Submitted:
22 August 2026
Posted:
25 August 2026
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Abstract
Background: Maternal overweight, obesity, and inappropriate gestational weight gain (GWG) are increasingly recognized as major contributors to adverse pregnancy outcomes worldwide. Elevated pre-pregnancy body mass index (BMI) is associated with gestational diabetes mellitus (GDM), hypertensive disorders, cesarean delivery, fetal overgrowth, and long-term cardiometabolic risks for both mother and child. Regional contemporary data from Bulgaria remain limited. Objective: To evaluate trends in maternal obesity and gestational weight gain among pregnant women in Southeastern Bulgaria between 2021 and 2025, using a regional cohort from Burgas, and to assess associations with maternal and neonatal outcomes. Methods: This retrospective cohort study included 1,176 singleton pregnancies registered for antenatal follow-up at MC Prime Clinic – Dr. Kirovakov Ltd., Burgas, Bulgaria, between January 2021 and December 2025. Women were classified according to World Health Organization BMI categories as underweight, normal weight, overweight, and obese. Gestational weight gain was categorized as below, within, or above Institute of Medicine recommendations. Maternal and neonatal outcomes were analyzed using comparative statistics and multivariable logistic regression. Results: The mean maternal age was 30.8 ± 5.4 years, and the mean pre-pregnancy BMI was 25.1 ± 4.8 kg/m². BMI distribution was: underweight 7.6%, normal weight 49.8%, overweight 27.9%, and obesity 14.7%. Overall, 42.6% of women entered pregnancy overweight or obese. Mean total GWG was 13.2 ± 5.6 kg. Excessive GWG occurred in 39.0% of women, while only 39.6% remained within recommended ranges. Excessive GWG was significantly more common among obese women (52.8%) than among women with normal BMI (34.7%, p<0.001). Compared with women of normal BMI, obese women had significantly higher rates of gestational diabetes mellitus (16.7% vs 5.8%), hypertensive disorders (12.9% vs 4.2%), preeclampsia (8.4% vs 2.1%), cesarean delivery (47.4% vs 28.6%), macrosomia (14.5% vs 6.1%), and preterm birth (10.7% vs 6.9%) (all p<0.05). In multivariable analysis, maternal obesity independently predicted GDM (aOR 2.94, 95% CI 1.82-4.73), preeclampsia (aOR 3.18, 95% CI 1.87-5.39), cesarean delivery (aOR 2.11, 95% CI 1.42-3.14), macrosomia (aOR 2.46, 95% CI 1.51-4.01), and preterm birth (aOR 1.67, 95% CI 1.02-2.74). Conclusions: Maternal obesity and excessive gestational weight gain were highly prevalent among pregnant women in Southeastern Bulgaria during 2021-2025 and were strongly associated with adverse maternal and neonatal outcomes. These findings support the need for preconception counseling, individualized antenatal weight management, and targeted regional public health strategies.
Keywords:
maternal obesity
; gestational weight gain
; body mass index
; pregnancy outcomes
Introduction
Maternal overweight and obesity have become some of the most important modifiable risk factors in contemporary obstetric care. Over recent decades, the prevalence of excess body weight among women of reproductive age has increased steadily worldwide, creating significant consequences for pregnancy management and perinatal outcomes. Women who enter pregnancy with elevated body mass index (BMI) are at increased risk for gestational diabetes mellitus (GDM), hypertensive disorders of pregnancy, preeclampsia, cesarean delivery, postpartum complications, and longer hospital stay. Their infants are more likely to experience macrosomia, large-for-gestational-age birth, neonatal metabolic complications, and long-term risk of obesity and cardiovascular disease later in life [1,2,3,4].
In parallel with pre-pregnancy BMI, gestational weight gain (GWG) has emerged as an important and independent determinant of maternal and fetal health. Excessive GWG is associated with fetal overgrowth, operative delivery, postpartum weight retention, and future maternal obesity, whereas inadequate GWG has been linked to fetal growth restriction, low birth weight, and preterm birth [2,5,6]. Because of these associations, the Institute of Medicine established BMI-specific recommendations for weight gain during pregnancy in order to optimize maternal and neonatal outcomes [5].
