Introduction
Pregnancy is a critical window in maternal and child health, where gestational weight gain (GWG) emerges as a determinant factor for fetal well-being and development. Monitoring GWG is essential, serving as a prognostic marker for the health of the pregnant woman and the conceptus [
1‐
5].
Guidelines for GWG have changed over time, reflecting the understanding of its importance. In the 1950s, the recommendation was for a gain of 10–14 lb, aiming to prevent complications such as pre-eclampsia (Ferguson et al., 1950). The following decade recognized the positive association between higher GWG and birth weight [
5]. In 1990, the Institute of Medicine (IOM) of the USA established specific recommendations, with the most recent update in 2019, emphasizing the importance of not exceeding GWG targets to avoid obesity-related complications [
6]. To mitigate adverse impacts on maternal and fetal health, the IOM in 2009 outlined guidelines suggesting a total weight gain of 11 to 16 kg for women of normal weight, 7 to 11 kg for overweight women, and 5 to 9 kg for obese women [
7].
Excessive or insufficient GWG can increase the risk of negative outcomes for both the mother and the conceptus [
8‐
10]. Research indicates that GWG above IOM recommendations is associated with an increased risk of metabolic complications, hypertension, gestational diabetes, cesarean section, postpartum weight retention, macrosomia, childhood obesity, and cardiometabolic outcomes in childhood [
8‐
10]. Conversely, GWG below the recommendations is linked to an elevated risk of intrauterine growth restriction (IUGR), low birth weight (LBW), preterm birth, perinatal mortality, and a higher incidence of newborns small for gestational age (SGA) [
11‐
13]. Furthermore, studies indicate that GWG within the IOM-recommended ranges is associated with a lower incidence of LBW and better health outcomes [
14].
The possibility of mitigating the risks of gestational complications and adverse fetal outcomes in obese pregnant women by limiting GWG is an area of growing interest [
15,
16]. The literature has highlighted the importance of adjusting GWG in various interventions, including diet, physical activity, the use of probiotics, and psychological and behavioral approaches [
17].
In Brazil, although there are no standardized recommendations for GWG based on Brazilian population data, new guidelines for GWG have been proposed based on national GWG curves. Thus, the IOM recommendations, widely used to classify GWG, still constitute a viable alternative. Given this context, the objective of this study is to evaluate whether pregnant women with GWG outside the IOM-recommended range present adverse fetal and neonatal outcomes compared to those whose GWG is considered adequate, aiming to provide support for clinical practice and contribute to the development of effective intervention strategies that promote a healthy pregnancy and minimize risks to the mother and respective conceptus.
Discussion
In this study, we found that GWG outside the IOM recommendations is significantly associated with adverse outcomes, both fetal and neonatal. It was observed that a GWG below the recommendations increases the risk of IUGR, LBW, and prematurity. These findings align with the hypothesis that inadequate nutrition during gestation can compromise fetal development, which is corroborated by several studies [
11‐
14]. On the other hand, a GWG above the recommendations was associated with an increased risk of LGA and changes in birth weight and length, suggesting that excess weight gain may predispose to obstetric complications and negatively impact the long-term health of the conceptus.
These findings corroborate previous studies that also found associations between GWG below and above the recommendations and adverse outcomes, indicating that inadequate GWG can have negative effects on the health of the fetus and newborn [
14,
27‐
38].
Similar to our results, Goldstein et al. [
28] in a systematic review and meta-analysis that investigated the association between GWG, and maternal and infant outcomes observed that inadequate GWG, whether below or above the IOM recommendations, is associated with adverse outcomes. Similar findings were reported in other studies [
33,
35,
39]. The issue of prematurity deserves special attention, as women with premature babies have less time to gain weight during pregnancy, which may indicate reverse causality in the association between GWG and prematurity.
