Understanding the Causes of Miscarriage: 10 Key Factors You Should Know
- Rachael Robinson
- 12 minutes ago
- 4 min read
Table of Contents
Key takeaways
Miscarriage can have many underlying causes—some preventable, others not—and understanding them can offer guidance for next steps.
Common drivers include genetic factors, hormonal imbalances, immune system activity, and infections.
Comprehensive testing for both partners can provide valuable insight into recurrent pregnancy loss.
When you experience a miscarriage, the search for answers can feel all-consuming. I remember after my miscarriage and ectopic pregnancy, I desperately wanted to know why. I thought that if I had a clear reason, I could find closure and know what to do next.
Sometimes, testing gives us those answers. Other times, it doesn’t—and that uncertainty can be one of the hardest parts.
While not every miscarriage has an identifiable cause, research and clinical experience point to several common factors. Understanding these can empower you to have more informed discussions with your healthcare provider and take targeted action where possible.
10 Causes of Miscarriage
Below, I’ll walk you through 10 key drivers of miscarriage, what the science says, and where you can start if you suspect one or more may be affecting you.
1. Genetic Abnormalities
The most common cause of miscarriage—accounting for over half of cases—is genetic abnormalities in the embryo. These are often random errors during cell division and not something either parent could have prevented. In many cases, this is nature’s way of stopping a pregnancy that could not develop healthily.
If genetic issues occur repeatedly, your doctor may suggest karyotyping for both partners or testing the embryo during IVF (PGT-A).
2. Poor Mitochondrial Health
Although we cannot change DNA, when it comes to supporting the body from a cellular perspective, a key aspect is the health of mitochondria. Mitochondria are the “powerhouses” of cells, producing ATP needed for egg maturation, fertilisation, and early embryo development.
Mitochondrial health is central to egg quality, embryo development, and early placental function. Dysfunction can increase the risk of miscarriage, particularly age-related pregnancy loss.
Nutritional and lifestyle strategies that support mitochondrial function may help lower this risk, especially for women with recurrent miscarriage or those undergoing IVF.
Regular exercise, sleep, sunlight, and key nutrients such as CoQ10, carnitine, alpha lipoic acid, B vitamins and vitamin D all impact mitochondrial health. So the great news is that you have some control over this element of egg and sperm quality.
3. Anatomical Factors
The shape and structure of your uterus play a role in carrying a pregnancy. A weak cervix, irregularly shaped uterus, septum, or fibroids can increase miscarriage risk. These structural issues can interfere with implantation or blood supply to the developing pregnancy.
An ultrasound, hysteroscopy, or MRI can help detect structural differences, and in some cases, surgery can improve outcomes.
4. Infections
Certain bacterial infections—such as Ureaplasma or those linked to bacterial vaginosis—are associated with miscarriage risk. These bacteria can cause inflammation in the uterine environment, making it less hospitable for an embryo.
Vaginal microbiome testing can detect these infections, which are often treatable with targeted antibiotics or probiotics.
5. Low Levels of Protective Bacteria
It’s not just about avoiding harmful bacteria—having enough beneficial bacteria matters too. Lactobacillus is a key protective bacteria in the uterus and vagina.
A 2020 study found that 80% of women who had experienced miscarriage had low levels of lactobacillus. Without it, the risk of inflammation and infection rises.
Vaginal microbiome support, including probiotics and diet changes, can help restore balance.
6. Blood Clotting Disorders
Conditions like antiphospholipid syndrome can cause blood to clot too easily—sometimes called “sticky blood.” This can restrict blood flow to the placenta, impacting the nutrient and oxygen supply to the baby.
Blood clotting panels can identify these issues. If diagnosed, treatment may involve blood-thinning medication during pregnancy. An anti inflammatory diet can also support healthy blood flow.
7. Hormone Imbalances
Progesterone is essential for maintaining early pregnancy. Low progesterone, or imbalances between oestrogen and progesterone, can make it harder for the uterine lining to support implantation.
Cycle tracking, day 21 progesterone tests, and hormone panels can identify deficiencies. Supplementation may be an option in future cycles.
8. Thyroid Issues
Your thyroid helps regulate metabolism, energy, and hormone balance—vital for pregnancy. An underactive thyroid or raised thyroid antibodies have both been linked to early miscarriage.
Thyroid function and antibody testing should be part of recurrent miscarriage workups. Treatment can involve medication and targeted nutrient support including iodine, iron, zinc, selenium and tyrosine (all needed for thyroid hormone production).
9. Immune System Factors
The immune system should protect you without attacking the developing embryo. In some women, an overactive immune response—such as raised natural killer (NK) cells—can mistakenly target the embryo as a foreign invader.
Immune testing can help identify this, and some treatments aim to modulate immune activity during conception and pregnancy. Diet can make a huge difference in reducing triggers for an overactive immune system, whilst still giving the building blocks needed for healthy immune cell production.
10. Sperm Quality and DNA Fragmentation
It’s not just about egg health—sperm matters too. A 2019 study found men in couples with recurrent miscarriage had twice as much sperm DNA damage compared to controls. High DNA fragmentation can result from oxidative stress, infection, lifestyle factors, or age.
A DNA fragmentation test can assess this, and lifestyle, antioxidant support, or medical treatments may improve sperm health.
My conclusions
Miscarriage is rarely the result of a single factor. In many cases, it’s a combination of genetic, hormonal, immune, or structural influences. This is why a thorough, holistic approach—testing both partners, supporting overall health, and addressing any identified imbalances—offers the best chance of preventing recurrence.
When you’ve been through miscarriage, the need for answers is deeply human. While sometimes the cause remains unknown, there are many avenues to explore that could offer clarity and direction. Whether it’s optimising your microbiome, balancing hormones, supporting your thyroid, or improving sperm quality, each step you take builds a stronger foundation for future pregnancy.
If you’ve experienced one or more miscarriages and feel stuck or overwhelmed, I can help you create a personalised plan. Together, we’ll explore possible causes, arrange targeted testing, and build a strategy to support your next steps.
Arrange a 1:1 session [via the contact form] and we can work on a plan that supports you, whatever your situation and whatever you have been through.
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