Two of the most important factors in maternal and fetal health during pregnancy are maternal nutrition and body mass index (BMI). Body Mass Index (BMI) is a commonly used index of nutritional status before, or during, pregnancy. It is calculated as weight in kilograms divided by height in meters squared (kg/m²). Maternal BMI is a key predictor of pregnancy complications, with both low and high BMI being linked to adverse outcomes for the mother and/or the baby. Identifying women with abnormal BMI at the earliest opportunity provides an opportunity for targeted interventions during pregnancy, risk assessment, and nutritional counseling to improve outcomes [1,2]. This shift in dietary pattern, urbanization, sedentary lifestyle, and socioeconomic factors has led to the increasing prevalence of abnormal BMI among women of reproductive age all over the world. Although overweight and obesity are now a significant public health problem in many countries, undernutrition remains a significant problem for a large number of pregnant women in developing countries. Thus, healthcare systems may be confronted with the challenge of dealing with both underweight and obesity, which are associated with poor maternal and neonatal outcomes [3,4]. Maternal obesity has been associated with such pregnancy-related issues as gestational diabetes mellitus, gestational hypertension, preeclampsia, prolonged labor, cesarean delivery, postpartum hemorrhage, wound infection, and thromboembolic events. Obesity also contributes to fetal macrosomia, congenital anomalies, birth trauma, admission to the neonatal intensive care unit (NICU), and neonatal metabolic disorders as well. Hyperadiposity in the mother leads to insulin resistance, chronic inflammation, and altered placental function, which hurts fetal growth and development [5,6]. On the other hand, maternal underweight has been associated with poor nutritional status, poor fetal growth, anemia, preterm delivery, low birth weight, and high perinatal mortality and morbidity rates. Maternal nutritional status could affect placental growth and fetal nutrient transfer, leading to impaired fetal growth and poor neonatal outcomes. The complications remain prevalent in low- and middle-income countries, where undernutrition is widespread [7,8]. The World Health Organization (WHO) recommends that maternal BMI be routinely assessed during pregnancy to determine women's risk of pregnancy complications. Recognizing BMI abnormalities early enables health care providers to offer personal dietary advice, weight management plans, and better antenatal monitoring. Appropriate interventions before and during pregnancy have been shown to reduce adverse maternal and neonatal outcomes and improve pregnancy care [9,10]. Though there is increasing evidence of how maternal BMI is associated with pregnancy outcomes, data in Pakistan are still limited, especially from tertiary care hospitals with high-risk pregnancies. There may be differences in the relationship between BMI and pregnancy outcomes among the local population, depending on socioeconomic status, dietary habits, health care access, and maternal health services. Therefore, it is important to have locally generated evidence to inform the development of effective preventive strategies and the enhancement of maternal health service delivery.

Study Objective

To assess the correlation between maternal BMI and pregnancy outcome among women who gave birth at the tertiary care hospital and its maternal and neonatal complications in women with abnormal BMI.

