What happens in a spontaneous abortion (miscarriage)?

From the Guidelines

A miscarriage is the spontaneous loss of a pregnancy before the 20th week of gestation, typically beginning with vaginal bleeding and cramping pain, as the body expels the embryo or fetus and placental tissues from the uterus 1. During a miscarriage, the embryo or fetus and placental tissues are expelled from the uterus. This typically begins with vaginal bleeding, which may start as light spotting and progress to heavier bleeding with clots. Cramping pain in the lower abdomen, similar to menstrual cramps but often more intense, usually accompanies the bleeding. The body recognizes that the pregnancy is no longer viable and initiates contractions to expel the contents of the uterus. Most miscarriages occur in the first trimester due to chromosomal abnormalities in the embryo that prevent proper development. Some key points to consider in the context of miscarriage include:

• The term "early pregnancy loss" is now preferred to describe a pregnancy that may or will not progress, is in the process of expulsion, or has incompletely or completely passed 1.
• The risk of venous thromboembolism (VTE) is increased during pregnancy and the postpartum period, and women who experience a miscarriage may be at higher risk 1.
• Imaging, particularly with ultrasound, is the mainstay for making accurate diagnoses and for emergent guidance of management in cases of vaginal bleeding during pregnancy 1. After a miscarriage, bleeding may continue for 1-2 weeks, gradually decreasing in intensity. Some women may require medical intervention such as medication (misoprostol) to help complete the process or a procedure called dilation and curettage (D&C) to remove remaining tissue if the miscarriage doesn't complete naturally. Emotional responses to miscarriage vary widely, and many women benefit from support during this difficult time. Physical recovery typically takes a few weeks, while emotional healing may take longer.

From the Research

Definition and Prevalence of Miscarriage

• Miscarriage is generally defined as the loss of a pregnancy before viability 2
• An estimated 23 million miscarriages occur every year worldwide, translating to 44 pregnancy losses each minute 2
• The pooled risk of miscarriage is 15·3% (95% CI 12·5-18·7%) of all recognised pregnancies 2

Risk Factors for Miscarriage

• Risk factors for miscarriage include very young or older female age (younger than 20 years and older than 35 years), older male age (older than 40 years), very low or very high body-mass index, Black ethnicity, previous miscarriages, smoking, alcohol, stress, working night shifts, air pollution, and exposure to pesticides 2

Consequences of Miscarriage

• The consequences of miscarriage are both physical, such as bleeding or infection, and psychological 2
• Psychological consequences include increases in the risk of anxiety, depression, post-traumatic stress disorder, and suicide 2
• Miscarriage, and especially recurrent miscarriage, is also a sentinel risk marker for obstetric complications, including preterm birth, fetal growth restriction, placental abruption, and stillbirth in future pregnancies, and a predictor of longer-term health problems, such as cardiovascular disease and venous thromboembolism 2

Treatment Options for Miscarriage

• Curettage is more effective than expectant management in women with suspected incomplete evacuation after misoprostol treatment for first-trimester miscarriage 3
• Administering mifepristone before dilation and evacuation (D&E) with misoprostol in second-trimester abortions makes surgery easier and shorter and, to a certain extent, lessens the risk of cervical injuries 4
• D&C and misoprostol are both effective treatments for IVF patients with miscarriage, without an adverse effect on subsequent IVF treatment outcome 5
• Misoprostol can be used for cervical ripening prior to gynecological transcervical procedures, and is beneficial in cervical priming in pre-menopausal subjects 6