So you’ve missed your period and you’re wondering what to do now!
You’re likely to go straight out and buy a home pregnancy test.
But you might wonder how on earth peeing on a stick can give you the answer to your question: ‘Am I pregnant?’
Or you might wonder why you need a blood test when you visit your doctor.
During early pregnancy, your body starts producing human chorionic gonadotropin (hCG).
hCG is commonly known as the pregnancy hormone and it’s produced by the cells of what will become your baby’s placenta.
Your body begins to produce hCG once the embryo implants in the uterine wall.
Let’s explore what hCG levels are and what they should be each week of your pregnancy.
What does hCG do?
During pregnancy, hCG is responsible for maintaining a thick uterine lining.
Without this hormone, the lining begins to shred, putting the pregnancy at risk.
hCG is produced by cells that form the placenta, and this means it’s not usually present in the body unless a woman is pregnant.
In most, but not all, healthy pregnancies, hCG levels double every two or three days at the start of the pregnancy.
As the pregnancy progresses, this rate might slow, doubling every four days, but hCG levels are expected to continue to rise until some time between weeks 8 and 11.
Then the levels start to decrease, until week 16.
After that, hCG levels stay stable until you give birth.
Fertility drugs containing hCG can affect your hCG levels, so you should discuss this with your doctor before your levels are checked.
Some pregnancy tests use hCG levels to date the pregnancy, but this can be wildly inaccurate, as levels vary between women.
How can I check my hCG levels at home?
Home pregnancy tests are now so sensitive they can detect human chorionic gonadotropin in the urine of pregnant women as early as 3 weeks after the first day of the last period.
Taking a pregnancy test too early, though, can affect the results and cause a false-positive reading.
False-positive pregnancy tests are very rare and you can read about them here.
The best time to take a home test is after your missed period.
This is the time the hCG levels in your urine will be higher and you’ll be more likely to get a positive pregnancy result.
A urine sample taken first thing in the morning will be more accurate, as the urine is more concentrated.
What hCG level is considered pregnant?
An hCG level of less than 5mlU/ml (milli-international units per milliliter) will give you a negative pregnancy test result.
If your level of hCG is found to be 25mlU/ml or over, then you will get a positive pregnancy test result.
What is the hCG level at one week?
When a woman suspects she’s pregnant it’s usually because of a missed period.
Ovulation occurs around day 14 of a 28-day menstrual cycle, and fertilisation usually occurs within 24 hours of ovulation.
A few days after conception, the body sends signals to prepare for implantation and normal hCG levels start to rise.
Instead of shedding the lining of the uterus (endometrium), the rising hormone detected in the blood maintains and nourishes it, in preparation for the egg to implant itself.
The egg implants itself around 6-11 days after conception. At this point, you are officially pregnant.
Technically, however, pregnancy starts from the first day of your last period, and at this stage, you’re not actually pregnant!
I know, it’s confusing.
Normal hCG levels in non-pregnant women average less than 5.0 mIU/ml, so at one week this is what is expected.
hCG levels during pregnancy rise about three weeks after the first day of the last period.
hCG levels by week
It’s not routine for hCG levels to be checked throughout pregnancy.
This will only be done if you’re showing symptoms of a possible problem.
Firstly, it’s important to remember there’s no such thing as ‘normal’.
What’s normal for you might not be normal to the next pregnant woman.
And what’s normal for your first pregnancy might not be normal for your second.
The important part is the change in levels each week, not the individual result.
The following levels are a rough guide.
The chart shows an average level range for each week dated from the first day of the last menstrual period (LMP).
|hCG Levels During Pregnancy
(from last menstrual period)
|Women who are not pregnant: <5.0 mIU/ml|
|hCG levels at 3 weeks: 5 – 50 mIU/ml|
|hCG levels at 4 weeks: 5 – 426 mIU/ml|
|hCG levels at 5 weeks: 18 – 7,340 mIU/ml|
|hCG levels at 6 weeks: 1,080 – 56,500 mIU/ml|
|hCG levels at 7-8 weeks: 7, 650 – 229,000 mIU/ml|
|hCG levels at 9-12 weeks: 25,700 – 288,000 mIU/ml|
|hCG levels at 13-16 weeks: 13,300 – 254,000 mIU/ml|
|hCG levels at 17-24 weeks: 4,060 – 165,400 mIU/ml|
|hCG levels at 25-40 weeks: 3,640 – 117,000 mIU/ml|
|Women after menopause: 9.5 mIU/ml|
Is low hCG in early pregnancy bad?
Around 8% of pregnant women show low blood levels of hCG on their blood test.
This isn’t always cause for concern; many women go on to have a normal, healthy pregnancy.
A single serum beta hCG reading isn’t usually enough to give an accurate diagnosis of any potential conditions, so you should be medically reviewed.
If your doctor or pregnancy nurse reports low levels of hCG on your blood tests, they’ll repeat the test a couple of days later, so the numbers can be compared.
Low levels of hCG could be indicative of:
- Incorrect pregnancy dating; you’re not as pregnant as previously assumed – especially if you didn’t know the first day of your last menstrual period
- Possible miscarriage
- Ectopic pregnancy; this can occur when there are problems with the fallopian tube and the egg implants outside of the uterus.
What week do hCG levels start to drop?
As you can see from the chart above, blood hCG levels increase rapidly during early pregnancy.
They peak at 9 to 12 weeks of pregnancy, decline slightly at 13 to 16 weeks, and then remain fairly steady.
Interestingly, pregnant women who suffer morning sickness tend to start feeling better as the hCG hormone levels fall lower.
High levels of hCG
Your doctor or midwife should also medically review high hCG levels.
They could be indicative of:
- Incorrect pregnancy dating; you’re further along than previously thought
- Multiple pregnancies; you’re pregnant with twins or more. If you are carrying twins, your hCG levels could be 30-50% higher.
- Molar pregnancy; if a molar pregnancy occurs, there’s a growing mass in the uterus but it won’t develop into a baby. The mass is known as a hydatidiform mole and produces high levels of hCG. The mole will need to be removed.
hCG levels during miscarriage
A very early miscarriage could also cause a false positive test if your hCG levels haven’t dropped.
The pregnancy test will still pick up human chorionic gonadotropin in your body.
If you’re experiencing a miscarriage, your hCG blood test will show reducing amounts of the hormone as it’s no longer needed to support the pregnancy.
After a pregnancy loss, hCG should drop down to less than 5mlU/ml within around six weeks.
The time it takes to reduce will depend upon the level of the hormone at the end of the pregnancy, and how the loss occurred.
If you experience a pregnancy loss, your healthcare provider will recheck your hCG levels a few weeks later to make sure they have reduced.