Pregnancy
The HCG beta-subunit becomes detectable 6-12 days post implantation.
(1)
A b-HCG level of >25 IU/L is required for a definitive confirmation with
methods used at the IMVS.
At levels of 1,500 - 2,000 IU/L an intrauterine gestational sac becomes
visible on ultrasound examination.
Rate of b-HCG increase in pregnancy (2)
- b-HCG doubles every 1.5 days for 5 weeks post implantation
- b-HCG then doubles every 3.5 days from the 7th week post implantation
REFERENCE INTERVALS FOR b-HCG IN PREGNANCY
| Gestational Age weeks post LMP) |
IU/l |
| 2-3 |
10-70 |
| 3-4 |
10-750 |
| 4-5 |
200-7000 |
| 5-6 |
200-32,000 |
| 6-8 |
4,000-150,000 |
| 8-12 |
64,000-210,000 |
| 14 |
14,000-62,000 |
| 15 |
12,000-70,000 |
| 16 |
9,000-56,000 |
| 17 |
8,000-56,000 |
| 18 |
8,000-58,000 |
Ectopic Pregnancy and Abortion (3)
Indicated by:
- Falling levels of b-HCG
- Reduced rate of increase (Note: Approximately 1/3rd of cases of tubal pregnancy have normal rates
of b-HCG level increase)
The IMVS recommends that serial assays for bHCG be performed in the same
laboratory as variations in methods could lead to an inaccurate assessment
of the situation.
- Wilcox A, Baird DD, Weinberg CR. Time of implantation of the conceptus
and loss of pregnancy. NEJM 1999;340:1796-99
- Fits MA, Guo SM. Doubling time of hCG in normal pregnancy:
relationship to hCG concentration and gestational age.
Fertility and Sterility 1987;47:584-589
- Shepherd HR, Patton PE, Novy MJ, Burry KA. Serial data hCG measurements
in the early detection of ectopic pregnancy.
Obstetrics & Gynecology 1990;75:417-420
Document URL: http://www.imvs.sa.gov.au/hcginfo.htm
Last modified: Tuesday, 31st January 2006
© 2000 Institute of Medical and Veterinary Science Disclaimer