Why Do Miscarriages Happen, and Can They Be Prevented?

Understanding Miscarriages: Causes, Risks, and Prevention

Pregnancy is a complex and delicate process, and unfortunately, miscarriage—also known as pregnancy loss—is a reality that many individuals and couples face. While miscarriages can be emotionally devastating, understanding the reasons behind them and learning about preventive measures can help individuals take proactive steps in their fertility journey.

Dr. Minoos Hosseinzadeh, Founder and Medical Director at the Fertility Institute of San Diego, emphasizes: “Miscarriages, while common, are often misunderstood. Every pregnancy is unique, and by addressing risk factors early, we can optimize a patient’s chances of carrying a healthy pregnancy to term.”

What Is a Miscarriage?

A miscarriage is the spontaneous loss of a pregnancy before the 20th week. According to the American College of Obstetricians and Gynecologists (ACOG), approximately 10-20% of known pregnancies end in miscarriage, though the actual number is likely higher due to early pregnancy losses occurring before a woman even realizes she is pregnant.

Common Symptoms of a Miscarriage:

• Vaginal bleeding (light spotting to heavy bleeding)
• Cramping or abdominal pain
• Passing tissue or clots from the vagina
• Sudden loss of pregnancy symptoms (e.g., nausea, breast tenderness)

If you experience any of these symptoms, it is important to contact your doctor.

What Causes Miscarriages?

Miscarriages can happen due to various factors, ranging from genetic abnormalities to underlying medical conditions. Dr. Hosseinzadeh explains: “While some causes of miscarriage are beyond our control, others can be addressed with proper medical care and lifestyle adjustments.”

Primary Causes of Miscarriages:

1. Chromosomal Abnormalities

The most common cause of miscarriage is chromosomal abnormalities in the embryo. These genetic errors occur randomly during the cell division processes while the human embryo is forming. If the embryo’s cells have too many or too few chromosomes, then proper fetal development is affected.

2. Maternal Health Conditions

Certain health conditions increase the risk of miscarriage, including:

• Uncontrolled diabetes
• Thyroid disorders (hypothyroidism, hyperthyroidism)
• Autoimmune diseases (e.g., lupus, antiphospholipid syndrome)
• Hormonal imbalance disorders (Polycystic ovary syndrome (PCOS))

3. Lifestyle Factors

Dr. Hosseinzadeh advises: “A healthy lifestyle plays a critical role in pregnancy success. Smoking, excessive alcohol consumption, and drug use are known to contribute to miscarriage risk.”

• Smoking affects fetal oxygen supply
• Excessive caffeine intake (over 200mg daily) may increase miscarriage risk
• Substance abuse can impair fetal development

4. Uterine and Cervical Abnormalities

Structural issues in the uterus or cervix can lead to miscarriage, including:

• Fibroids or polyps
• Misshapen uterus (septate or bicornuate)
• Incompetent cervix (weakened cervical tissue leading to early pregnancy loss)

5. Low Hormonal Levels

Hormones regulate pregnancy maintenance, and imbalances in progesterone (the pregnancy-supporting hormone) can hinder embryo implantation. Low progesterone levels can affect the uterine lining, making it difficult for the pregnancy to continue progressing.

6. Age and Recurrent Miscarriages

Advanced maternal age (over 35) increases the likelihood of miscarriage due to declining egg quality. Women experiencing multiple pregnancy losses may need specialized fertility evaluations, fertility treatments, and/or advanced embryo testing.

7. Infections and Immune System Factors

Certain infections—such as bacterial vaginosis, cytomegalovirus (CMV), or toxoplasmosis—can trigger pregnancy loss.

Can Miscarriages Be Prevented?

While some miscarriages are unavoidable, many can be prevented through proper medical care and lifestyle modifications.

Prevention Strategies:

• Prenatal Health Screenings: Early evaluations help identify and manage underlying conditions.
• Optimizing Preconception Health: Maintaining a healthy weight, balanced nutrition, and managing stress contribute to pregnancy success.
• Limiting Toxins: Avoid smoking, alcohol, and high caffeine intake.
• Hormonal Support: For women with progesterone deficiencies, hormone therapy may help sustain pregnancy.
• Consult with a Fertility Specialist: For those with recurrent pregnancy loss, personalized fertility care is crucial.

Dr. Hosseinzadeh stresses: “The best approach is a proactive one—understanding your fertility health and working with a specialist to optimize pregnancy success.”

Treatment Options for Recurrent Miscarriages

• Genetic counseling and embryo screening (PGT-A/PGT-M)
• Hormone therapy for luteal phase defects
• Surgical correction of uterine abnormalities
• Blood-thinning medications for autoimmune-related losses

FAQs About Miscarriages