Causes of miscarriage

We don’t know why all miscarriages happen, but sometimes there can be underlying reasons for this type of pregnancy loss. It’s very unlikely that a miscarriage was caused by something you did or didn’t do.

At the moment, it sadly isn’t always possible to give a reason why a woman has a miscarriage. That’s why Tommy’s opened the UK’s only miscarriage research centre dedicated to understanding miscarriage and preventing it.

However, there are some reasons why a miscarriage may happen that we do know about.

Early miscarriage

If a miscarriage happens during the first 3 months of pregnancy (known as early miscarriage), it’s usually caused by chromosomal abnormalities in the baby. These happen by chance.Chromosomes are blocks of DNA, which contain instructions for your baby’s development.

Sometimes something can go wrong at the point when you get pregnant and the baby gets too many or not enough chromosomes. If this happens, the baby can’t develop properly.

If there's a problem with the development of the placenta, this can also lead to a miscarriage. The placenta is an organ that helps your baby grow and develop. It’s attached to the lining of the womb and is connected to your baby by the umbilical cord.

Late and recurrent miscarriage

There are several factors that may play a part in causing recurrent and late miscarriage. Recurrent miscarriage is usually defined as the loss of 3 or more consecutive pregnancies. Late miscarriage is when a baby dies between 14 and 24 weeks of pregnancy.

Antiphospholipid syndrome (APS)

Antiphospholipid syndrome (APS) is a syndrome that makes your blood more likely to clot. This is not common but can cause recurrent miscarriage and late miscarriage.


Thrombophilia is an inherited condition that means that your blood may be more likely to clot. This may cause recurrent miscarriage and late miscarriages.

Genetic factors

Recurrent miscarriage is sometimes caused by genetic factors. If one partner has an abnormality in one of their chromosomes, it can sometimes cause repeated miscarriages. The partner may not be aware of this abnormality. This happens in around 2–5% of cases.

Find out more about conception and your baby’s genes.

Weak cervix

If you miscarry between 14 to 23 weeks of pregnancy, it may be due to a weak cervix. Unfortunately, this can be difficult to diagnose when you are not pregnant. But it may be suspected if your waters broke early in a previous pregnancy, or if the neck of the womb opened without any pain in a previous miscarriage.

Find out more about cervical weakness.

Developmental problems with the baby

If the baby has any abnormalities, it may lead to a miscarriage. But these are unlikely to be the cause of recurrent miscarriage.


Any infection that makes you very unwell can cause a miscarriage. Milder infections that affect the baby can also cause a miscarriage.

Shape of the uterus

It is not clear how much an abnormally shaped uterus contributes to recurrent miscarriage or late miscarriages. Minor variations do not appear to cause miscarriage, but significant fibroids and polyps are associated with recurrent miscarriage.

Long-term health conditions

Some long-term health conditions can increase the risk of having a miscarriage in the second trimester, especially if they’re not treated or well controlled. These include:

  • diabetes
  • high blood pressure
  • lupus
  • kidney disease
  • an overactive thyriod gland
  • an underactive thyriod gland.

Polycystic ovary syndrome (PCOS)

Polycystic ovary syndrome is a common condition. It is when the ovaries don’t always release an egg in the middle of the menstrual cycle (the start of a period to the start of the next one). The ovaries can become larger than normal.

Polycystic ovary syndrome is related to hormonal changes in the ovaries and it can lead to problems getting pregnant. There's also some evidence to suggest it may also be linked to an increased risk of miscarriages in fertile women.


Medicines that increase your risk include:

  • misoprostol – used for conditions such as rheumatoid arthritis
  • retinoids – used for eczema and acne
  • methotrexate – used for conditions such as rheumatoid arthritis
  • non-steroidal anti-inflammatory drugs (NSAIDs) – such as ibuprofen, which are used for pain and inflammation.

Other medicines are unsafe during pregnancy. It’s always best to ask your doctor, midwife, pharmacist or dentist about any medications that you are taking.

Find out more about drugs and medicines in pregnancy.

Food poisoning

Food poisoning is caused by eating food that contains bacteria, viruses or parasites For example, pâté may contain listeria. These are bacteria that can cause an infection called listeriosis. Listeriosis is rare, but it can cause miscarriage, harm a baby during pregnancy or cause severe illness in a newborn.

