Miscarriage (early pregnancy loss)

Miscarriage is the spontaneous loss of an intrauterine pregnancy before 20 weeks gestation (or weighing less than 400g depending on the jurisdiction). It occurs in approximately 10-20% of all clinical pregnancies. The risk of miscarriage increases with increasing maternal age; miscarriage occurs in 21% of pregnancies between the age of 35-40 years old and increases to 41% above the age of 40 years old. Most miscarriages (~80%) are diagnosed between 8-12 weeks, with the risk of miscarriage decreasing as gestational age increases.

Causes of miscarriage

In the first trimester the most common cause of miscarriage is chromosomal abnormality (50-60%):

  • Autosomal trisomy is the most common abnormality – trisomy 16 is the most common trisomy in miscarriage
  • The most common single chromosomal anomaly is 45X karyotype
  • Maternal age is related to aneuploidy risk = increasing maternal age increases aneuploidy risk


In the second trimester miscarriage is commonly due to an incompetent cervix:

  • Important risk factor is previous cervical surgery


Other potential causes of miscarriage include:

  • Fetal malformations e.g. neural tube defects
  • Uterine structural abnormalities e.g uterine septum, Asherman’s syndrome, fibroids


  • Chronic maternal health factors:
    • Thrombophilia
    • Antiphospholipid syndrome
    • SLE
    • PCOS
    • Poorly controlled diabetes mellitus
    • Thyroid dysfunction


  • Active infections including:
    • Rubella
    • CMV
    • Herpes simplex virus
    • Listeria infection
    • Toxoplasmosis
    • Parvovirus B19


  • Iatrogenic causes:
    • Amniocentesis
    • Chorionic villus sampling


  • Social factors:
    • Tobacco
    • Alcohol
    • Cocaine


  • Exposure to environmental toxins
  • Advanced paternal age

Definitions of miscarriage

Miscarriage can be classified according to stage.


1. Threatened miscarriage

The fetus is “threatened” (i.e. a miscarriage may happen). There is some vaginal bleeding BUT the cervical os is CLOSED and ultrasound reveals a VIABLE intrauterine pregnancy.

IMPORTANT TO NOTE: 90% of threatened miscarriages will continue to grow to normal gestation.


2. Inevitable miscarriage

The miscarriage is “inevitable” i.e. a miscarriage is going to happen. There is vaginal bleeding +/- cramping abdominal pain AND the cervical os is OPEN but the products of conception have not yet passed.


3. Incomplete miscarriage

The miscarriage is “incomplete”, i.e. currently happening. There is heavy and increased vaginal bleeding, intense lower abdominal pain and passage of some products of conception. On examination the cervical os is OPEN and there are PRODUCTS OF CONCEPTION present in the canal.


4. Complete miscarriage

The miscarriage is “complete”. Products of conception have been passed. On examination the cervical os is CLOSED. Ultrasound reveals an EMPTY uterine cavity.


Other types of miscarriage

Missed miscarriage

The miscarriage was “missed” i.e. a NONVIABLE INTRAUTERINE pregnancy has remained inside the uterus (the fetus has not spontaneously aborted). The patient is amenorrhoeic but has not had any vaginal bleeding or abdominal pain. On examination there is no passage of tissue and the cervical os is CLOSED. Ultrasound confirms a non-viable intrauterine pregnancy.


Blighted ovum

Missed miscarriage in which embryonic development stopped before the embryonic pole was visible. The gestational sac may continue to grow.


Septic miscarriage

Miscarriage + sepsis (symptoms of fever / significant abdominal tenderness).


Recurrent miscarriage

Occurrence of 3+ miscarriages.

