Ask the experts: miscarriage causes and risk factors

Published October 2025 | 5 min read
Expert contributors: Samantha Payne, Co-Founder and CEO, The Pink Elephants Support Network; Associate Professor Jade Bilardi, Co-Lead, Miscarriage Australia
Words by Angela Tufvesson

One in four pregnancies ends in miscarriage, often leaving couples searching for answers. Experts explain why miscarriage is usually beyond your control.

Miscarriage is a heartbreaking reality for many Australians, with an estimated one in four pregnancies ending in loss. More than 100,000 couples are affected by miscarriage every year.

Adding to the anguish of losing a baby, many people find themselves searching for answers, hoping to understand what went wrong or if something could have been done differently.

“We know of many women who go down these rabbit holes thinking [a miscarriage occurred] because they worked so hard and were really stressed,” says Samantha Payne, Co-Founder and CEO of The Pink Elephants Support Network, which provides support for women and their partners experiencing miscarriage and pregnancy loss.

The truth is that miscarriage is usually beyond your control, explains Associate Professor Jade Bilardi, Co-Lead of Miscarriage Australia.

“Unfortunately, in most cases we don’t know why miscarriage occurs,” she says. “Women often feel guilt and self-blame around having a miscarriage, but it’s really important to remember that in almost all cases, it will have nothing to do with anything the pregnant person did.”

Samantha and Assoc Prof Bilardi address some of the most common questions about miscarriage causes and risks – and clear up some widespread myths.

What can cause miscarriage?

Early miscarriage refers to a pregnancy loss within the first 12 weeks. Around 85% of miscarriages happen during this first trimester, usually because the pregnancy isn’t developing properly. It’s estimated 50 to 80% of miscarriages are due to a random chromosomal abnormality.

Assoc Prof Bilardi says other causes of miscarriage can include problems with the placenta, cervical insufficiency (weak cervical tissue), problems with the lining of the uterus and blood clotting disorders.

Importantly, while there are some factors that may increase your risk – like age and previous miscarriage history – most miscarriages have no preventable or treatable cause.

“There's so much around the experience of miscarriage that's shrouded in false narratives, which then perpetuates the shame [and] stigma,” says Samantha. “Give yourself grace to be supported and held throughout this journey.”

What's recurrent miscarriage?

Recurrent miscarriage is defined as two or more pregnancy losses (which don’t have to be consecutive) before 20 weeks gestation and affects around 1 to 2% of women.

Previously, recurrent miscarriage was defined as three consecutive miscarriages, but the recent changes mean more women can access testing, investigations and care.

“In Australia, testing for the cause of miscarriage is not generally offered unless you have experienced recurrent miscarriage,” Assoc Prof Bilardi explains.

Can miscarriage be misdiagnosed?

False or misdiagnosed miscarriage is when a suspected pregnancy loss is diagnosed but a woman is still pregnant. This incorrect diagnosis can happen due to issues like inaccurate dating or issues with ultrasound technology, but it’s rare.

Does miscarriage risk increase with age?

Age is one of the biggest risk factors for miscarriage, says Assoc Prof Bilardi. “For women and men, the risk of miscarriage increases significantly after age 35 and even more so after age 40.” This is largely because chromosomal abnormalities are more common with increasing age.

Samantha adds that social expectations often delay family planning. “It’s not your fault that you've reached 35 or 40 and you're now considering having a baby,” she emphasises. “We expect women to have a beautiful family, but we also expect them to have careers. The timing of both has never been addressed by the system.”

Can stress cause a miscarriage?

Stress is a normal part of life, and typical day-to-day stress is generally not considered to be a significant risk factor for pregnancy loss. However, you should speak to your doctor if you’re experiencing prolonged levels of high stress during pregnancy.

Are polycystic ovary syndrome (PCOS) and endometriosis risk factors for miscarriage?

Assoc Prof Bilardi says there is a “slight increased risk” of miscarriage with PCOS, while studies examining the impact of endometriosis on miscarriage are ongoing.

Do other risk factors increase the likelihood of miscarriage?

It’s impossible to predict when a miscarriage will occur, but Assoc Prof Bilardi points to other factors that may increase your risk:

• Previous miscarriages
• Ethnicity – Black women have an increased risk of miscarriage
• Lifestyle factors like smoking, alcohol and high levels of caffeine
• Air pollution
• Being overweight or underweight
• Uncontrolled diabetes and untreated thyroid conditions
• Some infections
• Certain medications

Assoc Prof Bilardi says contrary to popular belief, the following factors are generally not linked to an increased risk of miscarriage:

• Having sex
• Flying
• Vaccines (though some are not recommended during pregnancy)
• A previous abortion
• Moderate exercise

“There are always cases in which a doctor may recommend you avoid activities such as sex, flying and exercising – depending on an individual’s situation,” she adds. “But generally, unless a doctor has advised against it, these things will not cause a miscarriage.”

What exercises are safe in early pregnancy?

Moderate activities like walking, swimming, jogging, cycling, yoga and pilates are generally safe and can be beneficial during pregnancy, says Assoc Prof Bilardi. If you have specific concerns, medical conditions or are unsure which type of exercise is right for you, check with your GP.

Can you prevent miscarriage?

While a miscarriage usually happens for no known reason, a healthy lifestyle can give you the best chance of a healthy pregnancy. Assoc Prof Bilardi offers the following tips for a healthy and balanced pregnancy:

• Avoid alcohol while trying to conceive and while pregnant.
• Minimise caffeine consumption – less than 200mg day.
• Take folic acid and vitamin D.
• Eat healthily.
• Maintain a healthy weight range.
• Enjoy regular moderate exercise.

She also recommends both partners quit smoking before trying for a baby.

Getting support after a miscarriage

Samantha says support from organisations like The Pink Elephants Support Network can be helpful after couples have experienced an early pregnancy loss.

“It’s perfectly healthy to need support through this time,” she says. “Often what we're told with miscarriage is ‘at least it happened early, at least you know you can get pregnant’.”

People respond to miscarriage in different ways, but there’s no right or wrong way to grieve.

“The loss of your baby can be devastating, and we encourage couples to reach out and get as much support as possible.”

These organisations can also provide support:

• Red Nose Grief and Loss
• Bears of Hope
• Rural Health Connect

Support after loss

Caring for your mental health after a miscarriage is paramount – and you don’t have to go through it alone. Eligible members can access one annual confidential HealthyMinds Check-in at no cost^*. This is a one-on-one chat from the comfort and privacy of your home with a psychologist who can offer tailored support and, depending on your needs, can direct you to your GP for a mental health treatment plan and Medicare-subsidised sessions or appropriate support programs and resources.