Study Design & Setting A cross-sectional study was conducted in the the Department of Obstetrics and Gynecology, Saidu Group of Teaching Hospital, Swat, Pakistan, from January 2025 to December 2025. Participants Consecutive nonprobability sampling was used to recruit 100 pregnant women admitted for delivery. They included women with singleton gestation at a gestational age of 28 weeks or more who gave written informed consent. In patients with multiple pregnancies, those with major fetal congenital anomalies, incomplete medical records, and severe chronic medical illnesses that could affect pregnancy outcome were excluded. A structured data collection form was used to collect maternal demography and clinical, obstetric, and neonatal data. Sample Size Calculation The WHO Sample Size Calculator was used to estimate the sample size, assuming a 50% prevalence of adverse pregnancy outcomes among women with abnormal body mass index, a 95% confidence level, and a 10% margin of error. The sample size was determined to be 96, the minimum number of participants required for the study; therefore, 100 pregnant women were enrolled to enhance the study's precision. Statistical Analysis Data were entered and analyzed using IBM SPSS Statistics version 26.0 (IBM Corp., Armonk, NY, USA). Continuous variables were assessed for normality using the Shapiro–Wilk test and are presented as mean ± standard deviation (SD). Categorical variables are expressed as frequencies and percentages. Differences in continuous variables between BMI groups were analyzed using the independent-samples t-test or one-way analysis of variance (ANOVA), as appropriate. Associations between categorical variables were evaluated using the Chi-square test or Fisher’s exact test when expected cell counts were less than five. Binary logistic regression was performed to estimate the association between abnormal maternal BMI and adverse maternal and neonatal outcomes, adjusting for potential confounders, including maternal age and parity. Results are presented as adjusted odds ratios (AORs) with 95% confidence intervals (CIs). A two-tailed p-value of less than 0.05 was considered statistically significant. Inclusion Criteria • Pregnant women between the ages of 18 and 45 years. • Singleton pregnancy of ≥28 gestational weeks. • Women admitted for delivery in the study period. • Written informed consent was obtained from women. Exclusion Criteria • Multiple pregnancies (twins or triplets). • Pregnancies complicated by major fetal congenital anomalies. • Women with incomplete clinical records. • Severe chronic systemic disease (e.g., chronic renal failure, malignancy, autoimmune disease) which may have an independent effect on pregnancy outcome. • Women unwilling to participate in the study. Diagnostic and Management Strategy Maternal height and weight were measured using standardized instruments, and BMI was calculated according to World Health Organization (WHO) guidelines. Standard care was provided during pregnancy and delivery in line with the hospital protocols. The obstetric team managed all maternal and neonatal complications, and outcomes were followed until hospital discharge.

A total of 100 pregnant women were included in the study. The mean maternal age was 28.9 ± 5.8 years. According to World Health Organization BMI classification, 18 (18%) women were underweight, 47 (47%) had normal BMI, 24 (24%) were overweight, and 11 (11%) were obese. The overall cesarean section rate was 36%, while 64% of women had spontaneous vaginal delivery. Overweight and obese women demonstrated significantly higher rates of cesarean delivery than women with normal BMI (52.9% vs. 27.7%; p=0.018). Gestational hypertension occurred in 22.9% of overweight/obese women compared with 7.7% of women with normal BMI (p=0.031), whereas gestational diabetes mellitus was observed in 17.1% and 5.1%, respectively (p=0.042). Neonatal macrosomia was significantly more common among overweight and obese mothers (14.3% vs. 3.8%; p=0.039), and NICU admission occurred more frequently in this group (20.0% vs. 8.9%; p=0.047). Conversely, underweight women had significantly higher rates of low-birth-weight infants (27.8% vs. 9.8%; p=0.028) and preterm delivery (22.2% vs. 10.9%; p=0.049). Overall, abnormal maternal BMI showed a statistically significant association with adverse maternal and neonatal outcomes, indicating that both underweight and overweight/obesity increase the risk of pregnancy-related complications.

Table 1. Baseline Demographic and Clinical Characteristics of the Study Participants (n = 100)

Values are presented as mean ± standard deviation or frequency (percentage). BMI was classified according to the World Health Organization criteria.

Table 2. Association Between Maternal BMI Category and Maternal Pregnancy Outcomes

Chi-square test was used to compare categorical variables. A p-value <0.05 was considered statistically significant.

Table 3. Association Between Maternal BMI Category and Neonatal Outcomes

Neonatal outcomes were compared across BMI categories using the Chi-square test. Statistical significance was defined as p<0.05.

Table 4. Summary of Significant Associations Between Maternal BMI and Pregnancy Outcomes

Maternal BMI demonstrated significant associations with several adverse maternal and neonatal outcomes. Overweight and obesity were associated with increased obstetric complications, whereas underweight was associated with low birth weight and preterm birth.