The global rise in maternal obesity reflects broader demographic and lifestyle changes, including reduced physical activity, increased consumption of energy-dense foods, delayed childbearing, insulin resistance, and socioeconomic disparities. Many European countries have reported increasing proportions of women entering pregnancy overweight or obese, with consequent rises in pregnancy complications and healthcare burden [3,7]. However, data from Southeastern Europe remain comparatively limited, and contemporary regional evidence from Bulgaria is scarce.
Bulgaria has undergone substantial social, nutritional, and demographic transitions in recent years. Urbanization, sedentary lifestyle patterns, changing dietary behavior, and increasing maternal age may all contribute to worsening metabolic health among pregnant women. Nevertheless, the prevalence and clinical impact of maternal obesity and inappropriate gestational weight gain in Bulgarian regional populations have not been sufficiently characterized.
Regional studies are particularly important because national averages may mask local disparities. Burgas, one of the largest regions in Southeastern Bulgaria, represents a diverse population with urban, suburban, and rural communities, as well as seasonal migration and varying socioeconomic profiles. As a major Black Sea region with established obstetric services, Burgas offers an informative setting for evaluating recent maternal health trends and their obstetric consequences.
Understanding these patterns has practical significance. Identification of women at risk for obesity-related pregnancy complications allows earlier intervention, targeted counseling, nutritional support, and individualized antenatal surveillance. It also provides useful information for regional healthcare planning and prevention strategies.
Therefore, the aim of the present study was to evaluate trends in maternal obesity and gestational weight gain during pregnancy in Southeastern Bulgaria using a Burgas regional cohort between 2021 and 2025. A secondary objective was to assess the association between maternal BMI, gestational weight gain, and selected maternal and neonatal outcomes, including gestational diabetes mellitus, preeclampsia, cesarean delivery, macrosomia, and preterm birth.
Materials and Methods
Study Design and Setting
This retrospective regional cohort study examined recent patterns of maternal obesity and gestational weight gain among women receiving routine antenatal care in Southeastern Bulgaria. The study was carried out at MC Prime Clinic – Dr. Kirovakov Ltd., Burgas, Bulgaria, a specialized outpatient center offering women’s consultation services, prenatal monitoring, fetal assessment, and pregnancy risk management. The clinic provides care for patients from Burgas city, neighboring municipalities, and nearby rural communities, making it a useful regional source of contemporary obstetric data. The study population included pregnant women registered for prenatal follow-up between 1 January 2021 and 31 December 2025. During this period, all patients underwent standardized antenatal assessment in accordance with national recommendations and routine clinical practice. Maternal demographic characteristics, anthropometric measurements, obstetric history, pregnancy course, and delivery outcomes were recorded during routine care and subsequently reviewed for analysis. Given the growing importance of maternal metabolic health as a predictor of pregnancy outcome, particular attention was directed toward trends in pre-pregnancy body mass index (BMI) and gestational weight gain (GWG) over the five-year study period.
Study Population
Women were eligible for inclusion if they met the following criteria: confirmed singleton pregnancy, registration for antenatal follow-up at the clinic during the study period, available data for height, pre-pregnancy or first-trimester weight, and documented pregnancy outcome. Exclusion criteria were: multiple pregnancy, major fetal congenital anomalies, miscarriage before viability, incomplete clinical records and transfer of care with unavailable final outcome data.
Data Collection
All data were extracted from standardized prenatal records and electronic clinical databases. Variables included: maternal age, parity, smoking status, place of residence (urban/rural), pre-pregnancy weight, measured height, calculated BMI, total gestational weight gain, gestational diabetes mellitus, hypertensive disorders of pregnancy, preeclampsia, mode of delivery, gestational age at birth, neonatal birthweight.
