At 18,000, you would approximately be somewhere between 7-8 weeks pregnant as seen by this chart...
Quote:
Guideline to hCG levels during pregnancy:
HCG levels in weeks from LMP (gestational age)* :
* 3 weeks LMP: 5 - 50 mIU/ml
* 4 weeks LMP: 5 - 426 mIU/ml
* 5 weeks LMP: 18 - 7,340 mIU/ml
* 6 weeks LMP: 1,080 - 56,500 mIU/ml
* 7 - 8 weeks LMP: 7, 650 - 229,000 mIU/ml
* 9 - 12 weeks LMP: 25,700 - 288,000 mIU/ml
* 13 - 16 weeks LMP: 13,300 - 254,000 mIU/ml
* 17 - 24 weeks LMP: 4,060 - 165,400 mIU/ml
* 25 - 40 weeks LMP: 3,640 - 117,000 mIU/ml
* Non-pregnant females: <5.0 mIU/ml
* Postmenopausal females: <9.5 mIU/ml
|
Found here:
Human Chorionic Gonadotropin (hCG)—The Pregnancy Hormone : American Pregnancy Association
However, as a Labor & Delivery nurse, I can tell you that as far as due dates go, we estimate your due date by your LMP, not your ovulation date or your HCG levels.
At 7-8 weeks the chance of seeing a fetus is slight, depending on how the ultrasound was performed. If performed transvaginally, it's more likely than and abdominal ultrasound. I will say, though, that it will be more like 10-12 weeks is more likely to see the fetus, from my lengthy experience.