Jun 22 2009

Chemical Pregnancies

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Have you ever had a late period and noticed that your flow was slightly different, maybe a bit heavier when it finally arrived? Perhaps your breasts felt more tender than usual. Or perhaps you had a positive result on a pregnancy test only to have a negative one a few days later?

If you answered yes, then there is a chance you may have had a chemical pregnancy.

The word pregnancy does not carry its normal meaning in this article. In this article it indicates an fertilized egg which is not implanted in the uterine wall.

When the egg gets fertilized by a sperm, it forms a hard barrier around it to prevent other sperm from entering. The egg and sperm DNA merge to form a Cygote. The Cygote keeps on moving down the fallopian tube on its way to the uterus. After 2 days the Cygote divided to form a clump of 16 cells called a Morula. The Morula keeps on moving towards the uterus and dividing to form a Blatocyst within 4 to 5 days after fertilization. The Blatocyst contains 2 compartments, one for the cells that will become the placenta and one that will become the fetus. When the Blastocyst finally gets ejected from the fallopian tubes into the uterus its got some enzymes at the placenta end of the Blastocyst. These enzymes will melt the uterus lining and allow the Blatocyst to bury itself into the blood and nutrient rich uterus lining and attach itself to the uterus where it will become an embrio and grow into a fetus by week 7.

What is a Chemical Pregnancy?

A chemical pregnancy occurs when a fertilized egg (Blastocyst) does not implant into the uterine wall.  If a pregnancy test is taken just at the right time it will be positive, however, when a repeat test is taken several days later it will be negative. 

The vast majority of women who have a chemical pregnancy never know they conceived before their bodies eject the fertilized egg (Blastocyst) and begin what they think is their normal menstrual cycle a little bit late. It is thought that about 50% fertilized eggs end up as chemical pregnancies.

What Causes a Chemical Pregnancy?

The true cause of a chemical pregnancy is not known, however, it is believed that it is due to abnormal chromosomes or other problems within the fertilized egg. These chromosomal abnormalities can be due to several factors including poor quality sperm or egg, abnormal cell division of the fetus, and / or genetic abnormalities of either mother or father.  Even after the fertilized egg implant, it is thought that approximately 50% to 60% of first trimester miscarriages are due to some type of chromosomal abnormality.  Other causes of a chemical pregnancy are thought to be related to

  • Infections like Chlamydia, Cytomegalovirus, Genital herpes, Syphilis, Toxoplasmosis, and Rubella),
  • Abnormal uterine anatomy (ie. unicornate uterus or septate uterus)
  • Abnormal hormonal levels within the mother (ie. low progesterone)
  • Systemic illnesses (ie. untreated thyroid disease)

Signs and Symptoms of a Chemical Pregnancy

Due to the fact that in a chemical pregnancy a fertilized egg does not implant into the uterus most women do not experience signs and symptoms of pregnancy (ie. tender breast, nausea, and / or fatigue).  There are a few reports of women who have been pregnant in the past who state that they felt pregnant with their chemical pregnancy.  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.


Because the majority of women never knew that they had a fertilized egg that attempted to implant or does not experience anything other than a slightly abnormal mestruation, it is common to not be aware that you are pregnant or have experienced a miscarriage, it is unlikely that you will schedule an appointment with your health care provider for follow-up.

Women who were aware of the pregnancy should have the pregnancy followed to ensure that their hCG levels go down until they produce a negative pregnancy test. Due to the possibility of the pregnancy being an ectopic pregnancy, it is necessary to ensure that a full miscarriage has occurred, even if a woman has had a period.

If an infection is deemed to be the reason for your chemical pregnancy, sometimes antibiotics can be prescribed. This can clear up the infection, helping you to avoid repeated chemical pregnancies.

Future Pregnancies

In general, a chemical pregnancy should not interfere with your ability to become pregnant. However, if you are having recurrent chemical pregnancies, you may want to have the issue investigated by your health care provider.

To help you avoid future miscarriages due to a chemical pregnancy, you may be prescribed vitamin B6, progesterone cream or possibly baby aspirin. While these remedies are not guaranteed to prevent a chemical pregnancy, they may help to lower your risk.

There is no specific treatment that is required for a chemical pregnancy.  The most important follow-up test is to ensure that the women’s hCG level has returned to non-detectable levels after a chemical pregnancy.  There is no impact on future pregnancies and the majority of women become pregnant and deliver without difficulty.  The most difficult aspect of a chemical pregnancy is coping with the excitement of being pregnant and then the realization that you are now coping with a miscarriage.  If a couple has experienced several early miscarriages (2-3) there is genetic counseling available through their physician.  To learn more Go to Treatment of Miscarriage.

It is recommended that a couple wait at least one regular menstrual cycle before trying to conceive again after a chemical pregnancy.

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