Miscarriage

Miscarriage is a devastating to experience and it is important for both parents to seek the emotional support they need, as well as addressing any physical causes. We cover miscarriage in more detail in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy. In this section, we look at:

• How common is miscarriage?
• What is miscarriage?
• Causes of first trimester miscarriage
• Male factor contribution to miscarriage
• Causes of second trimester miscarriage
• What happens if I have a miscarriage?
• Ectopic pregnancy
• Recurrent miscarriage
• Causes of recurrent miscarriage
• Underlying health and miscarriage
• Emotional support after miscarriage

How common is miscarriage?

About a quarter of all women will experience a miscarriage at some time in their lives and the risk remains similar if you have already had children. Miscarriage occurs in 15–30 per cent of all naturally-conceived pregnancies and this includes very early losses that means a period comes a little later or is heavier than usual, or sometimes simply having what seems to be a normal period. If you experience a miscarriage, it doesn’t always mean you have a particular problem or that you are likely to miscarry again and suffer recurrent miscarriage.

What is miscarriage?

A miscarriage is the loss of a baby (fetus) at any time up to 24 weeks’ gestation, which is usually considered to be the age of viability. The loss of a pregnancy after this time is termed a stillbirth. Most miscarriages (about 85 per cent) occur during the first trimester – the first 12 weeks of pregnancy. A miscarriage involves the uterus (womb) expelling the pregnancy and usually starts with pain and bleeding, similar to the start of a period. Sometimes a pregnancy isn’t identified as not being viable until the first scan. This is termed a ‘missed miscarriage’ or, in rather old-fashioned terminology, a ‘blighted ovum’ (that is literally a non-viable egg). Some use the term spontaneous abortion to signify a miscarriage, as opposed to a therapeutic abortion, to refer to a termination of pregnancy.

A pre-clinical or biochemical miscarriage occurs when there is a measurable human chorionic gonadotropin (hCG – the hormone produced during pregnancy and used to detect pregnancy by pregnancy test kits) in your blood, usually less than 50IU/L, which remains high for a few days only and results in a delay to your period of no more than 14 days.

A clinical miscarriage occurs after the hCG has continued to rise to a time when an intrauterine gestation sac can be seen by ultrasound, either with or without a fetal pole or heartbeat, but then a miscarriage occurs.

You can find out about pregnancy monitoring when there is a risk of miscarriage in The Fertility Book: Your definitive Guide to Achieving a Healthy Pregnancy.

Causes of first trimester miscarriage

The causes and management of a single miscarriage tend to be different compared to recurrent miscarriage and don’t always mean there is an underlying problem. Understanding this distinction and what might be going on for you can help you avoid unnecessary heartache and a very prolonged journey to parenthood.

One of the main factors leading to miscarriage is increasing age – particularly of the mother, and relates to the fact that the eggs have been there since birth and, as they get older, so does their ability to develop into a genetically normal embryo.

While it is thought that at least half of miscarriages are a result of a chromosomal (genetic) problem, this has usually developed within the pregnancy itself and is not a reflection of either mother or father having abnormal chromosomes themselves (either in their bodies or in their eggs or sperm). In other words, it occurs when something has gone wrong after the sperm has fertilised the egg.

The risk of miscarriage is also increased in women who are overweight and those who smoke, so lifestyle and general health are very important, not only for fertility but also in sustaining a pregnancy. There are certain conditions that have been associated with an increased risk of miscarriage, such as polycystic ovary syndrome (PCOS), although in reality this appears to be associated more with the increased likelihood of being overweight in women with PCOS.

Miscarriage may also occur if there are problems with the developing placenta and the way that it attaches to the inside of the uterus and links in with the maternal blood supply. This is still an area where a lot more research is required.

Infections during pregnancy can also cause miscarriage. Infection may get through the cervix and affect the pregnancy, which ultimately causes a miscarriage. Miscarriage can also happen after fertility treatment, though on the whole fertility treatments don’t appear to increase the likelihood of miscarriage over and above the age-related risk. One exception appears to be the use of clomiphene citrate, which is used to stimulate ovulation for women with PCOS. Those who respond by having high levels of luteinising hormone (LH) during the follicular phase have both a reduced chance of conception and an increased risk of miscarriage. Therefore, if LH levels are found to be elevated it is sensible to use alternative treatments.

