Miscarriage is more common than most people expect. At the same time, it often feels unexplained.

Many patients are told: “It just happens.” While this can be true, it is not the full picture.

In the UK and globally, around 1 in 4 pregnancies (approximately 20–25%) end in miscarriage. Most occur early, before 12 weeks, with the highest likelihood in the first 6–8 weeks of pregnancy.

Many happen before a scan has even taken place. In some cases, there is no clear cause. In others, there are contributing factors that can be investigated and, in some situations, managed.

This article walks through the most common reasons for miscarriage and what steps may be considered next.

TL;DR

  • Around 25% of pregnancies end in miscarriage, most before 12 weeks
  • The most common cause is chromosomal abnormality in the embryo
  • Other causes include:
    • Hormonal imbalances
    • Uterine factors
    • Immune or blood clotting conditions
    • Sperm DNA quality
  • Not all miscarriages can be prevented
  • Close pregnancy monitoring (including frequent blood tests and hormone tracking) can help guide early treatment decisions
  • After recurrent miscarriage, targeted testing and personalised care are usually recommended
  • Plan Your Baby focuses on identifying individual causes and adjusting treatment in real time where possible

When Does Miscarriage Usually Happen?

  • Before 6 weeks: often before a scan confirms pregnancy
  • 6–10 weeks: most common timing
  • 10–12 weeks: risk begins to decrease

After 12 weeks, miscarriage becomes less common. This early window is where monitoring and timely adjustments can matter most.

5 Common Causes of Miscarriage — And What Can Be Done

1. Chromosomal Abnormalities (Most Common Cause)

The most frequent reason for miscarriage is a problem with the embryo’s chromosomes.

This means:

  • The embryo has too many or too few chromosomes
  • It cannot develop as expected

This can happen even when:

  • You are healthy
  • Conception occurs naturally

As discussed in patient consultations, this is often the first factor considered in recurrent miscarriage  .‍

What can be done:

  • This cannot be directly prevented in natural conception
  • In IVF, PGT-A testing may be considered to identify embryos with typical chromosomal profiles

2. Hormonal Imbalances

Hormones support early pregnancy, particularly progesterone. If levels are not optimal:

  • Implantation may be affected
  • Early pregnancy may not be sustained‍

What can be done:

  • Blood tests at specific cycle points
  • Hormonal support where needed

In practice, timing matters. Hormone levels can change quickly in early pregnancy.

3. Uterine Factors

The uterus needs to support implantation and growth.This may be affected by:

  • Fibroids
  • Polyps
  • Scar tissue
  • Structural differences‍

What can be done:

  • Imaging (ultrasound, hysteroscopy)
  • Treatment if clinically relevant

Not all findings require intervention.

4. Immune and Blood Clotting Factors

Some patients have underlying conditions affecting:

  • Blood flow
  • Immune response to pregnancy‍

What can be done:

  • Blood tests
  • Medication (such as blood thinners) in selected cases

These are used only when indicated.

5. Sperm Quality and DNA Fragmentation

Sperm contributes half of the embryo’s genetic material.

Even when standard tests are normal:

  • DNA fragmentation may be elevated

As noted in clinical discussions, this can contribute to miscarriage even with otherwise normal results  .‍

What can be done:

  • DNA fragmentation testing
  • Targeted treatment or IVF lab techniques where appropriate

The Role of Monitoring in Early Pregnancy

This is one of the most practical areas where care can differ.

After a positive pregnancy test:

  • hCG blood tests confirm and track progression
  • Hormone levels are assessed
  • Medication can be adjusted based on results

In many systems, monitoring happens at fixed intervals.

In a more responsive model:

  • Blood tests may be done every 48 hours in early pregnancy
  • Medication doses can be adjusted in real time
  • Additional support can be introduced when needed

This does not prevent all miscarriages.
But it allows earlier intervention where there is something to act on.

When Should You Consider Testing?

  • After one miscarriage:
     Often no investigation is needed
  • After two or more miscarriages:
     A more detailed assessment is usually considered

This may include:

  • Genetic testing
  • Hormonal assessment
  • Uterine imaging
  • Immune and clotting tests
  • Sperm DNA testing

Testing is tailored to your history.

How Plan Your Baby Approaches Miscarriages

The focus is on identifying what may be contributing in your specific case and acting on it early.

1. Detailed Review Before Treatment

Your doctor reviews:

  • Previous pregnancies
  • Prior test results
  • IVF cycles if applicable

This avoids repeating unnecessary steps.

2. Targeted Testing (Not One Fixed Panel)

Testing may include:

  • Genetic factors
  • Hormonal profile
  • Uterine assessment
  • Immune and clotting markers
  • Sperm DNA testing

As discussed in clinical sessions, testing is adapted to each patient rather than standardised  .

3. Medication Adjusted to Your Cycle

Treatment is not fixed.

Depending on your case:

  • Medication may start before conception or embryo transfer
  • Dosages may change during the cycle
  • Additional support may be introduced based on results
4. Close Monitoring in Early Pregnancy

From a positive test:

  • Blood tests are typically done every 48 hours in early stages
  • Hormones are monitored closely
  • Medication is adjusted based on results

Monitoring continues before NHS support typically begins, so early changes can be made if needed.

5. Ongoing Communication

Instead of waiting for appointments:

  • You can contact your care team
  • Decisions can be made based on current results

This allows treatment to adapt as your body responds.

A Final Note

Miscarriage is often described in general terms, but each situation is different. Some causes cannot be prevented. Others can be identified and managed. The key step is understanding what applies in your case — and acting on it early.

Next Step

If you have experienced miscarriage and want to understand what may be contributing, you can speak to a doctor at Plan Your Baby.

A first conversation can help you:

  • Review your history
  • Understand what testing may be relevant
  • Explore next steps

There is no obligation to proceed. It is simply a way to move forward with more clarity.