Pregnancy is a complex biological process, and while often straightforward, various conditions can arise. Among these are vanishing twin syndrome and subchorionic hemorrhage. Understanding these conditions, and whether one might influence the other, provides clarity for those navigating their pregnancy journey.
Vanishing Twin Syndrome Explained
Vanishing twin syndrome (VTS) refers to the spontaneous loss of one fetus in a multiple pregnancy, with the remaining fetus continuing to develop. It usually occurs in the first trimester. It is often detected during routine ultrasound examinations when a previously seen gestational sac or fetal pole is no longer visible, or significantly smaller, alongside a healthy co-twin.
The prevalence of vanishing twin syndrome affects 20% to 30% of multifetal pregnancies. When one twin vanishes, its tissue is usually reabsorbed by the mother’s body, the placenta, or the surviving twin. This reabsorption is usually complete, leaving no lasting trace of the lost twin.
Subchorionic Hemorrhage Explained
A subchorionic hemorrhage (SCH) is bleeding between the gestational sac and the wall of the uterus. It forms a clot within the chorion, which is the outermost membrane surrounding the embryo. Common symptoms include vaginal bleeding, ranging from light spotting to heavier flows, sometimes with abdominal cramping.
Diagnosis of subchorionic hemorrhage is made by ultrasound, which visualizes the blood collection. SCH is the most common cause of bleeding in early pregnancy, affecting 18% to 22% of first-trimester pregnancies. While often resolving on its own, its presence can indicate potential complications.
The Potential Link Between Vanishing Twin and Subchorionic Hemorrhage
A connection exists between vanishing twin syndrome and subchorionic hemorrhage. When a twin vanishes, the reabsorption process involves the breakdown of fetal and placental tissue. This can disrupt local blood vessels.
This tissue breakdown can lead to localized bleeding, forming a subchorionic hematoma. The body’s reabsorption of the non-viable twin can result in a collection of blood. This bleeding is a direct consequence of the reabsorption process, as the body clears the remnants of the lost fetus. The size of the vanishing twin and its gestational age at the time of demise may influence the extent of the bleeding. While a link is recognized, subchorionic hemorrhages can also arise from other causes unrelated to a vanishing twin.
Managing Pregnancy with These Diagnoses
When a vanishing twin or subchorionic hemorrhage is diagnosed, medical monitoring involves serial ultrasounds. Ultrasounds track the health and development of the continuing pregnancy, assessing the size and resolution of any subchorionic hematoma. For a vanishing twin, monitoring focuses on the growth and well-being of the surviving fetus.
The prognosis for pregnancies complicated by these conditions is favorable, especially if the subchorionic hemorrhage is small or resolves. Many pregnancies proceed to term without issues, even after diagnosis of a vanishing twin or a subchorionic hemorrhage. Following the guidance of healthcare providers is important, which may include recommendations for rest or activity modifications.