Truths About Causes of Miscarriage

A Reality Check for Common Claims About Miscarriage

People hear a lot of things about what does and does not cause miscarriages, and much of the information available is confusing at best and harmful at worst. The truth is that while some miscarriages have a known cause, most don't and experts still don't fully understand all the complexities of pregnancy loss. Often, what research reveals are miscarriage risk factors, or things that are correlated with miscarriage and may increase a person's risk of experiencing one.

But it's important to note that correlation is not necessarily causation, meaning that while something might be associated with miscarriage, it does not necessarily cause it. Here is what the research tells us.

There Is No Evidence That Video Display Terminals Cause Miscarriage

There was one study in the 1980s that found an increased risk of miscarriage in women who used video display terminals for a lengthy period of time on a regular basis. But subsequent research has not found a link between video display terminals and miscarriage.

It's been noted that there are potential biological effects associated with electromagnetic fields that raise some concern over their role in miscarriage, but the lack of data does not reveal any clear causal link.

Abortion Doesn't Increase Risk of Miscarriage in Future Pregnancies

While there are a couple of studies that have suggested an increased risk of miscarriage in people who had previously terminated a pregnancy, the evidence overwhelmingly indicates that elective abortion is safe and not linked to future pregnancy loss.

Any increased risk of future miscarriage appears to be limited to people who experienced post-surgery complications such as severe infection or uterine scarring after a surgical abortion via dilation and curettage (D&C). And there is no evidence that medical abortion, or an abortion using medications rather than surgery, is associated with future miscarriages.

In fact, a large study published in The New England Journal of Medicine found that elective medical abortion was not associated with any increased risk of subsequent miscarriage.

Severe Stress May Increase Miscarriage Risk, But it's Complicated

There is some evidence that stress during pregnancy may elevate miscarriage risk. There have been several studies that found evidence of a link between stress and miscarriage or stillbirth, although the evidence doesn't prove that the stress is what caused the miscarriages in those cases.

It is very difficult to evaluate the role of stress in miscarriage, and while many studies have investigated this relationship, the answer is still unknown.

Everyone experiences stress. It's important to note that we all process stress differently. For example, one person may feel "very stressed" by relatively minor stressors, while another may feel only "moderately stressed" when faced with greater obstacles.

That said, there is some biological evidence pointing towards the role of stress in miscarriage. Stress leads to the release of "stress hormones" such as cortisol in the body. Elevated cortisol levels, in turn, have been associated with an increased risk of miscarriage in some studies.

Looking at population studies, ordinary stress has not often been associated with an increased risk of miscarriage, but "major stress," such as the economic downturn in Denmark was linked with a greater risk of miscarriage. Evidence suggests that it's that unusual or chronic stress may be more important when considering miscarriage risk.

One of the most comprehensive studies to date published in 2017 suggested that stress increases the risk of miscarriage by around 42%.

The Relationship Between Aspirin and Miscarriage Risk Is Complex

There is some research that taking aspirin during pregnancy may increase miscarriage risk. However, evidence of causation is unclear, as some studies show no such link.

Additionally, some doctors even prescribe ​low-dose aspirin as a part of recurrent miscarriage treatment, although evidence of the efficacy of this treatment is mixed. Daily low-dose aspirin is also recommended to prevent preeclampsia in high-risk pregnant people.

For people who have recurrent miscarriages due to antiphospholipid syndrome, a type of clotting disorder, low-dose aspirin may lessen the risk of miscarriage. For people without a history of recurrent miscarriages, some research has shown an association between aspirin use in early pregnancy and an increased risk of miscarriage, although other studies have shown no such link.

Using non-steroidal anti-inflammatory drugs (NSAIDs), such as Advil (ibuprofen) and Aleve (naproxen), however, may slightly increase the risk of early miscarriage. But more research is needed to understand the link, as it's possible that some may be taking NSAIDs to treat pain caused by an impending miscarriage (in which case the NSAIDs aren't the cause of the miscarriage).

Additionally, the Food and Drug Administration (FDA) only recommends taking NSAIDs before 20 weeks of gestation due to rare but serious (and potentially fatal) complications that can occur when taken in the latter half of pregnancy.

Birth Control Pills and Emergency Contraception Don't Cause Miscarriage

Although taking a large dose of birth control pills within a few days of intercourse can work as emergency contraception, there is no evidence that birth control pills will cause a miscarriage in an established pregnancy or that taking birth control pills will increase the risk of future miscarriage.

You Can Safely Breastfeed While Pregnant

There's no evidence that continuing to breastfeed an older child during a new pregnancy causes miscarriage or any harm whatsoever to the developing baby.

Pregnant people who want to continue breastfeeding an older child while pregnant can do so without worry.

Moderate Exercise Is Safe and Recommended During Pregnancy

No one knows for sure whether strenuous exercise increases miscarriage risk, but most obstetricians recommend exercise during pregnancy. There was a large study in 2007 that indicated women who engaged in ​strenuous exercise were more likely to have miscarriages, but there have been several other studies that found no link between exercise and miscarriage.

Light and moderate exercise during pregnancy are almost certainly beneficial. Some doctors advise keeping your heart rate under 140 beats per minute (bpm) to be on the safe side.

High Body Temperature May Increase Miscarriage Risk

Hot tub use during pregnancy may increase the risk of miscarriage according to a 2003 study. In that study, the risk of miscarriage was doubled on average with early first-trimester hot tub use and increased further with greater frequency of use.

The problem with hot tubs, saunas, and hot baths isn't the devices themselves but rather the increase in body temperature associated with their use. Allowing your body temperature to get too high during pregnancy has also been linked with neural tube defects and is not recommended.

For those who desire to spend some time in a hot tub or hot bath, program your hot tub to a lower temperature, don't allow your body temperature to exceed 101 degrees F, and spend no longer than 10 minutes in the tub.

