Reacción a "Two-thirds of women experience excessive or insufficient weight gain during pregnancy, according to data from 1.6 million pregnant women"

This meta-analysis is robust and relevant as it synthesizes existing evidence from contemporary observational data (2009-2024) on gestational weight gain (GWG) from 1.6 million pregnant women from various regions of the world. It does so by applying systematic and pre-registered methods: exhaustive search, duplicate assessment, and analysis with random effects models, sensitivity, and bias assessment. In addition, they relate their conclusions to the recommendations made by the World Health Organization (WHO) or the US National Academy of Medicine (IOM), with the aim of helping to optimize the criteria for action and standards to improve perinatal outcomes related to GWG in pregnant women worldwide.

Their findings showed that the consequences of weight gain during pregnancy above the recommendations were associated with an increased risk of cesarean section, preeclampsia, large-for-gestational-age newborns, macrosomia, and admission to the neonatal ICU. Conversely, weight gain during pregnancy below the recommended level was associated with an increased risk of prematurity, small-for-gestational-age newborns, and low birth weight. All of these consequences are consistent with previous studies and individual patient data, and they expand the evidence by including more regions and neonatal outcomes such as factors such as respiratory distress or neonatal ICU admissions.

One of the important limitations of this meta-analysis is that the data are aggregated, i.e., they are not recorded on a patient-by-patient basis. It also happens that many series lack key stratified covariates, such as smoking, parity, or ethnicity, which prevents meta-regression and leads to the possibility of residual confounding and reverse causality, such as premature birth shortening the time to gain weight or preeclampsia producing edema that causes weight gain. In addition, geographical representation is incomplete, as there are still no studies conducted in Africa or heterogeneity in Asia due to different body mass index (BMI) cutoffs, which limits generalization and justifies the WHO's initiative to create global standards based on more representative individual databases.

The observation that the classic IOM guidelines come from predominantly white populations and the 1980s is a valid and explanatory criticism (those guidelines were based on cohorts with lower BMI and maternal age and with little diversity). This work shows that the basic associations between weight gain during pregnancy and pregnancy outcomes remain in contemporary and more diverse populations, but it also highlights the need to update thresholds and adapt recommendations by region/ethnicity.

The implications for public health could be: to strengthen screening and monitoring of gestational weight gain as a useful clinical indicator; prioritizing lifestyle-based interventions, such as making recommendations on diet, physical activity, or psychosocial support, aimed at preventing both excess and insufficient weight gain during pregnancy; and encouraging the WHO to finalize recommendations, with global standards based on individual and representative data to guide policies and programs in diverse populations and contexts.

There is no exact calculation linking the cost of the economic consequences of newborns with problems arising from weight gain during pregnancy, both above and below the recommendations, but a reasonable estimate can be made with the existing data and it can be pointed out what is most cost-effective in terms of the healthcare system.

According to the Spanish Ministry of Health, the average cost of hospitalization for a very low birth weight newborn (500-1,000g) is €52,508.5 per admission. Another study points out that treating premature (very immature) babies is one of the most expensive processes in the National Health System. In addition, obstetric events such as premature births between 28 and 32 weeks have an average cost per patient (neonatal) of approximately €44,709 according to an analysis of obstetric/neonatal costs. The cost to the public system of treating newborns with complications resulting from fetal overgrowth, such as macrosomia, ICU admission, or necessary interventions, can be very high for each serious case, which would mean tens of thousands of euros per newborn, including their stay in the ICU, treatment, and follow-up. If only a portion of the serious cases resulting from GWG (which may not be very high) were reduced through better maternal monitoring, the savings could be significant. Therefore, it could be concluded that interventions to control weight gain during pregnancy would have a cost, but would be much cheaper per woman than the cost of caring for a newborn or its mother with serious complications.