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Human chorionic gonadotropin (HCG) is the hormone which is produced during pregnancy – it is a wonderful indicator of a pregnancy. Human chorionic gonadotropin is produced by cells formed in the placenta right when implantation first takes place. Human chorionic gonadotropin is thought to be important in converting the normal corpus luteum into the corpus luteum of pregnancy – hormone producing structure that grows on the surface of the ovary after ovulation takes place. The biological function of HCG is to keep the corpus luteum producing another important pregnancy hormone progesterone. Progesterone increases the body temperature and prevents next expected menstrual period. Actually the increasing levels of HCG insure the further production of progesterone and preparation of the endometrium (internal uterine lining) for implantation. Menstrual bleeding will not occur thanks to the dynamic interaction between human chorionic gonadotropin and progesterone.

Pregnancy tests are based on levels of human chorionic gonadotropin. Pregnancy blood test or pregnancy serum test measures the exact amount of human chorionic gonadotropin in the bloodstream. First positive tests detecting HCG in blood usually appears about 11 days after conception and in urine about 12-14 days after conception. Pregnancy tests detect human chorionic gonadotropin at 20mIU, which is typically the level achieved at about a week or so following ovulation. In most cases (85%) of normal pregnancy the HCG levels double every 48-72 hours reaching its peak in the first 8-11 weeks of pregnancy – HCG levels continue to increase throughout the first trimester of pregnancy and reach its peak 60-80 days after the fertilized egg implants.

Traditionally human chorionic gonadotropin hormone is measured in milli-international units per milliliter (mIU/ml). Level of human chorionic gonadotropin less than 5mIU/ml is considered negative for pregnancy, and anything above 25mIU/ml is considered positive for pregnancy.

Every week of pregnancy has adequate norms of HCG levels:

HCG levels during pregnancy

Sometimes normal pregnancy may have low levels of human chorionic gonadotropin and result in normal delivery and perfectly healthy baby. The results from an ultrasound after 5 -6 weeks gestation are much more accurate than using HCG-numbers.

Pregnancy hormone

Decreased levels of HCG

Decreased levels of this hormone should be rechecked during 48-72 hours. In general, low levels of human chorionic gonadotropin could be signs of:

Increased levels of HCG

Increased levels of hormone also should be checked during 48-72 hours. In general, high (increased) levels of human chorionic gonadotropin could be signs of:

  • Multiple pregnancy (duplets, triplets);
  • Miscalculation of last menstrual cycle and pregnancy dates;
  • Molar pregnancy;
  • Trophoblastic tumor.

When HCG levels should be checked

Routine tests of human chorionic gonadotropin during pregnancy are not common. Usually these tests are recommended only in cases of potential problems during first trimester of pregnancy (bleeding, history of miscarriage, signs of interrupted pregnancy, etc.) or in cases of molar pregnancy and trophoblastic tumors.

It is recommended to check HCG levels after natural delivery, spontaneous abortion, artificial voluntary abortion or ectopic pregnancy. In most cases the level of human chorionic gonadotropin returns to non-pregnant range (<5.0 mIU/ml) after 4-6 weeks.

HCG false levels

Sometimes women could experience false pregnancy test (false positive pregnancy test or false negative pregnancy test). Some conditions could trigger false tests including certain types of cancer, very early miscarriage, antibodies and some medications.

If you have infertility and using some hormones (fertility drugs designed to induce ovulation), you can have false pregnancy test more often. All other medications such as antibiotics, pain killers, contraception or other hormone medications should not have any effect on HCG tests.

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