Clinical assessment



  • Amenorrhoea
  • Vaginal bleeding (details regarding quantity and pattern) +/- syncope (indicating significant blood loss)
  • Cramping abdominal pain
  • Passage of any fetal tissue
  • Fever ?septic miscarriage

Menstrual cycle: LMP / cycle length / days bleeding / clots / flooding

If known to be currently pregnant: dating based on LMP / USS results


Past obstetric history:

  • Outcomes from previous pregnancies and complications
  • Previous miscarriage or ectopic pregnancy increases the risk


Past gynecological history:

  • Including cervical / uterine surgery
  • Risk factors for ectopic pregnancy –  previous ectopic, previous STI/PID, IUD, previous tubal surgery
  • Contraception
  • Pap smears – abnormal results – LETZ surgery


General medical and surgical history

Family history

Medications / Allergies

Social history: Smoking / Alcohol / Illicit drug use


Important points on examination

Vitals: assessment of haemodynamic stability / pyrexia

Abdominal examination: benign in miscarriage (if rebound tenderness present consider ectopic pregnancy)


Pelvic examination considerations:

  • Speculum examination
    • Determine the source of the bleeding
    • Quantify the bleeding
    • Is the cervical os open or closed?
    • Evidence of products of conception in the cervical os
    • Purulent cervical discharge ? septic miscarriage


  • Bimanual examination
    • Uterine size
    • Cervical motion tenderness (if present increases likelihood of ectopic pregnancy)
    • Adnexal mass ?ectopic pregnancy


Blood tests

Complete blood count with differential.


Quantitative b-hCG:

  • A single level to assist in USS interpretation (discussed below)
  • Level may be less than expected for dates in miscarriage (b-hCG doubles every 48 hours reaching 100 000 at 10 weeks, and then plateauing and decreasing to 10 000 at term)
  • Serial testing every 48 hours showing a falling b-hCG indicates a failing pregnancy (if less than 10 weeks gestation)


If bleeding is significant: group and hold / cross match

Antibody screen: rhesus negative patients will require anti-D

Transvaginal ultrasound

Ensure that the b-hCG level is above that of the discriminatory zone:

  • The discriminatory zone is the level of serum b-hCG above which the gestational sac is visible on USS
  • To confirm a pregnancy by transvaginal ultrasound the b-hCG must be above 1500.
  • This correlates with a gestational age of approximately 5 weeks gestation.
  • The discriminatory zone for an abdominal ultrasound is 6500.


Five points to check in pregnancy:

  • Dating
  • Location: is the pregnancy intrauterine? = important to rule out ectopic pregnancy
  • Multiple pregnancy
  • Molar pregnancy = “snowstorm” appearance
  • Nonviable pregnancy includes:
    • Gestation sac > 25mm diameter with no yolk sac or embryo
    • No cardiac activity: fetal heart rate is typically detected at 5.5 to 6 weeks
  • Look for retained products of conception (if from the history the miscarriage is incomplete or complete)


Histological examination of any tissue passed vaginally.

Differential diagnosis of early pregnancy bleeding

1) Miscarriage

2) Ectopic pregnancy

3) Molar pregnancy

4) Implantation bleed

5) Genital tract trauma

6) Cervical pathology: ectropion / polyp / malignancy


Management considerations

  • Emergency
  • Surgical
  • Medical
  • Expectant
  • Psychological support


In every case:

  • Is the patient haemodynamically stable?
  • Rule out ectopic pregnancy
  • Check rhesus status, if rhesus negative give anti-D


Emergency management (haemodynamically unstable)

The key points in this situation are to make an accurate assessment of the patient, initiate basic resuscitation (ABCD) and inform seniors as soon as possible. 

Resuscitation of the patient using the ABCD approach.

Urgent O&G specialist input – consultant / registrar input is essential.

Urgent speculum examination to remove POC as clinically indicated:

  • This may stop the bleeding and restore blood pressure (POC in the cervical os causes cervical dilatation which causes a vasovagal response)

Urgent ultrasound scan: exclude ectopic pregnancy

Anti-D should be considered if the patient is rhesus negative.


Continued bleeding in a haemodynamically unstable patient warrants surgical evacuation.


Surgical evacuation (dilation & curettage)

Dilation and curettage (D&C) refers to the dilation (widening) of the cervix and surgical removal of part of the lining of the uterus and/or contents of the uterus by scraping and scooping (curettage).


This procedure is indicated in the following situations:

  • Haemodynamic instability
  • Excessive bleeding
  • Infected retained tissue
  • Suspected molar pregnancy
  • Unsuccessful expectant or medical management


Risks of the procedure:

  • Risks of general anaesthesia (e.g. N/V, DVT/PE )
  • Risks of any operation (e.g. infection, haemorrhage)
  • Possibility of retained products after operation
  • Uterine perforation
  • Cervical tears
  • Intrauterine adhesions (Asherman’s syndrome)

Medical management

Medical management involves the use of a prostaglandin agent to induce uterine contractions and effacement of the cervix (Misoprostol is commonly used).

