Optimal maternal nutrition during pregnancy is crucial for foetal growth and newborn health. One of the most critical indicators of maternal nutritional status is gestational weight gain (GWG), which reflects the physiological changes needed to support a growing foetus. The Institute of Medicine (IOM), now known as the National Academy of Medicine, issued guidelines in 2009 detailing the recommended ranges of GWG based on a woman’s pre-pregnancy body mass index (BMI). These guidelines suggest that women who are underweight, normal weight, overweight, or obese at the time of conception should gain between 12.5-18 kg, 11.5-16 kg, 7-11.5 kg, and 5-9 kg, respectively.
Despite the value of these recommendations, they were developed using data primarily from high-income countries. More recently, the INTERGROWTH-21st Gestational Weight Gain (IGGWG) international standards have been introduced. These standards aim to evaluate GWG among women from diverse regions and socioeconomic backgrounds, offering a more global perspective on what constitutes healthy weight gain during pregnancy.
The Consequences of Suboptimal GWG
The risks associated with suboptimal GWG, whether inadequate or excessive, are significant. Inadequate GWG has been linked to low birthweight, small-for-gestational-age infants, and preterm birth, all of which can increase the risk of mortality and long-term health challenges. On the other hand, excessive GWG has been associated with large-for-gestational-age infants, macrosomia, and a heightened risk of preterm birth. These adverse birth outcomes often have far-reaching consequences, including suboptimal infant growth, neurodevelopmental delays, and cardiometabolic complications later in life.
While these risks are well-documented in high-income settings, where most studies on GWG have been conducted, the burden of adverse birth outcomes is disproportionately higher in low and middle-income countries (LMICs). Regions like sub-Saharan Africa and South Asia account for the majority of preterm births, low birthweight cases, and small-for-gestational-age births globally. This disparity illustrates the need to examine GWG and its implications in LMICs, where maternal nutritional challenges are often more pronounced.
GWG in Low and Middle-Income Countries
Research indicates that women in LMICs often fail to meet the minimum GWG recommendations established for women of normal weight. In these regions, women on average gain less than 60% of the recommended weight. A meta-analysis of 53 studies from 24 countries found that 78% of women experienced suboptimal GWG, either gaining too little or too much weight during pregnancy. Severely or moderately inadequate GWG was associated with increased risks of low birthweight, small-for-gestational-age infants, short-for-gestational-age infants, microcephaly, and stillbirth. Meanwhile, excessive GWG was linked to large-for-gestational-age infants, macrosomia, and preterm birth.
The relationship between GWG and neonatal outcomes was found to vary based on pre-pregnancy BMI and maternal age. Underweight women faced a stronger association between inadequate GWG and adverse outcomes, while adolescent mothers (<20 years) were particularly vulnerable to the effects of both inadequate and excessive GWG. These demonstrate the intricate interaction of maternal nutrition, weight gain, and demographic factors in influencing birth outcomes.
Mechanisms Linking GWG and Birth Outcomes
The mechanisms through which GWG impacts neonatal outcomes are multifaceted. Inadequate GWG often reflects macronutrient and micronutrient deficiencies, which can impede foetal growth. For instance, insufficient maternal weight gain may reduce plasma volume expansion or limit the development of maternal tissues needed to sustain the foetus. Conversely, excessive GWG can result from metabolic imbalances such as gestational diabetes or hypertension, which are associated with complications like preterm birth.
The effects of GWG extend beyond birthweight. Few studies have explored how GWG influences other markers of foetal development, such as birth length and head circumference. These indicators provide insights into skeletal and brain growth, respectively. Research suggests that inadequate GWG is linked to shorter birth lengths and smaller head circumferences, while excessive GWG may disrupt nutrient transfer between the mother and foetus.
Brain growth, in particular, may be prioritised over other forms of foetal development in cases of maternal malnutrition. Some researchers have found that while inadequate GWG results in smaller overall size at birth, head circumference may remain relatively spared, reflecting a biological mechanism that prioritises brain development to enhance survival prospects.