Some Food-Borne Infections Are Associated With Miscarriage Risk

The advice that you should avoid soft, unpasteurized cheese and cold deli meats while pregnant is valid but incomplete. The risk associated with certain cheeses and deli meats isn't limited to these food items.

In practice, pregnant people should do their best to avoid common sources of food-borne illness, including unpasteurized cheese and cold cuts. Not only are you more likely to develop food poisoning while pregnant, but some of the organisms that cause food poisoning are linked with an increased risk of miscarriage. These include:

  • Listeria
  • Salmonella
  • E. coli
  • Toxoplasmosis

It's important to note that you don't have to avoid all cheese or deli meats during pregnancy.

Most cases of food poisoning linked to miscarriage are related to dairy products (such as soft cheeses) that have not been pasteurized, meats that have not been thoroughly cooked, or vegetables that haven't been washed.

Having Sex During Pregnancy Does Not Cause Miscarriage

There's no evidence that sex during pregnancy poses any risk of miscarriage. Sex doesn't even seem to be able to trigger labor in people with full-term pregnancies, so you should definitely not worry about orgasms or related uterine contractions causing miscarriage.

Sex is generally considered safe during all phases of pregnancy, but there are a few exceptions such as after your water has broken or if you are experiencing vaginal bleeding. Be sure to discuss any concerns with your provider.

In Most Cases, Getting Pregnant Again Right After a Miscarriage Doesn't Increase Your Chances of Another Miscarriage

There's always a risk of miscarriage in any pregnancy, but there's no real evidence that you need to wait any set period of time after a first-trimester miscarriage before you try again in order to prevent another miscarriage. There may, however, be other reasons for waiting.

In the past, it was often recommended that people wait a few months before trying again. One of the reasons behind this recommendation was that it can be more difficult to date a pregnancy that occurs immediately following a miscarriage, but with the advent of early ultrasound, this is rarely a concern today.

An older study also suggested a higher rate of miscarriage when a person becomes pregnant right away after having a pregnancy affected by a neural tube defect, but this may be related to low folate levels prior to the first pregnancy that persist for the second pregnancy.

Doctors may still advise waiting for different reasons for individual people, so be sure to check with your doctor about their recommendations for you.

For example, if a person has a miscarriage related to a medical condition such as uncontrolled diabetes, it's important to stabilize the medical condition before trying again.

Progesterone Cream Is Not a Universal Solution for Miscarriage Prevention

Don't rush out and buy that cream yet. Some doctors do believe that progesterone supplements might help certain people with a history of recurrent miscarriage but the opinion is controversial. There's no strong evidence that progesterone supplementation helps prevent miscarriage with the exception of people who are undergoing in vitro fertilization (IVF) and a small subset of people with recurrent miscarriages.

As for over-the-counter progesterone creams, the dosage varies heavily and some of the creams don't even contain any active progesterone. If you would benefit from progesterone supplementation during your pregnancy, it's best to get a prescription from your doctor.

Having a Bicornuate Uterus Doesn't Cause Miscarriage

A bicornuate uterus can mean an increased risk of preterm labor, but there's no evidence that it increases the risk of miscarriage. However, a uterine septum can mean an increased risk of miscarriage, and the two malformations look similar on imaging tests.

Learn more about the different types of uterine abnormalities and miscarriage risk.

Minor Abdominal Injury Isn't Linked to First-Trimester Miscarriage

Minor trauma such as falling, being hit in the abdomen, or having a fender bender is not likely to cause a first-trimester miscarriage, but it can cause placental abruption in the second or third trimester and potentially lead to late pregnancy loss.

In contrast, high-velocity trauma, such as a motor vehicle accident or major fall can significantly increase the risk of miscarriage. Plus, the risk of a fall or trauma of any kind is much greater later in pregnancy.

The Research About Roller Coasters and Miscarriage Is Lacking

No one has researched the safety of riding roller coasters during pregnancy, or the effect of other amusement park rides. There is a theoretical risk that the jerking motions could lead to placental abruption later in pregnancy, and although riding a roller coaster in very early pregnancy is most likely not going to cause problems, no one really knows where the cut-off point lies for safe versus risky.

Due to the uncertainty over the effect of roller coasters on pregnancy, some experts recommend avoiding these rides no matter how far along you are in your pregnancy.

Obesity May Increase the Risk of Miscarriage

Obesity does appear to increase the risk of miscarriage, but the relationship between body weight and miscarriage is still not well understood.

Though obesity is linked with miscarriage and recurrent miscarriages, it's not known if being overweight is actually a cause of miscarriage.

Certain Illnesses During Pregnancy Are Associated With Increased Risk of Miscarriage

Certain bacterial and viral infections can increase the risk of a miscarriage. Examples include:

  • Fifth disease
  • Rubella (German measles)
  • Bacterial vaginosis
  • Chlamydia
  • Listeria

That said, the chance that these infections will result in miscarriage is usually much lower than the chance that a baby will be fine. If you become ill while pregnant, it's always a good idea to contact your provider.

Pregnant People Over the Age of 35 Have a Higher Risk of Miscarriage

The risk of miscarriage is slightly higher for moms over 35 and is almost 50% for pregnant people in their early 40s.

It's important to note, however, that for a pregnant person who is 35 years old, the chances of a healthy pregnancy are still higher than the chances of miscarriage.

Miscarriage Is Almost Never the Pregnant Person's Fault

Miscarriage almost never happens because of something that a pregnant person did or did not do. It is important to emphasize this point, as many people wonder what they may have done to cause their miscarriage.

Chromosomal abnormalities in the baby are the most common reason for a miscarriage, and these abnormalities are not caused by anything a pregnant person does or does not do, but happen by chance alone.

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