Find out more about foods to avoid in pregnancy and tips for food safety.

Your age

Your age isn’t something you can control. But unfortunately, the risk of miscarriage does increase with age. One medical study showed that the risk of having a miscarriage is 8.9% for women aged 20-24 years and increases to 74.7% in women aged 45. 

This is because the number and quality of eggs gets lower as you get older. This is also why it can take longer to get pregnant as you get older.

The risk of miscarriage also increases with the age of the father. This is because chromosomal anomalies in sperm are found more often as men get older. Chromosomes are blocks of DNA which contain the instructions for developing every single part of a baby. Anomalies can cause genetic abnormalities in the baby, which sometimes causes miscarriage.

The risk of miscarriage is highest among couples where the woman is aged 35 years or older and the man is aged 40 years or older.

A man’s ability to father a baby also declines with age, though not as much as in women.

Myths about the causes of miscarriage

There are several myths about what can cause a miscarriage. The following things are not linked to an increased risk of miscarriage:

Lifestyle changes you can make

It is important to know that miscarriages very rarely happen because of something you did or didn’t do. However, there are some lifestyle choices, such as smoking, that increase your risk of having a miscarriage. There are things you can do to try and reduce this risk. These include:

It’s important to remember that there is nothing you can do that will guarantee that you won’t have a miscarriage. However, we have lots of information about what you can do to try to reduce the risk and stay as healthy as possible before you try for a baby and during pregnancy.

Was it my fault?

Unfortunately, doctors can’t always give a reason why a miscarriage happens. This can be very difficult to come to terms with. Without having a reason why, some women and couples end up unnecessarily blaming themselves for what happened. We have answered some common questions that we hope will prevent this.

Find out more about why did I miscarry and was it my fault?

Tests and treatments after miscarriage

Sometimes doctors can do tests to try to find out why you had a miscarriage and what this means for any future pregnancies.

Most women go on to have a healthy pregnancy after a miscarriage, so tests are not usually offered until a woman has recurrent miscarriages or 1 late miscarriage. This may vary in different areas, so talk to your GP or midwife to find out more.


Read more about miscarriage

Read more about our miscarriage research

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Royal College of Obstetricians & Gynaecologists (2016) Early miscarriage

NHS Choices. Miscarriage (Page last reviewed 01/06/2018 Next review due: 01/06/2021)

NHS Choices. Foods to avoid in pregnancy (Page last reviewed: 23/01/2017 Next review due: 23/01/2020) 

Anderson, N  et al (2000) Maternal age and fetal loss: population based register linkage study. British Medical Journal. 2000 Jun 24; 320(7251): 1708–1712.

NICE Clinical Knowledge Summaries. Miscarriage (Page last reviewed: May 2018 Next review due: December 2023)

Clinical Knowledge Summaries (Feb 2019) Antenatal care – uncomplicated pregnancy

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    Last reviewed on March 12th, 2020. Next review date March 12th, 2023.

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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 Maliha Qureshi (not verified) on 24 Mar 2020 - 10:18

      I recently moved to uk with my husband , i used to live in germany where I delivered my only living child preterm at 30th week. And them continuous miscarriages. Lately i was in my home country and was diagnosed with aps and during pregnancy was put on aspirin progesterone and clexane injection but then i have to move here and doctors obviously were not providing me with my medication and i lost my baby. I also have under active thyroid which is in control now. So i want to ask how can i lead my case so i cant have more loses . I am diagnosed bit not here in UK.

    • By Anonymous (not verified) on 22 Jan 2020 - 22:00

      January 24th 2019 had an ultrasound gestational sac present but no yolk and no growth 2 weeks later so was given medicine to flush it out. January 22nd 2020 had 2nd ultrasound and could not find the heartbeat at 8 weeks when the heartbeat was found at 7 weeks beating at 153 bpm I don’t understand I’ve never had any complications til now I have a 12 year old son

    • By Rach (not verified) on 13 Jan 2020 - 16:35

      I started bleeding heavy plum like clots at around 17 weeks. At 19 weeks i was told there was not enough fluid around my baby and had to have a medical termination. Im so scared incase this happends again. What are the chances ?

