A missed miscarriage, sometimes referred to as a silent miscarriage, occurs when a pregnancy loss happens without the body showing typical signs like bleeding or cramping. Individuals may continue to experience pregnancy symptoms, making the diagnosis unexpected. This article explores how common this specific form of early pregnancy loss is.
Understanding Missed Miscarriage
A missed miscarriage is an early pregnancy loss where the embryo or fetus stops developing or never develops, but the pregnancy tissue remains inside the uterus. Unlike other miscarriages where the body expels the tissue, in a missed miscarriage, the body does not recognize the loss or initiate expulsion. This can lead to continued production of pregnancy hormones, resulting in ongoing pregnancy symptoms and positive pregnancy tests.
One specific form is an anembryonic pregnancy, also known as a blighted ovum. Here, a fertilized egg implants, and the gestational sac and placenta grow, but an embryo never forms or stops developing very early. The absence of outward signs like heavy bleeding or significant pain distinguishes missed miscarriages, often leading to detection only during a medical examination.
How Often Does It Occur?
Miscarriages are common, with 10% to 20% of known pregnancies ending in loss. This figure may underestimate the true incidence, as many, especially missed miscarriages, go undiagnosed.
Estimates for missed miscarriages vary, but they form a notable portion of early pregnancy losses. One study found they constituted 38.8% of participants’ miscarriages. Other sources suggest almost 3% of recognized pregnancies end this way. Overall, missed miscarriages are estimated to account for 1% to 5% of all pregnancies.
Their true commonality is hard to pinpoint because many occur without obvious symptoms until detected during a routine ultrasound. Advanced ultrasound technology may lead to more frequent detection than in the past.
Contributing Factors
The primary factor contributing to missed miscarriages, similar to other early pregnancy losses, is often chromosomal abnormalities in the developing embryo or fetus. These abnormalities usually occur randomly during conception, when the egg and sperm combine, leading to an incorrect number of chromosomes or structural issues. Such genetic errors typically prevent the embryo from developing properly, rendering the pregnancy non-viable.
Advanced maternal age is another contributing factor to missed miscarriages. As individuals age, the quality of eggs can decrease, increasing the likelihood of chromosomal abnormalities in the embryo. For example, the risk of miscarriage rises after age 30, reaching approximately 20% by age 35 and 40% by age 40.
While chromosomal issues are the most frequent cause, other factors can also play a role. These may include certain uterine abnormalities, such as fibroids or an abnormally shaped uterus. Additionally, underlying health conditions of the pregnant person, such as uncontrolled diabetes, certain infections, or hormonal imbalances, have been associated with an increased risk of miscarriage.
Detection and Next Steps
A missed miscarriage is typically diagnosed during a routine prenatal visit, often through an ultrasound scan. The ultrasound may reveal the absence of a fetal heartbeat when one would be expected for the gestational age, or an empty gestational sac where an embryo should be visible. In some cases, the embryo might be present but appears smaller than expected, indicating that its development ceased earlier. Blood tests measuring human chorionic gonadotropin (hCG) levels, a hormone produced during pregnancy, may also be used to monitor the pregnancy’s viability if there’s uncertainty.
Once a missed miscarriage is diagnosed, several management options are available, which are discussed with a healthcare provider. One approach is expectant management, which involves waiting for the body to naturally pass the pregnancy tissue. This process can take several days to weeks.
Another option is medical management, where medication is administered to help the uterus expel the tissue. This method typically initiates the process within a few hours to a couple of days. Finally, surgical management, such as a dilation and curettage (D&C) or dilation and evacuation (D&E), can be performed to remove the tissue from the uterus. This procedure offers immediate completion of the miscarriage.