The present study showed that there was a statistically significant association of maternal BMI with adverse pregnancy outcomes in women delivered at a tertiary care hospital. Underweight and overweight/obese women had more complications during their pregnancies and deliveries than normal weight women, and more complications in their newborns. Cesarean delivery was significantly associated with overweight and obesity. In contrast, gestational hypertension, gestational diabetes mellitus (GDM), macrosomia, and neonatal intensive care unit (NICU) admission were significantly associated with overweight and obesity. Maternal underweight was associated with low birth weight (LBW) and preterm birth. These results confirm the importance of maintaining an optimal BMI before and during pregnancy to improve maternal and newborn health outcomes [11,12]. The trend of higher cesarean rates in overweight and obese women seen in our study has been confirmed in the last 5 years. A large, multicenter cohort study in the South Asian population has also confirmed that overweight and obesity are independent risk factors for cesarean section, even after controlling for maternal age and parity [13]. Our study on gestational hypertension and GDM is consistent with some recent systematic reviews and prospective studies. Studies showed that in pregnant women, maternal obesity is linked with insulin resistance, endothelial dysfunction, and chronic low-grade inflammation, all of which are associated with hypertensive disorders and impaired glucose metabolism. These findings suggest that the routine screening of women with elevated BMI during antenatal care for early diagnosis and timely intervention is supported by recent studies, which have shown that women with elevated BMI are at 2-4 times greater risk of developing GDM and pregnancy-induced hypertension, compared to women of normal BMI. [14,15] The perinatal outcomes in the present study are also consistent with recent literature. The incidence of macrosomia and admission to the NICU were significantly higher for the neonates of overweight/obese mothers. Recent birth cohort studies in Asia, Europe, and North America have also found that excess maternal adiposity is associated with fetal overgrowth, fetal trauma, fetal hypoglycemia, and fetal respiratory complications, as well as with admission to intensive care units after birth. Excess maternal adiposity promotes fetal hyperinsulinemia and increased placental nutrient transfer, resulting in fetal overgrowth and greater risk of delivery-related complications [16,17]. In contrast, mothers who were underweight in the current study had significantly higher rates of LBW and preterm birth [18]. This is similar to reported results in recent low- and middle-income country studies where maternal undernutrition is also common, leading to limited fetal growth and shortened gestation and inadequate nutritional reserves that lead to impaired placental development and reduced nutrient supply to the fetus [19]. These findings show that undernutrition is also an important health problem in today's world, especially in developing countries, alongside obesity [20]. The advantages of the current study are the use of the WHO-standardized BMI classification, the inclusion of both maternal and neonatal outcomes, and the fact that the women were delivering in a tertiary care facility with a high prevalence of high-risk cases and pregnancies [21]. There are, however, several caveats [22]. The study was conducted at a single site and had a small sample size (n = 100), which may limit the extent to which the findings can be generalized. Furthermore, the cross-sectional design does not allow for the establishment of causal relationships, and confounding factors, including dietary intake, gestational weight gain, physical activity, socioeconomic status, and smoking, were not assessed [23]. Larger-sample-size prospective multicenter studies are recommended to confirm this study's findings and to determine independent predictors of adverse pregnancy outcomes [24]. In general, the results of this study are in line with the current international evidence, confirming that low and high BMI of the mothers are significantly linked with unfavorable outcomes for mothers and children. To prevent complications in pregnancy and ensure good maternal and neonatal outcomes, there is a need to incorporate regular BMI assessment, personalized nutrition counseling, weight-optimization strategies, and regular antenatal surveillance into maternal health programs [25]. Limitations The study was carried out at a single tertiary care hospital with a small sample of 100 patients, and the generalizability of the results may be limited. The cross-sectional study design did not allow causal inference, and some confounding factors, such as gestational weight gain, diet, physical activity, and socioeconomic status, were not assessed.

BMI is a significant factor in the outcome of pregnancy. Underweight and overweight/obese women have higher risks for maternal and neonatal complications. Normal BMI evaluation, preconception weight optimization, nutritional counseling, and suitable antenatal care are crucial to optimize pregnancy outcomes and to minimize pregnancy-related morbidity.