Male factor contribution to miscarriage

There is debate about the degree to which male factors may influence the risk of miscarriage. If there are abnormal semen parameters severe enough to affect fertility (such as a low count or motility), there does not appear to be a correlation with an increased risk of miscarriage. However, genetically abnormal sperm that achieve fertilisation may lead to the development of an abnormal fetus, and the risk also increases with advancing paternal age. There is also evidence to suggest that DNA fragmentation (damage to the genetic material in sperm cells) is more common in the partners of women who have had more than three miscarriages.

Causes of second trimester miscarriage

Miscarriage after the first 12 weeks of pregnancy may occur if there is an abnormality with the shape or function of the uterus – for example, the cervix may be weak (known as an ‘incompetent cervix’) and start to open up. The use of a stitch may be of benefit when the cervix has started to open up, however a large scientific review has failed to find evidence of a benefit for cervical cerclage in reducing recurrent miscarriage. A typical cause of cervical weakness is past treatment for an abnormal smear, so discuss this with your doctor if you conceive and this applies to you. There is also increased risk if the size of the uterus is smaller than average because it has developed abnormally or is distorted by fibroids.

Some medical conditions also increase the risk of miscarriage including poorly controlled diabetes, high blood pressure, kidney disease, thyroid problems and coeliac disease.

You can find out more about all causes of miscarriage and recurrent miscarriage in The Fertility Book: Your definitive Guide to Achieving a Healthy Pregnancy.

What happens if I have a miscarriage?

If you find yourself in the heart-breaking situation of experiencing a miscarriage you may be offered either expectant or active management, depending upon how much you are bleeding and your wishes. Expectant management – waiting for bleeding to stop and a natural and complete resolution of the miscarriage – does not affect future fertility any more than medical management or surgery to empty the womb. If bleeding has already started, then it is more likely you will miscarry without the need for treatment than if a non-viable pregnancy is detected on ultrasound scan in the absence of any symptoms. Active management is often offered if you have a non-viable pregnancy after fertility treatment as the problem is usually detected before signs of impending miscarriage (e.g. bleeding or pain) and expectant management could involve a wait of days or even weeks. This can involve either surgery or drugs to help pass the miscarriage.

Whatever treatment you have, it is a very difficult experience, so the decision as to how best to manage things is very personal to you. It’s also important to take the time to recover emotionally as well as physically: remember also that the majority of miscarriages are a ‘one-off’ occurrence and the likelihood of a second miscarriage is very low.

You can find out more about what happens after miscarriage in The Fertility Book: Your definitive Guide to Achieving a Healthy Pregnancy.

Ectopic pregnancy

An ectopic pregnancy may occur if a pregnancy develops within the fallopian tube or sometimes other places outside the main cavity of the uterus. As an ectopic pregnancy enlarges it cannot survive and so will start to bleed within the pelvis, causing pain and serious problems if it ruptures. It is important to make the diagnosis of an ectopic pregnancy as early as possible so as to treat it before it ruptures. A ruptured ectopic pregnancy is an emergency and can be a potentially life-threatening situation.

If you experience pain or bleeding or if there are concerns about the possibility of an ectopic pregnancy, you should have a blood test to measure hCG. As well as bleeding, symptoms to look out for include fainting and pain in the tip of your shoulder. We can understand more about the pregnancy by monitoring the rate of rise of hCG levels. In a normal pregnancy, the serum hCG concentration doubles every two to three days from six weeks’ gestation (see above). If the rise in hCG is less than 66 per cent in a 48-hour period, a non-viable pregnancy (ectopic or miscarriage) is likely in 80 per cent of cases.

If you have signs of a ruptured ectopic pregnancy, it is essential to have an urgent operation (a laparoscopy). While the vast majority of ectopic pregnancies can be managed by laparoscopic surgery (also known as minimal access or ‘keyhole’ surgery), occasionally it is necessary to do a bigger operation to open up the abdomen (laparotomy).

We cover ectopic pregnancies, their medical treatment and impact on future fertility in much more detail in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy.

Recurrent miscarriage

If you have experienced a miscarriage it is unlikely that it will happen again. Some couples, however, experience repeated or recurrent miscarriage/recurrent pregnancy loss (RPL), which usually means at least three miscarriages occurring at the same stage in pregnancy. There are different (though sometimes overlapping) causes for recurrent miscarriage, and understanding the distinction will help you get the medical care that you need. Most couples with recurrent miscarriage are fertile as they will have experienced at least three consecutive miscarriages. Some, however, have coexistent subfertility and so the repeated loss of long-awaited pregnancies adds to the trauma that they have already experienced.