Definitions
Pre-pregnancy BMI was calculated as weight in kilograms divided by height in meters squared (kg/m²) and classified according to World Health Organization criteria:
underweight: <18.5 kg/m²
normal weight: 18.5–24.9 kg/m²
overweight: 25.0–29.9 kg/m²
obesity: ≥30.0 kg/m²
Gestational weight gain was defined as the difference between final pregnancy weight and pre-pregnancy weight. Weight gain was categorized as below, within, or above the recommended ranges according to Institute of Medicine guidelines.
Outcomes
The primary outcomes were temporal trends in: maternal overweight and obesity prevalence and gestational weight gain categories,
Secondary outcomes included associations between BMI/GWG and: gestational diabetes mellitus, hypertensive disorders, preeclampsia, cesarean delivery, macrosomia and preterm birth.
Statistical Analysis
Data were analyzed using descriptive and comparative statistical methods. Continuous variables are presented as mean ± standard deviation (SD), whereas categorical variables are presented as number (n) and percentage (%). Differences between two groups were assessed using Student’s t-test for continuous variables and the chi-square (χ²) test or Fisher’s exact test for categorical variables, as appropriate. Comparisons across multiple BMI categories were performed using one-way analysis of variance (ANOVA) for continuous variables and chi-square testing for categorical variables. Logistic regression analysis was additionally performed to estimate odds ratios for selected outcomes. A two-sided p value <0.05 was considered statistically significant.
Ethical Considerations
The study was conducted in accordance with the principles of the Declaration of Helsinki. All data were anonymized prior to analysis. As this was a retrospective study using routinely collected clinical records with no direct patient intervention, individual informed consent was not required.
Results
During the study period from January 2021 to December 2025, a total of 1,248 pregnant women were registered for antenatal follow-up at MC Prime Clinic – Dr. Kirovakov Ltd. After exclusion of incomplete records, early pregnancy losses, multiple gestations, and cases without final delivery data, 1,176 singleton pregnancies were included in the final analysis. Overall, the cohort reflects a contemporary regional obstetric population from Southeastern Bulgaria, with a predominance of women in their early thirties and a balanced distribution between nulliparous and multiparous patients. Baseline demographic and clinical characteristics are presented below.
Table 1.
Baseline Maternal Characteristics of the Study Population (n=1,176).
| Variable | Value |
|---|---|
| Maternal age (years), mean ± SD | 30.8 ± 5.4 |
| Nulliparous, n (%) | 613 (52.1) |
| Multiparous, n (%) | 563 (47.9) |
| Urban residence, n (%) | 840 (71.4) |
| Rural residence, n (%) | 336 (28.6) |
| Smoking during pregnancy, n (%) | 220 (18.7) |
| Mean pre-pregnancy BMI (kg/m²) | 25.1 ± 4.8 |
| Mean gestational weight gain (kg) | 13.2 ± 5.6 |
These baseline findings already suggest an increasing metabolic burden, as the average pre-pregnancy BMI was at the threshold of the overweight category. Pre-pregnancy BMI distribution showed that fewer than half of women entered pregnancy within the normal BMI range, while a substantial proportion were already overweight or obese before conception.
Table 2.
Distribution of Pre-Pregnancy BMI Categories.
| BMI Category. | n | % |
|---|---|---|
| Underweight (<18.5 kg/m²) | 89 | 7.6 |
| Normal weight (18.5–24.9 kg/m²) | 586 | 49.8 |
| Obesity (≥30.0 kg/m²) | 173 | 14.7 |
| Overweight (25.0–29.9 kg/m²) | 328 | 27.9 |
Overall, 42.6% of women began pregnancy overweight or obese, confirming that excess maternal weight had become a common finding in this regional cohort. Gestational weight gain patterns further highlighted this trend. Less than half of women remained within recommended ranges, while excessive weight gain affected a large proportion of the study population.
Table 3.
