Pregnancy Tests

A pregnancy test is a test to determine whether or not a woman is pregnant. more...

Home
Bath & Body
Dental Care
Dieting/ Slimming
Fragrances
Hair Care
Hair Removal
Health Care
Blood Pressure Testing
Family Planning/...
Condoms
Impotence Aids
Lubricants
Other Family Planning
Ovulation Kits
Pregnancy Tests
Feminine Care
First Aid
Other Health Care
Quitting Smoking
Relaxation Aids
Sleeping Aids
Make-Up/ Cosmetics
Massage
Mobility, Disability &...
Nails/ Manicure/ Pedicure
Natural/ Alternative...
Other Health & Beauty
Over-the-Counter Medicine
Skin/ Face Care
Tanning/ Sun Care
Tattoos/ Body Art
Vision/ Glasses/ Lenses
Vitamins/ Supplements

hCG measurement

All tests currently available to test for the presence of a pregnancy look for the presence of the beta subunit of hCG or human chorionic gonadotropin in the blood or urine. They are usually performed after a missed menstruation or 2-3 weeks after ovulation.

HCG can be detected in urine or blood after implantation, which occurs six to twelve days after fertilization. Some home pregnancy tests claim to detect hCG as early as 4 days before the next expected period. Whether that statement is accurate for an individual woman depends on the length of her luteal phase and on how soon that individual embryo implanted. Quantitative blood (serum beta) tests can detect hCG levels as low as 1 mIU/mL, while urine tests have published detection thresholds between 20 and 100 mIU/mL, depending on the brand. Qualitative blood tests generally have a threshold of 25 mIU/mL, and so are less sensitive than some available home pregnancy tests.

This hormone is released by trophoblastic tissue in the placenta. In rare cases, it may be produced by a choriocarcinoma or some other germ cell tumours, or even other forms of cancer, e.g. lung cancer.

Doubling rule

Doctors can also perform quantitative serum beta hCG levels. The measurement is done in mIU/ml, and a level above 25 mIU/ml usually indicates the presence of a pregnancy. Two tests are usually necessary to verify a normal increase, usually 2-3 days apart. The increase in serum hCG can be interactively monitored. Below an hCG level of 1,200 mIU/ml the hCG usually doubles every 48-72 hours, though a rise of 50-60% is still considered normal. Between 1,200 and 6,000 mIU/ml serum the hCG usually takes 72-96 hours to double, and above 6,000 mIU/ml, the hCG often takes more than four days to double. Failure to increase normally may indicate that the pregnancy is not developing well and can be an early sign for a possible miscarriage or an ectopic pregnancy. After a miscarriage, HCG levels fall steadily back to the non-pregnancy range. Also, an ectopic pregnancy may be suspected when hCG levels fail to double, particularly if the HCG level rises, falls and rises again.

Quantitative beta hCG readings are also used in evaluation of trophoblastic and other germ cell tumors.

Correlation to obstetric ultrasonography

Once a pregnancy has advanced past the first 6-8 weeks, a pregnancy is usually easier to follow by sonography as more information is obtained in real time. In general a pregnancy is detectable 25 days after ovulation by transvaginal sonography (usually corresponding to an hCG level of > 1,500 miu/ml).

Read more at Wikipedia.org