Introduction

Gestational diabetes mellitus (GDM) is a common preg-nancy complication and represents a major risk factor for later development of type 2 diabetes mellitus (T2DM) [1]. In 2021, approximately 21.1 million live births (16.7%) were affected by GDM worldwide, and the prevalence in Italy is estimated at 14.3% [2]. Although glucose intoler-ance typically resolves after delivery, women with previ-ous GDM exhibit a markedly elevated risk of progression to T2DM, with reported conversion rates ranging from 2 to 12.5% within the first postpartum year [3–5]. Multiple car-diometabolic risk factors cluster in women with prior GDM, including overweight/obesity, hypertension, dyslipidaemia, and metabolic syndrome [6, 7]. A meta-analysis evaluating risk factors in women with GDM found that family history of diabetes increased risk by 70% and elevated postpartum BMI was associated with a 2-fold greater risk [8]. Inde-pendent of BMI, postpartum weight gain was identified as a risk factor [9]. Advanced maternal age was also associ ated with a 20% greater risk of T2DM. Moreover, other pregnancy-related factors were predictors of progression to T2DM. Insulin requirement was associated with a 3.7-fold greater risk and elevated HbA1c was associated with 2.6 greater T2DM risk [10, 11]. Moreover, maternal obesity at the onset of pregnancy has been proposed as a contributing factor that may increase the risk of developing depression or poor quality of life post-partum [12]. Lifestyle factors play a key role in modulating postpartum metabolic risk. Adherence to healthy dietary patterns—particularly the Mediterranean diet—has been associated with improved weight control, glycaemic regulation, and reduced incident diabetes. Likewise, regular physical activity supports insu-lin sensitivity and cardiometabolic health; however, adher-ence tends to decline after childbirth due to reduced time, childcare demands, and psychosocial barriers [13, 14].

    Professional societies —including The American Col-lege of Obstetricians and Gynecologists ACOG [15], the American Diabetes Association (ADA) [16], The Interna-tional Federation of Obstetrics and Gynaecology (FIGO) [17], and National Institute for Health and Care Excellence (NICE) [18]—recommend OGTT at 6–12 weeks postpar-tum and periodic lifelong screening every 1–3 years. Con-versely, current Italian guidelines [19], focus solely on the early postpartum window and do not address assessment at one year. In Italy, adherence to postpartum follow-up after GDM is frequently inadequate, as highlighted by Dalfrà et al. [20], and further confirmed by the STRONG study [21], which identified high-risk subgroups and substantial gaps in postpartum screening, who reported significant dropout rates despite structured programs.

    This study characterizes metabolic changes during the first postpartum year in women with a history of GDM and identifies clinical, behavioural, and psychosocial predictors of altered glucose tolerance. We performed comprehensive statistical analyses to investigate the interplay between anthropometric, lifestyle, and quality-of-life variables and their implications for clinical management.

Materials and methods

Study population

This single-center observational study included 134 women with a history of gestational diabetes mellitus (GDM) diagnosed according to the IADPSG criteria. These crite-ria utilize a 75-g oral glucose tolerance test (OGTT) with the following diagnostic thresholds: fasting plasma glu-cose≤92 mg/dL, 1-hour glucose≤180 mg/dL, and 2-hour glucose≤153 mg/dL. Participants were evaluated at the Diabetes Unit of the Fondazione IRCCS Ca’ Granda Osped-ale Maggiore Policlinico (Milan, Italy). Assessments were conducted at 6–12 weeks postpartum (T0) and at one year (T1). The study protocol was approved by the institutional Ethics Committee (ID 4613-4613_17.07.2024_P_bis). Written informed consent was obtained from all partici pants. Study procedures were performed in accordance with the Declaration of Helsinki ethical principles for medical research involving human subjects.

Clinical and laboratory assessments

Anthropometric parameters (weight, height, BMI) [22], blood pressure, and biochemical variables (fasting glucose, HbA1c, lipid profile) were collected. OGTT was performed at both time points. Body composition was evaluated through bioelectrical impedance analysis (BIA), including measurements of total body water, fat-free mass, fat mass, and muscle mass.

