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Kelsey McLaughlin, PhD


What is miscarriage?


Miscarriage is the spontaneous loss of a pregnancy before 20 weeks. ‘Spontaneous loss’ means that the body naturally ends the pregnancy without medical intervention.


Miscarriage is different than stillbirth, which is defined as the spontaneous loss of a pregnancy after 20 weeks of pregnancy.

All miscarriages are considered ‘previable’ – meaning that if the baby was born, it would not be developed enough to survive, even with medical therapy and hospital care.

Miscarriage is considered the most common pregnancy complication - as many as 25-50% of women may experience a miscarriage. The true rates of miscarriage are difficult to estimate, as women can have a pregnancy loss before they even know they are pregnant.

Following a miscarriage

Miscarriage is a difficult, sometimes traumatic event. It affects every woman differently, and can have a significant impact on the mental health of women and all members of the family.

Following an early pregnancy loss, more than 25% of women experience probable post-traumatic stress disorder one month following their loss, with high rates of depression and anxiety also. Many women continue to experience psychological impacts 3 months following a pregnancy loss.
There are numerous support communities available to those impacted by miscarriage, including:

Types of miscarriage

Miscarriage can be categorized as:

  • Complete miscarriage: all of the pregnancy tissue has been passed from the uterus

  • Incomplete miscarriage: some of the pregnancy tissue has been passed from the uterus, but some still remains

  • Missed miscarriage: the pregnancy has stopped progressing, but the pregnancy tissues are still in the uterus

  • Threatened miscarriage: bleeding and cramping threatens the pregnancy; however, the pregnancy is still progressing and cervix remains closed

  • Septic miscarriage: pregnancy tissues become infected, causing widespread infectious symptoms and increasing the risk of sepsis, a serious complication

  • Recurrent miscarriage: 3 or more consecutive pregnancy losses

(Please note that the term 'pregnancy tissue' refers to the developing fetus, membranes and placenta.)

Woman in Pain
Flower Arrangement

What causes miscarriage?

For most miscarriages, there is no identified cause.

However, for miscarriages which have an identifiable cause, chromosomal anomalies in the developing fetus has been identified as a common cause of early miscarriage. As discussed in our first trimester screening article, a normal cell in the body has 46 chromosomes that form 23 pairs of chromosomes. If a fetus' cells have more than 46 chromosomes (known as aneuploidy, meaning an abnormal number of chromosomes), this can lead to significant changes to the fetus’ development. Some fetuses with extra chromosomes will have a live birth (for example, Trisomy 21 or Down Syndrome), however, many embryos that have an extra chromosome do not survive and as a result the pregnancy results in an early miscarriage. In a study of 80 women who experienced miscarriage, a high number of miscarriages that occurred between 6-20 weeks of pregnancy were found to have genetic abnormalities.

Other conditions that can cause miscarriage include:

  • Anatomical abnormalities in a woman’s reproductive system that may impact the ability of the embryo to implant and maintain growth, including uterine fibroids, structural anomalies or polyps

  • Cervical insufficiency

  • Placental insufficiency

  • Bacterial or viral infections

  • Physical trauma

Risk factors for miscarriage

The risk of miscarriage is highest in the first 12 weeks of pregnancy. Large population studies have identified some risk factors for miscarriage, including: 


  • Health factors

    • Hormone imbalances 

    • Low or high pre-pregnancy maternal body mass index (underweight or overweight)

    • Pre-existing maternal health issues (diabetes, hypertension, kidney disease, thyroid disease, thrombophilia)

Symptoms of miscarriage


A miscarriage will usually carry out over several days. When a miscarriage occurs, there are a wide range of signs and symptoms that women can experience, including:


  • Vaginal bleeding (the most common symptom)

  • Tissues or clots passing from the vagina

  • Abdominal or pelvic cramping

  • Pain in the back or pelvis


Symptoms of miscarriage are typically more intense the further along in pregnancy a woman was. Some women experience more severe symptoms of miscarriage, including:


  • Heavy vaginal bleeding, known as hemorrhage

  • Infection, with symptoms of severe abdominal/pelvic pain, discharge or fever 


Woman Looking At Lake

Testing & investigations for miscarriage


If pregnant women do not have any symptoms of miscarriage, they may only find out when they attend a standard perinatal appointment.


Here is how doctors assess a woman for miscarriage:


  • Detailed medical history review

  • Physical exam: in cases of vaginal bleeding, doctors will check for the source of the bleeding, see if the cervix is dilated, and check for evidence of pregnancy tissue

  • Ultrasound: doctors will check for the presence of pregnancy in the uterus, as well as the status of the fetus heart rate

  • Blood test: women can have their human chorionic gonadotropin (hCG) blood levels tested 

All of these factors are included together to diagnose the status of the pregnancy or miscarriage.

Treatment & management of miscarriage


Most miscarriages occur before 12 weeks of pregnancy, and don’t require any treatment.


Miscarriages that do not pass on their own, have heavy bleeding or infection, or occur later in pregnancy will likely require medical or surgical intervention. If pregnancy tissues remain inside a woman who has had a miscarriage, this can be cause very serious, life-threatening illness. 


A medication called misoprostol is prescribed for some women who do not have a complete miscarriage. This medication will cause the cervix to soften and open, and cause the uterus to contract; these contractions will push out any pregnancy tissue remaining in the uterus. Misoprostol typically causes cramping and bleeding within 6-8 hours. Common side effects of this misoprostol include nausea, vomiting, diarrhea and fever. However, this first dose of misoprostol may not completely remove pregnancy tissues from all women.


If pregnancy tissues remains in the uterus, a second dose of misoprostol or surgery may be needed to clear it.


The surgical procedure for manually removing pregnancy tissue from the uterus is called dilatation and curettage (D&C). Doctors will dilate the cervix and use a special instrument to gently scrape the lining of the uterus to remove all the remaining pregnancy tissue.

Doctors will also check a woman’s blood type and Rhesus (Rh) status, referring to a protein located on the red blood cells. If a woman is Rh-negative (meaning her blood cells don’t have the Rh protein on their blood cells), she will need a shot called ‘RhoGam or WinRho’. This shot is protective for future pregnancies by preventing the maternal immune response from reacting to the developing baby, if the baby is Rh-positive.

Prevention of miscarriage


There are currently no treatments to prevent miscarriage. Scientists have identified some lifestyle factors that are associated with a lower risk of miscarriage, including taking vitamins, eating fresh fruits & vegetables, dairy, chocolate and white meat and maintaining low stress levels.

Current evidence does not support bed rest to prevent miscarriage. Further work is needed to determine if progesterone therapy could be a useful for miscarriage prevention.



Miscarriage is the loss of a baby before a woman is 20 weeks pregnant. This is the most common pregnancy complication and is associated with vaginal bleeding and cramping. The majority of miscarriages are spontaneous or caused by a chromosomal abnormality. Miscarriage can have a significant impact on a woman’s physical and mental health. Talk your doctor if you are concerned about any of these symptoms or have concerns in early pregnancy.   


Every woman and every pregnancy is unique. Pregnant women should speak to their healthcare provider to ensure maternal and fetal safety. This article is meant to provide readers with current information and opinions. All medical and treatment decisions should be discussed with your healthcare provider.

This article was written by Dr. Kelsey McLaughlin and edited by Dr. Melanie Audette.

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