    • By Nsha (not verified) on 20 Dec 2019 - 14:32

      I don’t know where to begin with. This feeling inside me is indescribable. Day before yesterday i went for my regular scan and found out that my baby has no heartbeat and stopped growing since last two weeks. But i had 3 normal deliveries before this, no complications. How can it happen all of a sudden. All my blood and glucose test were normal.i am waiting to naturally deliver my missed miscarriage since 2 days no cramps ,pain or period .All I believe is i will see my little angle in the heaven .i hope and pray no parents should go through such difficult situation where Your happiness turns into grieve and sorrow. That one sentence of the sonographer felt like a knife in my heart, and what is more frustrating is doctors have no answer to what could have cause this to happen.

    • By Anonymous (not verified) on 28 Oct 2019 - 14:59

      I would like some advice, Iv had 2 misscaridges now, 1 at 6 weeks and other 1 at 11 weeks 2 days. I have rhesus negative A blood and no one has told me about the anti D injection. Could this be why I had a miscarriage?

    • By Unknown. (not verified) on 16 Mar 2020 - 21:25

      It's hard to accept. I'm in the situation ryt now 2 miscarriages in 10 months. I feel like I'm done. This is too much for me.

    • By Yealie Sesay (not verified) on 24 Oct 2019 - 00:18

      I also just had a miscarriage at 24 weeks

    • By Malika (not verified) on 18 Oct 2019 - 05:03

      I'm 3 weeks pregnant is there still a chance I can have a miscarriage this early? Because I've been having trouble eating, breathing, I'm always nauseated while smelling certain things and show mood swings... I need to know what should I do. This would be my first, even though I wouldn't mind having a child, but it's just not the time or place for me to have one until I'm financially stable to have a baby.

    • By Afreen khalfe (not verified) on 29 Sep 2019 - 15:42

      Sorry to hear from all of u
      I had recurrent 3 miscarriages
      First 2 were natural conception third one was IVF ...that too failed
      All my babies heartbeat stops suddenly after 6 weeks
      Doctors are not able to give a sound proof reason
      But I still remember that my first gynaecologist after my miscarriage had suggested me tuberculosis drugs for eliminating all the viruses or bacteria which are present in females genitals which is usually left unrecognised by us ...
      Feeling regretted should have started at that time only
      God please listen to our prayers and bless everyone who are waiting for their child to be born
      Please listen to our prayers

    • By Doreeen (not verified) on 6 Nov 2019 - 08:06

      I need advice

    • By Anonymous (not verified) on 26 Sep 2019 - 16:26

      I had consecutive miscarriages thrice. The first one was at 7 weeks, no heartbeat. Second one was at 8 weeks 4 days, we lost both the heartbeats. Third one was at 8 weeks 3 days, we lost both the heartbeats which happened today.Trying to get pregnant with IVF itself was a very emotional, having miscarriages is emotionally draining.My doc couldn't identify the problem why it was happening around the same time. Looking for answers. Is anyone having the same situation or anything to share plmk.

    • By Preeti (not verified) on 26 Sep 2019 - 10:13

      This was my first pregnancy, I was experiencing lots of pregnancy symptoms like breast pain, heavyness, nousea, craving for food, cramps at Tommy for whole month. After 1 month of waiting I did the home pregnancy test which shows it was positive. I was very happy, to confirm it I took the blood test to check my HCG level in blood, it shows I was 5 week pregnant. I waited for 2 weeks to start my antenatal care. After 2 weeks in the ultrasound, it shows there is nothing in my womb. By gyno advice I took the blood test to check my HCG level, it was very low. Then only I came to know that I had a miscarriage. I m shettered by pain and emotional shock. I m still unable to understand what happened.

    • By Anonymous she (not verified) on 13 Sep 2019 - 04:32

      My sister does not want to keep the baby but she is 20weeks is it posable?

    • By Sarah (not verified) on 15 Sep 2019 - 16:48

      Why has she waited until 20 weeks??

    • By douglas (not verified) on 4 Sep 2019 - 10:18

      i have two miscarriages under six months, all unkown factor. can i go for the third time.

    • By Jesenia (not verified) on 3 Aug 2019 - 06:21

      I have lost 5 pregnancies. On February 2019 I had a ruptured deadly etopic pregnancy which resulted in having my right Fallopian tube removed. It took me 2 years to get pregnant but before that i had 3 miscarriages no more than 8 weeks. Just this may I found out I was having twins. Yet I have PCOS. only have 6 periods in 2 years. Well I lost them after going to the ER because I had a dream that I lost my babies and I did. I carried my babies in my tummy for 1 month before I passed them. They told me I have low progesterone and will need medication or injections throughout my whole pregnancy when I decide to try again.