Disclaimer: Nil

Conflict of Interest: Nil

Funding Disclosure: Nil

Authors Contributions

Concept & Design of Study: Rukhsana1,Saima Ali2

Drafting: Neelam Akbar3,Safeena Arif4

Data Collection & Data Analysis:Farhadia Sadaf5  

Critical Review: Tabassum Ikram6

Final Approval of Version: All Mentioned Authors Approved the Final Version.

1. Dalfra MG, Burlina S, Lapolla A. Weight gain during pregnancy: a narrative review on the recent evidence. Diabetes Res Clin Pract. 2022;188:109913. doi:10.1016/j.diabres.2022.109913. PMID:35568262.
2. Hartge D, Spiegler J, Schroeer A, Deckwart V, Weichert J. Maternal super-obesity. Arch Gynecol Obstet. 2016;293(5):987-992. doi:10.1007/s00404-015-3921-9. PMID:26498605.
3. Li H, Miao C, Xu L, Gao H, Bai M, Liu W, et al. Maternal pre-pregnancy body mass index, gestational weight gain trajectory, and risk of adverse perinatal outcomes. Int J Gynaecol Obstet. 2022;157(3):723-732. doi:10.1002/ijgo.13922. PMID:34498265.
4. Van der Linden EL, Browne JL, Vissers KM, Antwi E, Agyepong IA, Grobbee DE, et al. Maternal body mass index and adverse pregnancy outcomes: a Ghanaian cohort study. Obesity (Silver Spring). 2016;24(1):215-222. doi:10.1002/oby.21210. PMID:26574712.
5. Smid MC, Dotters-Katz SK, Silver RM, Kuller JA. Body mass index 50 kg/m² and beyond: perioperative care of pregnant women with superobesity undergoing cesarean delivery. Obstet Gynecol Surv. 2017;72(8):500-510. doi:10.1097/OGX.0000000000000469. PMID:28817167.
6. Martens DS, Plusquin M, Gyselaers W, De Vivo I, Nawrot TS. Maternal pre-pregnancy body mass index and newborn telomere length. BMC Med. 2016;14(1):148. doi:10.1186/s12916-016-0689-0. PMID:27751173. PMCID: PMC5067896.
7. Schlueter A, Doshi U, Garg B, Hersh AR, Caughey AB. Adverse pregnancy outcomes associated with maternal syphilis infection. J Matern Fetal Neonatal Med. 2022;35(25):5828-5833. doi:10.1080/14767058.2021.1895740. PMID:33678095.
8. Marshall NE, Biel FM, Boone-Heinonen J, Dukhovny D, Caughey AB, Snowden JM. The association between maternal height and body mass index and perinatal outcomes. Am J Perinatol. 2019;36(6):632-640. doi:10.1055/s-0038-1673395. PMID:30292175. PMCID: PMC6453733.
9. Foo XY, Greer RM, Kumar S. Impact of maternal body mass index on intrapartum and neonatal outcomes in Brisbane, Australia, 2007 to 2013. Birth. 2016;43(4):358-365. doi:10.1111/birt.12246. PMID:27500501.
10. Martin H, Thevenet-Morrison K, Dozier A. Maternal pre-pregnancy body mass index, gestational weight gain and breastfeeding outcomes: a cross-sectional analysis. BMC Pregnancy Childbirth. 2020;20(1):471. doi:10.1186/s12884-020-03156-8. PMID:32807132. PMCID: PMC7433137.
11. Wang T, Li L, Wu C, Cao R, Li Q, Yu L, et al. Body mass index and gestational weight gain are associated with maternal and neonatal outcomes in Chinese women. J Diabetes Res. 2021;2021:4542367. doi:10.1155/2021/4542367. PMID:34869777. PMCID: PMC8635902.
12. Hu R, Yin H, Li X. Changing trends of adverse pregnancy outcomes with maternal pre-pregnancy body mass index: a join-point analysis. Front Med (Lausanne). 2022;9:872490. doi:10.3389/fmed.2022.872490. PMID:35721058. PMCID: PMC9203895.