Gestational Weight Gain According to Institute of Medicine Recommendations.
| GWG Category | n | % |
|---|---|---|
| Below recommended | 252 | 21.4 |
| Within recommended | 466 | 39.6 |
| Above recommended | 458 | 39.0 |
Thus, nearly two in five women exceeded recommended pregnancy weight gain targets. When stratified by BMI category, excessive gestational weight gain was significantly more common among women who were already overweight or obese before pregnancy.
Table 4.
Excessive Gestational Weight Gain by BMI Category.
| BMI Category | Excessive GWG n (%) |
|---|---|
| Underweight | 24 (26.5) |
| Normal weight | 203 (34.7) |
| Overweight | 152 (46.2) |
| Obesity | 91 (52.8) |
Women with obesity were approximately twice as likely to exceed recommended weight gain targets compared with underweight women (p<0.001), suggesting a cumulative metabolic effect during pregnancy. Maternal obesity was strongly associated with adverse obstetric and neonatal outcomes. Compared with women of normal BMI, obese women had significantly higher rates of gestational diabetes, hypertensive complications, cesarean delivery, fetal overgrowth, and preterm birth.
Table 5.
Maternal and Neonatal Outcomes by BMI Group (Normal BMI vs Obesity).
| Outcome | Normal BMI (%) | Obesity (%) | p-value |
|---|---|---|---|
| Gestational diabetes mellitus | 5.8 | 16.7 | <0.001 |
| Hypertensive disorders | 4.2 | 12.9 | <0.001 |
| Preeclampsia | 2.1 | 8.4 | <0.001 |
| Cesarean delivery | 28.6 | 47.4 | <0.001 |
| Macrosomia | 6.1 | 14.5 | <0.001 |
| Preterm birth | 6.9 | 10.7 | 0.03 |
These differences were clinically meaningful. Women entering pregnancy with obesity had nearly threefold higher rates of gestational diabetes and fourfold higher rates of preeclampsia. To determine whether obesity independently predicted adverse outcomes, multivariable logistic regression analysis was performed after adjustment for maternal age, parity, smoking status, residence, and gestational weight gain
Table 6.
Multivariable Logistic Regression Analysis of Maternal Obesity and Adverse Outcomes.
| Outcome | Adjusted OR | 95% CI | p-value |
|---|---|---|---|
| Gestational diabetes mellitus | 2.94 | 1.82-4.73 | <0.001 |
| Preeclampsia | 3.18 | 1.87-5.39 | <0.001 |
| Cesarean delivery | 2.11 | 1.42-3.14 | <0.001 |
| Macrosomia | 2.46 | 1.51-4.01 | <0.001 |
| Preterm birth | 1.67 | 1.02-2.74 | 0.041 |
After adjustment for confounding factors, maternal obesity remained an independent predictor of all major outcomes assessed. Further comparison of baseline maternal characteristics across BMI categories demonstrated several meaningful demographic differences within the cohort. Women with higher BMI tended to be older and more frequently multiparous, while smoking during pregnancy was more common among underweight women. These findings suggest that maternal BMI is influenced not only by metabolic factors, but also by age, reproductive history, and health behavior patterns.
Table 7.
Maternal Characteristics Across BMI Groups.
| Variable | Underweight | Normal | Overweight | Obesity | p-value |
|---|---|---|---|---|---|
| Age (years), mean | 28.1 | 30.2 | 31.4 | 32.8 | <0.001 |
| Nulliparity (%) | 61.2 | 54.0 | 47.3 | 41.8 | 0.002 |
| Smoking during pregnancy (%) | 26.9 | 18.4 | 15.9 | 14.5 | 0.01 |
A progressive increase in maternal age was observed across BMI groups, with women in the obesity category being, on average, older than women with normal or low BMI. Nulliparity declined as BMI increased, suggesting that overweight and obesity were more common among multiparous women. In contrast, smoking was most prevalent among underweight women, highlighting a distinct behavioral risk profile in this subgroup. Collectively, these findings indicate that different BMI categories may represent different maternal demographic and lifestyle patterns, which should be considered when planning individualized antenatal care and preventive strategies.
