Vaginal bleeding or spotting is a common occurrence in the first half of pregnancy, affecting about 20% to 25% of pregnancies before 20 weeks of gestation. This symptom prompts immediate medical attention and warrants a specific diagnosis. When bleeding occurs, but the pregnancy still shows signs of health and continuation, healthcare providers use the clinical term “threatened abortion.” Although the language may sound alarming, this diagnosis does not mean that pregnancy loss is certain; the majority of these situations result in a successful live birth. This classification simply indicates that a potential risk exists and requires close medical monitoring.
Defining Threatened Abortion
Threatened abortion is defined by a set of clinical criteria that must be present simultaneously. The primary symptom is vaginal bleeding, which can range from light spotting to a flow resembling a menstrual period, and may be accompanied by mild uterine cramping or lower back pain. This bleeding must occur before the 20th week of pregnancy for the condition to be classified as threatened.
The defining characteristic differentiating this condition from inevitable pregnancy loss is the status of the cervix. During an examination, the cervical os, the opening to the uterus, must remain closed. Furthermore, the pregnancy must be considered viable, meaning an ultrasound confirms the developing fetus is located within the uterus and shows a detectable heart rate.
These features distinguish a threatened abortion from other types of spontaneous pregnancy loss. For example, in an inevitable or incomplete abortion, the cervix has begun to dilate or open, and the loss of the pregnancy is considered unavoidable. The threatened classification signals that while the pregnancy is at risk, the process of miscarriage has not progressed to the point of no return.
Common Causes and Contributing Risk Factors
The precise reason for bleeding is often not identifiable, but several underlying factors can contribute to the symptoms. One common cause is a subchorionic hematoma, a collection of blood that forms between the uterine wall and the outer membrane surrounding the fetus. Bleeding from this collection can be reabsorbed or expelled through the cervix.
Hormonal imbalances, such as lower levels of progesterone, can also be a contributing factor. In many cases, the bleeding is related to the implantation process or minor changes in the cervix itself. However, the most frequent cause of any spontaneous pregnancy loss is a random chromosomal abnormality in the developing fetus.
Contributing Risk Factors
Several factors increase the risk of experiencing a threatened abortion. Advanced maternal age, considered over 35 years old, is a risk factor due to the higher likelihood of chromosomal issues. A history of previous spontaneous abortions also increases the risk. Maternal health conditions, such as uncontrolled diabetes, obesity, and thyroid disorders, have been linked to a higher incidence of bleeding in early pregnancy.
Medical Evaluation and Confirming the Diagnosis
The medical evaluation focuses on confirming the pregnancy is intrauterine and viable, that the cervix remains closed, and ruling out urgent conditions like an ectopic pregnancy. A physical examination, including a speculum examination, is performed to visualize the cervix, check the source of the bleeding, and confirm the cervical opening is not dilated.
A transvaginal ultrasound is a foundational diagnostic tool, providing detailed images of the uterus and the developing fetus. The ultrasound confirms the location of the gestational sac, measures the embryo’s development, and verifies fetal cardiac activity. This scan also allows the provider to check for the presence and size of a subchorionic hematoma, which may influence the prognosis.
Blood tests measure specific hormone levels to monitor the pregnancy’s progression. Serial testing of human chorionic gonadotropin (hCG) is often ordered a few days apart to ensure levels are rising appropriately. Low or slow-rising hCG or low progesterone levels can indicate a less favorable outlook. The patient’s blood type is also checked to determine if Rh immune globulin is required if the patient is Rh-negative, a standard precaution following any bleeding.
Recommended Management and Potential Outcomes
The standard management involves watchful waiting and supportive care, as no specific treatment is proven to stop a miscarriage once the process has begun. Healthcare providers commonly recommend a period of reduced activity, including avoiding strenuous exercise, heavy lifting, and sexual intercourse until the bleeding has stopped for several days. Scientific evidence does not conclusively prove that strict bed rest improves the outcome.
In cases where low progesterone levels are identified, or for patients with a history of recurrent miscarriage, hormonal support may be considered. Progesterone supplementation, often administered vaginally or orally, is sometimes prescribed to help support the uterine lining. However, its effectiveness in all cases of threatened abortion is still an area of ongoing study.
Potential Outcomes
The potential outcomes for a threatened abortion are largely favorable, with approximately 75% to 80% of cases resolving successfully and continuing to term. However, pregnancies that continue have an increased risk of certain adverse outcomes later on. These risks include preterm labor, premature rupture of membranes, and placental abruption. Patients must seek immediate medical attention if they experience heavy bleeding, severe cramping, or pass any tissue-like material, as these symptoms signal progression to an inevitable pregnancy loss.