Lifestyle Intervention to Improve Twin Pregnancy Outcomes

The primary outcome is gestational age at delivery, measured in weeks and days. This is calculated based on the last menstrual period and confirmed via early ultrasound dating (before 13 weeks and 6 days) for spontaneous pregnancies or based on embryo age at transfer for IVF patients. The study aims to evaluate whether a multi-component lifestyle intervention can delay delivery by at least one week, thereby enhancing pregnancy outcomes. Gestational age data will be collected from medical records to ensure accuracy and consistency.

Birth weight in grams and percentile.

Small for gestational age in at least one twin, defined as below the 10th percentile according to twins' nomograms

Offspring mortality- defined as the death of one or both twins occurring at any time from foetal viability (24 weeks' gestation) until 28 days postpartum (neonatal period).

Offspring infection- defined as neonatal sepsis, congenital pneumonia, neonatal meningitis, or necrotizing enterocolitis (NEC) with infection within the first 72 hours of delivery.

Early neurodevelopmental morbidity- defined as diagnosis of Intraventricular haemorrhage (IVH) Grade III-IV, periventricular leukomalacia (PVL), hypoxic-ischemic encephalopathy (HIE), and neonatal seizures.

Gastrointestinal morbidity- defined as diagnosis of NEC and spontaneous perforation.

Respiratory morbidity- defined as diagnosis of respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD), transient tachypnoea of the newborn (TTN) or persistent pulmonary hypertension of the newborn (PPHN)

Any admission to the Neonatal intensive care unit (NICU) within 72 hours of delivery.

Number of days in the NICU

Gestational Weight Gain (GWG) corrected to pregnancy duration.

Maternal quality of Life based on questionnaire EQ-5D-5L.

Postpartum weight recorded 6 weeks postpartum

Maternal mortality- defined as death of the mother during pregnancy or within 42 days postpartum, due to any cause related to or aggravated by pregnancy or its management.

Maternal pregnancy related hypertension- defines as Pregnancy-induced hypertension or preeclampsia as defined by the International Society for the Study of Hypertension in Pregnancy (ISSHP).

Maternal gestational diabetes mellitus as defined by diagnosis of diabetes after week 20 in a two-step approach according to the Carpenter/Coustan criteria.

Maternal anaemia defined by haemoglobin under 10 g/dL during pregnancy.

Food consumption change based on 32-item semi-quantitative Food Frequency Questionnaire

Physical activity level based on the Kaiser Physical Activity Survey.

Change in lifestyle habits based on Lifestyle behaviour questionnaire.

Recruitment Success (RE-AIM Principle: Reach and Adoption): assessment the ability to recruit participants over the course of the pilot. Recruitment efforts will focus on engaging a diverse demographic, particularly including women from low SES and high-risk backgrounds.

Midwife Engagement (RE-AIM Principle: Adoption): Midwives at all centres will undergo a two-day training program tailored to the LIFETWIN intervention. Retention and engagement of midwives will be monitored throughout the pilot study.

Intervention Fidelity (RE-AIM Principle: Implementation): We will assess how consistently the intervention (8 lifestyle sessions) can be delivered during the pilot study, both face-to-face and remotely, ensuring quality and adherence across all pilot centres.

Participant Retention (RE-AIM Principle: Maintenance): Monitor retention rates of participants throughout the pilot study period, with reasons for lack of adherence and dropout carefully recorded. This will help us understand both the feasibility of maintaining participant engagement and the practical challenges in long-term implementation

Qualitative Feedback (RE-AIM Principle: Maintenance): Midwives and participants will be interviewed during/after the pilot phase, to assess how the intervention is perceived, experienced, and sustained over time. Insights from this feedback will be critical for informing the next phase of the study (i.e. the main trial), especially regarding long-term adoption and sustainability.