What Chemical Pregnancies Indicate

woman with stomach pain

Unless you are going through fertility treatment, and are being closely monitored for conception, you may be unfamiliar with the terms “chemical pregnancy” or “clinical pregnancy”.

What is a Chemical Pregnancy?

A chemical pregnancy–also known as a “biochemical pregnancy”– describes a miscarriage that is so early that it happens before or around your expected period, which means it’s possible to have one without knowing it.

When a sperm and egg unite and the resulting embryo starts to grow, cytotrophoblast cells in the placenta manufacture and secrete human chorionic gonadotropin (hCG), a hormone.

“Measuring this hormone in a woman’s blood or urine is the first documentation of a pregnancy,” says Dr. Carl Herbert, a reproductive endocrinologist and fertility specialist at Pacific Fertility Center in San Francisco.

The volume of hCG increases as the number of placental cells increase. During the first several weeks of a pregnancy, the value of hCG in a woman’s blood should approximately double every 48 hours. This “doubling time” can help in early diagnosis of an eventual miscarriage or an ectopic pregnancy.

Herbert notethat hCG comes from placental cells, not fetal cells. This means that hCG values can rise normally for a period of time after conception, even if the fetus does not grow.

“A conception, which has measurable hCG but does not develop far enough to be seen on an ultrasound, is considered a ‘chemical’ pregnancy,” notes Herbert. “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,” he adds.

What’s the Difference Between a Chemical Pregnancy and a Clinical Pregnancy?

If a pregnancy is not viable, the hCG levels don’t double in the 48-hour period as it should. This is true of all miscarriages.

In a clinical pregnancy, once it’s 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 as a ‘clinical pregnancy,’” Herbert says.

Are Chemical Pregnancies a Sign of Other Fertility Issues?

“The inability of a pregnancy to progress from a chemical to a clinical pregnancy may be related to either the embryo itself or the uterine environment,” Herbert says.

An embryo that has chromosome abnormalities may have limited potential to grow, and will stop developing quite early in a pregnancy. This can happen in a woman at any age, but is more likely to occur in her late 30s and beyond.

“A chemical pregnancy might also occur because the uterus or endometrial lining is inadequate to support full pregnancy development,” Herbert says.

A chemical pregnancy from natural conception documents the ability of the sperm to fertilize an egg and early embryo attachment, or implantation. In fertility treatments, fertilization occurs in a lab and is transferred to the uterus. A chemical pregnancy will document early embryo attachment.

What Conditions May Cause Chemical Pregnancy?

Conditions that may be related to early pregnancy failure and lead to chemical pregnancy include:

  • uterine fibroids
  • congenital uterine malformations such as uterine septums
  • endometrial polyps
  • hormonal abnormalities which create luteal phase defects (i.e., poor endometrium development)

What Role Does the Sperm Play in a Chemical Pregnancy?

“There remains significant controversy and inadequate scientific knowledge about the effect of sperm quality on embryo quality and implantation,” Herbert says. “However, it is possible that sperm or male factor infertility could contribute to the production of chemical pregnancies which do not progress normally.”

How Does a Chemical Pregnancy Affect Future Pregnancies?

A chemical pregnancy from natural conception documents the ability of the sperm to fertilize an egg and early embryo attachment, or implantation.

In fertility treatments, fertilization occurs in a lab and is transferred to the uterus. A chemical pregnancy documents early embryo attachment.

If you conceive naturally but have a chemical pregnancy, you should be evaluated for a possible cause, including the conditions mentioned above.

“However, if the evaluation does not reveal an obvious cause, the likelihood of success in the subsequent pregnancy is quite high,” Herbert said.

If you’ve experienced a chemical pregnancy through fertility treatment, are over 38 years old, and have known egg compromise, the outlook for future success may be somewhat decreased.

“While achieving even a chemical pregnancy can in some ways reassuring — the eggs and the sperm are getting together — repeated loss definitely should trigger a full evaluation of the couple,” Herbert says.

Dr. Alan Copperman is a board-certified reproductive endocrinologist and infertility specialist with a long history of success in treating infertility and applying fertility preservation technologies. He serves as Medical Director of Progyny, a leading fertility benefits management company, and co-founded and serves as Medical Director of RMA of New York, one of the largest and most prestigious IVF centers in the country.  Dr. Copperman is also the Vice Chairman and Director of Infertility for the Icahn School of Medicine at Mount Sinai, and Chief Medical Officer of Sema4, a health information company. Dr. Copperman has been named to New York magazine’s list of Best Doctors 17 years in a row. He has been recognized by his peers and patient advocacy organizations for his commitment to patient-focused and data-driven care. He has published more than 100 original manuscripts and book chapters on reproductive medicine and has co-authored over 300 scientific abstracts on infertility, in vitro fertilization, egg freezing, ovum donation, and reproductive genetics.