    • By BB (not verified) on 23 Sep 2019 - 04:19

      I'm so sorry... keep your chin up. You are not alone.

    • By Sam (not verified) on 17 Jul 2019 - 18:19

      I have just had my second miscarriage in 6 months. This one was natural at 11 weeks, my previous was a missed miscarriage at 13weeks, surgical management and was due to Edwards syndrome.

      I am34 with 3 children all normal births, 2 girls and a boy. I just don't understand why this is happening. I keep being told "just bad luck". It feels like it's something more.

      Is there anything I can do to check the quality of my eggs? I just don't understand why this is happening after 3 healthy pregnancy's.

      Both losses were following a scan hearing heartbeats and seeing a normal fetus, it seems like when the placenta takes over the loss occurs and i just don't know what i can do to prevent this from happening again?

    • By Jodie (not verified) on 27 Jul 2019 - 09:58

      Hello, I hope your okay, I’m the same as you I have had three healthy babies 2 girls and one boy, I have also had three miscarriages but and currently only a couple weeks pregnant, I am fretting incredibly so as I’m unsure on whether this baby will survive or it may be my fourth miscarriage in a row. The one thing I do know is that after 2 miscarriages the chances of it reoccurring is 28% and after the third it’s 48%. It’s a devastating problem for any woman to go through! I really do understand your pain and concerns, I lost one at 13 weeks, one at 8 weeks and one at 6 weeks, all after hearing heartbeat, my last miscarriage was happening whilst I had my scan and they told me my baby was fine when in fact it wasn’t because the next day I went back to hospital and I was having my baby taken away from me! I really want answers too! I wish they could scan me to find out what’s wrong but they won’t

    • By Sameera (not verified) on 28 Oct 2019 - 21:59

      same happening to me, I have two healthy kids with natural birth without any difficulties or medical issues, i'm 34 now having 9 weeks pregnancy, i had an ultrasound a week ago and everything was normal heart beat was there my all test were clear but suddenley i got blood spotting two days ago and my doctor took an urgent ultrasound and there was no single heart beat. I am shocked that what suddenly happened. Am on my way of miscarriage.

    • By Anonymous (not verified) on 11 Jun 2019 - 20:34

      Miscarriage.I had two miscarriages both at 5weeks ...what could be the reason because the doc could not identify the cause of loss

    • By Sarah (not verified) on 4 Jun 2019 - 09:41

      First was in February at 12 week scan showing 5- 6 week embryo. I grieved and put it down to one of those horrible things. We tried again after my first full cycle and I couldn't believe my luck to fall pregnant so soon. I had a 7 week scan and everything was great with a heartbeat. So I was sure it would be all okay. Only to find yesterday at my 12week scan a lifeless baby at 11.4 weeks. I already knew I asked them to turn the screen off before starting. Both times I had zero bleeding. Are there any online chats I can use to talk to others. Once I could cope with but 2 in such quick succession is proving very difficult. I'm not myself at all

    • By Anonymous (not verified) on 18 May 2019 - 11:33

      Can I try another baby just after 8 week it any harmful again ?

    • By Anonymous (not verified) on 18 May 2019 - 11:24

      2weeks ago i had my scan done it was at 10weeks 2days everything was alright but now at 12weeks 6days all the pregnancy signs have diminished the tummy completely flat i look just normal could anything be the matter since my next appointment is in 2weeks time should be worried

    • By sue (not verified) on 26 Apr 2019 - 07:02

      First was ectopic preganancy, second I had miscarriage at week9 as baby's heart beat was not developed. Doctors are unable to tell the reason of miscarriage. Please help

    • By Anonymous (not verified) on 10 Jul 2018 - 19:11

      I've had 2 ectopics and had my left tube removed since then I've had a miscarriage at 13 weeks and now another at 6 weeks. Nothing present during the early scan and HCG level is 166 so nurse said it's an early miscarriage. I've had a blood test to check for Thrombophillia, but awaiting the results. Keep being told that NHS won't do anything until I've had 3 miscarriages, I am going to go private as I can't take the pain and loss anymore but is there something specific I should be checking for as to why I keep having these loses such as clots or cervical checks?

