To get an understanding of what a chemical pregnancy is, exactly, it's helpful to look at what happens to the body immediately following conception.
"When a sperm and an egg unite and the resulting embryo starts to grow, special cells known as cytotrophoblast cells (the placenta) manufacture and secrete pregnancy hormone (human Chorionic Gonadotropin_hCG)," Dr. Herbert explains. “Measuring this hormone (hCG) in a woman’s blood or urine is the first documentation of a pregnancy. As the number of placental cells increases, more hCG is secreted. Using quantitative measurements of blood hCG values, one can estimate the health and viability of an early pregnancy. During the first several weeks of a pregnancy, the value of hCG in a woman’s blood should approximately double every 48 hours. This is known as the “doubling time” and can help in the early diagnosis of an eventual miscarriage or an ectopic pregnancy. Remember, hCG, i.e., pregnancy hormone is derived from placental cells, not fetal cells. Therefore, if the placenta grows but the fetus does not, the hormone values may remain normal for a period of time."
So if a pregnancy is not viable, the hCG levels don't rise within a 48 hour period as they should. If that's true of all miscarriages, what is the difference between a chemical pregnancy and a clinical pregnancy?
"Once a pregnancy has progressed to about five weeks gestational age, the embryonic sac becomes visible on ultrasound examination. After the sac is seen on ultrasound, the pregnancy is labeled a “clinical” pregnancy. A conception, which has measurable hCG but does not develop far enough to be seen on an ultrasound, is considered a “chemical” pregnancy. Therefore, all chemical pregnancies are, by definition, unsuccessful and the only evidence that an early pregnancy existed is the measurement of hCG in a woman’s blood or urine."
Because chemical pregnancy occurs early in a pregnancy, women may not even realize that they’ve conceived when they experience a chemical pregnancy.
Light spotting or bleeding following a positive pregnancy test can be signs of pregnancy rather than a miscarriage.
However, the following may be signs of a chemical pregnancy:
Call your doctor immediately if you have heavy bleeding and/or cramping after a positive pregnancy test.
Experts are unsure what causes a chemical pregnancy, but most believe it happens for the same reasons other miscarriages happen — abnormal chromosomes in the developing embryo. Abnormal chromosomes can be the result of many factors, such as poor quality of the sperm or egg, genetic abnormalities passed down by the mother or father, or an abnormal cell division of the fetus. Experts believe half of all chemical pregnancies are due to some form of chromosomal abnormality. Additional potential causes may include:
According to the American Pregnancy Association, approximately 50 to 75 percent of all miscarriages are chemical pregnancies. The reason for this variable percentage is that it can be hard to track. Women who are not actively trying to conceive and not closely watching their menstrual cycles may have chemical pregnancies and never know it. In other cases, chemical pregnancy could be a reason (but not the only possible reason) why a menstrual period arrives a few days late.
Chemical pregnancies happen early enough that they have little effect on women’s bodies, and in many cases, they can be mistaken for a normal period that is a few days late (or even on time).
While the bleeding from a chemical pregnancy may be accompanied by more cramps than usual, recovery should be fairly swift.
Although very early pregnancy losses usually don’t require medical intervention, make sure to visit your practitioner if you think you’ve experienced one; she may be able to confirm if that’s the case depending on how far along you were in the pregnancy and how recently you lost it.
If you’ve been trying to get pregnant for a few months, sometimes have late periods and are concerned that they might actually be chemical pregnancies, talk to your doctor.
Going through one or two chemical pregnancies can feel devastating, but it’s not cause for alarm. If you have three in a row, your doctor may want to run tests to rule out any medical problems that may be causing them before sending you to an infertility specialist. If a health condition is contributing to your chemical pregnancies, most can be treated so you can go on to conceive a healthy baby. Which means as soon as you’re ready, you can start trying again.
verywell.com, whattoexpect.com, everydayhealth.com, madeformums.com, pregnancycorner.com,