Lifestyle and dietary assessments

Dietary intake was assessed using a 3-day food diary and analysed using Metadieta® Professional. Adherence to the Mediterranean diet was evaluated with the 14-item PRE-DIMED score [23]. Physical activity was measured using the International Physical Activity Questionnaire (IPAQ) [24]. Quality of life was assessed using the SF-36 questionnaire.

Statistical analysis

Continuous variables are presented as mean±standard deviation (SD), and categorical variables as absolute num-bers and percentages. Between-group comparisons were performed using Student’s t-test or Mann–Whitney U test, as appropriate, while categorical variables were compared using chi-square or Fisher’s exact test. Univariate logistic regression analyses were conducted to explore associations between individual clinical, anthropometric, metabolic, lifestyle, and psychosocial variables and altered glucose tolerance at one year postpartum (defined as altered OGTT and/or type 2 diabetes). Variables entered into the multi-variate logistic regression model were selected based on a combination of statistical and clinical criteria. Specifically, variables showing a significant or borderline association in univariate analyses (p<0.10) and variables considered clini-cally relevant a priori according to existing literature (e.g. age, family history of diabetes, body composition parame-ters, and insulin therapy during pregnancy) were considered for inclusion. Given the limited number of dysglycaemic events, the number of covariates included in the multivari-ate model was deliberately restricted to minimise overfit-ting and ensure model stability. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. A two-sided p-value≤0.05 was considered statistically significant. All analyses were performed using SPSS Statistics ver-sion 26.0 (IBM Corp., Armonk, NY, USA).

Results

Participant characteristics

The cohort included 134 women with a mean age of 37.3±4.6 years. Of these women, 76.5% were of Caucasian ethnicity. Pre-pregnancy BMI was 25.3±4.7 kg/m² and cur-rent BMI 24.8±4.9 kg/m² (Table 1). At baseline, 67.2% had normal glucose tolerance (90 women- group N) and 32.9% (44 women) presented altered OGTT (group A) (24 women with IFG, 14 with IGT, and 3 who exhibited both meta-bolic alterations). One year later this proportion increased to 38.8%, and T2DM prevalence rose from 2.2% to 5.2% (Fig. 1). BIA parameters did not differ significantly between women with normal (group N) and altered OGTT (group A). Body composition analysis by BIA was available for 89 participants. No significant differences were found in total body water (TBW), extracellular water (ECW), intracellular water (ICW), body cell mass (BCM), fat-free mass (FFM), fat mass (FM), or muscle mass (MM) between groups (all p>0.05). 41% required insulin during pregnancy. In the uni- variate logistic regression model fat mass (FM) (OR=1.06, p=0.04) was associated with an increased risk of altered OGTT at one year. Adherence to the Mediterranean diet (PREDIMED score) remained moderate, while physical activity levels (IPAQ) tended to decrease (Table 2).

Determinants of glycaemic outcomes

Breastfeeding was significantly associated with normal glycaemic status (p=0.009). Insulin therapy in pregnancy emerged as the strongest predictor of altered OGTT in both univariate and multivariate models (OR 3.5, 95% CI 1.28– 9.50, p=0.015). (Table 3).

Quality of life

Women with altered OGTT reported significantly lower

SF-36 scores in:

• Role limitations due to physical health (p=0.016).
• Health change (p=0.030).

