Pregnancy hormones: Ask a Health Question

Question: I am 7 weeks pregnant and experienced a small bleed. My doctor ordered a series of blood tests to measure my hCG levels. What is a hCG level and what number should my level be?

Answer:

The hormone human chorionic gonadotropin (or hCG) is produced during pregnancy by the placenta. A woman's hCG levels increase steadily though the first trimester of her pregnancy, generally doubling every 2-3 days. At the 8-11 week mark hCG levels peak and then decline. The hCG hormone is measured in milli-international units per millilitre or mIU/ml.

What is considered a 'normal' hCG level varies greatly from woman to woman and from pregnancy to pregnancy. For example, at 7-8 weeks from the last menstrual period, a normal hCG level can be anywhere from 7,650 mIU/ml to 229,000 mIU/ml. Levels at both ends of the range (and everything in between) are considered normal with a reading at the higher end not necessarily considered 'better' than one from the lower end. Unfortunately there is a lot of misinformation on the internet about hCG levels and what numbers are considered 'normal'.

A single reading of the hCG level does not provide enough information about how the pregnancy is progressing. This is why doctors generally order more than one blood test. By conducting a series of blood tests, taken a few days apart, the doctor will get a more accurate picture of the hCG levels. It is the change in the levels that is important, not the actual number itself.

If the pregnancy is not progressing normally the hCG levels do not rise sufficiently or rise too much. If the hCG levels do not increase as expected, it can mean a miscarriage has occurred. When a miscarriage occurs the hCG levels fall rapidly. Less than expected hCG levels can also indicate an ectopic pregnancy (where the fertilised egg has implanted outside the uterus, usually in the fallopian tube). In an ectopic pregnancy hCG is still produced but at a lower amount than with a normal pregnancy.

Conversely, if the hCG levels are too high it can indicate a molar pregnancy. A molar pregnancy or hydatidiform mole, as it is also known, occurs when the tissue that would normally form an embryo grows abnormally in the uterus. Molar pregnancies are extremely rare, occurring in about one in 1,200 pregnancies. A multiple pregnancy (twins/triplets) can also result in higher than expected hCG levels.

Vaginal bleeding is a symptom of miscarriage, ectopic pregnancy and molar pregnancy. The results of blood tests and hCG levels will provide your doctor with important information about how the pregnancy is progressing. Depending on the results of the hCG levels and any further symptoms more tests may be required. For example, if an ectopic pregnancy is suspected an ultrasound will be conducted as it is a medical emergency.

Last updated: October 2013

© Women's Health Queensland Wide Inc. This article was written by Kirsten Braun and reviewed by the Women's Health Queensland Wide editorial committee. It was first published in Health Journey Issue 3 2013.

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