Preoperative Risk Factors Shape Twin-Twin Transfusion Syndrome Outcomes

Research study background

Twin-twin transfusion syndrome (TTTS) is a rare but potentially life-threatening condition that occurs in pregnancies with identical twins who share a placenta and develop unbalanced blood flow through connecting vessels. This uneven circulation can cause serious complications for both babies, including preterm birth, heart and neurological damage, or even death.

Fetoscopic laser photocoagulation (FLP), a surgical technique that uses laser ablation on the connecting vessels, is the most effective treatment for severe cases of TTTS. Recent studies report survival rates of 90% for at least one twin and 60% to 70% for both twins, reflecting substantial and progressive improvements in survival since the first outcomes data were reported two decades ago.

The Colorado Fetal Care Center at Children’s Hospital Colorado is a leading center for diagnosing and treating TTTS. In collaboration with the North American Fetal Therapy Network (NAFTNet), our experts led this multi-site prospective cohort study to identify the preoperative factors associated with fetal loss in TTTS and to improve counseling and care planning for families.

The team analyzed 1,066 TTTS pregnancies treated with FLP between 2001 and 2023 across participating NAFTNet centers. They evaluated maternal characteristics, gestational age at intervention, placental location, disease stage, cervical length and measures of fetal growth restriction (FGR) to determine their effects on single and dual survival outcomes.

The analysis identified that severe, late-stage diagnosis of TTTS (indicated by Quintero stages III and IV), anterior placental location and FGR less than the 10^th percentile were factors associated with reduced survival of both twins. Notably, anterior placenta and FGR were independent predictors for reduced dual survival. Survival probabilities for one or both twins progressively reduced as the number of preoperative risk factors increased. The survival rate for both twins was 78.3% when no risk factors were present yet fell below 55% with two or more risk factors.

Clinical implications

Additionally, study authors noted modifiable risk factors that may improve survival. This includes identifying and diagnosing chorionicity in the first trimester, conducting early TTTS screening and careful management of pregnancies with a short cervix. These findings highlight the importance of early screening and diagnosis for improved outcomes.

The published study includes a table outlining crude numbers and predicted survival probability based on the type and number of preoperative risk factors that may be present, which could be useful when fetal surgeons counsel families before surgery.