Why Do Miscarriages Happen?

A miscarriage is the unplanned loss of a pregnancy before 20 weeks of gestation. Medically, it is sometimes referred to as spontaneous abortion, though this term refers only to pregnancy loss and is unrelated to elective abortion.

Miscarriage is more common than many realize.. It is more common than many realize: an estimated 10–20% of clinically recognized pregnancies end in miscarriage, though the actual number may be higher. Many early miscarriages happen before a person even realizes they are pregnant, as they may be mistaken for a late or heavy period.

Most miscarriages occur due to factors beyond anyone’s control, such as genetic or medical conditions, and are not caused by anything a person did or didn’t do. While most people who experience one miscarriage go on to have healthy pregnancies, those who have had two or more consecutive losses may want to consult a doctor to assess potential underlying causes.

The majority of miscarriages happen in the first trimester, with more than half of these losses resulting from chromosomal abnormalities.

These abnormalities occur when an embryo has too many or too few chromosomes, leading to improper development. In most cases, these genetic issues are random and not inherited, making them difficult to predict or prevent.

Hormones play a crucial role in maintaining a healthy pregnancy. If certain hormone levels are too high or too low, they can interfere with fetal development.

For example, low progesterone can prevent the fertilized egg from implanting properly in the uterus, leading to early pregnancy loss.

Additionally, thyroid disorders such as hypothyroidism or hyperthyroidism have been linked to increased miscarriage risk. Managing these conditions before and during pregnancy can improve outcomes.

Certain structural differences in the uterus or cervix can contribute to miscarriage, especially in the second trimester. Conditions such as fibroids, a uterine septum, or an incompetent cervix may make it difficult for the pregnancy to progress. Many of these issues can be diagnosed through imaging and treated with medical or surgical interventions.

Some infections, whether sexually transmitted or otherwise, have been associated with pregnancy loss.

Research suggests that conditions such as bacterial vaginosis, syphilis, listeriosis, and cytomegalovirus can increase the risk of miscarriage. Early screening and treatment can help reduce these risks.

Certain lifestyle factors may increase the risk of miscarriage, both before and during pregnancy. Smoking, alcohol consumption, and excessive caffeine intake (more than 300 mg per day) have all been associated with higher miscarriage rates. Maintaining a healthy weight is also important, as being significantly underweight may impact pregnancy viability.

Making healthy lifestyle choices can support a healthy pregnancy.

• Schedule regular prenatal checkups and follow your healthcare provider’s recommendations for tests and screenings.
• Avoid smoking and alcohol consumption.
• Eat a well-balanced diet to support overall health.
• Get enough folic acid—your doctor can help determine the right amount for you.
• Stay physically active.

Underlying health conditions can also play a role in pregnancy loss.

Conditions such as high blood pressure, diabetes, lupus, and autoimmune disorders have been associated with increased miscarriage risk. Proper management of these conditions before and during pregnancy may improve the chances of a successful pregnancy.

Formerly known as geriatric pregnancy, the age for advanced maternal age pregnancy is considered older than 35, and increases the risk of chromosomal abnormalities, which are the primary cause of miscarriage.

For example, the risk of chromosomal trisomy, in which there are three chromosomes instead of two, is between two and three percent for women in their twenties but 30 percent for women in their forties. Early primary care can help support women through these pregnancies, and some genetic testing that can diagnose chromosomal abnormalities and other disorders can be done as early as the tenth week of pregnancy for those who wish to complete it.

Exposure to harmful substances in the environment can contribute to miscarriage. For example, research has found that short and long-term exposure to air pollution may increase the risk of pregnancy loss.

Endocrine disrupting chemicals, like phthalates found in some cosmetics and fragrances, BPA found in some food packaging, and atrazine, a common herbicide, can contribute to miscarriage, as can exposure to radiation or heavy metals.

Significant physical trauma, such as a car accident or a severe fall, can sometimes lead to pregnancy complications.

While minor bumps and regular physical activity are generally safe, serious injuries may cause placental abruption or other pregnancy complications.

In some cases, the exact cause of a miscarriage is never identified. This can be frustrating, but it does not necessarily mean that future pregnancies will be affected.

If you have experienced multiple miscarriages, your doctor may recommend further testing to look for underlying conditions that could be addressed.

If you experience symptoms such as severe abdominal pain, heavy bleeding, fever, or foul-smelling vaginal discharge during pregnancy, seek medical attention immediately. Early intervention can sometimes prevent complications or provide important medical care.

Miscarriage take a significant emotional toll. Coping with pregnancy loss may involve seeking support from a partner, family, friends, or a mental health professional.

Everyone grieves differently, and it’s important to allow yourself time to process the loss.