What is a chemical (or biochemical) pregnancy? How is it different from a clinical or regular pregnancy? How can you be a little bit pregnant?

A chemical pregnancy occurs when an embryo does not implant properly. The embryo produces enough HCG (human chorionic gonadotropin, the molecule which is unique to pregnancy) so that it can be detected on the beta HCG blood test and the sensitive uterine pregnancy home tests (hence its name, because it can be detected using chemical tests), but because it does not develop normally, the HCG levels decline. No pregnancy sac can be seen on ultrasound scanning. It is a very early miscarriage and is a type of non-viable pregnancy. It needs to be differentiated from a clinical pregnancy (when a scan can be seen on ultrasound scanning; and an ectopic pregnancy). A chemical pregnancy leaves the couple to cope with the difficult news of thinking they are pregnant when in reality they are miscarrying.

Signs and Symptoms of a Chemical Pregnancy

Most women have no symptoms at all. There may be mild abdominal cramping as well as mild spotting just prior to what most women think is their normal menstrual cycle. The menstrual cycle usually begins on time or a few days late. Nature is not efficient at making babies, and modern research shows that the vast majority of fertile women who have a chemical pregnancy never even knew they were pregnant before they begin what they think is their normal menstrual cycle.

Causes of a Chemical Pregnancy

The commonest cause is a genetic abnormality in the embryo, and nature prevents this abnormal embryo from developing any further. Genetic abnormalities can be because of multiple factors, but most of them are random and unpredictable.

Treatment of a Chemical Pregnancy

No specific treatment is required for a chemical pregnancy. The most important follow-up test is to ensure that the hCG levels decline to zero (non-detectable levels ) after a chemical pregnancy (in order to differentiate it from an ectopic pregnancy). There is no impact on future pregnancies and the prognosis for future fertility remains good.

The most difficult aspect of a chemical pregnancy is a false hope that it creates - you get excited that you are finally pregnant - and then you have to deal with the crushing disappointment of having to cope with a miscarriage. For many couples, this can be the last straw that breaks the camel's back. They often find it easier to deal with a negative HCG result; rather than a result which starts of offering hope by being positive, and then declines.

The commonest question patients ask after a chemical pregnancy is - Why did this happen? Did I do something to harm the embryo? Does this mean I am never destined to have a baby? Does this mean my uterus is defective and is rejecting the baby? None of this is true! The fact that the HCG was positive means that the embryo implantation process did start, and this means that the prognosis for a healthy pregnancy in the future is actually better than for someone with a negative HCG!

You should wait for at least one regular menstrual cycle before trying to conceive again after a chemical pregnancy.

Authored by : Dr Aniruddha Malpani, MD and reviewed by Dr Anjali Malpani.

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