Stillbirth - Causes of stillbirth

A large proportion of stillbirths seem to occur in otherwise healthy babies and the cause often cannot be explained.

However, many stillbirths are linked to placental complications. This means that for some reason the placenta (the organ that links the baby's blood supply to the mother's and nourishes the baby in the womb) is not functioning properly.

A poorly functioning placenta may be the direct cause of the stillbirth, or it may have contributed to the baby's death because the baby's growth and development have been held back.

If there have been problems with the placenta, stillborn babies are usually born perfectly formed, though often small. With more research, it is hoped that placental causes may become better understood, leading to better detection of placental problems and better care for these babies.

Other conditions that can cause stillbirth or may be associated with stillbirth include:

• bleeding (haemorrhage) before or during labour
• placental abruption – when the placenta separates from the womb before the baby is born. 
• pre-eclampsia – a condition that causes high blood pressure in the mother
• a problem with the umbilical cord, which attaches the placenta to the baby's tummy button – the cord can slip down through the entrance of the womb before the baby is born (known as cord prolapse), or it can be wrapped around the baby's neck
• intrahepatic cholestasis of pregnancy (ICP) or obstetric cholestasis – a liver disorder during pregnancy characterised by severe itching
• a genetic physical defect in the baby
• gestational diabetes – a type of diabetes developed by the mother during pregnancy
• infection in the mother that also affects the baby

Infections

Around 1 in 10 stillbirths is caused by an infection. The most common kind of infection is a bacterial infection that travels from the vagina into the womb (uterus). These bacteria include group B streptococcus, escherichia coli (E.coli), klebsiella, enterococcus, haemophilus influenza, chlamydia, and mycoplasma or ureaplasma.

Some bacterial infections – for example, chlamydia and mycoplasma or ureaplasma, which are sexually transmitted infections – can be prevented using barrier contraception such as condoms.

Other infections that can cause stillbirths include:  

• rubella – commonly known as German measles
• flu – it is recommended that all pregnant women have the seasonal flu vaccine irrespective of their stage of pregnancy
• parvovirus B19 – this causes slapped cheek syndrome, a common childhood infection that is dangerous for pregnant women
• coxsackie virus – this can cause hand, foot and mouth disease in humans
• cytomegalovirus – a common virus spread through bodily fluids, such as saliva or urine, which often causes few symptoms in the mother
• herpes simplex – the virus that causes cold sores
• listeriosis – an infection that usually develops after eating food contaminated by bacteria called Listeria monocytogenes (listeria); it may cause vomiting and diarrhoea in the mother (see preventing stillbirth for more information about the foods to avoid during pregnancy)
• leptospirosis – a bacterial infection spread by animals such as mice and rats, which can be caught by getting contaminated soil or water in your mouth, nose, eyes or open cuts
• Lyme disease – a bacterial infection spread by infected ticks
• Q fever – a bacterial infection caught from animals such as sheep, goats and cows
• toxoplasmosis – an infection caused by a parasite found in soil and cat faeces
• malaria – a serious tropical disease spread by mosquitoes

Increased risk

There are also a number of things that may increase your risk of having a stillborn baby, including:

• having twins or a multiple pregnancy
• having a baby who does not reach his or her growth potential in the womb
• being over 35 years of age
• having gestational diabetes, high blood pressure or a blood-clotting disorder
• smoking, drinking alcohol or misusing drugs while pregnant
• being obese (having a body mass index over 30)
• having a pre-existing physical health condition such as epilepsy

Growth potential

Midwives check the growth and wellbeing of your baby at every antenatal appointment. They use a tape measure to work out the distance from the pubic bone to the top of the uterus (womb). They plot your baby's growth on a chart to ensure he or she is continuing to grow.

Every baby is different and should grow to the size that's normal for him or her. But all babies should continue to grow steadily throughout the pregnancy. Some babies are naturally small, usually because their mothers are small.

If a baby seems to be smaller than it should be, or his or her growth pattern tails off as the pregnancy continues, this is described as "growth restriction", being "small for gestational age", or not reaching his or her "growth potential".

If a baby does not reach his or her growth potential in the womb, this may be because the placenta is not working properly. This increases the risk of stillbirth.

Problems with a baby's growth should be picked up during antenatal appointments. However, it's important to be aware of your baby's movements to try to spot any problems as early as possible.

See preventing stillbirth for more information.