13. Saadia Z. Association between maternal obesity and cesarean delivery complications. Cureus. 2020;12(3):e7163. doi:10.7759/cureus.7163. PMID:32257706. PMCID: PMC7112709.
14. Chen Xu J, Coelho Â. Association between body mass index and gestational weight gain with obstetric and neonatal complications in pregnant women with gestational diabetes. Acta Med Port. 2022;35(10):718-728. doi:10.20344/amp.15896. PMID:35471140.
15. Misan N, Korszun P, Gruca-Stryjak K, Paczkowska K, Nowak A, Wozniak P, et al. Does predelivery body mass index really matter in pregnancy? Ginekol Pol. 2022;93(11):922-929. doi:10.5603/GP.a2022.0005. PMID:35325456.
16. Butwick AJ, Abreo A, Bateman BT, Lee HC, El-Sayed YY, Stephansson O, et al. Effect of maternal body mass index on postpartum hemorrhage. Anesthesiology. 2018;128(4):774-783. doi:10.1097/ALN.0000000000002082. PMID:29346134. PMCID: PMC5849500.
17. Pratt A, Howat P, Hui L. Maternal and perinatal outcomes for women with body mass index ≥50 kg/m² in a non-tertiary hospital setting. Aust N Z J Obstet Gynaecol. 2020;60(3):361-368. doi:10.1111/ajo.13064. PMID:31581307.
18. Xie D, Yang W, Wang A, Xiong L, Kong F, Liu Z, et al. Effects of pre-pregnancy body mass index on pregnancy and perinatal outcomes in women: a retrospective cohort study. Sci Rep. 2021;11(1):19863. doi:10.1038/s41598-021-98892-y. PMID:34615905. PMCID: PMC8494740.
19. Enomoto K, Aoki S, Toma R, Fujiwara K, Sakamaki K, Hirahara F. Pregnancy outcomes based on pre-pregnancy body mass index in Japanese women. PLoS One. 2016;11(6):e0157081. doi:10.1371/journal.pone.0157081. PMID:27280958. PMCID: PMC4900523.
20. Cojocaru L, Salvatori C, Sharon A, Seung H, Nyman K, Kodali BS, et al. General versus regional anesthesia and neonatal outcomes: a propensity score-matched study. Am J Perinatol. 2023;40(3):227-234. doi:10.1055/s-0042-1757861. PMID:36181759.
21. He F, Li RR, Liu PS, Yang YL, Huang CJ, Chen DJ. Maternal cardiac arrest: a retrospective analysis. BJOG. 2021;128(7):1200-1205. doi:10.1111/1471-0528.16625. PMID:33314514.
22. Chen CN, Chen HS, Hsu HC. Maternal prepregnancy body mass index, gestational weight gain, and risk of adverse perinatal outcomes in Taiwan: a population-based birth cohort study. Int J Environ Res Public Health. 2020;17(4):1221. doi:10.3390/ijerph17041221. PMID:32074959. PMCID: PMC7068269.
23. Metsälä J, Stach-Lempinen B, Gissler M, Eriksson JG, Koivusalo S. Risk of pregnancy complications in relation to maternal prepregnancy body mass index: population-based study from Finland 2006-10. Paediatr Perinat Epidemiol. 2016;30(1):28-37. doi:10.1111/ppe.12248. PMID:26447743.
24. Neal K, Ullah S, Glastras SJ. Obesity class impacts adverse maternal and neonatal outcomes independent of diabetes. Front Endocrinol (Lausanne). 2022;13:832678. doi:10.3389/fendo.2022.832678. PMID:35399939. PMCID: PMC8987983.
25. Kim T, Burn SC, Bangdiwala A, Pace S, Rauk P. Neonatal morbidity and maternal complication rates in women with a delivery body mass index of 60 or higher. Obstet Gynecol. 2017;130(5):988-993. doi:10.1097/AOG.0000000000002316. PMID:29016490.