Public Health Implications and the Need for Interventions
The outcome indicates the critical need for targeted interventions to promote optimal GWG, particularly in LMICs. The World Health Organisation (WHO) emphasises the importance of weight monitoring, nutrition counselling, and physical activity support during antenatal care visits. However, in many resource-constrained settings, such practices are not routinely implemented. A lack of international consensus on GWG guidelines personalised to LMICs further complicates efforts to address this issue.
Interventions to support maternal nutrition, including the provision of micronutrient supplements, balanced energy-protein supplements, and lipid-based nutrient supplements, could help reduce the prevalence of inadequate GWG. Multisectoral approaches that address cultural beliefs, economic factors, and food security are also essential. For instance, in some communities, cultural norms may discourage women from gaining weight during pregnancy due to fears of difficult labour or social stigmas, further exacerbating nutritional challenges.
Lifestyle interventions aimed at reducing excessive GWG have shown promise in high-income settings, particularly those that incorporate dietary guidance and physical activity plans. However, these approaches need to be adapted to LMICs, where women may face additional barriers such as limited access to healthcare, food insecurity, and competing household responsibilities. Scaling up community based programs that integrate nutrition education with practical support could be an effective strategy to address these challenges.
Strengths, Limitations, and Future Research Directions
The study that informed these findings had several strengths, including the pooling of data from 53 studies across 24 countries and the use of consistent metrics for GWG and neonatal outcomes. This robust dataset allowed researchers to analyse the associations between GWG and birth outcomes across diverse populations, providing valuable insights into global trends.
However, there were notable limitations. The reliance on IOM guidelines, which were developed in high-income settings, may not fully reflect the needs of women in LMICs. Additionally, pre-pregnancy weight data were unavailable for a significant proportion of participants, requiring imputation based on predictive models. This approach, while necessary, may have introduced some degree of uncertainty into the findings.
Further research is needed to establish GWG thresholds that are personalised to diverse populations in LMICs. Understanding how maternal factors such as age, parity, and pre-pregnancy nutritional status interact with GWG to influence birth outcomes will also be critical. Furthermore, exploring the effects of routinely administered drugs, such as antimalarials and antiretrovirals, on GWG could provide additional insights into how maternal health interventions impact pregnancy outcomes.
Another area for future investigation is the long-term impact of suboptimal GWG on child health and development. While the immediate consequences of inadequate or excessive GWG are well-documented, less is known about how these patterns influence growth, cognitive development, and metabolic health in later life. Addressing these gaps in knowledge will be essential for designing effective public health strategies to improve maternal and child health.
Conclusion
Gestational weight gain serves a vital role in determining maternal and neonatal health outcomes. While much of the existing evidence comes from high-income settings, the burden of suboptimal GWG is particularly pronounced in LMICs, where adverse birth outcomes are more common. Addressing this issue requires a comprehensive approach that combines improved weight monitoring, nutrition counselling, and targeted interventions to support maternal health.
By adapting GWG guidelines to the unique challenges faced by women in LMICs and prioritising research in these regions, public health efforts can better support maternal nutrition and improve neonatal outcomes. Ensuring optimal weight gain during pregnancy is not just a matter of individual health, it is a pathway to healthier generations and more equitable global health outcomes.
Finally, acquiring women with the knowledge and resources to achieve healthy GWG will require sustained investment in healthcare infrastructure, community education, and policy reform. Through these efforts, the global community can make meaningful progress toward reducing the burden of adverse birth outcomes and improving the well-being of mothers and children worldwide.
Reference
Perumal, N., Wang, D., Darling, A. M., Liu, E., Wang, M., Ahmed, T., Christian, P., Dewey, K. G., Kac, G., Kennedy, S. H., Subramoney, V., Briggs, B., Fawzi, W. W., & GWG Pooling Project Consortium. (2023). Suboptimal gestational weight gain and neonatal outcomes in low and middle income countries: individual participant data meta-analysis. BMJ (Clinical Research Ed.), 382, e072249. https://doi.org/10.1136/bmj-2022-072249