Miscarriage (Spontaneous Abortion)

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PatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

See also: Miscarriage and Bleeding in Early Pregnancy written for patients

Miscarriage is defined as the loss of a pregnancy before 24 weeks of gestation. Ectopic pregnancy and gestational trophoblastic disease are not included. 

Bleeding after 24 weeks is termed 'antepartum haemorrhage'.

Classification of miscarriage is as follows:

  • Threatened miscarriage: mild symptoms of bleeding. Usually little or no pain. The cervical os is closed.
  • Inevitable miscarriage: usually presents with heavy bleeding with clots and pain. The cervical os is open. The pregnancy will not continue and will proceed to incomplete or complete miscarriage.
  • Incomplete miscarriage: this occurs when the products of conception are partially expelled. Many incomplete miscarriages can be unrecognised missed miscarriages.
  • Missed miscarriage: the fetus is dead but retained. The uterus is small for dates. A pregnancy test can remain positive for several days or even weeks in some cases. It presents with a history of threatened miscarriage and persistent, dirty brown discharge. Early pregnancy symptoms may have decreased or gone.
  • Habitual or recurrent miscarriage: three or more consecutive miscarriages.

Often no cause is found but common recognised causes include:

  • Abnormal fetal development.
  • Genetically balanced parental translocation.
  • Uterine abnormality.
  • Incompetent cervix (second trimester).
  • Placental failure.
  • Multiple pregnancy.
  • Immunological.
  • Infections.
  • Endocrine - eg, luteal phase deficiency, polycystic ovarian syndrome.

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  • Early pregnancy loss accounts for over 50,000 admissions in the UK annually.[1]
  • Miscarriage occurs in 15-20% of recognised pregnancies.
  • 85% of spontaneous miscarriages occur in the first trimester.

Risk factors

  • Age: it is more frequent in women aged >30 years and even more common in those aged >35 years (due to an increased risk of random chromosomal abnormalities).
  • Incidence increases with the number of births: 6% in the first and second pregnancies and 16% in further pregnancies.
  • Cigarette smoking of >14 per day doubles the risk over non-smokers.
  • Excess alcohol. Even low amounts - four units a week of alcohol consumption during early pregnancy - have been shown to increase the risk of spontaneous abortion substantially.[2]
  • Illicit drug use.
  • Uterine surgery or abnormalities - eg, incompetent cervix.
  • Connective tissue disorders (systemic lupus erythematosus, antiphospholipid antibodies - lupus anticoagulant/anticardiolipin antibody).
  • Uncontrolled diabetes mellitus.
  • Most cases present with vaginal bleeding and pain that should be worse for the patient than a period.
  • The patient may also have seen products of conception but may confuse these with clots.
  • Approximately half of women with a threatened miscarriage will miscarry but this increases further if they have bleeding that is increasing, bleeding that is heavier than a normal menstrual period or bleeding with clots.
  • A history of continued pregnancy-associated vomiting associated with bleeding in early pregnancy decreases the risk of miscarriage to approximately 30%.
  • Signs to look for in cases of first-trimester bleeding:
    • Is the patient shocked through blood loss?
    • Are there products of conception in the cervical canal? (Remove with sponge forceps.)
    • Is the cervical os open? (External os of multigravida usually admits the tip of the finger.)
    • Is bleeding from cervical lesions and not from the uterus?
    • Is the uterine size appropriate for dates?
  • Ectopic pregnancy:
    • The single most important diagnosis to exclude.
    • In ectopic pregnancy, the pain is usually greater, may be unilateral and usually precedes the bleeding.
    • Compared to a miscarriage, the loss is usually less heavy and darker - almost black in some cases - and there is acute pain on manipulating the cervix (cervical excitation).
  • Neoplasia.
  • Hydatiform mole.
  • Chorionic cyst.
  • Subchorionic haemorrhage.
  • Provided GPs have access to an effective Early Pregnancy Assessment Unit (EPAU), hospital admission can be avoided in up to 40% of patients.
  • The ideal EPAU should have an efficient system for appointments, ultrasound equipment (including transvaginal probes) and easy access to laboratory facilities for rhesus antibody testing and selective serum human chorionic gonadotrophin (hCG) and progesterone estimation.
  • The EPAU should be available seven days a week for women with early pregnancy complications.
  • It should be staffed by healthcare professionals with training in sensitive communication and breaking bad news.
  • Printed literature should be available for patients and standardised discharge letters sent.
  • Women who may be at risk in the future (eg, with a history of previous ectopic pregnancy or recurrent miscarriage) should be told how they can access the service in the event of a future pregnancy.


