Illustration by Katrin Friedman
What causes a miscarriage?
Miscarriage: It’s more common than you think
Article originally published on July 1, 2016.
*Miscarriage is sometimes referred to as "spontaneous abortion." We've also written about what to expect before during and after an induced abortion.
Miscarriage is a common part of the reproductive cycle (1). A miscarriage can be a very difficult experience for some people, for others, it can be a relief. Understanding why and how frequently miscarriage occurs can help people process the experience.
Why does miscarriage happen?
Most miscarriages happen for the same reason that most fertilized eggs do not lead to pregnancy — chromosomal abnormalities (1). This is when there is something unexpected in the genes of the egg, the sperm, or in the two together. These variabilities are usually caused by typical, random errors that happen when cells divide — not because there is a larger problem in the genes of either parent. Miscarriage prevents these chromosomal differences from becoming developed pregnancies (2).
Between 5 and 7 of every 10 early miscarriages are caused by chromosomal abnormalities in the embryo (3, 4).
Occasionally, a miscarriage can also be caused by a medical condition in the pregnant person. This can be a hormonal condition such as polycystic ovary syndrome (PCOS), a thyroid disorder, or a physical issue in the uterus, from conditions like uterine fibroids or endometriosis (5-8). Some other risk factors for miscarriage include older age for either parent, previous miscarriage, assisted conception, frequent, high alcohol intake (more than 14 drinks a week), and stress (9, 10).
After an early pregnancy stops developing, the inner tissue of the uterus, along with any new tissue that has grown, usually sheds by itself via the vagina (11). By the time bleeding occurs, the pregnancy has already ended, meaning an early miscarriage cannot be “stopped” by stopping bleeding or cramping (11).
The majority of people who've had one, two, and even three unexplained miscarriages can go on to have a healthy pregnancy (12, 13).
How common are miscarriages?
Miscarriage occurs in up to 1 in 5 detected pregnancies (14). The miscarriage rate is closer to 1 in 3 when accounting for undetected pregnancies (15-17). Miscarriage is not caused by the actions, behavior, or even the body of the pregnant person in the majority of cases.
Despite this, there is still a lot of confusion, silence, and misinformation around the topic. Understanding what miscarriage is and why it happens is an important step in removing the stigma around it.
A late period may actually be a miscarriage
A miscarriage is a pregnancy that ends in the first 20 weeks, but most happen within the first eight weeks (18). Miscarriage can even happen before a pregnancy is detected (2).
In people having unprotected intercourse, it is not uncommon for an irregular cycle to be due to a miscarriage before someone even knows they are pregnant (2, 17, 19).
Because a miscarriage can happen around the same time someone expects their period, it can be mistaken for menstruation (2).
Not all fertilized eggs lead to pregnancy
When a sperm meets an egg in the fallopian tube, it can become fertilized. If this happens, the fertilized egg then grows and develops a bit, before it can implant in the uterus (2). Many fertilized eggs don't make it past this stage — they don't start to develop at all, or they cannot implant (2). In these cases, a person doesn't become pregnant and the menstrual cycle continues as usual.
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You can be fertile immediately after a miscarriage
It can take anywhere from a few hours to several weeks for the blood and tissue from a miscarriage to completely expel from the uterus (20). If a miscarriage happens within the first eight weeks of pregnancy, it usually takes 4–6 weeks for menstruation to return (20). It is possible to be fertile again immediately after a miscarriage, meaning a person can become pregnant even before their menstruation returns (20).
Emotions can vary after miscarriage
Up to 1 in 2 people will experience significant emotional symptoms in the weeks and months following a miscarriage (21). Anxiety, sadness, grief, and depression are common feelings that can last weeks or months (21). Other people may feel relief if they did not wish to be pregnant.
Acknowledging a painful loss can be a helpful tool in emotional recovery (22).
Some people who experience miscarriage will need to seek out help for strong emotions that last, and become overwhelming.
Knowing your options can help
Most miscarriages do not necessarily need intervention and can be medically managed with a process called "watchful waiting" (11, 23, 24). Some people may choose intervention to have some control over the experience, and/or they would like it to be over more quickly. Others may have an intervention because they are at risk of a complication, or because a miscarriage didn't complete on its own. Depending on timing, interventions include an aspiration procedure to remove the uterine contents, or a pill to help shed it more quickly (11).
Contact a healthcare provider if you think you may be having a miscarriage. They will ask you some questions and make sure everything is okay. Some people may need a blood test. In certain cases a miscarriage doesn't complete on its own, requiring treatment. If you experience sharp pain, dizziness, fever, or shoulder pain, see your healthcare provider or go to the emergency room to rule out complications like ectopic pregnancy.
Tracking bleeding patterns and other symptoms with Clue during and/or after a miscarriage can help provide a record of how things are changing. It may also help spot when something might be off, or when a miscarriage may need further treatment. If you are concerned about your cycle or any symptoms, talk to a healthcare provider.
Remember, you can make sure a miscarriage (or other unexpected cycles) won't affect Clue's predictions (and your statistical averages) by later on.
Understanding how common miscarriage really is, and why it happens, can help to shape and inform decision-making and emotional processes. And the more we can talk about miscarriage, the more we will break down problematic cultural stigma.
Download Clue to learn more about your period and keep track of changes.