If haemodynamically stable, women may prefer this option.

It has an 85% success rate.


Risks include: 

  • Bleeding that may continue for up to 3 weeks
  • Increased pain in association with the bleeding
  • Infected products of conception


Patient education – it’s essential to inform the patient of the potential risks and explain the need to seek review

Follow up – patients are usually followed up approximately 1 week later


Expectant management

Expectant management involves waiting for spontaneous passage of the products of conception, without any medical or surgical intervention.


Risks include: 

  • Bleeding that may continue for several weeks
  • Increased pain in association with the bleeding
  • Infected products of conception


Patient education – it’s essential to inform the patient of the potential risks and explain the need to seek review

The patient may require anti-D if they are rhesus negative.

Follow-up review at 7-10 days with ultrasound – if continued bleeding, pain or evidence of retained POC on ultrasound discuss further management (suction curettage)


Psychological support

Break bad news appropriately and ensure support.

Provide written information.

Communicate to general practitioner via letter.

Offer referral to relevant healthcare professionals and support groups prior to discharge – particularly for counseling/psychological support.

Risk of recurrence

There is no increased risk of having another miscarriage after having one miscarriage (10-20% for the general population).

After two miscarriage the risk of having another miscarriage is 25%.

After three miscarriages the risk is approximately 40%.

Recurrent miscarriages

3+ miscarriages, requires specialist review

There is an underlying cause in 50% of patients.


Causes include:

  • Increased maternal age
  • Parental genetic factors (balanced translocations, mosaicism)
  • Thrombophilic disorders
  • Endocrine disorders (diabetes mellitus, thyroid disorders, PCOS)
  • Structural uterine abnormalities


Pertinent features on history:

  • Menstrual cycle history
  • Medical Hx: clotting (DVT, PE), endocrinopathy (diabetes mellitus, thyroid dysfunction)
  • Hx of cervical surgery or uterine instrumentation (cervical incompetence, Asherman’s syndrome)
  • Hx of congenital abnormalities that may be heritable
  • Detailed family history
  • Exposure to environmental toxins (e.g. occupational exposures)


Physical examinations –  should include general physical assessment, any signs of endocrinopathy and any pelvic organ abnormalities.



  • Cytogenetic analysis performed on the products of conception of the third and any subsequent miscarriages
  • Parental karyotyping and genetic counseling
  • Female requires:
    • Pelvic ultrasound and MRI, sonohysterography, hysteroscopy for further structural evaluation
    • Thrombophilia screen
    • Antiphospholipid antibody screen, anticardiolipin antibodies and lupus anticoagulant
    • Thyroid function: TSH, free T4, thyroid peroxidase antibodies


Ensure adequate psychological support.

The chance of subsequent success of an intrauterine pregnancy is still up to 75%,

The prognosis is improved if one live birth has occurred.


  • “Early Pregnancy” Loss by Elizabeth Puscheck on Medscape http://reference.medscape.com/article/266317-overview
  • Early Pregnancy Loss, Maternity and Neonatal Clinical Guidelines, Queensland Clinical Guidelines, QLD Department of Health, published Sept 2011 amended July 2015, 33 pages.
  • Examination in Obstetrics and Gynaecology by Judith Goh and Michael Flynn, Churchill Livingstone, 3rd edition, 2010, 324 pages ISBN-10: 0729539377
  • Gynaecology by Ten Teachers, edited by Ash Monga and Stephen Dobbs, CRC Press, 19th edition, 2011, 216 pages, ISBN-10: 034098354X
  • Miscarriage and Recurrent Miscarriage articles on UpToDate
  • Obstetrics and gynaecology: an evidence-based guide by Jason Abbott, Lucy Bowyer and Martha Finn, Churchill Livingstone, 2nd edition, 396 pages, IBSN-10: 0729540731
  • Toronto Notes A Comprehensive Medical Reference and Review for MCCQE and USMLE II, Editors: Miliana Vojvodic & Ann Young, Toronto Notes for Medical Students, 30th edition, Toronto Canada, 2014 pp.OB23-OB24.


Print Friendly, PDF & Email