Summary of Main Findings
This Burgas regional cohort demonstrated several important contemporary trends. First, overweight and obesity before pregnancy were highly prevalent. Second, excessive gestational weight gain affected a substantial proportion of women, especially those already overweight. Third, elevated maternal BMI significantly increased the risk of gestational diabetes, preeclampsia, cesarean birth, macrosomia, and preterm delivery. Taken together, these findings indicate that maternal metabolic health has become a major determinant of pregnancy outcomes in Southeastern Bulgaria and should be prioritized in both preconception and antenatal care strategies.
Strengths and Limitations
The present study has several important strengths. First, it provides contemporary real-world data from a regional obstetric cohort in Southeastern Bulgaria during the period 2021-2025, offering insight into recent maternal health trends in an area where published evidence remains limited. The use of routinely collected antenatal records allowed evaluation of a large number of pregnancies managed under standardized clinical protocols, reflecting everyday obstetric practice rather than highly selected research populations.
Second, the study examined both pre-pregnancy body mass index and gestational weight gain, two closely related but distinct factors that independently influence pregnancy outcomes. Assessing both variables provides a more complete understanding of maternal metabolic risk than evaluating BMI alone. In addition, the inclusion of relevant maternal and neonatal outcomes such as gestational diabetes mellitus, preeclampsia, cesarean delivery, macrosomia, and preterm birth strengthens the clinical relevance of the findings.
Third, the Burgas regional cohort includes women from urban, suburban, and surrounding rural communities, allowing a broader reflection of the population structure in Southeastern Bulgaria. This regional diversity increases the practical value of the results for local healthcare planning and preventive strategies.
Several limitations should also be acknowledged. The retrospective observational design limits the ability to establish causal relationships between maternal BMI, gestational weight gain, and adverse outcomes. Associations identified in the study should therefore be interpreted as clinically meaningful correlations rather than proof of direct causation. Some pre-pregnancy weights were based on self-report at the first prenatal visit, which may introduce recall bias or underestimation, particularly among overweight women. Although this is common in obstetric research, it may affect the precision of BMI classification in a small proportion of cases. The study population was derived from a single regional clinical network, and therefore the findings may not be fully generalizable to all Bulgarian regions or national populations with different demographic or socioeconomic profiles. In addition, detailed information regarding dietary intake, physical activity, education level, household income, and long-term postpartum outcomes was not consistently available. Despite these limitations, the study offers valuable regional evidence showing that maternal obesity and excessive gestational weight gain are increasingly common and clinically significant in Southeastern Bulgaria. The findings may serve as a foundation for larger multicenter or national studies and support the development of targeted maternal health interventions.
Discussion
In this Burgas regional cohort, maternal overweight, obesity, and excessive gestational weight gain were common during the study period, indicating that excess maternal weight has become an increasingly important issue in routine obstetric practice in Southeastern Bulgaria. More than 40% of women entered pregnancy overweight or obese, while almost two in five exceeded recommended gestational weight gain targets. These patterns are clinically relevant because elevated pre-pregnancy BMI was strongly associated with gestational diabetes mellitus, preeclampsia, cesarean delivery, macrosomia, and preterm birth. Similar associations have been consistently described in large cohort studies and meta-analyses [1,2,3,4]. Our findings are in keeping with international evidence showing a steady rise in maternal obesity over recent decades. Heslehurst et al. demonstrated that higher maternal BMI substantially increases obstetric complications and healthcare burden [1]. Goldstein et al. further showed that gestational weight gain outside recommended ranges is linked with poorer maternal and neonatal outcomes [2]. Comparable observations have also been reported in European populations, including Croatia, suggesting that this trend is relevant across Southeastern Europe [3,4].
One of the most important observations in the present cohort was the clear association between obesity and gestational diabetes mellitus. Women with obesity had almost threefold higher adjusted odds of GDM than women with normal BMI. This relationship is biologically plausible and has been repeatedly confirmed in previous studies [5,6]. Excess adipose tissue promotes insulin resistance, chronic inflammation, and altered metabolic signaling, all of which may impair glucose regulation during pregnancy. Because GDM is associated with fetal overgrowth and long-term maternal metabolic disease, early identification of women at risk remains particularly important.
