Methods:
All rounds were conducted using Google Forms, with the first three rounds occurring within a 24-hour period during the PI meeting. The first round involved collecting demographic information and obtaining informed consent. Potential surrogate markers were identified through an open-ended question.In the second round, participants were presented with a feedback report that introduced the subsequent phase. The suggested surrogate markers were categorized as antenatal, maternal, neonatal, or placental markers, with overlapping variables consolidated. Each marker was then ranked on a scale from very important (5) to irrelevant (1), with the option for non-medical scientists to selectively choose ’no opinion’. The third round involved participants indicating agreement on marker inclusion. A median score of 5 indicated inclusion, a median score of 4 indicated potential inclusion, a median score below 4 indicated exclusion. Consensus was reached when 70% agreement was achieved. A follow-up online round was conducted after 3 months to confirm the condensed final list of surrogate markers and identify the measurement instruments to be used, requiring 80% agreement for consensus.