their body at all times. Hence, these kits are may not be reliable in women above the age of 40.

3. They are not reliable when medications containing fertility drugs, are already pregnant or taking birth control pills.

Trying to conceive may be one of the most trying times you go through in life. While the methods discussed above may help you to a certain extent, maintaining a healthy lifestyle and a great sex life is the most important aspect of getting pregnant.

Also read Ovulation – pregnancy percent by day

Fertility quacks are not beyond giving heavy doses of hormones to a woman to make her ovulate (be it the conventional mother-to-be or the surrogate). Such is the social stigma attached to infertility in our society that women (there seems to be no ART for infertile men) are willing to go to any lengths to conceive. But first what is infertility? The medical definition of infertility is the failure to conceive following twelve months of unprotected intercourse. Infertility treatment looks to undo this.

 If you indeed are looking to conceive using any of the ART methods be aware of the treatment you’re being given and its side-effects. We’ve tried to list some of the drugs used and their side-effects:

1. Drugs which act by suppressing the natural menstrual cycle (Lucrin, Synarel, etc.) can have side-effects similar to menopause. You could experience hot flushes and mood swings. 
2. Gonadotrophin (Puregon/Gonalf/Humegon) is a hormone that stimulates the ovaries to produce more eggs. Side-effects may include weariness, mood swings, nausea and headache. Since the ovaries swell up some patients complain of additional pelvic pressure. In rare cases, the ovary may rotate and twist leading to bleeding and requires surgery. These conditions usually continue for the second half of the cycle and may last up to three months if pregnancy is successful.
3. Human Chorionic Gonadotrophin (HCG/PROFASI/PREGNYL) facilitates the final maturing of the oocyte (oocyte is a cell that goes on to become the ovum or the egg and is more uncomfortable than other injections. It’s often called the ‘trigger’ injection.
4. Another drug which is used is Clomiphene (Clomid/Serophene) which looks to stimulate the pituitary to produce extra oocytes. Here too the side-effects include headaches, weariness, occasional visual disturbance and hot flushes.
5. Some drugs like doxycycline and progesterone don’t actually help produce oocytes but help in other ways by protecting the embryo or thickening the uterine walls. Side-effects of doxycycline include nausea, vomiting, diarrhoea, skin rashes and photosensitivity whereas progesterone can cause perianal pain, headaches, nausea and drowsiness.

Ovarian Hyper Stimulation Syndrome

A more specific problem which occurs in about 1-2% of patients who undergo super-ovulation induction is a problem called Ovarian Hyper-stimulation syndrome (OHSS).

 Essentially fluid from the bloodstream leaks into the abdominal cavity causing it to swell. Several symptoms include respiratory issues, kidney failure and arterial and venous thrombosis. Rarely cases could see a lack of blood supply to the brain and other vital organs. Patients who suffer severe OHSS must be hospitalised and treated. This treatment would involve the infusion of intravenous fluids and the fluid in the abdomen may need draining off. 

The ICMR guidelines dictate that it’s the doctor’s the duty to tell their patients about all the side-effects of the treatments. It’s imperative to know them before going for any procedure. Women who suffer from health issues, particularly cardiovascular or blood pressure issues have to be even more careful. Having children may seem like the most important thing in the world, but conceiving shouldn’t be at the cost of your partner’s, wife’s or even an unknown surrogate’s health and well-being.

•  Click here to read about tips to conceive faster.
• Click here to read about Bollywood mothers’ fitness regimes
  Source: Health Guru