Info about early symptoms/testing/HCG

[Kittykins]

I've found myself mentioning the stuff below at various points over the past few months so thought I'd put it in a new thread for people to see.

I'm not an expert, this is just stuff I've read/been told/found on the internet and happen to have collated.

How do pregnancy tests work?

Lots of women ask how early they can test for pregnancy. Home pregnancy tests (HPTs) work by detecting a particular hormone, HCG, in the urine. HCG has a similar structure to luteinising hormone (LH), but with an 'extra bit'. LH is detected by ovulation predictor kits (OPKs), which is why an OPK may pick up pregnancy but an HPT won't detect ovulation.

However, whilst all women have a certain amount of LH present in their urine throughout the cycle (which is why an OPK is not a good substitute - some women will always get faint lines on OPKs), HCG is only produced in pregnancy and specifically, after the fertilised egg (blastocyst) has implanted. This means that HPTs will not detect pregnancy until after implantation. Implantation usually occurs between 7 and 10 days after ovulation. In most cases, the hormone takes 12-48 hours to appear in urine. The levels are low to begin with (1-5mi) and should double roughly every 36-48 hours. Most HPTs detect HCG at levels of 25mi+; some claim to detect at 10mi. First morning urine is least diluted, which is why it is recommended to test first thing in the morning (N.B. OPKs are usually directed for use later in the day - the LH surge normally begins early morning and takes 6hrs+ to appear in urine samples).

How early can I test?

Therefore, the earliest 'normal' time to see a BFP on an HPT is 7+1+2 days on a 10mi test (i.e. 9 days post ovulation). At the other end of the scale, it would be unreasonable to detect a BFP before 10+2+5 days on a 25mi test (i.e. 17 dpo). The average, according to Fertility Friend, is 14dpo - which fits well with these assumptions. Of course, there are exceptions to all rules, but it seems very probable that in cases of early BFPs (reported at 4 or 5 dpo), the tester was in fact mistaken about the day of ovulation.

So how is it possible to 'feel' pregnant before implantation? Why isn't there a test for use at 1 or 2 dpo?

Once the egg is fertilised (<12 hours from ovulation, as that is when an unfertilised egg starts to disintegrate), it starts to divide. This blastocyst produces a protein (and possibly lots of other chemicals, I couldn't find much research here!) known as 'early pregnancy factor', or EPF. EPF is an immunosuppressant, and it is thought it may be responsible for some of the very early pregnancy symptoms such as colds, sore throats, tiredness, etc.

In fact, it is possible to test for pregnancy the day after ovulation, by testing for the presence of EPF in urine. The reason that these tests aren't commercially available (yet! I'm sure the big companies must be desperate to get these out!) is because the tests are very expensive to conduct and ethically problematic - they would tell you that the egg has been fertilised, but would not give you any idea as to whether the blastocyst would implant. It's thought that up to 50% of fertilised eggs simply pass out of the body during menstruation. If you were testing that early, the chances of disappointment would be so incredibly high that it's not worth doing. Many of us already know the disappointment of an early BFP, only for it to result in a very early miscarriage (<6 weeks).


By the way, when I visited my GP the other day, he told me that his clinic used to use tests very similar to the internet cheapies many of us have been using (I took an unused(!) one in to show him, as I'd had several faint lines over a few weeks), but had stopped because they had had too many false positives and false negatives. His conclusion was that the unbranded ones are just not accurate enough. The clinic now uses 20mi clearview (same as ClearBlue) tests.

I hope this helps. If you want to read more, there's a useful Wiki page on EPF here: http://en.wikipedia.org/wiki/Early_pregnancy_factor .

I'm sure the knowledge won't stop us all POASing at 8 dpo , but it may help prevent unrealistic expectations and disappointment!

 

[skairdykat]

Great thread hun, well done

 

[reallyoldmum]

Kitty you never cease to amaze me - what a fantastic post x x x x

 

[Mildly]

This would be a really good sticky

 

[CB23]

I agree - make it a sticky. Great post, thanks Kitty!

