Spontaneous pregnancy loss prior to 20 weeks gestation occurs in over 15% of conceptions. The early loss of a once viable fetus is also referred to as spontaneous miscarriage or spontaneous abortion.
In many spontaneous miscarriages, women are not even aware they were pregnant, hence the uncertainty and undercounting in the frequency of spontaneous abortions.
“Recurrent pregnancy loss” is now defined as two or more spontaneous miscarriages ending a pregnancy prior to 20 weeks from the last menstrual period. While only a few percent of women experience recurrent pregnancy loss, its exact frequency and causes remain hard to pin down.
Drawing on the 2009 paper “Recurrent Pregnancy Loss: Etiology, Diagnosis, and Therapy,” the most common causes of spontaneous miscarriage and pregnancy loss, in rough order of frequency, include:
- Endocrine and metabolic disorders including diabetes, thyroid disease, and luteal phase (the last phase of the menstrual cycle) defects;
- Anatomic abnormalities that interrupt blood flow in the uterus, such as intrauterine adhesions, and uterine fibroids and polyps;
- Unexplained environmental etiologies including exposures to chemicals, organic solvents, radiation, and other toxicants; and
- Genetic factors such thrombotic mutations.
The Heartland Study will shed new light on the contribution of prenatal herbicide exposures to spontaneous miscarriage rates, and pioneer methods to link chemical exposures to epigenetic changes.
Research has linked herbicide exposure to increased risk of spontaneous miscarriage, including for glyphosate, the # 1 herbicide in the U.S. and the world that is widely applied throughout the Midwest. We summarize some key studies below, or access all relevant records in our bibliography here.
- From 1999-2002, a trio of epidemiological studies were released that looked at the rate of spontaneous miscarriages among farm families. Two (Arbuckle et al., 1999 and Arbuckle et al. 2001) analyzed data from the Canadian Ontario Farm Family Health Study, and found increased miscarriage rates following preconception exposure to some herbicides (phenoxy acetic acid herbicides, glyphosate, and thiocarbamates.) A third study of farmers from Minnesota’s Red River Valley (Dr. Vincent Garry’s key paper from 2002) found a “modest but significant increase in risk for miscarriages” for women whose spouses applied fungicides and herbicides, and for women who were were directly engaged in pesticide application.
- Two more recent papers by Medardo Avila-Vasquez point out that agricultural communities in Argentina with high glyphosate application rates have dramatically increased rates of miscarrage and other health problems. See Avila-Vasquez et al., 2015 and Avila-Vasquez et al., 2018 for the details.