Causes of premature birth

It's not always possible to explain the causes of preterm birth and why it happens. There are risk factors for being born early, such as infection, placental problems or genetic problems, but in many cases the cause is unknown.

Most preterm babies arrive early without warning. However, some pregnancies are known to be at risk of ending in preterm birth.

We still have a lot to learn about premature birth so it's not always possible to explain the causes and why it happens. There are maternal and baby risk factors for being born early, such as infection, placental problems or genetic problems for example, but in many cases the cause is unknown. 

This is partly why prevention of premature birth is still in need of extensive research - without knowing the causes, a treatment is difficult. Tommy's invests more than £400,000 annually into prematurity research.

Although the cause of premature birth cannot often be determined all the conditions below are risk factors for premature birth. This means that if you have one of these premature birth is more likely to happen.

  • Diagram of cone biopsy

    Cone biopsy and LLETZ

    LLETZ and cone biopsy are both treatments to remove abnormal cells in cervical area. LLETZ stands for Large Loop Excision of the Transformation Zone.

  • Itching hands

    Intraheptic cholestasis of pregnancy (ICP)

    Intrahepatic cholestasis of pregnancy (ICP), also known as obstetric cholestasis (OC), is a liver disorder that can develop during pregnancy.

  • Doctor taking pregnant woman's blood pressure.

    Pre-eclampsia and premature birth

    Pre-eclampsia is a serious condition that only occurs during pregnancy, typically after 20 weeks. It is a combination of hypertension (high blood pressure) and proteinuria (protein in your urine).

  • Profile of pregnant woman drawn in chalk on black board.

    Intrauterine infection (chorioamnionitis)

    Intrauterine infection, also known as chorioamnionitis, is infection within the womb.

  • Pregnant woman being checked by midwife.

    Fetal growth restriction (Intrauterine growth restriction)

    Fetal growth restriction (FGR) is a condition where a baby is smaller than expected or when a baby's growth slows or stops during pregnancy. It is also called intrauterine growth restriction (IUGR).

  • Woman with diabetes in pregnancy talking to health professional.

    Type 1 or 2 diabetes in pregnancy

    There are risks in every pregnancy, but if you have type 1 or 2 diabetes the risks are higher for both mother and the baby. However, there are lots of things you can do to reduce the risks and give your baby the best possible start in life.

  • Premature baby.

    Lifestyle factors and premature birth

    The way your life is lived can have an effect on your risk of premature birth.

  • Pregnant woman talking to health professional.

    Antiphospholipid syndrome (APS)

    Antiphospholipid syndrome is an immune system disorder. It can cause pregnancy complications, but treatment can help to reduce the risks for you and your baby.

  • Pregnant woman being checked by health professional.

    Uterine abnormality - problems with the womb

    Some women have a congenital uterine abnormality, which is a womb/uterus that formed in an unusual way before birth.

  • Infographic of cervical stitch

    Cervical incompetence

    When the cervix shortens and opens in the second trimester (16 to 24 weeks) or early in the third trimester without any other symptoms of labour it may be referred to as cervical incompetence or cervical insufficiency.

  • Infographic of PPROM

    Waters breaking early (PPROM)

    Preterm prelabour rupture of membranes (PPROM) is when your waters break before 37 weeks of pregnancy. If this happens, you will need to get medical help straight away.

  • Plancental abruption infographic

    Information about placental abruption

    The placenta is your baby’s support system in the womb. If your placenta doesn’t work properly, your baby is at risk of health problems. Placental abruption is when your placenta comes away from the wall of your womb.

  • Clinician scanning a pregnant woman

    Low-lying placenta (placenta praevia)

    The placenta is your baby’s support system in the womb. If the placenta doesn’t work properly, your baby is at risk of health problems.

  • Woman having blood sugar level check by health professional.

    Gestational diabetes

    Gestational diabetes is a type of diabetes that can develop during pregnancy. Some women are able to manage it by eating a healthy, balanced diet, staying active and maintaining a healthy weight. Others may need to take medication.

Read more about premature birth

    Last reviewed on April 1st, 2017. Next review date April 1st, 2020.

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    Please note that these comments are monitored but not answered by Tommy’s. Please call your GP or maternity unit if you have concerns about your health or your baby’s health.
    • By Anam naeem (not verified) on 15 Jan 2020 - 18:05

      I last week gave premature birth to 26 weeks older son through c section. My son passed away after 4 hours. I couldn't even saw him. A very painful nd helpless time of my life.

    • By Esther 0905 (not verified) on 27 Oct 2019 - 04:43

      Hi my 1st was born at 20 weeks n passed on after 3 days. He weighed less than 700g. Then I had a baby girl who was bor at 27 weeks in 2012 weighing 1.4kg, shestayed in hospital for 6 weeks and discharged at when her weight was 1.8kg she us now 7yrs old and has asthma n on chronic meds for the breathing problems. Then in 2016 I delivered another girl at home while waiting for the ambulance, at 26 weeks, upon arrival at the hospital she weighed 930g. I had a my cervix stitched with this pregnancy and was confident she will come at full term. Boom surprise she came at earlier tearing those stitches on my cervix. Her stay in hospital was 10 weeks and had a series of problems e.g NEC.

    • By Margaret Carragher (not verified) on 7 Mar 2019 - 22:04

      My youngest daughter now 14yrs old was born at 24 weeks weighing 1lb, she came home from hospital after 11 weeks with no help or anything for her breathing and a scar on her septum where the cpap mask made a hole, her weight being 4lb 2oz, she contacted the rsv virus when she was a year old and spent her 2nd Christmas in hospital, when she was 2yr6m, she swallowed a penny that got lodged in her windpipe and had to go to theatre to have it removed under general anaesthetic, when she was 4 she was hit on the back of her head with a brick and was taken to hospital to have the wound glued and when she was 7 she was hit by a car!, despite the accidents she progressed through nursery school and then primary school pretty good with no major health issues, since starting High School her health seems to be deteriorating, right now she is on the most asthmatic medicine she could possibly be, she has chronic rhinitis, an altered breathing pattern and is waiting for an appointment to be tested for the condition Paradoxical Vocal Cord Dysfunction (PVCD), her breathing has gotten so bad that she needs a lift-pass at High School because she can't cope with the stairs between 3 floor and gets very shortof breath,

    • By G. Guillermo (not verified) on 7 Jun 2019 - 06:59

      How is your daughter's breathing now? How was the appointment? My son was born at 23 weeks 1 pound 6 oz. (5 and a half months in the NICU) and was put on the most evasive breathing machines for so long :( Not days or weeks but months! His lung collapsed as well.
      He's almost 5 now, but I'm very afraid he'll have breathing issues when he's older too.
      I hope you and your daughter are finding the answers you need! I'm sorry she's going through this now in high school. She'll be in my prayers. She is sooooo strong! And you are too! Hang in there! Keep being vigilant about her health! Us moms are our kids best advocates!

    • By Anonymous (not verified) on 24 Oct 2019 - 00:25

      Our prayers are with u

    • By Miriam (not verified) on 31 Mar 2020 - 16:41

      Sorry about your daughter i advice you to accept Christ Jesus into your lives and believe him to heal you daughter. "By His stripes we were healed according to the bible 1peter 2:24" God protect your family.

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