A blighted ovum, also known as an anembryonic pregnancy, is a common form of early pregnancy loss. It occurs when a fertilized egg implants in the uterus, but the embryo fails to form or stops developing very early. Because the body still registers as pregnant, the timeline for diagnosis and resolution is highly variable. This article clarifies the biological process and the options available for managing this type of miscarriage.
Defining Anembryonic Pregnancy
An anembryonic pregnancy begins when a fertilized egg successfully implants into the uterine wall. After implantation, the gestational sac, placenta, and surrounding structures develop normally. However, the embryo itself either does not form within the gestational sac or stops growing at a microscopic stage and is reabsorbed.
Because the placenta continues to develop, the body produces human chorionic gonadotropin (hCG). Since tests detect hCG, a positive result occurs, and the person may experience common pregnancy symptoms like nausea and breast tenderness. This hormonal signal can persist for weeks, masking the non-viable status. Chromosomal abnormalities in the fertilized egg are the primary underlying cause, leading to the early cessation of embryonic development.
The Duration of Carrying and Diagnosis
The time a person can carry an anembryonic pregnancy before it is diagnosed or spontaneously miscarries varies widely. In many cases, the body does not recognize the non-viable status immediately, allowing the gestational sac to continue growing for several weeks. The diagnosis is most often made during a routine first-trimester ultrasound, typically between 8 and 13 weeks of gestation.
A transvaginal ultrasound is the definitive diagnostic tool, clearly showing an empty gestational sac. Diagnostic criteria involve identifying a gestational sac of a certain size—often 25 millimeters or greater—without a visible embryo or yolk sac inside. Once the diagnosis is confirmed, the time until a spontaneous miscarriage begins can range from a few days to several weeks. This period of waiting for the body to naturally pass the tissue is highly unpredictable.
Management and Treatment Options
Once an anembryonic pregnancy is confirmed, a healthcare provider will discuss three primary options for resolution, depending on the patient’s preference and clinical stability. The first option is expectant management, which involves waiting for the body to miscarry naturally. This approach is non-invasive, but the timing is uncertain and can take anywhere from a few days to over a month.
The second path is medical management, which uses oral or vaginal medication, most commonly misoprostol, to induce uterine contractions and expedite the process. This method offers a faster and more predictable resolution than expectant management. Misoprostol therapy is highly effective, yielding a complete termination in a large majority of cases.
The final option is surgical management, typically performed as a dilation and curettage (D&C), where the pregnancy tissue is removed from the uterus. This procedure is the fastest and most predictable method, often recommended for patients experiencing heavy bleeding, signs of infection, or those who prefer a swift resolution. Regardless of the chosen path, follow-up care, including emotional support and serial monitoring of hCG levels, remains a part of the recovery process.