Liu et al. [
30], in a retrospective cohort study with a sample of 9 million mother-child pairs to investigate the associations between GWG and adverse birth outcomes, showed that both insufficient and excessive GWG were associated with a higher risk of adverse outcomes, such as LBW, prematurity, and SGA. These findings highlight the importance of achieving an adequate balance in GWG, avoiding both restriction and excessive weight gain during gestation.
Furthermore, the relationship between GWG and adverse outcomes may be influenced by other factors, such as pre-gestational BMI. Studies by Chiavaroli et al. [
32] and Liu et al. [
30] reported that both maternal BMI and GWG are associated with adverse outcomes, suggesting that weight control before and during gestation is crucial. These findings are supported by other research, such as the study by Athukorala et al. [
33], which found an increased risk of adverse outcomes in pregnant women with overweight or obesity, including prematurity and LBW.
However, it is important to note that GWG is just one of many factors that can influence birth weight. Other factors, such as maternal health, nutrition, smoking, and alcohol consumption, can also play a significant role. Additionally, the effect of GWG may vary in different populations, depending on factors such as BMI, age, ethnicity, parity, and underlying medical conditions of the mother [
40].
Similar to our results, Goldstein et al. (2017b) in a systematic review and meta-analysis that investigated the association between GWG and maternal and infant outcomes observed that inadequate GWG, whether below or above the IOM recommendations, is associated with adverse outcomes. Similar findings were reported in other studies (Athukorala et al., 2010b; Chowdhury et al., 2022; Truong et al., 2015b). The issue of prematurity deserves special attention, as women with premature babies have less time to gain weight during pregnancy, which may indicate reverse causality in the association between GWG and prematurity.
Liu et al. (2022), in a retrospective cohort study with a sample of 9 million mother-child pairs to investigate the associations between GWG and adverse birth outcomes, showed that both insufficient and excessive GWG were associated with a higher risk of adverse outcomes, such as LBW, prematurity, and SGA. These findings highlight the importance of achieving an adequate balance in GWG, avoiding both restriction and excessive weight gain during gestation.
Furthermore, the relationship between GWG and adverse outcomes may be influenced by other factors, such as pre-gestational BMI. Studies by Chiavaroli et al. (2021) and Liu et al. (2022) reported that both maternal BMI and GWG are associated with adverse outcomes, suggesting that weight control before and during gestation is crucial. These findings are supported by other research, such as the study by Athukorala et al. (2010b), which found an increased risk of adverse outcomes in pregnant women with overweight or obesity, including prematurity and LBW.
However, it is important to note that GWG is just one of many factors that can influence birth weight. Other factors, such as maternal health, nutrition, smoking, and alcohol consumption, can also play a significant role. Additionally, the effect of GWG may vary in different populations, depending on factors such as BMI, age, ethnicity, parity, and underlying medical conditions of the mother [
40],
In Brazil, a systematic review by Godoy et al. (2015) analyzed the recommendations for GWG and its impact on fetal outcomes. It was observed that both GWG below and above the recommendations are associated with adverse outcomes. Women with pre-gestational overweight or obesity have a higher risk of excessive gestational weight gain, which is associated with fetal macrosomia and high cesarean rates. Conversely, insufficient GWG can also lead to complications such as LBW and IUGR. In studies conducted in the Northeast and Southeast regions of Brazil, an association between macrosomia and women with pre-gestational overweight or obesity was observed [
41‐
43]. In one of these studies, it was found that women with excessive GWG were more likely to have newborns with macrosomia [
44]. Not only excessive weight and obesity influence perinatal outcomes, but insufficient GWG can also lead to complications, such as LBW and IUGR. Women with low pre-gestational body weight are more likely to have babies with LBW [
45]. These findings highlight the importance of maintaining adequate GWG in Brazil to improve perinatal outcomes and reduce complications such as macrosomia and LBW. However, our study stands out by considering specific contextual variables of the Brazilian population, which may influence GWG and its outcomes. For example, the research by Drehmer et al. [
46], in Brazil also noted the importance of the socioeconomic context in GWG and its effects on newborn health, but our study expands this understanding by including more detailed analyses of fetal and neonatal outcomes. Another point of distinction is our analysis of variables such as physical activity and smoking, which are known lifestyle factors that influence GWG. Studies like that of Nascimento et al. [
47], in Brazil have shown that physical activity during pregnancy can help maintain GWG within the recommendations, which is consistent with our observations that maintaining adequate physical activity was low among women in the study.
