Miscarriage: Data from scientists that may change what you know about it
By Daniel Rappolee, PhD
I have two brothers and I am the middle child. My mother suffered a miscarriage between me and my younger brother, which she attributed to heavy fumes from lead-based paints at a new house shortly before the miscarriage. Many women have suffered through miscarriage, and speculations on causes are called “anecdotes” in science. But science is systematic and requires larger epidemiological associations between hypothetical causes and events of miscarriage. These data are remarkably hard to get.
But there is a persistent problem of obtaining funding and getting miscarriage data. Despite poor funding, the scope of the issue is immense. The Fertility and Infertility Branch of the National Institute of Child Health and Development (NICHD) recently posted that miscarriage occurs in 70% of fertilized embryos and their Strategic plan #2 is studying miscarriage mechanisms (https://www.nichd.nih.gov/about/org/der/branches/fib).
This gap of knowledge should be compared with our knowledge of sperm, where number and quality have been quantified for nearly a century. The first human sperm counts in the US were recorded in 1934, and 50-year reviews occurred 30 years ago (Carlsen et al., 1992). The conclusions were that sperm counts have dropped precipitously, from 113 to 66 million/small volume, suggesting environmental influence. In contrast, access to human embryos and oocytes is very low, but screening toxicant effects on pluripotent stem cells acting as proxies for embryos can predict miscarriage in humans.
Have miscarriage rates increased in the last 50 years and what are the environmental causes of higher miscarriage? Since the first in vitro fertilization (IVF) birth in 1978 (Steptoe and Edwards, 1978), and the production of accurate tests for early pregnancy hormones by 1988 (Wilcox et al., 1988), scientists reported early miscarriage rates. To this day most Google searches for “miscarriage” cite only a 10% miscarriage rate of later gestation fetuses that endanger maternal health and are easily detectable. Because 70% of miscarriage occurs in early pregnancy, detectable only recently, questions on environmental causes or associations with miscarriages are surprisingly hard to answer.
How do we get data on oocyte and embryo number and quality? Environmental influences are being studied by zip code level measurements of environmental pollutants and their associations with miscarriage. Cell phone apps measure urban stresses telemetrically and test for their association with miscarriage. One telephone app detects loud noises associated with increased stress hormones. In animal models, cortisol slows growth of early pregnancy embryos that may contribute to miscarriage (Puscheck et al., 2015), and cortisol can sensitize rodents to environmental toxicants, increasing embryo loss.
In controlled studies in animal models like rodents, the maternal stress hormone cortisol exacerbates embryo loss caused by environmental pollutants such as BPA (Borman et al., 2015) when both stress stimuli are applied to normal females after fertilization. Thus, BPA and cortisol exacerbate loss of normal embryos. Current studies in our lab will test whether stress hormone levels in women in early pregnancy during the first trimester, when almost all miscarriages occur, exacerbate cellular changes which would lead to miscarriage induced by environmental pollutants.
Our project started over 15 years ago, with stress effects on early post-fertilization mouse embryos in IVF culture, and their component embryonic and placental trophoblast stem cells (ESC and TSC, respectively). Our lab developed an in vitro approach 8 years ago using high throughput screens (HTS) in stem cells to test for environmental and hormonal stresses that may cause miscarriage or birth defects.
During early pregnancy when most miscarriages occur, the embryo is simple. Soon after fertilization, the embryo is composed only of ESC and TSC. We use ESC and TSC with viable status reporters of stemness/differentiation/cell cycle status to report time and dose-dependent effects of stress hormones (cortisol), toxicants (phthalates, PFAS) and drugs (e.g., aspirin, retinoids) in HTS to test many single and mixed stress effects. For a small toxicant set, initial studies suggest that TSC are more sensitive and differentiate more stem cells than ESC (Puscheck et al., 2022). We will test this hypothesis on a larger set of environmental and hormonal stressors.
Understanding stress effects during pregnancy could be used to inform risk assessment decisions to make policy changes and increase pre- and postnatal health. It seems likely that embryos surviving this period of immense loss and miscarriage may survive some exposure to stress. Thus, a second important aspect of research on this development period is to understand the exposures and types of stress that do not cause embryo loss but cause stress that leads to postnatal effects. The 70% embryo loss is a massive issue to understand for environmental causes, but the 30% surviving embryos (e.g., many that developed and may be reading this blog!), are unlikely to have traversed early development without making some developmental (lineage imbalance) and epigenetic adaptations that affect health.
