“What are my chances of a miscarriage?”
This question plagued me as I was on my quest to find as much information as possible once I started experiencing what I thought were signs and symptoms of miscarriage.
There are several websites out there that claim to provide statistics of miscarriage, but how can you tell whether the information is reliable? The sample sizes of the studies are usually small and are structured to track only one variable. Also, these studies don’t appear to break down important factors like the mother’s age, how far along the pregnancy was, whether there was a confirmed fetal heartbeat, whether it was the mother’s first pregnancy or whether she had prior miscarriages to name just a few factors.
How common are miscarriages?
From what I could find online there are 3 primary studies that websites love to reference when talking about miscarriage statistics.
One study on the “Incidence of early loss of pregnancy“, followed 221 women who were attempting to conceive. To do this, they tracked hormone levels of each woman by collecting daily samples of urine. The study found that the total rate of pregnancy loss after implantation was 31%. 
If you take this study at face value, that means that about 1 in 3 pregnancies miscarry. Before you start to stress out over this number, keep in mind that this study population of women was confirmed to be pregnant at the scientifically earliest point in time to detect a pregnancy. Their urine was analyzed daily while they were attempting to conceive up until loss of pregnancy or labor. Most women find out that they are pregnant at a much later point in time (usually after a missed period) than those women who participated in this study. Keep in mind that the risk of miscarriage drops as the pregnancy progresses.
A study cited by UpToDate showed that up to 20% of women who know they are pregnant have a miscarriage before they reach 20 weeks of pregnancy. Of those, 80% of them occur in the first 12 weeks.  About Health claims that this is the most realistic statistic to go off of for the average pregnant woman. They state that “If you’re more than 5 weeks pregnant but still in the first trimester, this statistic is probably the most relevant one for you.”
Another study on the “Miscarriage risk for asymptomatic women after a normal first-trimester prenatal visit“, outlined the following conclusions based on a sample of 697 women.  The study found that women without symptoms who have had their first prenatal visit between 6 – 11 weeks has a 1.6% or less chance of miscarriage.
There are many additional studies that I came across which again, only analyzed a single variable or accounted for only a couple of variables. Unsurprisingly, all of the studies had mixed results regarding miscarriage statistics. Which leaves our initial question of “how common are miscarriages?” still, for the most part, unanswered.
Why is this important?
With so many studies out there with varying statistics, how can you tell what your chances really are of having a miscarriage? If this is your first pregnancy do you statistically fit into the same group as a woman who has miscarried before? What about if you are 10 years younger than another woman who miscarried?
What I think is missing from the majority of the studies that I came across is accounting for critical pieces of information. While this site references a bunch of miscarriage research statistics for studies that took into account a single factor that I mention below, what I find interesting is that there doesn’t seem to be a study that combines them all.
Some of the key factors that I think are worth taking into account are:
- Mother’s age
- Whether it was her first pregnancy
- Whether it was her first miscarriage
- How far along the mother was in her pregnancy before miscarriage
- Whether it was a single pregnancy or multiples
- Whether the mother had an ectopic pregnancy
- The father’s age
- The mother’s overall health and pre-existing conditions
- The mother’s risk factors such as smoking, drinking, or drug use during pregnancy
- Whether the mother was on any prescription drugs
That’s why I’ve tried to create a comprehensive questionnaire to poll women who have had a miscarriage. Not only will this take into account all of the variables mentioned above, but will also take into consideration signs and symptoms that a miscarriage was about to happen, what a mother experienced during the miscarriage, and what her symptoms were after the miscarriage.
Miscarriages are generally a topic that people don’t want to talk about or think about, and when it happens to a woman, she is left wondering whether it was her fault or something she had done. Together we can shed more light on this taboo topic and help inform women that they are not alone, and that what they are experiencing isn’t something abnormal.
If you have had a miscarriage, I implore you to take a few moments to fill out this questionnaire. The results will go a long way towards helping other women know what to expect and help make the process, should they be going through it, a little less frightening.
- Wilcox AJ, Weinberg CR, O’Connor JF, et al. Incidence of early loss of pregnancy. N Engl J Med 1988; 319:189.
- Togas Tulandi, MD, MHCM. Patient information: Miscarriage. UpToDate. Accessed: 28 December, 2015.
- Tong S, Kaur A, Walker SP, Bryant V, Onwude JL, Permezel M. Miscarriage risk for asymptomatic women after a normal first-trimester prenatal visit. Obstet Gynecol. 2008 Mar;111(3):710-4.