Miscarriage is the unplanned loss of a foetus during the first 20 weeks of pregnancy. Symptoms of miscarriage include vaginal bleeding and abdominal pain and cramps. Causes usually relate to developmental abnormalities in the baby or health issues affecting the mother.
Miscarriage is medically referred to as spontaneous abortion, which is a term that refers to naturally occurring events and not to a medical or surgical abortion. Miscarriage is also known as early pregnancy loss.
Estimates suggest that 15-20% of confirmed pregnancies result in miscarriage. The actual number is likely to be much higher because many miscarriages occur before a woman even knows that she is pregnant. Most miscarriages (approximately 80%) occur within the first three months of pregnancy.
Losing a pregnancy after 20 weeks is called stillbirth. Stillbirth is much less common than miscarriage. A stillbirth may occur due to problems with the placenta, genetic problems in the foetus, poor foetal growth or infection.
Miscarriage is a process that has four stages:
- Threatened miscarriage: any vaginal bleeding during early pregnancy, usually without severe pain although mild cramps may occur. Less than 50% of threatened miscarriages proceed to an actual miscarriage.
- Inevitable miscarriage: vaginal bleeding accompanied by dilation (opening) of the cervical canal. Bleeding is usually more severe than with threatened miscarriage and is associated with abdominal pain and cramping.
- Incomplete miscarriage: vaginal bleeding and dilation of the cervix occur with partial loss of tissue associated with the pregnancy. The bleeding is heavy and the cramping severe.
- Complete miscarriage: patients may present with a history of bleeding, abdominal pain, and tissue passing from the vagina. The bleeding and pain have usually stopped by the time the miscarriage is complete. Examination reveals a closed cervix and ultrasound demonstrates an empty uterus.
Most miscarriages occur because of chromosomal abnormalities in the baby that make it impossible for the baby to develop normally. Chromosomes carry genetic information and chromosomal errors can occur as the baby’s cells divide and grow. Chromosomal abnormalities account for 50-65% of all miscarriages.
Miscarriages can also be caused by a variety of factors related to the health of the mother. Maternal factors can be acute (sudden and short-lasting) or chronic (long-lasting).
Acute maternal health factors:
- Infections, e.g. rubella, cytomegalovirus (CMV), mycoplasma or listeria infections
- Physical trauma or severe injury
- Severe emotional shock.
Chronic maternal health factors:
- Severe high blood pressure (hypertension)
- Kidney disease
- Thyroid disease, i.e. hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid)
- Hormonal problems
- Problems with the uterus or cervix
- Systemic lupus erythematosus
- Untreated diabetes
- Polycystic ovary syndrome.
A variety of lifestyle and other factors can increase the risk of miscarriage, including:
- Increasing age
- Previous miscarriages
- Exposure to environmental or workplace toxins or radiation
- Alcohol and recreational drug abuse
- Excessive consumption of caffeine
- Being underweight or overweight
- Certain medications, e.g. isotretinoin, which is used to treat acne.
There is no conclusive evidence that working, physical exercise or having sex cause miscarriage.
Signs and symptoms
Symptoms of miscarriage may include:
- Vaginal bleeding, which varies from light spotting to heavy bleeding
- Fluid, blood clots or tissue passing from the vagina
- Abdominal pain or cramping
- Lower back pain
- Fever and chills.
If you think you are experiencing a miscarriage you should contact your obstetric health clinic or general practitioner immediately, or go to the nearest emergency department.
Symptoms such as fever or chills may indicate a septic miscarriage, which is a spontaneous miscarriage complicated by a pelvic infection.
A pelvic examination and an ultrasound test will be performed to confirm a miscarriage.
Your doctor will also take your patient history, including date of last menstrual period, number of pads or tampons used, estimated length of gestation, bleeding disorders, and previous miscarriage or elective (planned) abortions.
If there has been a lot of blood loss, your blood pressure will be measured. Blood samples may be taken to determine the amount of blood loss and whether anaemia is present, check for evidence of infection, and measure hormone levels.
No treatment is required if a miscarriage is complete. Occasionally, however, the uterus may not empty completely (incomplete miscarriage) and a dilation and curettage (D&C) procedure is required. D&C is a surgical procedure that involves dilation (opening) of the cervix and the removal of any remaining foetal or placental tissue from the uterus.
An alternative to the D&C procedure is the use of a drugs, such as misoprostol and oxytocin, to induce the body to expel the contents of the uterus. Oxytocin also helps to restore blood pressure and prevent bleeding.
Immune globulins may be administered to suppress immune response and antibody formation if the mother has been exposed to foetal red blood cells.
Regular prenatal care from a doctor, nurse, or midwife throughout your pregnancy is the best prevention for miscarriage and other complications of pregnancy.
Miscarriages caused by medical conditions, such as diabetes and hypertension, can be prevented by diagnosing and treating the condition before becoming pregnant.
Avoidance of other risk factor, such as x-rays, smoking, recreational drugs, and alcohol, will help to reduce the likelihood of miscarriage.
Further information and support
Miscarriage Support Auckland Inc.
Gaufberg, S.V. (2017). Early pregnancy loss in emergency medicine (Web page). Medscape Drugs and Diseases. New York, NY: WebMD LLC. https://emedicine.medscape.com/article/795085-overview [Accessed: 07/05/18]
Mayo Clinic (2016). Miscarriage (Web Page). Rochester, NY: Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/diseases-conditions/pregnancy-loss-miscarriage/symptoms-causes/syc-20354298 [Accessed: 07/05/18]
O’Toole, M.T. (Ed.) (2013). Spontaneous abortion. Mosby’s Dictionary of Medicine, Nursing & Health Professions (9th ed.). St Louis, MI: Elsevier Mosby.
Puscheck, E. E. (2017). Early pregnancy loss (Web page). Medscape Drugs and Diseases. New York, NY: WebMD LLC. https://reference.medscape.com/article/266317-overview [Accessed: 07/05/18]
Office on Women’s Health (2018). Pregnancy loss (Web Page). Washington, DC: U.S. Department of Health and Human Services. https://www.womenshealth.gov/pregnancy/youre-pregnant-now-what/pregnancy-loss [Accessed: 07/05/18]
Reviewed May 2018
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