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What Are the Common Causes of Miscarriage?

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Whether it’s your first time trying to conceive, or you are expanding your family, having a miscarriage can be confusing, scary, and emotionally painful.
In this article, we’ll review the different types of miscarriage and common causes to help bring understanding and build awareness of pregnancy loss. Unfortunately, the cause of a miscarriage cannot always be established. If you have had one or more miscarriages, and have questions about your unique situation, it’s important to speak with your healthcare provider.

What is Miscarriage?

Miscarriage is defined as the loss of a pregnancy before the 20th week of gestation. Miscarriages are very common and are thought to affect up to 26% of all pregnancies — although this number may be higher (up to 50%) since many occur early in pregnancy, often before the first pregnancy test.

The Types of Miscarriage

Some common types of miscarriage include:

Early vs Late Miscarriage

An early miscarriage describes the loss of a pregnancy before 12 weeks of gestation, while a late miscarriage describes the loss of pregnancy between weeks 12 and 20.

Complete vs Incomplete Miscarriage

During a complete miscarriage, the body expels all the pregnancy tissue from the uterus. During an incomplete miscarriage, it does not. An incomplete miscarriage will require a procedure to help empty the uterus.

Chemical Pregnancy

An early miscarriage whereby the egg becomes fertilized, but does not properly implant or develop. A chemical pregnancy will not be visible on an ultrasound scan, and many who experience this type of miscarriage aren’t aware they were pregnant.

Blighted Ovum

A type of miscarriage that takes place early in pregnancy where a fertilized egg implants, but does not develop properly. On an ultrasound scan, all one may see is an empty gestational sac. A blighted ovum might conclude on its own or may require additional help for the body to recover.

Missed Miscarriage

Also known as a silent miscarriage. In this case, the pregnancy has stopped, but there are no symptoms of miscarriage. It tends to be picked up on an ultrasound scan. A missed miscarriage may complete on its own but tends to require medical assistance.

Common Causes of Miscarriage

Though the reason(s) why a miscarriage occurs cannot always be established, there are some common underlying causes. These include:

Chromosomal Abnormalities

An embryo having the wrong amount of genetic content is believed to be the main cause of early miscarriages, accounting for up to 50% of pregnancy losses during the first trimester. As people with ovaries become older, the chance of a chromosomal abnormality increases. This also means that the risk of a miscarriage is higher with increased age.

Illness or Infection

Conditions like the Zika virus, some sexually transmitted infections, measles, and the flu can sometimes trigger a miscarriage. It’s thought that infections may account for 15% of early and 66% of late miscarriages.

Reduced Sperm Quality

DNA damage in sperm has been linked to an increased risk of miscarriage. Risk factors for sperm DNA damage include smoking, increased age, and infection. If you are concerned about sperm quality, you can have a DNA fragmentation test to assess for signs of DNA damage.

Polycystic Ovary Syndrome (PCOS)

People with PCOS are 3 times more likely to suffer a miscarriage than people without this condition. If you have PCOS and have experienced a miscarriage, we encourage you to speak with your healthcare provider to review treatment options, which may reduce the risk of subsequent pregnancy losses.

Body Weight

The miscarriage rate is about 3x higher in the overweight and obese population.

Medical Conditions

Research suggests that individuals with long-term medical conditions, such as lupus, thyroid disorders, and/or diabetes may be at an increased risk of having a miscarriage. If you have a medical condition, your healthcare provider can review your options to improve the chances of carrying a pregnancy to term. In the example of someone with an underactive thyroid, more frequent blood work throughout the pregnancy may be required, as well as a higher dose of thyroid medication.

Structural Abnormalities

Certain structural abnormalities in the reproductive tract, such as uterine fibroids, a septate uterus, or a weakened cervix, can increase the risk of miscarriage. Your doctor may perform specific tests, along with a detailed medical history, to determine if you have any structural abnormalities before fertility treatment occurs.

Ectopic Pregnancy

An ectopic pregnancy is a pregnancy that implants outside of the uterus. Unfortunately, this type of pregnancy is not viable, as the uterus is the only place in the body that can support a growing fetus. An ectopic pregnancy is considered a medical emergency and should be treated by a professional as soon as possible.

Lifestyle Factors

Certain lifestyle factors like smoking, drinking alcohol, and workplace exposure to chemicals may increase the risk of experiencing a miscarriage. If you are concerned about how your lifestyle may impact a pregnancy, please speak to your physician or fertility naturopath for guidance.

Recurrent Miscarriage

Unfortunately, some people will experience more than one miscarriage in their lifetime. If you have had 2 or more consecutive miscarriages, you may hear the term ‘early recurrent pregnancy loss (also known as RPL).
Your specialist will look deeper at the reproductive, hormonal, and autoimmune factors that contribute to pregnancy loss. It may involve personalized testing, monitoring, and treatment to optimize your chances of having a healthy pregnancy. You can read more about TRIO’s RPL program.

The Bottom Line

Unfortunately, miscarriages are a very common event that affects many people on their path to parenthood. Whatever the cause, pregnancy loss can be devastating, and it may take time before you are ready to try again. Some individuals find it helpful to speak to a fertility counsellor or join a support group.
For more information about how TRIO can support you, please get in touch. Our team is here to provide you with the care and guidance you need on your fertility journey.