hCG Levels During First Trimester

Human chorionic gonadotropin hormone (hCG) is produced by the placenta after the fertilised egg becomes attached to the wall of the uterus, in early pregnancy. Its levels can be detected in a blood test around 11 days after the baby is conceived. After 12 - 14 days of conception, it can be detected in a urine test.

Measuring hCG levels in the First Trimester

Studies show that the HCG levels will double every 2-3 days in early pregnancy. For 85% of normal pregnancies it doubles every 72 hours. It reaches its peak at about 8-10 weeks of pregnancy and then declines, remaining at lower levels for the rest of the pregnancy.

hCG levels are measured in milli-international units per millilitre (mIU/ml). There is a large variation in a "normal" hCG level for any given time in pregnancy and may greatly vary from one woman to another, as well as from one pregnancy to another.

In general, its level is as follows (week-wise):

• 3rd week: between 5 and 50 mIU/ml
• 4th week: between 5 and 426 mIU/ml.
• 5th week: between 18 to 7,340 mIU/ml.
• 6th week: between 1,080 and 56,500 mIU/ml.
• 7th week: 8th weeks - 7,650 to 229,000 mIU/ml.

hCG levels during the first trimester peak sometime around 9 to 12 weeks of pregnancy and by the final weeks of the first trimester weeks (13 and 14), they decline and are around 13,300 - 254,000 mIU/ml.

It is important to remember that typically, doubling time increases with higher hCG level.

Pregnancies destined to miscarry and ectopic (tubal) pregnancies initially have normal and eventually lower levels. 

Role of hCG in First Trimester

hCG plays a vital role in maintaining pregnancy by inducing the secretion of the hormone, progesterone. Progesterone enriches the uterus with a thick lining of blood vessels and capillaries to sustain the growing foetus. Owing to its high-negative charge, hCG repels the immune cells of the mother, protecting the foetus during the first trimester. hCG also helps in the growth of the foetus by helping in the division of cells.

As hCG plays an important role in maintaining pregnancy, many women are informed of an impending miscarriage if their levels do not double in most three days. 

However, one should remember that:

• Some normal pregnancies have low levels of HCG during pregnancy and yet deliver perfect babies.
• hCG that does not double every two to three days does not necessarily indicate a problem.
• Once the pregnancy is visible on ultrasound, one should rely more on ultrasound than hCG for monitoring a pregnancy, as the variations in hCG levels are frequently misleading.

Consult your doctor if you are worried about hCG levels. Avoid stress by not reading too much about hCG levels once the intrauterine pregnancy is visible on ultrasound.

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