  • Ultrasound:
    • The majority of women will require a transvaginal ultrasound (TVS) and 98% of complete miscarriages can be diagnosed in this way.
    • If a transvaginal ultrasound scan is unacceptable to the woman then a transabdominal ultrasound scan should be offered and the woman should be made aware of the limitations of this method of scanning.
    • If there is no visible heartbeat then a second scan should be performed. This is either done at a minimum of 7 or 14 days, depending up the measurements of the crown-rump length or the mean gestational sac.[1]
  • Serum hCG:
    • Urine-based hCG tests can be used in the majority of women attending an EPAU. The main use of this test is to exclude an ectopic pregnancy in women with a complete miscarriage (or pregnancy of unknown location), determined by ultrasound.
    • Serial tests will often be required. At levels above 1500 IU/L, an ectopic pregnancy will usually be seen with TVS. Levels below 1000 IU/L are seen in pregnancy of unknown location or complete miscarriage but a rapid increase (often double the initial level) is highly suspicious of ectopic pregnancy.
    • Rare causes of a raised hCG should also be borne in mind, including gestational trophoblastic disease or cranial germ cell tumour, which must be considered.
  • Progesterone:
    • One meta-analysis has shown that a single low progesterone measurement for women in early pregnancy, presenting with bleeding or pain and inconclusive ultrasound assessments, can rule out a viable pregnancy.[3]
  • Admission to hospital can be avoided in 40% of women with threatened or actual early pregnancy loss.
  • Following a miscarriage, all women should have access to support, follow-up and formal counselling when necessary.
  • Anti-D rhesus prophylaxis (250 IU) should be offered to all rhesus-negative women who have a surgical procedure to manage a miscarriage.
  • However, anti-D rhesus prophylaxis does not have to be given to those women who:
    • Receive solely medical management for an ectopic pregnancy or miscarriage.
    • Have a threatened miscarriage.
    • Have a complete miscarriage.
    • Have a pregnancy of unknown location.
  • There is no evidence to support a couple delaying attempts to conceive following a miscarriage.[4]

Conservative management

  • If a scan at the EPAU confirms a first-trimester miscarriage, expectant management (waiting to see if the miscarriage will resolve naturally without intervention) for 7-14 days can be offered as the initial management strategy. However other management options should be considered for those women with:
    • An increased risk of haemorrhage (for example, she is in the late first trimester).
    • A previous adverse or traumatic experience associated with pregnancy (such as stillbirth, miscarriage, or antepartum haemorrhage).
    • An increased risk from the effects of haemorrhage (for example, if she has coagulopathies or is unable to have a blood transfusion).
    • Any evidence of infection.
  • If bleeding and pain have not started or bleeding and pain are persisting and/or increasing then these women should have a repeat ultrasound examination performed. Alternative management may be offered to those whose miscarriage is incomplete or has not started.
  • Those women who have resolution of bleeding and pain should perform a pregnancy test after three weeks. If this is still positive, they need to be reviewed and considered for either medical or surgical management.
  • Women should be counselled so they are fully aware of what to expect. In most cases, resorption of fetal tissue occurs without much bleeding. However, loss of fetal tissue vaginally can be associated with heavy bleeding and pain and the patient may prefer to opt for medical or surgical management rather than cope with this.
  • When disposing of fetal tissue which is not being sent for histology, the guidelines of the Human Tissue Authority should be followed.[5]