Since GWG is a modifiable risk factor, it is possible to identify and correct its variations during gestation. Although various studies have demonstrated that appropriate interventions based on dietary changes can be effective in controlling weight gain and reducing the risk of complications during gestation [
29], promoting healthy GWG can be an important element in avoiding adverse consequences for both the mother and the conceptus. Another important reference is the study by Dodd et al. [
40], which conducted a systematic review of randomized clinical trials on antenatal interventions for overweight or obese pregnant women. The authors concluded that interventions such as dietary counseling and physical activity during gestation can result in modest reductions in maternal weight gain but did not have a consistent effect on the perinatal outcomes assessed. The target of the intervention should be women with abnormal weight, more prone to having adverse outcomes in future pregnancies. It is also concerning the increased risks of preterm birth, LBW, and IUGR in pregnant women with low weight, compared to those of normal weight. Even in the normal weight group, the risk of cesarean section, preterm birth, and excessive fetal growth increases with the elevation of BMI. Therefore, it is important to be concerned with women with overweight or obesity before gestation, but it is also necessary to strengthen the management of women with low weight and normal weight, who are often neglected. The findings of this study reinforce the need for clear and personalized guidelines for GWG, as well as the importance of regular weight monitoring during gestation. Nutritional and lifestyle interventions should be prioritized to help pregnant women achieve a healthy GWG.
In this study, we identified a notable and unprecedented finding: a significant association between insufficient GWG and reduction in the area of the fetal subcutaneous tissue of the arm but no reduction in the area of the subcutaneous tissue of the thigh or the thickness of the abdominal subcutaneous tissue, suggesting a regionalized response of fetal adipose tissue to maternal nutrition. This phenomenon may have important implications for neonatal health, as adipose tissue plays an essential role in energy reserves and thermoregulation of the newborn [
48]. The uneven distribution of fetal adipose tissue may reflect an adaptation to a restrictive intrauterine environment, which may predispose the child to long-term metabolic and health challenges [
49]. Furthermore, metabolic programming, which can be influenced by GWG, is a potential mechanism that may explain variations in the accumulation of fetal adipose tissue and its consequences for child health [
50]. Maternal obesity and excessive GWG have been associated with epigenetic changes that may affect fetal development and the risk of metabolic diseases later in life [
51]. On the other hand, prenatal exposure to insufficient GWG and very severe maternal obesity have also been associated with adverse neuropsychiatric outcomes in children, highlighting the importance of nutritional balance during gestation [
52,
53].]
Limitations of this study include the lack of dietary data from pregnant women and the observational nature of the study, which prevents the inference of direct causal relationships. Additionally, despite adjustment for various covariates, we cannot rule out the possibility of residual bias. Future research should focus on better understanding the biological mechanisms linking GWG to adverse outcomes and on developing effective interventions to promote healthy GWG. Despite these limitations, the study has potentialities, such as being prospective and population-based, which allows the evaluation of a wide range of maternal, fetal, and neonatal outcomes. The prospective cohort approach and the use of objective measures, such as ultrasonography and air displacement plethysmography, contribute to obtaining accurate information about fetal development. The inclusion of various covariates related to socioeconomic, demographic, lifestyle, obstetric history, and clinical profile of pregnant women allows a comprehensive analysis of the factors associated with the outcomes evaluated.
Therefore, the need for more personalized GWG guidelines and the importance of targeted nutritional interventions during gestation are reinforced by these findings. Understanding the underlying mechanisms governing the distribution of fetal adipose tissue and its implications for child development and long-term health is crucial for optimizing perinatal outcomes and for the formulation of effective public health policies.
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