 

[Emma79]

Great post, with lots of useful info.

You're right though, most of us will carry on poas regardless, me included

 

[Loola]

Brilliant thread Kitty, thank you!

 

[Kittykins]

glad you enjoyed it!

Umm - I'm not sure how to go about making it a sticky - do I have to PM a mod or something?

 

[1588]

Wow that answered loads of questions........... thankies

 

[choklatemunky]

Just thought I would add some stuff to Kitty's post......there is some info in there about HCG levels when pregnant and some (maybe) interesting info that some people will only detect pregnancy later on. According to this, HCG levels could still be too low on the day your AF is due to show up on even the most sensitive tests....its not over 'til the witch comes to visit!

Human Chorionic Gonadotrophin
The most common test used to detect a pregnancy in the very early weeks uses hCG.

The hCG hormone starts to be released into the woman's blood stream soon after the baby implants into the lining of her uterus at about 8 to 12 days after conception. The hCG blood level will initially start off very low (5 IU/L), but then rapidly increase, doubling every 2 to 3 days, so that within a few days to a week or so the hCG level becomes high enough to be detected in the woman's urine, at about 50 to 80 IU/L. Once this level is achieved, a urine pregnancy test will show as being 'positive'.

Normal hCG levels vary widely between different women and in different pregnancies for the same woman. Be very careful when trying to 'interpret the numbers'. During the first 12 weeks of pregnancy, the level itself is NOT as important, as is, how much it is rising every few days.

Some normal pregnancies will have quite low hCG levels and still progress, ending in the birth of a healthy baby. The best way to confirm if a pregnancy is progressing is to repeat with a blood test in 2 to 3 days time, and perhaps again 2 to 3 days after that. This is aimed at seeing if the hCG level is rising adequately.

hCG levels
The following is a guide to what hCG levels can be during pregnancy.
For those of you who are interested, or are having hCG monitoring, here are the suggested reference ranges for a single baby pregnancy. As you can see the range of normal levels is very wide. hCG levels can be 30 to 50% higher than for a single baby pregnancy, in twin and multiple gestations.

Week 3, 7days after conception= 0 to 5(mIU/ml)
Week 4, 14 days after conception(next period due)= 5 to 430(mIU/ml)
Week 5, 21 days after conception =180 to 7400(mIU/ml)

These should be used as a guide only.

hCG levels double approximately every 48 hours during early normal pregnancy. It reaches a peak at about 10 week of gestation (since last menstrual period). At which time the average hCG levels in samples is around 60,000 mIU/ml. There is a very big variation in individual hCG concentrations. At this time, the extremes of normal levels are approximately 10,000 to 250,000 mIU/ml.

In the next 10 weeks (10 to 20 weeks of gestation), hCG levels decline, reaching a average concentration of about 15,000 mIU/ml. Again, wide variation is found among individuals, concentrations ranging from 3,000 to 90,000 mIU/ml. The hCG concentrations remains at around this level, and with this variation from this time until term (20 to 40 weeks of gestation).

If you have any concerns you should always discuss your results with your Doctor.

What is hCG?
Pregnancy begins with fertilisation of the egg and implantation of the fertilised egg in the lining of the uterus. Implantation will normally occur about 8 to 12 days following conception. hCG begins to be produced around the time of implantation. The tiny amount of hCG that enters the maternal circulation around day 21 (less than 5 mIU/ml in serum or plasma, while too small to be detected by pregnancy tests, is sufficient to stimulate the corpus luteum of the ovary to produce progesterone.

A pregnancy will usually only continue after implantation if menstruation is prevented. Estrogen and Progesterone are produced by the Corpus Luteum and prevent menstruation by maintaining the lining of the uterus. The corpus luteum itself is maintained by hCG that is produced by the trophoblast cells of the placenta after implantation of the fertilised ovum. hCG enters the maternal circulation almost immediately after implantation of the embryo (blastocyst) on about day 21 of the menstrual cycle.

