Conjoined twins are typically diagnosed early in pregnancy with prenatal ultrasound. The optimal evaluation period for additional prenatal testing is after 18 weeks gestation.
An evaluation consisting of a Level II ultrasound, fetal echocardiogram and ultrafast fetal MRI is particularly important for conjoined twins, as the location and extent of where the twins are joined and what organs are shared plays a crucial role in deciding whether the twins will be separable. Expectant mothers visiting the Center for Fetal Diagnosis and Treatment at CHOP will undergo a full day of advanced imaging to collect a detailed picture of the shared organs and any associated anomalies. Prenatal diagnosis will help identify the optimal treatment and delivery plan, and potential for separation after birth. The following imaging tests are used to diagnose and evaluate conjoined twins:
Indicators of conjoined twins include lack of a separating membrane between the twins, inability to separate the fetal bodies, and constant position of the fetal heads. At the end of the day, expectant parents will meet with a multidisciplinary team to discuss the results of their tests, and outline all options for prenatal management, delivery and treatment so that the family can make an informed decision about how to move forward. After the visit, our team will also contact the referring physician to provide details about the consultation.
Example of conjoined twins connected at the chest with a shared liver and pericardium.
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The prognosis for conjoined twins depends on where the twins are connected.
Conjoined twins are generally classified three ways:
The common twin types include:
For the duration of the pregnancy, the Center team will work closely with the referring obstetrician to ensure comprehensive prenatal monitoring of the expectant mother. In some cases, care will be transferred to the Center around 28 weeks gestation or earlier to optimize management of the pregnancy and prepare for delivery.
Patients carrying conjoined twins have the option of delivering in CHOP’s Garbose Family Special Delivery Unit, the world's first birthing unit dedicated to mothers carrying babies with known birth defects. The SDU offers unmatched continuity of care for both mother and baby, with complete labor and delivery services in immediate proximity to the care the babies will need after birth – neonatal intensive care, cardiac intensive care, pediatric operating rooms and more.
Delivering in a location with direct access to all the advanced, specialized services both mom and baby might need is particularly important for high-risk conjoined twin pregnancies that require a C-section or a potential ex-utero intrapartum therapy (EXIT) delivery. The EXIT procedure is a "partial delivery" in which the fetus is partially removed from the uterus but remains attached to the circulation carried by the umbilical cord and placenta so that surgeons can correct airway blockages before performing a full delivery.
A comprehensive post-delivery assessment will determine the long-term plan for a potential separation surgery. While some life-threatening conditions may require immediate emergency surgery, a full assessment of shared structures should be performed before separation is attempted. Comprehensive evaluation of the cardiovascular system is particularly important in determining if separation is an option.
If the conjoined twins are candidates for separation surgery, CHOP’s pediatric surgical team will work with the multidisciplinary team including neonatologists, cardiologists, advanced practice nurses and maternal-fetal medicine specialists to monitor the babies and determine the timeline and approach for the surgical procedure.
One of the many procedures required to prepare twins for separation is the insertion of tissue expanders to increase the skin surface available to cover exposed tissue after surgery. As separated twins recover after surgery, they are closely followed by nutritionists, developmental pediatricians and other specialists to ensure their ability to thrive and grow.
When the conjoined twins share a heart, successful surgical division is usually not possible.
Since 1995, 70 pairs of conjoined twins have been referred to the Center for Fetal Diagnosis and Treatment, and 39 pairs have undergone prenatal evaluation. Not all conjoined twins are candidates for separation, and the success rates for separating conjoined twins vary depending on the connection.
The Children’s Hospital of Philadelphia has successfully separated 21 pairs of conjoined twins, the first in 1957.
Updated: November 2012