hCG

What does hCG mean?

hCG: The pregnancy hormone that home pregnancy tests detect in your pee. It starts to be made about 6 days after the egg is fertilised.

How it is used in the Splash library

• Tests detect hCG, which starts being made about 6 days after fertilisation.

  From “Early pregnancy signs & when to test”

• All home tests look for the hormone hCG.

  From “Early pregnancy symptoms and testing”

• Testing earlier can give a false negative because there is not yet enough hCG in your urine.

  From “Implantation bleeding: what it looks like and when”

hCG explained

hCG (human chorionic gonadotrophin) is the hormone made by cells that will form the placenta, soon after a fertilised egg implants in the womb. It tells the corpus luteum to keep making progesterone, which supports the early pregnancy.

Home pregnancy tests detect hCG in urine. Blood tests can measure the exact amount and pick up lower levels earlier.

What's typical

hCG starts to be made after implantation, which usually happens 8 to 10 days after ovulation (Wilcox, 1999). In early pregnancy it typically rises quickly, roughly doubling every two to three days, and peaks at around 8 to 11 weeks.

Most home tests are reliable from the first day of a missed period (NHS). Levels vary widely between pregnancies, so a single number means little on its own; the trend over 48 hours matters more.

hCG can stay detectable for a few weeks after a miscarriage, birth or abortion. Some fertility medicines also contain hCG.

When to talk to a GP, nurse or pharmacist

• You have a positive test with pain on one side, shoulder-tip pain, bleeding or dizziness: get urgent help, as this can be an ectopic pregnancy.
• Your test is positive. Contact a GP or midwife to start antenatal care.
• Tests are negative but your period is more than a week late, or tests stay positive weeks after a pregnancy loss.

In the UK you can call NHS 111 for advice at any time. In an emergency call 999 (UK) or 911 (US). This is general information, not medical advice.