In the UK, current guidelines stipulate that women have to have experienced three miscarriages to have extended testing, and many other countries have similar criteria, but we believe this needs to change. Relatively few couples (approximately 1 per cent) will experience recurrent miscarriages and this is when further investigations should be performed.

While up to a third of couples with recurrent miscarriage have experienced fertility problems at some time, we are often faced with couples attending the fertility clinic who have experienced one or two miscarriages. They might have undergone extensive fertility investigations and received various fertility therapies and so are naturally concerned that their next pregnancy is viable should they conceive after further treatment. Using the above criteria, they do not have ‘recurrent’ miscarriage and so would not usually warrant investigation, yet because their concerns are understandable, it is our view that all women who have experienced one or more miscarriages should also have initial tests, without having to wait to have three miscarriages. We cover our recommendations in detail in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy.

Causes of recurrent miscarriage

An underlying cause is most likely to be found if the repeated miscarriages occur at a similar stage in pregnancy. First trimester (the first 12 weeks of pregnancy) losses account for 75 per cent of recurrent miscarriages and second trimester losses the remaining 25 per cent. Even if a cause is found there is always the possibility that future miscarriages might be due to another cause. Miscarriages are of a sporadic nature and so any treatment that is offered has to allow for the fact that future miscarriages may not be due to the condition that has been treated.

The causes of recurrent miscarriage may have genetic, anatomical, infective, hormonal or immune origins. While often no cause is found, it may be that with future research currently unknown issues may be identified.

Factors that are common causes of single miscarriage, and sometimes of recurrent miscarriage, include:

• Toxic environmental factors including occupational exposure to chemicals (toluene, xylene, formalin, some chemical disinfectants, glues, paints), alcohol and smoking.
• Infection
• Hormonal abnormalities including poorly controlled diabetes and thyroid disease

Factors that may cause or contribute to the risk of recurrent miscarriage include:

• Genetic cause
• Anatomical abnormalities
• Luteal phase defects
• Immunological factors
• Coeliac disease when not managed with a gluten-free diet
• Sperm DNA fragmentation

We cover all of these factors in detail in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy.

Underlying health and miscarriage

If you experience either one or more miscarriages, it is always worth looking at your underlying health and any symptoms you may be experiencing. Coeliac disease often goes undiagnosed for years, for instance, and many people do not experience classic digestive symptoms (diarrhoea, bloating, abdominal discomfort etc) or a noticeable reaction to wheat but undiagnosed coeliac disease can increase the risk of miscarriage. Digestive symptoms generally may be a sign you are not absorbing the nutrients from food well and should be investigated. Ensuring you have sufficient levels of key nutrients for fertility and pregnancy is helpful. Ensuring any pre-existing health conditions are well managed is also important as part of a preconception care programme. Optimising diet, health and nutrient levels in the father and the mother before you conceive supports the health of the pregnancy and the future health of your child. You can find out more in our Health and Wellbeing and Nutrition sections of this Fertility Guide, our Fertility and Preconception Care course and The Fertility Book: Your definitive Guide to Achieving a Healthy Pregnancy.

Emotional support after miscarriage

It goes without saying that if you experience miscarriage you should be offered support and counselling as the loss of a pregnancy is heart-breaking for you and your partner. We fully appreciate how difficult it is and recommend seeking support through your clinic, counsellors, local and national support organisations. The Miscarriage Association is one organisation that provides support for people who have experienced miscarriage.

Remember that you are not alone, even though it may feel like it. For most people the sad loss of a pregnancy is a single event and the greatest likelihood is that your next pregnancy will be fine. Alongside individual support, you may find strategies to help cope with the general stress of infertility in the Fertility, Stress and The Mind section helpful.

Talk to your doctor next time you get pregnant so that you are monitored carefully and supported during what will naturally be an anxious time. You can find out more about all aspects of miscarriage and recurrent miscarriage to help ensure you have the right investigations and treatments in The Fertility Book: Your definitive Guide to Achieving a Healthy Pregnancy.

References

1. Adam Balen and Grace Dugdale. The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy. Penguin Random House (Vermilion) 2021
2. McQueen, D. B., Zhang, J., & Robins, J. C. (2019). Sperm DNA fragmentation and recurrent pregnancy loss: A systematic review and meta-analysis. Fertility and Sterility, 112(1), 54–60.
3. American College of Obstetricians and Gynecologists (2014). Cerclage for the management of cervical insufficiency. ACOG Practice Bulletin no. 142. Obstetrics & Gynecology, 123(2 Pt 1), 372–9.

Copyright © 2025 Balance Fertility