Discussion

This study demonstrates that a substantial proportion of women with previous GDM experience glycaemic dete-rioration within the first postpartum year, even when early postpartum testing is normal. Nearly 40% of participants exhibited altered glucose tolerance at one year, and the prev-alence of overt T2DM more than doubled. These findings corroborate prior evidence indicating that up to 10–20% of women with previous GDM develop glucose intolerance or diabetes within the first postpartum year [1, 25]. Consistent with prior evidence, insulin therapy during pregnancy was the strongest independent predictor of dysglycaemia (OR = 3.5, 95% CI 1.28–9.50, p = 0.015), reflecting underlying β-cell dysfunction. This observation reinforces the concept that insulin requirement during GDM reflects a more severe degree of beta-cell dysfunction, which persists beyond pregnancy. Identifying such women at the time of diagno-sis may therefore help clinicians to tailor closer postpartum surveillance and lifestyle counseling. The observed increase of 16% in AGT and T2DM from 6–12 weeks to one year postpartum likely reflects persistent β-cell dysfunction unmasked by declining insulin sensitivity and lifestyle adherence over time, even in women who initially show nor-mal glucose tolerance (NGT) [26]. Although body weight remained stable, physical activity tended to decrease and dietary quality did not improve, suggesting that behavioural and physiological factors jointly contributed to early meta-bolic deterioration. The predictive value of insulin therapy at T1 — also evident at T0 — supports its role as a marker of intrinsic β-cell impairment rather than a transient indica-tor of pregnancy severity. Although body composition and biochemical variables showed no significant inter-group dif-ferences, quality-of-life (QoL) assessments captured clini-cally meaningful disparities. Specifically, lower scores in ‘role limitations due to physical health’ and ‘health change’ suggest that subtle functional and psychosocial impairments may serve as early markers of metabolic vulnerability [27, 28]. Breastfeeding emerged as a protective factor, aligning with studies demonstrating improved insulin sensitivity and reduced long-term diabetes risk among lactating women [29, 30]. Yet, adherence to healthy diet and physical activity remained suboptimal, underscoring persistent barriers dur-ing the postpartum period. Similar behavioral patterns have been reported previously, with women describing barriers such as lack of time, motivation, and childcare responsibili-ties that limit engagement in lifestyle interventions [31, 32].

The persistence of sedentary behavior and suboptimal diet quality likely contributed to the observed metabolic dete-rioration. Our findings are consistent with real-world Italian evidence. The STRONG study [20] demonstrated that post-partum diabetes screening remains significantly suboptimal, with many high-risk women failing to complete OGTT test-ing. Similarly, Dalfrà et al. [21] reported relevant dropout rates even within structured follow-up programs. These converging data suggest that both clinical risk stratification and behavioural adherence barriers contribute to missed opportunities for early detection of dysglycaemia [33]. This study provides the opportunity to track long-term trends in metabolic alterations and to identify both the determi-nants of abnormal glucose tolerance (AGT) and the protec-tive factors against the development of such impairments. These findings support the implementation of a structured follow-up at one year postpartum—currently absent from Italian recommendations—particularly for women treated with insulin. Integrating lifestyle counselling, psychosocial assessment, and breastfeeding support may help attenu-ate early metabolic deterioration. These women constitute a high-risk subgroup warranting targeted follow-up and early preventive intervention. Given the mean BMI of the cohort, the presence of alternative forms of diabetes, such as Type 1 Diabetes (T1D) or Maturity-Onset Diabetes of the Young (MODY), cannot be entirely excluded, although these conditions are considerably less prevalent. Future pro-spective studies and interventional trials, particularly those centered on lifestyle modifications, are essential to imple-ment effective primary prevention strategies - specifically during the first postpartum year - to reduce incident T2DM and improve long-term cardiometabolic outcomes.

Conclusions

One year after delivery, over one-third of women with pre-vious GDM exhibited altered glucose tolerance. Insulin requirements during pregnancy emerged the most robust predictor of postpartum dysglycaemia, while breastfeeding and quality-of-life indicators were significantly associated with glycaemic outcomes. These findings underscore the necessity of comprehensive, long-term monitoring and life-style-based interventions that extend beyond the traditional early postpartum window.

Acknowledgements This work was partially supported by Ricerca Corrente Funds from the Italian Ministry of Health to Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico.

Author contributions A.G. and V.R. conceptualized and designed the study, drafted the initial manuscript, and reviewed and revised the manuscript. A.G., Y.P, M.M., G.R., G.M., I.C., V.G. and F.G. col-lected data, carried out the initial analyses, and reviewed and revised the manuscript. A.G., M.M., V.R. E.O. designed the data collection instruments, coordinated and supervised data collection, and critically reviewed the manuscript All authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work. A.G. is the guarantor of this work and, as such, had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Declarations

Conflict of interest The authors declare that the research was con-ducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Ethical approval The studies involving humans were approved by the Ethics Committee of our Institution (Lombardia 3). The studies were conducted in agreement with the local legislation and institutional re-quirements. Written informed consent was obtained from the individu-als for the publication of any potentially identifiable images or data included in this article.

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 This article is excerpted from the 《Acta Diabetologica》 by Wound World.