    • By Midwife @Tommys on 12 Jul 2018 - 14:08

      I am so sorry to hear what you have been through and continue to go through. The general guidance is that the NHS do not normally offer tests and investigations until three consecutive miscarriages, which is what you have been told, and it is understandably extremely frustrating and upsetting. Sometimes some basic test are offered but this is down to the discretion of the health professional and they are not under any obligation to do so.
      With regards to cervical checks, it would be unlikely that it was your cervix that is the problem as all your losses have been in the first trimester, cervix problems are often a cause of second trimester losses not first. You are already having a blood test for thrombophillia, so when you get the results of this this may give you some more information about if you need to take aspirin and/or heparin in next pregnancy.
      It is completely your choice if you would like to access private care in the meantime, if this is an option for you. They will discuss what tests they can offer you and what their plan would be based on your history so far.
      I wish you all the best, please do be in touch with us if we can support you further.
      Best wishes
      Tommy's midwives

    • By Anon (not verified) on 8 May 2018 - 17:31

      I had a miscarriage at 11 weeks. I had a scan at 10 weeks strong heart beat and perfect little fetus developing. I got a temperature and couldn’t reduce it by the 4 day I had pain and cramping told not to worry by early pregnancy unit and then at 13 week booking had a scan to check and all had gone. I believe the temperature a virus cause the miscarriage but when I speak about this now people think I’m wrong. That it must be genetic. Why do health professionals not listen to patients after miscarriage - maybe if we did we would understand much more about the causes and risks.

    • By Midwife @Tommys on 10 May 2018 - 14:36

      Hi there
      I am so sorry that you lost your baby and you feel as if nobody has listened to you. Unfortunately, there can be many reasons for miscarriage, so it really is difficult to know if your virus/temperature may or may not have contributed in some way to the loss. It is possible that it wouldn't have helped, but i feel that it is foolish of your team caring for you to dismiss it entirely. However, whatever the reason for it, it is not possible to determine it for sure. It sounds as if you are really struggling emotionally with the loss, which is totally understandable. If you feel you need some advice and information about how to access counselling, we can assist you with this. You can get in touch via email [email protected] or 0800 0147800
      I really hope that you are doing ok and get in touch if you need us
      All the best
      Sophie Tommy's Midwife

    • By Kate (not verified) on 6 Nov 2018 - 21:29

      The exact same thing happened to me at the beginning of this year. I’m still convinced it was my flu and high temperature over 3 days or so that caused it after my healthy scan at 10 weeks

    • By Anonymous (not verified) on 6 Aug 2017 - 08:26

      I saw,the baby and HB at 8.5 weeks and all looked OK. At 12 weeks there was no HB and baby measured 8.2, days. The midwife said the baby likely passed after the internal scan. Could the scan be the reason I miscarried. When she was checking stuff it did hurt me

    • By Midwife @Tommys on 7 Aug 2017 - 11:51

      I am so sorry about your miscarriage and hope that you have good support to help you. There is no evidence to suggest that a vaginal scan can harm the growing baby. It is more likely that the timing was by chance. Best wishes to you x

    • By Midwife @Tommys on 12 Aug 2016 - 10:43

      We are so very sorry to hear that you are currently experiencing a miscarriage, I hope that you have support from the hospital and people around you. If you would like to talk please do call us on 0800 0147 800 or email [email protected] Please look after yourself

    • By Anonymous (not verified) on 12 Aug 2016 - 09:57

      My pregnacy was 8weeks and i just hade a miscarriage.and bleeding badly

    • By [email protected]'s on 19 Jul 2016 - 10:07

      We are very sorry for your and your daughter’s loss. Internal examinations are not normally carried out in early pregnancy unless there is a specific reason for it. Whatever the reason was, an internal examination does not cause miscarriage or pregnancy loss. Without knowing more about your daughter’s pregnancy history we can’t give any more information. If you (or she) would like to call us on 0800 0147 800 or email on [email protected] we can talk it through with you. Sorry again for your loss.

    • By Anonymous (not verified) on 13 Jul 2016 - 12:42

      My daughter was 9 weeks pregnant and miscarried, this one day after an internal examination which expectant mothers I am told have to go through. Could this internal examination have been the direct cause of her miscarrying her baby?

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