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. Normal HCG values vary up to 20 times between different pregnancies, however, and an 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.
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 HCG levels at least 48 hours apart to get an idea how a pregnancy is progressing.
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 HCG. 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%.
My general recommendations regarding the appropriate use of HCG testing are summarized below. By following these guidelines, unnecessary testing that might lead to needless worry might be avoided, and just the right information will be obtained.
1. If you're pain-free and you're not bleeding and you're at low-risk for an ectopic pregnancy, try to avoid the temptation to monitor HCG levels. Generally no bleeding (no news) is good news. The pregnancy is on autopilot, and there's little you can do to influence it at this stage. Try to relax and wait and see.
2. IF HCG monitoring is indicated, try not to read too much into the absolute numbers and rates of increase of the HCG levels. Trust your doctor's knowledge and experience to tell you if and when to repeat the tests, when and how to react to the numbers, and when to have an ultrasound. I can't tell you how many patients I've had who convinced themselves that their pregnancy was doomed based on inappropriate interpretation of HCG levels, only to discover that everything is fine when an appropriately timed ultrasound is performed.
3. Once an intrauterine pregnancy is visible on ultrasound, do not put any faith in HCG measurements. Frequently pregnancies and their HCG levels don't fit the mold, and the numbers don't increase the way they "ought" to. Rely on time, and predictable ultrasound changes to determine pregnancy viability.
So basically ultrasound is more indicative of what is happening and HCG level may not necessarily mean much at this stage-seemd it is used before you can see anything useful on u/s so don't worry! I read another post from someone that their HCG was 21000 and they couldn't see a hearbeat (mine got to well over 16000 when I had a blighted ovum at 8weeks so no baby no heartbeat) so it is a good sign that you have seen that.