Background: Open spina bifida (OSB) is one of the most common congenital central nervous system defects and leads to long-term physical and cognitive disabilities. Open fetal surgery for OSB improves neurological outcomes and reduces the need for ventriculoperitoneal shunting, compared to postnatal surgery, at the expense of increased prematurity. It however confers significant morbidity to the mother in the index pregnancy and potential risks to future pregnancies. Fetoscopic surgery may prevent maternal morbidity yet the question remains whether the procedure is neuroprotective and reduces prematurity. Comparison of outcomes between different treatment options is challenging due to inconsistent outcome reporting. We aim to develop and disseminate a core outcome set (COS) for fetal OSB, to ensure that outcomes relevant to all stakeholders are collected and reported in a standardised fashion in future studies. Methods: The COS will be developed using a validated Delphi methodology. A systematic literature review will be performed to identify previously reported outcomes focused on prenatally diagnosed OSB. Outcomes assessed will include maternal (primary and subsequent pregnancies), fetal, neonatal and childhood to adolescence. In a second phase, semi-structured interviews with stakeholders will be performed to ensure representation of additional relevant outcomes that may not have been reported in the literature. We will include patients and parents, as well as health professionals involved in the care of these pregnancies and children (fetal medicine specialists, fetal surgeons, neonatologists/paediatricians, and allied health). Subsequently, an international group of key stakeholders will rate the importance of the identified outcomes using three sequential, online, rounds of a modified Delphi Survey. Final agreement on outcomes to be included in the COS, their definition and measurement will be achieved through a final face-to-face consensus meeting with all stakeholder groups represented. Dissemination of the final COS will be ensured through different media and relevant societies. Discussion: Development and implementation of a COS for fetal OSB will ensure consistent outcome reporting in future clinical trials, systematic reviews, and clinical practice guidelines. This will lead to higher quality research, better evidence-based clinical practice and ultimately improved maternal, fetal and long term childhood outcomes. Trial registration: Core Outcome Measures in Effectiveness Trials (COMET): 1187. International Prospective Register of Systematic Reviews (PROSPERO): CRD42018104880.

Background: Open spina bifida (OSB) is one of the most common congenital central nervous system defects and leads to long-term physical and cognitive disabilities. Open fetal surgery for OSB improves neurological outcomes and reduces the need for ventriculoperitoneal shunting, compared to postnatal surgery, but is associated with a significant risk of prematurity and maternal morbidity. Fetoscopic surgery comes with less maternal morbidity yet the question remains whether the procedure is neuroprotective and reduces prematurity. Comparison of outcomes between different treatment options is challenging due to inconsistent outcome reporting. We aim to develop and disseminate a core outcome set (COS) for fetal OSB, to ensure that outcomes relevant to all stakeholders are collected and reported in a standardised fashion in future studies. Methods: The COS will be developed using a validated Delphi methodology. A systematic literature review will be performed to identify outcomes previously reported for prenatally diagnosed OSB. We will assess will maternal (primary and subsequent pregnancies), fetal, neonatal and childhood outcomes until adolescence. In a second phase, we will conduct semi-structured interviews with stakeholders, to ensure representation of additional relevant outcomes that may not have been reported in the literature. We will include patients and parents, as well as health professionals involved in the care of these pregnancies and children (fetal medicine specialists, fetal surgeons, neonatologists/paediatricians, and allied health). Subsequently, an international group of key stakeholders will rate the importance of the identified outcomes using three sequential online rounds of a modified Delphi Survey. Final agreement on outcomes to be included in the COS, their definition and measurement will be achieved through a face-to-face consensus meeting with all stakeholder groups. Dissemination of the final COS will be ensured through different media and relevant societies. Discussion: Development and implementation of a COS for fetal OSB will ensure consistent outcome reporting in future clinical trials, systematic reviews, and clinical practice guidelines. This will lead to higher quality research, better evidence-based clinical practice and ultimately improved maternal, fetal and long term childhood outcomes.Trial registration: Core Outcome Measures in Effectiveness Trials (COMET): 1187. International Prospective Register of Systematic Reviews (PROSPERO): CRD42018104880.