A threatened miscarriage is a common complication in early pregnancy, characterized by the sudden onset of vaginal bleeding. While the appearance of blood can be alarming, this diagnosis means a miscarriage is possible, not certain. Many pregnancies continue successfully after active monitoring and rest. This specific medical classification requires professional assessment to distinguish it from other, more serious pregnancy complications.
Defining Threatened Miscarriage
A threatened miscarriage is clinically defined as vaginal bleeding, with or without abdominal cramping or backache, occurring before the 20th week of gestation. The most critical diagnostic feature is the status of the cervix. During a pelvic examination, the healthcare provider confirms that the cervical opening, or os, remains closed.
The diagnosis is confirmed through an ultrasound showing a viable intrauterine pregnancy, typically evidenced by a fetal heart rate. This combination of a closed cervix and a live fetus differentiates a threatened miscarriage from other types of pregnancy loss. For instance, an inevitable miscarriage involves cervical dilation, while a complete miscarriage involves the passage of all pregnancy tissue. Symptoms, which can range from light spotting to heavier bleeding, signal the need for close monitoring.
Factors Influencing Symptom Duration
There is no fixed timeline for how long the active symptoms of a threatened miscarriage—bleeding and cramping—will last, as the duration is highly variable. Symptoms can persist for only a few hours, resolve within a couple of days, or continue intermittently for several weeks. The source of the bleeding often influences this duration, with some causes leading to longer symptom periods.
One common source of bleeding is a subchorionic hematoma, a blood clot that forms between the gestational sac and the wall of the uterus. The reabsorption or discharge of this clot can cause spotting or bleeding that may continue until the hematoma is fully resolved. Generally, lighter initial bleeding and a later gestational age at symptom onset are associated with a shorter duration. Conversely, heavier bleeding, particularly if it exceeds the flow of a typical menstrual period, can indicate a higher risk and symptoms lasting longer.
Outcomes and Prognosis
The prognosis following a threatened miscarriage is often positive, especially once a fetal heartbeat has been confirmed. When a viable fetus with cardiac activity is identified on ultrasound, the likelihood of the pregnancy continuing to term is high, often reported to be between 70% and 83%. The success rate is high in the first trimester; studies show that 90% to 96% of pregnancies with confirmed cardiac activity between seven and eleven weeks do not progress to miscarriage.
A strong fetal heart rate is a significant predictor of a positive outcome. If the fetal heart rate is slower than 120 beats per minute, it may indicate a higher risk for pregnancy loss. While the immediate prognosis is generally good, a history of a threatened miscarriage slightly increases the risk for some later complications. These include preterm delivery, low birth weight, and placental issues. For the majority of women experiencing this complication, the pregnancy proceeds normally after the bleeding resolves.
Immediate Medical Guidance and Monitoring
Following a diagnosis of threatened miscarriage, the focus shifts to careful monitoring and supportive care. A healthcare provider often orders serial quantitative measurements of human chorionic gonadotropin (hCG) to ensure levels are rising appropriately. Repeat ultrasounds are also scheduled to check on fetal growth and the resolution of any underlying cause, such as a subchorionic hematoma.
For Rh-negative patients, anti-D immunoglobulin (RhoGAM) is often administered to prevent the development of antibodies that could affect future pregnancies. Current evidence does not support strict bed rest, and patients are encouraged to take it easy and avoid strenuous activity. Pelvic rest, meaning no sexual intercourse, is commonly recommended until the bleeding has stopped completely.
Immediate emergency care is necessary if symptoms worsen significantly, such as heavy bleeding that soaks two or more sanitary pads in an hour for two consecutive hours. Severe or rapidly escalating abdominal pain not relieved by over-the-counter medication also warrants immediate medical evaluation.