HCG.The most common blood test used to detect a pregnancy in the very early weeks, or to determine if a pregnancy is likely to continue or miscarry is a 'quantitative serum human chorionic gonadotrophin' (QHCG). This is also known as a 'beta HCG' (or 'B-HCG'). The earliest time a blood 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 blood HCG level by about 11 to 12 days after conception (or a couple of days before the next period would have been due). 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.
The HCG hormone starts to be released into the woman's blood stream soon after the baby implants into the lining of her uterus (about 8 to 12 days after conception). The HCG blood level will initially start off very low (at least 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 least 50 to 80 IU/L). Once this level is achieved, a urine pregnancy test will show as being 'positive'.
The HCG hormone peaks to its highest levels between 8 and 11 weeks of the pregnancy. Then the level slowly decreases, lowering at 12 weeks and again at about 16 weeks of the pregnancy. The HCG level remains lower until several weeks after the birth of the baby. As the HCG levels lower, the maturing placenta takes over the role of producing other hormones to support the pregnancy (at around 12 weeks). HCG levels that are higher than expected may indicate a multiple pregnancy or the woman being more advanced in her pregnancy than calculated, or a molar pregnancy.
A blood HCG level of 5 IU/L may only 'indicate' that a pregnancy is possible. But it may also indicate that a pregnancy has recently existed (particularly if the woman is bleeding and in the process of miscarrying). If the blood test is repeated in 2 to 3 days and the beta HCG has approximately doubled, then this confirms that the pregnancy is continuing. A beta HCG of at least 25 IU/L is definitely regarded as being a 'positive' pregnancy blood test. If the pregnancy is less than 12 weeks and the levels start to lower, this is fairly indicative that the pregnancy will, or is in the process of miscarrying.
Normal HCG blood 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 in 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 the 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.
NOTE:Be aware that even when a pregnancy is miscarrying the levels can slightly increase for a while, but not at the rate expected if the pregnancy was progressing normally. For example a serum HCG level of 3,400 IU/L on Saturday, followed by a level of 3,600 IU/L on Monday may be of concern, as the level should be more like 5,000 to 7,000 IU/L. Also it is normal for the HCG level to start decreasing after 12 weeks of pregnancy. However, essentially, after about 8 weeks of pregnancy the use of ultrasound will tend to be more reliable in checking the growth and wellbeing of the baby, rather than blood pregnancy tests, which are more relied upon from 4 to 8 weeks of pregnancy.
The HCG hormone can stay in a woman's blood at low levels for up to 4 to 6 weeks after a miscarriage.
The following table is a guide to what beta HCG levels can be during pregnancy. As you can see the range of normal levels is very wide.
Weeks of pregnancy after last period Days after conception HCG level for single baby (mIU/ml or IU/L)
Week 3 7 0 to 5
Week 4 14 (next period due) 5 to 426
Week 5 21 18 to 7340
Week 6 28 1,080 to 56,500
Weeks 7 to 8 35 to 42 7,650 to 229,000
Weeks 9 to 12 49 to 70 25,700 to 288,000
Weeks 13 to 16 77 to 100 13,300 to 254,000
Weeks 17 to 24 4,060 to 165,400
Weeks 25 to birth of baby 3,640 to 117,000
4 to 6 weeks after birth Less than 5
Progesterone.The hormone progesterone helps to build the lining of the woman's uterus for the fertilised egg to implant into. Pregnant women have about 10 times more progesterone in their blood during pregnancy (compared to when they are not pregnant). Progesterone levels slowly increase as the pregnancy progresses.
Low levels are known to be a physical sign of miscarriage during the first 12 weeks. It used to be thought that a lack of progesterone may be a cause of miscarriage. However, it is now believed that low progesterone levels are simply the body's normal response to the inevitable loss of a pregnancy (meaning that treatments with progesterone are of no benefit). You can read more in recurrent miscarriage.
Some caregivers will also perform progesterone blood tests, along with the HCG blood tests. However, the HCG tests are usually adequate on their own. It is possible to measure progesterone levels in a woman's urine, but she must collect all her urine over a 24 hour period to do this. Abnormally high levels of progesterone may indicate you are having twins or more, or it may be a sign of a molar pregnancy.
The following table is a guide to what the progesterone levels can be during pregnancy. Again, you can see the range of normal levels is very wide.
Weeks of pregnancy Progesterone levels for a single baby (ng/ml)
Before pregnancy 1 to 28
Conception to 12 weeks 9 to 47
12 to 28 weeks 17 to 146
28 weeks till birth 55 to 200
Posted by: happie01 Posts: 48 :: 10-12-2006 :: | Reply to this Message