What are the causes of stillbirth?

In many cases, it may not be possible to find a reason why a stillbirth happened.

It’s sadly not always possible to find a reason why a baby was stillborn. This can be particularly hard to hear when you’re grieving your baby and want to understand what happened and why your baby died. It’s important to remember that stillbirth is very unlikely to be caused by anything you’ve done or not done.

A report of all UK stillbirths in 2018 showed around 35.5% of stillbirths were unexplained. Although this proportion of stillbirths remain unexplained, we do know some possible causes. We have explained the most common causes here.

Problems with the placenta

Many stillbirths (32.5%) are linked to complications with the placenta. The placenta is an organ that helps the baby grow and develop. It’s attached to the lining of the womb and is connected to the baby by the umbilical cord. The placenta passes oxygen, nutrients and antibodies from the mum/birthing parent’s blood supply to the baby. 

If the placenta doesn't work properly, the baby doesn’t receive enough nutrients or oxygen and fails to grow or develop. This is called intrauterine growth restriction (IUGR) or fetal growth restriction (FGR).

If there were problems with the placenta, stillborn babies are usually born looking perfectly formed, although often small. Sometimes, a post-mortem examination can help to diagnose IUGR or FGR by comparing the size of baby’s liver and brain. If the baby’s brain is more than 4.5 times bigger than their liver, then this makes growth restriction more likely.  

Placental abruption

Sometimes the placenta can separate from the womb before the baby is born. This is called placental abruption. It can lead to stillbirth because the placenta that has separated from the womb is not working as it should.

In most cases there isn’t a clear reason why placental abruption has happened. Placental abruption can be caused by a blow or impact to the stomach such as following a care accident. Or it sometimes linked to a condition such as pre-eclampsia or IUGR or FGR.

The symptoms of placental abruption are:

  • pain in the back and stomach
  • contractions
  • tender womb
  • vaginal bleeding (this can be very light). 

If you are experiencing any of the symptoms above, you should get medical help immediately.

Read more about placental abruption.


Pre-eclampsia is a condition that occurs typically after 20 weeks of pregnancy and causes high blood pressure and protein in urine. If you're told you have pre-eclampsia, it's important that you attend appointments to check your blood pressure and wellbeing. You may be offered the option of having an early birth to prevent complications. 

Sometimes it's not clear that you have pre-eclampsia until after your baby has died or even after you have given birth. 


4.2% of stillbirths happened because of an intrauterine (womb) infection.  

Bacterial infections can move from the vagina into the womb, for example, Group B strep, chlamydia, klebsiella, enterococcus, haemophilus influenza, mycoplasma or ureaplasma and escherichia coli (E.coli). These can sometimes cause inflammation of the placenta and membranes around the baby (called chorioamnionitis) or the umbilical cord (funisitis).

Other infections can harm a baby, including:

  • rubella (German measles)
  • flu
  • Lyme disease
  • toxoplasmosis
  • parvovirus
  • coxsackie virus
  • cytomegalovirus
  • Herpes simplex
  • Listeriosis
  • Q fever
  • malaria
  • Covid-19.

Read more about infections in pregnancy.

Reduced fetal movements

Reduced fetal movements is not a cause of stillbirth but it is one of the signs that a baby may not be getting enough food or oxygen. Reduced fetal movements were noticed in around 55% of stillbirths. 

This is why health professionals ask you to monitor the pattern of your baby's movements. 

If you notice a reduction in your baby’s pattern of movements, get in touch with the hospital immediately. Never go to bed at night worried about your baby’s movements. 

Read more about how to monitor your baby's movements in pregnancy.

Other conditions that are linked to stillbirth

There are some other conditions that have been linked to stillbirth: 

Understandably, many parents desperately want to know what happened to their baby. A post-mortem can sometimes offer answers or at least can help rule out possible reasons for the stillbirth. Your midwife can talk to you about the different options and help support you. 

How Tommy's research is helping understand why stillbirth happens

Without more research, we will never know why so many babies die before birth. Tommy’s Manchester Research Centre is focused on learning more about the main causes of stillbirth and how it can be prevented.

The Manchester Placenta Clinic is a specialist service for pregnant women at risk of placental problems, which can potentially lead to fetal growth restriction. We believe the majority of stillbirths could be prevented and we want to find out how. 

Our research depends on fundraising and donations. Find out more about how you support our research

Review dates
Reviewed: 11 February 2022
Next review: 11 February 2025