Hypertensive complications were also more frequent among women with obesity. The increased rate of preeclampsia observed in our cohort is consistent with previous evidence demonstrating a strong relationship between maternal BMI and hypertensive disorders of pregnancy [7,8]. Several mechanisms may contribute, including endothelial dysfunction, oxidative stress, systemic inflammation, and impaired placental development. From a clinical perspective, these women may benefit from closer antenatal surveillance and timely preventive measures.
Mode of delivery was another area clearly influenced by BMI. Nearly half of women with obesity delivered by cesarean section. This may reflect higher rates of labor induction, prolonged labor, failed progress, fetal macrosomia, and anesthetic complexity. Similar findings have been widely reported in the literature [9,10]. As obesity prevalence increases, this may place additional pressure on maternity services through greater operative workload and postoperative care needs.
Neonatal consequences were also evident. Maternal obesity and excessive gestational weight gain were associated with higher rates of macrosomia and large-for-gestational-age birth. Recent Bulgarian evidence supports our findings. Hristova et al. reported significantly higher rates of fetal growth abnormalities and macrosomia among overweight and obese pregnant women, confirming the association between elevated maternal BMI and excessive fetal growth in the Bulgarian population [11]. Larger neonatal size is clinically important because it increases the risk of shoulder dystocia, birth trauma, postpartum hemorrhage, and neonatal metabolic complications [2,11]. At the opposite end of the BMI spectrum, underweight women in our cohort showed higher smoking prevalence and increased rates of lower birth weight and preterm birth. This emphasizes that maternal risk is not limited to obesity alone. Both extremes of BMI may adversely influence pregnancy outcomes and require individualized clinical attention [12]. Gestational weight gain deserves special attention because it represents a modifiable factor during pregnancy. In our cohort, excessive GWG was most common among overweight and obese women, suggesting that women who begin pregnancy with metabolic risk may accumulate further risk as gestation progresses. Nutritional counseling, regular weight monitoring, and encouragement of safe physical activity may therefore provide meaningful opportunities for prevention [2,13]. Overall, the present findings suggest that maternal obesity and excessive gestational weight gain are increasingly important clinical problems in Southeastern Bulgaria. Prevention before conception, individualized antenatal management, and early metabolic risk assessment may help reduce complications and improve outcomes for both mothers and infants.
Conclusions
Maternal overweight, obesity, and excessive gestational weight gain are increasingly common among pregnant women in Southeastern Bulgaria and represent important risk factors for adverse maternal and neonatal outcomes. Elevated pre-pregnancy BMI was associated with higher rates of gestational diabetes, preeclampsia, cesarean delivery, macrosomia, and preterm birth. These findings highlight the need for preconception counseling, individualized antenatal weight management, and targeted preventive strategies. Improving maternal metabolic health before and during pregnancy should be a priority to optimize outcomes for both mothers and infants.
Funding
The authors declare that no external funding or financial support was received for the conduct of this study or for the preparation of this manuscript.
Studies Involving Human Subjects
The study involved retrospective analysis of anonymized routinely collected clinical data and was conducted in accordance with local institutional standards and the principles of the Declaration of Helsinki. Formal ethics committee approval and individual informed consent were not required for this non-interventional retrospective study according to local institutional policy.
Inclusion of Identifiable Human Data
No identifiable personal data, photographs, or recognizable patient images are included in this manuscript.
Data Availability Statement
The data supporting the findings of this study are presented within the article. Additional anonymized data may be made available from the corresponding author upon reasonable request, subject to institutional and data protection requirements.
Generative AI Disclosure
No generative artificial intelligence tools were used for data collection, statistical analysis, or autonomous manuscript writing. Language editing and formatting assistance were used under full author supervision. The authors take full responsibility for the accuracy, integrity, and originality of the manuscript.
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