Medical management

  • Women may opt for medical management at the initial stage or following expectant treatment.
  • Medical management can cause more pain and bleeding than surgical management but patients who opt for this approach cite 'being in control' and avoiding general anaesthesia as the main reasons for their choice.
  • All women should be given analgesics and anti-emetics as needed.
  • Vaginal misoprostol should be offered for the medical treatment of missed or incomplete miscarriage.
  • Oral misoprostol is an acceptable alternative if this is the woman's preference.
  • Mifepristone should no longer be given as a treatment for missed or incomplete miscarriage.
  • Women should be advised that bleeding can continue for up to three weeks.
  • Women should perform a pregnancy test three weeks after receiving medical management, unless they have worsening symptoms. If these occur, they should be reviewed to ensure there is no molar or ectopic pregnancy.

Surgical management

  • Clinical indications for offering surgical evacuation include persistent excessive bleeding, haemodynamic instability, evidence of infected retained tissue and suspected gestational trophoblastic disease.
  • Where clinically appropriate, women should be offered a choice of:
    • Manual vacuum aspiration under local anaesthetic in an outpatient or clinic setting.
    • Surgical management in a theatre, under general anaesthetic.
  • Vacuum aspiration is safe, quick to perform and less painful than sharp curettage.[6]
  • Serious complications of surgery include perforation, cervical tears, intra-abdominal trauma, intrauterine adhesions and haemorrhage.
  • Screening for infection, including for Chlamydia trachomatis, should be considered in women undergoing surgical uterine evacuation.
  • Tissue obtained at the time of miscarriage should be examined histologically to confirm pregnancy and to exclude ectopic pregnancy or gestational trophoblastic disease.
  • Expectant management has been shown to lead to a higher risk of incomplete miscarriage, need for unplanned (or additional) surgical emptying of the uterus, bleeding and need for transfusion.[7]
  • However, risk of infection and psychological outcomes are similar for expectant and surgical management.
  • After complete miscarriage, bleeding normally ceases within 10 days. If part of the placenta remains, bleeding may continue with cramps. If this occurs then a repeat ultrasound should be undertaken and surgery is often required.
  • Threatened abortion is associated with risk of preterm delivery.
  • Increased risk of further miscarriages. After three of these, consider as recurrent spontaneous miscarriage.
  • Encourage reduction of alcohol consumption.
  • Smoking cessation and stopping illicit drug use.

Further reading & references

  1. Ectopic pregnancy and miscarriage: diagnosis and initial management; NICE Clinical Guideline (December 2012)
  2. Andersen AM, Andersen PK, Olsen J, et al; Moderate alcohol intake during pregnancy and risk of fetal death. Int J Epidemiol. 2012 Apr;41(2):405-13. doi: 10.1093/ije/dyr189. Epub 2012 Jan 9.
  3. Verhaegen J, Gallos ID, van Mello NM, et al; Accuracy of single progesterone test to predict early pregnancy outcome in women with pain or bleeding: meta-analysis of cohort studies. BMJ. 2012 Sep 27;345:e6077. doi: 10.1136/bmj.e6077.
  4. Bhattacharya S, Smith N; Pregnancy following miscarriage: what is the optimum interpregnancy interval? Womens Health (Lond Engl). 2011 Mar;7(2):139-41.
  5. Disposal of human tissue, The Human Tissue Authority, 2006
  6. Tuncalp O, Gulmezoglu AM, Souza JP; Surgical procedures for evacuating incomplete miscarriage. Cochrane Database Syst Rev. 2010 Sep 8;(9):CD001993. doi: 10.1002/14651858.CD001993.pub2.
  7. Nanda K, Lopez LM, Grimes DA, et al; Expectant care versus surgical treatment for miscarriage. Cochrane Database Syst Rev. 2012 Mar 14;3:CD003518. doi: 10.1002/14651858.CD003518.pub3.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Dr Colin Tidy
Current Version:
Peer Reviewer:
Dr John Cox
Document ID:
1744 (v23)
Last Checked:
Next Review:

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