A Step Toward Understanding Miscarriage

A miscarriage is defined as the spontaneous loss of a fetus before the 20th week of pregnancy (1). The technical term for miscarriage is spontaneous abortion, which is a natural sequence of events not to be confused with medical abortions.  The miscarriage can be complete (all products of conception are expelled from the body), incomplete (products of conception are only partially expelled), or missed (none of the products of conception are expelled). In the case of incomplete and missed miscarriages, surgical intervention may be necessary to remove the products of conception to prevent infection from developing. An estimated that 15-20% of all pregnancies result in miscarriages, however, this number could be as high as 30% considering miscarriages that occur before a woman knows she is pregnant. The majority of miscarriages occur in the first seven weeks of pregnancy. The most common cause is chromosomal abnormality resulting in poor embryonic development. This is generally unrelated to any medical condition or any fault of the pregnant woman. Risk of miscarriage increases as women age and may increase for women who have previously miscarried, although this is not always the case (1).

It is interesting to me that although miscarriage is quite common, it still remains rather taboo. A woman is not likely to share this medical condition with others as she would any other medical diagnosis. Although overwhelming medical evidence indicates that most miscarriages cannot be predicted or prevented, a woman who miscarries may experience a great sense of guilt and feelings of inadequacy. Women may experience a strong sense of connection, even during very early pregnancy, in anticipation of a new life.  It may be hard for others, men and women alike, to understand how losing something that is no more than a cluster of cells or that looks like a jelly bean on a monitor can be so devastating.

According to a recent article published in PLoS ONE (2), 1–2% of women trying to conceive are diagnosed with Recurrent Miscarriage (RM) when they experience three or more consecutive miscarriages. While this can arise from genetic issues or uterine issues, no cause is identified for over 50% of these women. Experts in the field have struggled to understand if viable pregnancies are continually rejected, or if non-viable embryos are implanting, resulting in positive pregnancy tests, when these embryos would normally go undetected in women without RM. The article by Weimar et al., investigates the latter and hypothesizes that that the endometrial cells of women with RM allow both viable and non-viable embryos to implant.

[Refresher: Once a sperm fertilizes an ovum (generally in the fallopian tubes), the zygote travels to the uterus as it begins dividing into a mass of multiple cells. Once it reaches the uterus (in about 6–12 days), it implants into the endometrium, which is the tissue lining the uterine wall. Following implantation, human chorionic gonadotropin (hCG) begins to rise, which is the hormone detected by home pregnancy tests.] (3)

The study used endometrial biopsies from six women with RM and six women who have conceived without issue. These cells were cultured and monolayers were plated in close proximity to surplus cryopreserved embryos. Embryos were defined as high or low quality based on morphology and whether they had developed as expected. Endometrial cells from women with RM migrated towards both types of embryos, while endometrial cells from women who had not had issues conceiving only migrated toward the high-quality embryos. (Scroll to the bottom of the article to download a movie showing migration of endometrial cells (2)!)

BBC News Health (4) provided a synopsis of this study and quoted Professor Nick Macklon saying, “Many affected women feel guilty that they are simply rejecting their pregnancy. But we have discovered that it may not be because they cannot carry, [but] it is because they may simply be super-fertile…” While the theory investigated in this study may not explain all causes of RM, and will certainly not assuage the emotional turmoil, it may offer some comfort to women by dispelling feelings of inadequacy. In any case, it is one step closer to determining a cause for a common and emotionally devastating medical condition.


  1. Miscarriage – PubMed Health. 2010. Retrieved 21, 2012, from http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002458/
  2. Weimar CHE, Kavelaars A, Brosens JJ, Gellersen B, de Vreeden-Elbertse JMT, et al. (2012) Endometrial Stromal Cells of Women with Recurrent Miscarriage Fail to Discriminate between High- and Low-Quality Human Embryos. PLoS ONE 7(7): e41424. doi:10.1371/journal.pone.0041424
  3. Implantation (human embryo). (2012, September 1). In Wikipedia, The Free Encyclopedia. Retrieved 06:32, September 21, 2012, from http://en.wikipedia.org/w/index.php?title=Implantation_(human_embryo)&oldid=510231136
  4. Gallagher, J. (2012, August 23). Super-fertility offers clue to recurrent miscarriage. BBC News – Health. Retrieved from http://www.bbc.co.uk/news/health-19361432
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Karen Reece

Senior Research Scientist at Promega Corporation
Karen is a Senior Research Scientist in Nucleic Acid Technologies at Promega. She has a BS in Biochemistry and MS and PhD in Physiology, all from University of Wisconsin-Madison. Karen was born and raised in Madison, WI and every time she would think of moving away something would come up, so she just decided to stay. When she’s not doing research and/or development, Karen enjoys the local music scene (particularly Hip-Hop), playing the cello and singing, and fighting for social justice.

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