Early Pregnancy Lifestyle and Glucose Patterns: A Substudy of TOFFFY

Early-Pregnancy Chronobehavioural Profiles and Continuous Glucose Dynamics: A Nested Randomised Pilot Study of TOFFFY

The goal of this clinical trial is to examine how daily behavioral patterns in early pregnancy, including sleep, physical activity, and meal timing, influence continuous glucose dynamics and subsequent risk of gestational diabetes mellitus (GDM) in pregnant women without pre-existing diabetes.

The main questions it aims to answer are:

1. Do early-pregnancy chronobehavioral patterns (e.g., irregular sleep, night eating, and unstable rest-activity rhythms) relate to continuous glucose patterns measured using continuous glucose monitoring (CGM)?
2. Can early behavioral and CGM-derived measures predict glucose regulation and metabolic outcomes later in pregnancy (24-28 weeks)?
3. Does real-time self-monitoring using wearable devices and food logging improve glycemic outcomes compared to usual care?

This study is a prospective, nested randomized pilot trial embedded within the ongoing Towards Optimal Fertility, Fathering and Fatherhood studY (TOFFFY) cohort (NCT06293235) at KK Women's and Children's Hospital, Singapore. A total of 140 pregnant women without pre-existing diabetes, recruited at ≤13 weeks gestation, will be randomized in a 1:1 ratio to either a pilot arm (wearable-based self-monitoring) or a control arm (usual care).

Participants in the pilot arm (n=70) will undergo intensive behavioral and metabolic monitoring over a 14-day period in early pregnancy, including continuous glucose monitoring using a CGM device, wrist actigraphy to assess sleep-wake and rest-activity patterns, and an AI-supported mobile application to record meal timing and dietary intake. Participants will have real-time access to their glucose data and behavioral feedback, enabling self-monitoring and potential behavioral adjustments.

Circadian disruption during pregnancy is increasingly recognized as an important, yet understudied, contributor to impaired glucose regulation and gestational diabetes mellitus (GDM). Emerging evidence suggests that nocturnal eating, irregular sleep timing, reduced rest-activity rhythm (RAR) stability, and greater behavioral variability may impair glucose homeostasis through pathways involving reduced insulin sensitivity, altered β-cell stress, and inflammation.

Most studies assess chronobehaviors using questionnaires, which are limited by recall bias and poor temporal granularity. Recent technological advances enable high-resolution measurement of circadian and metabolic physiology using wrist actigraphy and continuous glucose monitor (CGM). These tools allow objective quantification of sleep timing, RAR, activity fragmentation, and 24-hour glycaemic patterns. Integrating these data in early pregnancy may enable earlier identification of at-risk women, allowing intervention before the onset of overt hyperglycaemia.

The ongoing TOFFFY study (NCT 06293235) provides a unique opportunity to embed such a pilot study among well-phenotyped Singaporean pregnant women. Leveraging this cohort will support mechanistic insights into the interplay between circadian rhythms, meal timing, and glucose regulation, and provide preliminary data to power a larger mother-fetus chronometabolic project. Findings from this pilot will provide high-resolution insight into how early-pregnancy circadian, behavioral, and glycemic patterns interact to shape metabolic physiology. By capturing glucose responses such as glucose AUC, insulin resistance, and C-peptide, the study will identify early mechanistic pathways through which chronobehavioral disruption contributes to dysglycemia.

Inclusion Criteria:

• Enrolled in the Towards Optimal Fertility, Fathering and Fatherhood studY (TOFFFY) (NCT06293235)
• Females who are currently pregnant and with viable intrauterine pregnancy at ≤13 weeks gestation at enrolment

Exclusion Criteria:

• Females with pre-existing diabetes mellitus (Type 1 or Type 2) and/or chronic medical conditions affecting glucose metabolism
• Females who are taking medications known to significantly affect glucose metabolism
• Females with multiple pregnancy (e.g., twins or higher-order gestation)
• Females who are unable to comply with study procedures, including: Inability to use smartphone-based applications and inability to wear wrist actigraphy device