EMBodied psychOsocial Impacts of Weight Stigma During Pregnancy (EMBODY): A Prospective Cohort Study

The specific research questions for each objective are:

Objective 1 RQ1.1: Does weight stigma experienced during pregnancy in a healthcare setting reported up to 34 weeks gestation mediate the association between pre-pregnancy obesity (BMI ≥30) and gestational diabetes mellitis (GDM) (primary outcome)?

RQ1.2: Does weight stigma experienced during pregnancy in a healthcare setting reported up to 34 weeks gestation mediate the association between pre-pregnancy obesity (BMI ≥30) and (i) induction of labour; (iv) mode of birth; (ii) gestational hypertension (any); (iii) infant birth weight; and (iv) establishment of breastfeeding by 6 weeks postpartum (secondary outcomes)?

Objective 2:

RQ2.1: Do weight cycling, history of trauma, history of eating disorders, and internalised weight bias explain any of the variance in the mediation relationships described above? Methods 800 participants will be recruited through the Adelaide Women's and Children's Hospital and Royal Brisbane and Women's Hospital. While waiting for their booking appointment, women will be approached by the researcher or research midwife and asked if they would like to hear about the study. Women who agree will be assessed for eligibility and provided a brief explanation of the research. Eligible women will be given the study information sheet and counselling about their potential participation by the researcher or research midwife. A brief video containing information about study objectives and participation may also be displayed in the waiting areas or available to women to access and watch. Interested women will be invited to scan a QR code to express their interest and provide consent via an online version of the consent form. Consenting participants will complete a online survey question at 20-20 weeks' gestation, 29-31 weeks' gestation, 35-7 weeks' gestation, and 6 weeks postpartum. Additional data will be extracted from their EMR. Information will be collected. The questionnaire will be completed online via the REDCap. Each time, participants will be invited to complete the questionnaire within the next two weeks. At each time point, women who do not complete the questionnaire within the two-week period will be followed up a maximum of three times via email or text message (reminders at 1 week, 11 days, and 14 days post initial survey request).

The survey will collect data on primary and secondary outcomes, as well as independent and potential confounding variables. The primary outcome is gestational diabetes mellitus (GDM). Secondary outcomes include induction of labour, mode of birth, gestational age at birth, infant admission to the neonatal unit, hypertensive disorders of pregnancy (HDP), infant birth weight and length, and infant feeding practices, including the establishment of exclusive breastfeeding.

Independent and potential confounding variables include BMI, experiences and sources of weight stigma, weight loss and weight cycling, medication, supplement, or herbal/homeopathic use, history of trauma, eating disorders or disordered eating, Midwifery Continuity of Care (CoC) model, women's experiences of respectful maternity care, mental health, self-esteem, body image, and labour pain relief measures.

Data will be presented as mean (standard deviation) or median (25th-75th percentile) for continuous variables and as count (percentage) for categorical variables. Comparisons of women's profiles across the outcomes will be performed using Fisher's exact test and t-test and Mann-Whitney tests, as appropriate. For the binary outcomes, univariable and multivariable logistic regression analyses will be conducted to estimate unadjusted and adjusted odds ratios (ORs), respectively. The conceptual models, including the mediation effect of the weight stigma on obesity - adverse outcomes relationships, will be assessed in the structural equation modelling framework