Between 10% and 15% of pregnancies end in miscarriage. The risk of miscarriage is highest in the early weeks of pregnancy, when women may not know they are pregnant and a miscarriage could be mistaken for a late menstrual period.
Since the 1970s, prenatal care has significantly improved and home pregnancy tests have become widely available, allowing women to quickly and easily confirm their pregnancy without having to see a doctor. While improved prenatal care could lower miscarriage rates, earlier detection of pregnancy could increase reported miscarriages. Scientists supported by the Population Dynamics Branch analyzed how reported miscarriage rates may have been affected by these changes from 1970 to 2000.
The researchers found that rates of reported miscarriages increased by about 1% per year. The greatest increase occurred in the first 7 weeks of pregnancy, and there was no increase in reported miscarriages after 12 weeks of pregnancy. Additionally, although highly educated women were typically more likely to have access to prenatal care, women at higher education levels were more likely to report miscarriages.
Taken together, these two findings suggested that the use of home pregnancy tests may have increased the awareness of otherwise unnoticed pregnancies, leading to more miscarriages being reported.
The study also showed that although many health outcomes are worse for African American and Hispanic women, these groups had a lower risk of miscarriage than did white women, especially during early pregnancy. These findings suggest possible differences in either knowledge of pregnancy-related symptoms or use of home pregnancy tests.
Therefore, researchers should consider awareness of pregnancy and knowledge about reproduction when analyzing older data related to pregnancies and miscarriages (PMID: 22718315).