Background: Adults who were born prematurely (<37 weeks gestation) are at increased cardiovascular disease risk, but it is unclear when in the life course this risk emerges. Our aim was to compare trajectories of multiple cardiometabolic risk factors from childhood to early adulthood between those who had and had not been born preterm. Methods: Multilevel models were used to compare trajectories from early childhood (ranging from birth to 9 years) to age 25 years of BMI, fat mass, lean mass, systolic and diastolic blood pressure (BP), lipids, glucose and insulin, between participants born preterm (N=311-733, range 25-36 completed weeks gestation) and term (N=5365-12097) in a contemporary UK birth cohort study. We also investigated gestational age as a continuum. Results: In children born preterm (versus term), systolic and diastolic BP were higher at age 7 (mean predicted differences 0.6mmHg; 95%CI -0.3, 1.5 and 0.6mmHg; 95%CI 0.03, 1.3, respectively). By age 25 years, the difference in SBP persisted (1.4, 95%CI -0.1, 2.9 mmHg) and in DBP (-0.2, 95%CI -1.3, 0.9 mmHg) disappeared. Participants born preterm (versus term) had lower BMI between 7 and 18 years, but by age 25, there was no difference. Lean mass and fat mass (measured from age 9 only) trajectories were consistent with BMI. HDL-c was higher, and triglycerides lower at birth in those born preterm, but this difference also disappeared by 25 years. There was no evidence of differences in glucose and insulin between participants born preterm compared to term. Conclusions: There were few, modest differences in cardiometabolic health measures during early life in those born preterm versus term. All disappeared by age 25, except the small difference in SBP. Longer follow-up is needed to establish if and when trajectories of measures of cardiometabolic health in term and preterm born people diverge.

DAL has received support from Roche Diagnostics and Medtronic Ltd in the last 10 years for work unrelated to that presented here.

The UK Medical Research Council and Wellcome (Grant ref: 217065/Z/19/Z) and the University of Bristol provide core support for ALSPAC, with additional support from a wide range of national and international funders (a comprehensive list of grant funding is available on the ALSPAC website; http://www.bristol.ac.uk/alspac/external/documents/grant-acknowledgements.pdf). This publication is the work of the authors and all authors will serve as guarantors for the contents of this paper. This research was funded in whole, or in part, by the Wellcome Trust [Grant Ref: 102215/2/13/2]. For the purpose of Open Access, the author has applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission. The European Union's Horizon 2020 research and innovation programme under grant agreement No 733206 (LifeCycle), funds GLC's salary. GLC, AF, LDH and DAL work in, or are affiliated with a Unit that is funded by the UK Medical Research Council (Grant Refs: MC_UU_00011/6) and University of Bristol. and DAL is a National Institute for Health Research Senior Investigator (NF-0616-10102) and BHF Chair (CH/F/20/90003). AF is funded by a UK MRC fellowship (MR/M009351/1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Dr Adam Lewandowski was funded by a BHF Intermediate Research Fellowship (FS/18/3/33292). LMOK is supported by a Health Research Board (HRB) of Ireland Emerging Investigator Award (Grant ref: EIA-FA-2019-007 SCaRLeT). LDH was supported by Health Foundation grant: Social and economic consequences of health status - Causal inference methods and longitudinal, intergenerational data. This was awarded under the Social and Economic Value of Health programme (Award reference 807293) and a Career Development Award from the UK Medical Research Council (MR/M020894/1).

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes