The loss of one twin during pregnancy, particularly around 20 weeks, is a rare and emotionally challenging event for expectant parents. This scenario, known as single fetal demise (SFD), represents a significant concern due to its potential impact on both the surviving twin and the mother.
Understanding Single Fetal Demise in Twin Pregnancies
Single fetal demise (SFD) refers to the death of one twin while the other continues to develop. This differs from “vanishing twin syndrome,” which typically involves the loss of a twin much earlier in the first trimester, usually without lasting consequences for the surviving twin. When SFD occurs in the second or third trimester, particularly after 17 weeks, it can lead to increased risks for the surviving twin and the mother.
Diagnosis is typically made through ultrasound, detecting the absence of a fetal heartbeat and movements. While the precise cause of SFD at 20 weeks often remains unknown, potential factors include twin-to-twin transfusion syndrome (TTTS), placental insufficiency, placental abruption, severe growth restriction, fetal abnormalities, or cord accidents. In many instances, SFD is not preventable.
Considerations for the Surviving Twin
The well-being of the surviving twin is a primary concern. The gestational age at which the demise occurs and whether the twins share a placenta (monochorionic) or have separate placentas (dichorionic) significantly influence the risks. Monochorionic pregnancies, where twins share a placenta and blood vessels, carry a higher risk for the surviving twin due to potential blood flow disruptions.
A significant risk is neurological complications, such as cerebral palsy or periventricular leukomalacia. This damage can occur if blood from the surviving twin acutely shifts into the deceased twin’s low-pressure circulation through shared placental connections, leading to a period of reduced blood flow and oxygen to the survivor’s brain. Studies suggest that the risk of neurological abnormality in a surviving monochorionic twin can be around 18%, compared to about 1% in dichorionic twins. The risk of neurological damage may be higher if the demise occurs after 24 weeks.
Another concern is an increased risk of preterm birth for the surviving twin. The median gestational age at delivery after single fetal demise is often lower, around 32 weeks, compared to 36.7 weeks for uncomplicated twin pregnancies. Intrauterine growth restriction (IUGR) is another potential complication, where the surviving twin may not grow as expected. Close monitoring of the surviving twin through regular ultrasounds, including Doppler studies of the middle cerebral artery, and potentially fetal MRI, is advised to assess for these risks and guide management.
Maternal Health and Management
The death of one twin in utero can present medical challenges for the expectant mother. While rare, potential complications include disseminated intravascular coagulation (DIC), a serious blood clotting disorder. DIC can arise from substances released from the deceased fetus into the mother’s bloodstream, which can disrupt the body’s clotting mechanisms. The incidence of maternal DIC after single fetal demise is generally low and often develops several weeks after the demise.
Infection is another concern, as the retained demised twin can potentially increase the risk. Regular monitoring of the mother’s health, including coagulation profiles, is part of the management plan. The decision regarding the timing and mode of delivery for the surviving twin is carefully considered, balancing the risks to the mother and the surviving fetus.
In most cases, the surviving twin is carried to term or near-term, and the demised twin is delivered at the same time. Expectant management, meaning waiting for spontaneous labor, is often favored, especially if the surviving twin is premature and the mother’s health is stable. However, if maternal complications arise or the surviving twin shows signs of distress, earlier intervention, such as induced labor or a Cesarean section, may be considered.
Emotional Support and Coping
Experiencing single fetal demise profoundly impacts parents emotionally and psychologically. This unique form of grief involves mourning the loss of one twin while simultaneously anticipating the birth and caring for the surviving baby. Parents may experience a wide range of emotions, including denial, guilt, anxiety, and a sense of failure or disappointment.
The grief can be complex because family and friends may focus primarily on the surviving baby, sometimes inadvertently minimizing the loss of the other twin. It is important to recognize that having a living baby does not lessen the pain of losing the co-twin.
Support mechanisms such as counseling, support groups, and open communication with healthcare providers and loved ones can be beneficial in navigating this challenging journey. Professional support helps parents process their emotions and prepare for the future with their surviving child.