Chemical pregnancy symptoms and causes

Dr Juliet McGrattan (MBChB)
·7-min read
Photo credit: Maskot - Getty Images
Photo credit: Maskot - Getty Images

From Netdoctor

What is a chemical pregnancy? The term chemical pregnancy can be misleading, so many people prefer to call it a very early miscarriage. This type of early pregnancy loss usually happens just after the embryo implants at around five weeks, so you may have had a chemical pregnancy and not even know it.

If you are concerned that you might have had a chemical pregnancy or you’re looking for information on the subject, Dr Juliet McGrattan offers her expert advice on chemical pregnancy causes, symptoms and treatment options:

What is a chemical pregnancy?

A chemical pregnancy is a very early pregnancy loss. It’s named a chemical pregnancy because there are chemical changes in the blood or urine that show up on a pregnancy test. You can have a positive result but it is too early to see anything on an ultrasound scan. Most miscarriages happen before 12 weeks of pregnancy but those that happen before anything can be seen on a scan, usually before five weeks, are called chemical pregnancies.

What are the chemicals in a chemical pregnancy?

When a sperm meets and fertilises an egg, an embryo begins to develop. The cells which surround the embryo produce the hormone human chorionic gonadotropin (hCG). The release of hCG signals that pregnancy has begun and the body starts preparing itself. Pregnancy tests detect hCG, either in urine or in blood.

The usual advice is to test for pregnancy a week after a missed period but in fact many tests can detect hCG only a day after your missed period. The most sensitive tests can even pick it up eight days after you have conceived so you could have a positive test before your period was even due.

Photo credit: Getty Images
Photo credit: Getty Images

Chemical pregnancy symptoms

How do you know if you've had a chemical pregnancy? Chemical pregnancies usually happen before five weeks of pregnancy which means you can detect very early pregnancies just before or just after a missed period. There are three common situations:

• You don’t know you’ve had a chemical pregnancy

You may have a very early miscarriage without even knowing that you were pregnant. Your period may be the same as normal, it may be a little heavier or painful and it may be a day or two late. Most women would agree that these situations would all be normal for them so they haven’t even checked for a pregnancy.

• You do a pregnancy test and it is positive

This means there is hCG in your urine from a developing embryo. You do a second one a few days later and it is negative. The pregnancy has not been successful.

• You’ve had a positive pregnancy test but started bleeding soon afterwards

The positive test indicates that an embryo was present and producing hCG but there won’t be anything to see yet on a scan.

Chemical pregnancies happen so early in pregnancy that none of the typical symptoms of pregnancy such as nausea or breast changes have had time to start.

What causes chemical pregnancies?

The most usual explanation for a chemical pregnancy is a problem with the chromosomes in the developing embryo. The chromosomes contain the DNA (genetic code) and there can be abnormalities in this that prevent the pregnancy from progressing. Some women who have had chemical pregnancies, and of course want a healthy baby, take comfort from knowing this. This is usually a ‘one off’ event and doesn’t mean it will happen again. It is not something you could have done anything about.

There may be other factors that cause a pregnancy to end very quickly. This is an area of many unknowns and ongoing research. Possible factors include:

• Abnormal implantation

To develop properly, embryos need to implant into the wall of the uterus (womb). If they try to implant elsewhere, such as in the fallopian tubes then the pregnancy fails.

• Hormonal abnormalities

When hCG is released, it triggers a range of other hormones in the body to spring into action to support the pregnancy. If there is any problem in this chain, the pregnancy could end early.

• Uterine abnormalities

An embryo can be prevented from implanting and growing if the uterus is an abnormal shape. This is usually something that is present from birth. Not all women with uterine abnormalities have problems with pregnancy.

• Infections

Infections of the fallopian tubes or wall of the uterus could prevent an embryo moving and implanting. These include bacterial infections such as chlamydia.

• Medical problems

Certain medical conditions may make chemical miscarriages more likely such as those which affect blood clotting.

Who has chemical pregnancies?

Anyone can have a chemical pregnancy. We will never know the true number because large numbers of women are unaware they have had one. It’s possible that chemical pregnancies may be responsible for over 50 per cent of all miscarriages.

Pregnancy tests are increasingly sensitive so more women find out they are pregnant at a very early stage and therefore the number of chemical pregnancies is higher than in years gone by. Chemical pregnancies can happen with both normal and IVF pregnancies. They are more common in women over 35 years of age.

When should you see a doctor?

Bleeding in early pregnancy does not necessarily mean you are having a miscarriage and can happen in some normal pregnancies. But bleeding can sometimes be a sign of a serious problem such as an ectopic pregnancy where the foetus is growing outside of the womb which can be life threatening for the mother.

You should see your doctor if you know you are pregnant and have any vaginal bleeding, or you are pregnant and you have lower abdominal pains, particularly if they are low down on one side.

Chemical pregnancy treatment

Treatment isn’t usually needed for a chemical pregnancy. The pregnancy was at such an early stage that the body can resolve things on its own. You may have some bleeding and abdominal cramps and your period may be heavier than you’re used to but it may be completely normal too.

If you have had some unexpected bleeding and there is the possibility of a chemical pregnancy, your doctor or nurse may recommend that you do a follow up pregnancy test in a week to confirm that it is negative.

How you feel after a chemical pregnancy

There is no right or wrong way to feel after a chemical pregnancy and you might feel a range of emotions. Knowing you were pregnant and then discovering you weren’t can be devastating for some women, regardless of how many weeks pregnant they were. This can be particularly hard to cope with if you have been trying to get pregnant for a long time. It’s normal to feel grief and be very upset.

It’s equally normal to feel accepting and relieved that the pregnancy loss has occurred very early on rather than later in the pregnancy when the foetus is more developed and you have begun to make plans.

Some women are very matter of fact about it and able to put it behind them and move on with trying to conceive again. If you are struggling with how you are feeling, then do reach out and talk to someone.

Getting pregnant after a chemical pregnancy

Because most chemical pregnancies are thought to be due to chromosomal abnormalities of the embryo and happen randomly and as ‘one off’ events, this means it’s highly likely that next time you get pregnant, everything will be fine. There’s no need to delay trying for pregnancy again.

It is a very individual decision. You may not feel mentally ready and prefer to leave it for a while and that is OK. You may also choose to have a normal period before you try again but there is usually no medical reason to do this.

⚠️ If you have had three or more consecutive early pregnancy losses, speak to your GP about having some investigations to check for any reason why this may be happening.

Further help and support

For further help and support with anything related to chemical pregnancies try one of the following resources:

  • Samaritans: free, 24/7 emotional support to anyone in distress.

  • Tommy's: UK charity carrying out research into pregnancy loss.

  • Miscarriage Association: support for anyone affected by miscarriage, ectopic or molar pregnancy.

Last updated: 03-02-2021

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