Miscarriage: Cause, Symptoms and Diagnosis

Miscarriage is the common term used to describe spontaneous abortion of pregnancy. This refers to spontaneous loss of pregnancy prior to 20 weeks from the last menstrual period.

Spontaneous abortion is a common complication of early pregnancy, occurring in 8 to 20% of recognized pregnancies.

Risk Factors for Miscarriage

• Advanced age of the mother: while the overall rate of spontaneous abortion was 11%, the rates increased with increasing age with a 20% risk at 35 years, ranging up to 80% at 45 years
• Previous spontaneous abortion
• Smoking: There is an increased risk with maternal smoking especially with heavy smokers (over 10 cigarettes a day). Paternal smoking has also shown increased risk of spontaneous abortion.
• Alcohol consumption
• Cocaine use
• Use of Non Steroidal Anti-inflammatory Drugs (NASIDs) around the time of conception

Causes of Miscarriage

• Chromosomal anomalies in the fetus: This refers to errors in the genetic makeup of the fetus which can prevent normal development within the uterus. This is the most common cause of early spontaneous abortion accounting for 50% of all miscarriages.
• Structural abnormalities in the uterus: The presence of fibroids or septations within the uterus reduce the space available for normal growth of the fetus leading to pregnancy loss.
• Trauma: Injury to the abdomen can damage the placental circulation and affect blood flow to the growing fetus leading to abortion
• Maternal illnesses: Diabetes, Thyroid abnormalities, bleeding and clotting diseases can all result in abnormal development of the placenta and the fetus leading to early pregnancy loss.

Types of Miscarriage

Miscarriage is classified based on the extent and completeness of pregnancy loss and the size of the cervical opening (the opening at the lower end of the uterus through which the products of conception are removed)

• Threatened abortion: this refers to the presence of vaginal bleeding with a closed cervix. No pregnancy loss has occurred, but there is an increased risk.
• Missed abortion: this refers to the failure of pregnancy without loss of the products of conception from the uterus. The cervical opening remains closed, and the woman may not have had any bleeding. It is identified at a later date and requires medical or surgical removal of the uterine contents.
• Inevitable abortion: This refers to a situation where the woman experiences vaginal bleeding and upon examination, an open cervix is noted with descending products of conception. The fetus may still be viable, but there is no way of preventing a complete abortion.
• Complete abortion: Here, the products of conception are not viable and are completely expelled out through the vagina.
• Incomplete abortion: This refers to the situation where the products of conception are nonviable but have not been completely eliminated through an open cervix.

Symptoms of Miscarriage

• A period of amenorrhea or absent menstruation with or without a confirmed pregnancy
• Lower abdominal pain
• Bleeding from the vagina
• Passage of products of conception through the vagina

Complications of Miscarriage

• Excessive blood loss with risk of shock
• Incomplete evacuation of the products of the concepts with a risk of infection

Diagnosis of Miscarriage

A combination of physical examination, laboratory investigation and imaging are carried out to confirm the spontaneous abortion

• Physical Examination: A pelvic exam is done to examine the vagina and cervix for blood and expelled products of conception. The opening of the cervix is noted to be open or closed.
• Urine pregnancy test: this is done as a screening tool to establish a pregnancy
• Blood testing for beta HCG: this is a more accurate test to measure the hormone that rises in pregnancy
• Ultrasound: This is an imaging study to confirm the presence of a pregnancy within the uterus. In a suspected spontaneous abortion, the products of conception may be completely absent or in the process of being expelled out of the uterus. Viability of the fetus can also be established using ultrasound.

Management of Miscarriage

The steps to manage a woman presenting with suspected spontaneous abortion depend on the type of abortion.

• Threatened abortion: Here there is a possibility of preventing abortion altogether. Complete bed rest is advised along with monitoring for progression of the abortion.

In the remaining types of abortion, the products of conception need to be removed. This can be done in the following ways

• Waiting for a natural expulsion of all products without using medications or surgery: this may be done is inevitable and incomplete abortions, where the cervix is dilated and the abortion is already underway. Occasionally this method may take even a few weeks to complete
• Medications: Drugs like misoprostol and mifepristone help to dilate the cervix and contract the uterus to remove the uterine contents
• Surgery: This involves directly removing the contents through dilatation and curettage (D&C). This is the quickest method of removing the uterine contents and is performed under sedation.

References

1. Tulandi T, et al. Spontaneous abortion: Risk factors, etiology, clinical manifestations, and diagnostic evaluation. http://www.uptodate.com/home. Accessed April 7, 2019.
2. Tulandi T, et al. Spontaneous abortion: Management. http://www.uptodate.com/home. Accessed April 7, 2019.