Miscarriage

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | References

Definition

Miscarriage refers to the spontaneous loss of a pregnancy before 24 weeks of gestation. It is a common complication of early pregnancy and can present in different forms, including threatened, inevitable, incomplete, and complete miscarriage.

• Threatened Miscarriage: Vaginal bleeding occurs, but the cervix remains closed, and the pregnancy may still continue.
• Inevitable Miscarriage: Vaginal bleeding is accompanied by cervical dilation, making pregnancy loss unavoidable.
• Incomplete Miscarriage: Some products of conception are expelled, but some remain in the uterus.
• Complete Miscarriage: All products of conception are expelled from the uterus, and bleeding subsequently stops.

Aetiology

Miscarriage can occur due to a variety of reasons, including:

• Chromosomal Abnormalities: The most common cause, particularly in the first trimester, where abnormal karyotypes lead to non-viable pregnancies.
• Infections: Infections such as rubella, cytomegalovirus, or sexually transmitted infections (STIs) can lead to pregnancy loss.
• Maternal Health Conditions: Chronic conditions like diabetes, thyroid disease, or hypertension may increase the risk of miscarriage.
• Trauma or Physical Injury: Severe trauma or injury to the abdomen can lead to pregnancy loss.
• Lifestyle Factors: Smoking, alcohol consumption, and illicit drug use are significant risk factors for miscarriage.

Pathophysiology

The mechanisms leading to miscarriage vary depending on the underlying cause. Chromosomal abnormalities typically result in early embryonic death and subsequent expulsion. Infections, maternal health conditions, or trauma can disrupt placental function or cause systemic inflammation, leading to fetal demise and miscarriage. Lifestyle factors such as smoking and substance abuse can impair placental development and function.

Risk Factors

• Advanced maternal age (35 years and older).
• Previous history of miscarriage or stillbirth.
• Chronic maternal health conditions such as diabetes, hypertension, or autoimmune disorders.
• Exposure to environmental toxins or radiation.
• Infection with certain viruses or bacteria.
• Multiple pregnancies (e.g., twins or triplets).

Signs and Symptoms

• Threatened Miscarriage: Vaginal bleeding, often without pain, and a closed cervix.
• Inevitable Miscarriage: Heavy vaginal bleeding, cramping, and cervical dilation.
• Incomplete Miscarriage: Severe cramping, heavy bleeding, and passage of some but not all products of conception.
• Complete Miscarriage: Cessation of bleeding and cramping after expulsion of all products of conception.

Investigations

• Ultrasound: The primary tool for assessing fetal viability, location, and the status of the cervix.
• Beta-Human Chorionic Gonadotropin (β-hCG) Levels: Serial measurements can help determine whether a pregnancy is progressing normally.
• Full Blood Count (FBC): To assess for anaemia or infection in cases of heavy bleeding or suspected infection.
• Blood Type and Rh Status: Important for determining the need for Rho(D) immune globulin in Rh-negative women.

Management

Management should be tailored to the type of miscarriage and the clinical condition of the woman. The NICE guidelines recommend:

• Primary Care and Initial Management:
  • Immediate Hospital Admission: Arrange immediate hospital admission if the woman has signs of haemodynamic instability, such as pallor, tachycardia, tachypnoea, hypotension, shock, and collapse. Resuscitate with intravenous fluids if available. Also, admit immediately if there is significant concern about the degree of bleeding or pain.
  • Referral to Early Pregnancy Assessment Unit (EPAU): Women with a positive pregnancy test and symptoms like abdominal pain, pelvic tenderness, or cervical motion tenderness should be referred to an EPAU or out-of-hours gynaecology service. Women with bleeding and signs of early pregnancy complications, especially if the pregnancy is 6 weeks gestation or more, should also be referred.
  • Expectant Management: For women with pregnancy of less than 6 weeks gestation who are bleeding but not in pain, and have no risk factors, such as a previous ectopic pregnancy, expectant management is advised. These women should be instructed to repeat a urine pregnancy test after 7–10 days and return if it is positive or if symptoms worsen.
• Secondary Care Management:
  • Diagnosis: Transvaginal ultrasound is the preferred method to assess the location and viability of the pregnancy. If transvaginal ultrasound is unacceptable or there are other pelvic pathologies, a transabdominal scan may be considered.
  • Expectant Management: First-line management for confirmed miscarriage. Women are advised to monitor for resolution of bleeding and pain over 7–14 days, with a follow-up pregnancy test after 3 weeks.
  • Medical Management: If expectant management is not appropriate or if symptoms persist after 14 days, medical management with 200 mg oral mifepristone followed by 800 micrograms of misoprostol is offered. For incomplete miscarriage, a single dose of misoprostol 600 micrograms is recommended.
  • Surgical Management: Surgical intervention may be required if medical management is unsuccessful or if the woman has ongoing symptoms after 14 days. Options include manual vacuum aspiration or surgical management under general anaesthetic.
  • Anti-D Immunoglobulin: Offered to all rhesus-negative women who have had a surgical procedure to manage miscarriage.

References

1. NHS (2024) Miscarriage. Available at: https://www.nhs.uk/conditions/miscarriage/ (Accessed: 24 June 2024).
2. National Institute for Health and Care Excellence (2024) Miscarriage: Diagnosis and Initial Management. Available at: https://cks.nice.org.uk/topics/miscarriage/management/suspected-miscarriage/ (Accessed: 24 June 2024).
3. British Medical Journal (2024) Management of Miscarriage in Primary and Secondary Care. Available at: https://www.bmj.com/content/350/bmj.h491 (Accessed: 24 June 2024).
4. American College of Obstetricians and Gynecologists (2024) Early Pregnancy Loss. Available at: https://www.acog.org/clinical/clinical-guidance/practice-bulletin/articles/2020/01/early-pregnancy-loss (Accessed: 24 June 2024).

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