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Corpus Luteum is a body of cells that forms after ovulation each month and occupies the space formerly occupied by the egg in the follicle. It produces progesterone and estrogen and is programmed by nature to disintegrate in about 14 days. When it does, diminishing hormone levels trigger menstruation.

In pregnancy, the corpus luteum, sustained by the pregnancy hormone hCG, continues to grow and produce progesterone and estrogen to nourish the baby until the placenta takes over. In most cases, it starts to shrink approximately 6 or 7 weeks after the last menstrual period and ceases to function at about 10 weeks.
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Pregnancy tests are based on the detection of elevated levels of human Chorionic Gonadotrophin (hCG) in serum or urine, which is produced by the developing placenta following implantation. Urine and serum samples of non pregnant females usually contain less than 5 mIU/ml hCG.

After conception and implantation, levels of hCG will increase rapidly in a normal pregnancy. By the day the period is due hCG levels of approximately 50 - 250 mIU/ml are expected. During the first trimester, levels of hCG should double every 48 - 72 hours with the levels reaching between 50,000 – 300,000 mIU/ml at the end of the first trimester. After the first trimester levels of hCG drop dramatically with the levels remaining well above the base level of 5 mIU/ml throughout the pregnancy.

The appearance and rapid rise in the level of hCG makes it an excellent marker for pregnancy.

When can hCG be detected?
The earliest time a hCG test will detect a pregnancy is about 8 days after conception or about 1 week before the next period is due. However, this is only possible for about 5% of women. Most women will show a positive hCG level by about 11 to 12 days after conception or a couple of days before the next period would have been due.

By day 28 (first day of missed menses) the hCG level in serum, plasma or urine is about 100 mIU/ml. This should be detectable by all pregnancy tests. There is a very big variation in individual hCG concentrations. At this time, the extremes of normal levels are approximately 5 to 450 mIU/ml in serum or plasma samples. Some pregnant women at this time will have a low level hCG and will not register on HPTs by the time they are a few days late for their period.

hCG can also be produced by early pregnancy loss (EPL) or pregnancies that fail to start or properly implant. hCG from these pregnancies can also be detected at this time

Women who have hCG injections for fertility treatments can have hCG in their system for 2 to 3 weeks after the injection. This means they may obtain an early 'positive' pregnancy test, yet not be pregnant.

How is hCG detected?
When a women first thinks she may be pregnant she might purchase a home pregnancy test (HPT). Home pregnancy tests (HPTs) are designed to detect hCG, a hormone released by the placenta right after the embryo begins implanting into the uterine lining. When the hormone is released it can be detected in a pregnant woman's blood and urine.

If a women visits her Doctor to test, a blood and/or urine sample will be taken.

A Urine tests at the doctor's office are not any more sensitive than home tests. These are usually the equivalent to home pregnancy tests, reading an hCG level of 15 to 25 mIU as positive. They are often the same tests as HPTs, bulk packed for Doctors, medical centers and clinics.

A quantitative blood test is more accurate, but not necessarily more sensitive. A quantitative blood test, usually called a beta hCG test, measures the exact units of hCG in the blood. That means it will detect even the most minimal level. Common levels for a positive blood test are 10 to 25 units.

A qualitative hCG blood test will give a simple yes or no answer to whether you are pregnant. This test is more like a urine test in terms of its accuracy. Levels for a positive blood test are 10 to 25 units, a level under 5 is considered negative. A test that is only triggered at 25 units of hCG is not any more sensitive than several of the urine HPTs.

How accurate is a positive HPT result?
Home pregnancy tests only check hCG levels and the hormone hCG is produced in pregnancy, which is released in a pregnant woman's urine. So, unless the woman has been given a medication that contains hCG (Profasi, Pregnyl, Novarel), then a positive HPT should indicate a new pregnancy.

If you had an hCG injection (such as Profasi, Pregnyl or Novarel), you should wait 7-14 days after your last injection before the shot is out of your system. If you test too soon, you might get a false positive. Wait 14 days after a 10,000 IU injection, 10 days for a 5,000 IU injection, for 2,500 IU injection 7 days.