Birth defects, epidemiology, and associated and causal findings in animal models, is a large international research endeavor. Due to inaccessibility and the focus of funding on surviving embryos (offspring), the area of miscarriage research is remarkably small. But this is likely to change. The recent Dobbs decision overturning Roe vs. Wade may bring new focus on early embryo health. There is an interest in what may cause embryonic death and long-term pre- and postnatal effects on the health of offspring when embryos survive the miscarriage period.
About the Author
Dr Rappolee received a bachelor’s degree at University of California, Santa Barbara (UCSB), a doctorate at University of California, San Francisco (UCSF), and has been on faculty at Northwestern University and Wayne State University (WSU). Dr. Rappolee’s lab, at WSU Medical School in midtown Detroit, MI, investigates the effects of stress on early embryonic development and how this affects the efficacy of fertility treatments clinically, and miscarriage and birth defects toxicologically. His lab’s goal is to make healthier babies.
Dr. Rappolee and his lab have had many collaborators. Dr Elizabeth Puscheck and Dr. Niyi Awonuga at WSU have helped with IVF stress effects during the miscarriage period. Dr. Ali Faqi, past head of Developmental and Reproductive Toxicology (D.A.R.T). at MPI Research, introduced them to the field of Developmental Toxicology. Advice from Dr. Tom Knudsen at the Environmental Protection Agency/National Center for Toxicogenomics/National Center for Computational Toxicology (EPA/NCT/NCCT), Josh Robinson at UCSF, and Dr. Doug Ruden at WSU advanced their studies. Dr. Hao Feng at Case Western Reserve University helped with scRNAseq “stress fingerprints”.
About the Society for Birth Defects Research and Prevention
Healthy pregnancies. Healthy babies. Better lives.
The mission of the Society for Birth Defects and Prevention (BDRP) is to understand the cause and pathogenesis of disorders of developmental and reproductive origin to prevent their occurrence and improve outcomes through research, collaboration, communication, and education.
BDRP is a multidisciplinary society of scientists from a variety of disciplines including researchers, clinicians, epidemiologists, and public health professionals from academia, government, and industry who study birth defects, reproduction, and disorders of developmental origin. Our members include those specializing in cell and molecular biology, developmental biology and toxicology, reproduction and endocrinology, epidemiology, nutritional biochemistry, and genetics, as well as the clinical disciplines of prenatal medicine, pediatrics, obstetrics, neonatology, medical genetics, and teratogen risk counselling.
BDRP convenes an annual scientific meeting annually where members and others share their research, gain new knowledge and continuing education, mentor the next generation of researchers in the field, and network. The Society publishes the peer-reviewed scientific journal, Birth Defects Research. Learn more at http://www.birthdefectsresearch.org. Find BDRP on LinkedIn, Facebook, Twitter and YouTube.
References
Borman, E. D., Foster, W. G., Greenacre, M. K. E., Muir, C. C. and deCatanzaro, D. (2015). Stress lowers the threshold dose at which bisphenol A disrupts blastocyst implantation, in conjunction with decreased uterine closure and e-cadherin. Chemico-Biological Interactions 237, 87–95.
Carlsen, E., Giwercman, A., Keiding, N. and Skakkebaek, N. E. (1992). Evidence for decreasing quality of semen during past 50 years. BMJ 305, 609–613.
Puscheck, E. E., Awonuga, A. O., Yang, Y., Jiang, Z. and Rappolee, D. A. (2015). Molecular biology of the stress response in the early embryo and its stem cells. Adv Exp Med Biol 843, 77–128.
Puscheck, E. E., Ruden, X., Singh, A., Abdulhasan, M., Ruden, D. M., Awonuga, A. O. and Rappolee, D. A. (2022). Using high throughput screens to predict miscarriages with placental stem cells and long-term stress effects with embryonic stem cells. Birth Defects Res.
Steptoe, P. C. and Edwards, R. G. (1978). Birth after the reimplantation of a human embryo. Lancet 2, 366.
Wilcox, A. J., Weinberg, C. R., O’Connor, J. F., Baird, D. D., Schlatterer, J. P., Canfield, R. E., Armstrong, E. G. and Nisula, B. C. (1988). Incidence of Early Loss of Pregnancy. New England Journal of Medicine 319, 189–194.