How accurate is a negative HPT result?
If you get a negative HPT result, you may be pregnant and just didn't have a high enough level of hCG to trigger the test. It is possible the test was performed improperly, done to early, that urine was too diluted to give an accurate reading, or that test was not stored properly before use.

If you think you are pregnant but got a negative result, re-test on another day. Most pregnant women will register on HPTs by the time they are a few days late for a period, but not everyone will.
If you suspect you are pregnant, you should see your doctor for a quantitative hCG blood test no matter what result you get from home pregnancy tests.

Early low level hCG Problems
It is only in the last ten years or so that it has been possible to carefuly monitor pregnancies in the first half of the first trimester. The early monitoring, if used properly can reassure women during uncertain times and prevent dangerous complications. Pregnancies that will miscarry and ectopic (tubal) pregnancies are likely to show lower levels and slower rises, but often have normal levels initially. Sometimes it takes three or more tests for hCG levels, at least 48 hours apart to get an idea how a pregnancy is progressing.

A single hCG value doesn't give enough information about the health or viability of the pregnancy. Within the first 2 - 4 weeks after fertilization, hCG usually doubles every 48 - 72 hours. That usually corresponds to hCG levels below 1200 IU. From 1200 - 6000, the hCG usually takes 72-96 hours to double. Above 6000 IU, the hCG often takes over four days to double. So, the rate of increase in hCG levels normally varies as a pregnancy progresses. hCG that does not double every two to three days does not necessarily indicate a problem with the pregnancy. Some normal pregnancies will have quite low levels of hCG, and result in perfect babies.

Once the hCG levels are above 1000 - 1500 IU, vaginal sonography usually identifies the presence of an intrauterine pregnancy. At that point an ectopic pregnancy is effectively ruled out. Once the pregnancy is visible on ultrasound, further hCG testing is less reliable than ultrasound for monitoring a pregnancy, as the variations in hCG levels are frequently misleading and cause unnecessary worry.

Since normal levels of hCG can vary tremendously, after 5-6 weeks of pregnancy, sonogram findings are much more predictive of pregnancy outcome than are hCG levels. Once the gestational sac is seen, most doctors will monitor with ultrasounds rather than drawing bloods for hCG tests.

Subsequent monitoring with ultrasound should reveal normal growth of the gestational sac, and the development of a fetal heartbeat by 6 to 7 weeks gestation (6-7 weeks after LMP). Once fetal activity has been detected by ultrasound, the chance of miscarriage is usually less than 10%.

If your home pregnancy test is positive and then a few days later your period arrives. Your period may be heavier than you're used to, which may mean your pregnancy has been lost. Experts estimate that about 20 to 30 per cent of all pregnancies end in miscarriage, so unfortunately this is very common.

It is only since pregnancy tests became so sensitive that people have realised how often early miscarriages can happen. In the past, these very early losses might not even have been noticed, and the woman would never have known she had been pregnant.

Think you are pregnant and got a negative HPT result?
If you get a negative HPT result, you may be pregnant and just didn't have a high enough level of hCG to trigger the test. It is possible the test was performed improperly, done to early, that urine was too diluted to give an accurate reading, or that test was not stored properly before use.

If you think you are pregnant but got a negative result, re-test on another day. Most pregnant women will register on HPTs by the time they are a few days late for a period, but not everyone will.
If you suspect you are pregnant, you should see your doctor for a quantitative hCG blood test no matter what result you get from an HPT.

 

[welshpolly]

All this info is fabulous, thank you for sharing xxx

 

This is very informative, I have to thank you too.

 

[mothernature]

it really worth reading these posts as they include such a huge amount of necessary information. Thanks for your post, choklatemunky and Kittykins.

 

[Jaidy]

This has refreshed my memory loads thanks hun!

 

[rusks]

this is fab and given me a glimmer of hope i tested too early thank you for sharing

 

[babyblonde]

what a really excellent post!