Maternal undernutrition and excessive body weight and risk of birth and health outcomes

Globally, overweight and obesity increasing rapidly especially in low- and lower middle- income countries. It has risen to 27.5% between 1980 and 2013 worldwide [1]. If secular trends continue, by 2030 there will be 2.16 billion overweight and 1.12 billion obese [2]. Overweight and obesity has become a major health problem both in developed and in developing countries. High-income countries reported more than double prevalence of obesity than low- and lower middle- income countries [3]. Men in developed countries were more overweight and obese, whereas in developing countries, overweight and obesity were more prevalent in women [3].

A wide variation of high BMI was observed between regions, country income categories and age-sex distribution [4]. High BMI was more prevalent in the American region (62% for overweight in both sexes, and 26% for obesity) and bit lower in the South East Asia region (14% overweight in both sexes and 3% for obesity) [5]. Asian countries have some of the lowest prevalence’s of overweight and obesity, but prevalence rates are increasingly rapidly [6, 7]. The boom in economic development and cultural factors are often cited as drivers. Almost one-half of the Indian adults living in urban area are overweight and obese [8]. Similar nutritional shifts were also observed during the last few decades in Asian countries including Pakistan [9], Nepal [10], and Bangladesh [11]. This may incur a high burden of nutrition-related diseases in these countries.

The growing epidemic of maternal overweight/obesity accounted for 1.1 million deaths in 1990, and 1.7 million deaths in 2010 [12, 13]. It is clear from the previous studies that maternal underweight, overweight or obesity are a threat to maternal and infant health [14‐16]. For instance, high maternal BMI has closely related to gestational diabetes, gestational hypertension, cesarean section, preeclampsia, gestational age, preterm birth, fetal death, still birth, perinatal death, neonatal death, and infant death. The results are not consistent across studies. Some found higher risk and some lower risk of birth outcomes in connection to BMI. This discrepancy may be due small sample size, study design, regional variation, or country income categories [17].

Furthermore, like many developed countries, overweight and obesity are also increasing rapidly in Bangladesh. Despite this growing burden of BMI, very few studies have been conducted to date to examine the association between dual burden of maternal BMI and risk of adverse birth and health outcomes [18‐20]. Most of these studies are limited to specific adverse outcomes and found mixed results between BMI and risk of maternal health outcomes. For instance, overweight and obesity was positively associated with risk of diabetes [21], and hypertension [22]. However, others found no significant association [23]. No study examined a comprehensive range of maternal health and birth outcomes in relation to maternal BMI using population based survey data. Thus, the present study is seeking to examine the association between maternal undernutrition and excessive body weight and risk of adverse birth and health outcomes.

This is the first nationally representative cross-sectional study in Bangladesh that has demonstrated the risk of birth and health outcomes in connection to maternal BMI. The findings suggest that between 2004 and 2014, maternal overweight and obesity increased to 240% in Bangladesh, while undernutrition declined to 54%. Maternal overweight or obese increased risk of pregnancy complication, cesarean delivery, diabetes, and hypertension and prolonged labor. The study also found that the risk of stunting and wasting was higher among underweight women than normal weight women.

In general, over time the prevalence of overweight and obesity is increasing and underweight is decreasing. In 2014, prevalence of underweight and overweight was 21.9% and 15.6%, respectively. This situation represents a double burden of nutrition condition that exists among women in Bangladesh. Similar nutritional problems are also observed in India [25], and others developing countries [26‐28]. There was an apparent socio-economic, demographic and regional distribution of underweight and overweight or obese. Women in low socio-economic status, with little or no education and rural residence experienced greater risk of underweight. Conversely, higher educated women, wealthier women and those residing in urban areas had higher prevalence of overweight and obesity. This is consistent with previous studies from many settings including Bangladesh [29], and others South Asian countries [25, 30].

Over the last few decades, Bangladesh has substantially reduced maternal mortality [31, 32]. In addition, infant and neonatal mortality, and total fertility rates have also declined sharply since 1990. An estimated 11,000-21,000 mothers die each year in Bangladesh due to the pregnancy related complication [33], and a further 320,000 women suffer from the injuries or disabilities caused by these complication during pregnancy and child birth [34]. Available findings suggest that controlling weight may significantly reduce the number of pregnancy complication. Thus individual and national level awareness about such adverse effect of overweight and obesity may lead to reduce the number of pregnancy complication which ultimately crop the frequency of mothers death and disabilities.

The association between diabetes and overweight (or obesity) in general population is well established in Bangladesh [35, 36], and other countries [37, 38]. However, comprehensive assessment especially among women is still lacking in Bangladesh. Study results indicate that overweight and obesity have an increased risk of developing diabetes among women in Bangladesh. Additionally this study found a substantially higher proportion of hypertension among overweight and obese women, a finding supported by others studies [39, 40]. A recent meta-analysis based on low- and lower middle-income countries also found the positive association between the maternal overweight and obesity with gestational diabetes, gestational hypertension, preeclampsia and post partum haemarroage [17]. All of these non-communicable diseases have become leading risk factors for deaths and disability in developing and developed countries [12]. In 2010, hypertension accounted for 2.9 million deaths among women (6% of total Disability Adjusted Life Years (DALYs)), high fasting plasma glucose accounted for 1.1 million deaths (3% of DALYs), ischemic heart diseases accounted for 1.7 million deaths (3% of DALYs), and stroke accounted for 2.0 million deaths (4% of DALYs) in developing countries [13].

Consistent with previous studies [41, 42], overweight and obese women were more likely to have cesarean delivery in our study. Weight management is important for every woman in reproductive age. Women with a normal BMI should strive for maintenance of a healthy weight, whereas underweight and overweight women should aim to healthy weight prior to the pregnancy. These contribute to reduce the effect of high maternal BMI on labor and delivery complications and cesarean delivery [42].

On average, the study found 15 stillbirths and 37 early neonatal deaths per 1000 live births. This is consistent with other low- and lower middle-income countries [43, 44]. Deaths during the neonatal period contribute around 38% of the total under five deaths [44]. The main causes of neonatal death are preterm birth (28%), severe infection (26%) and low birth weight (31%) [44, 45]. Complication during pregnancy and delivery is also another important determinant of neonatal survival [46]. The risk of overweight and obesity on these adverse outcomes is well known which greatly contribute to the increased risk of stillbirth, early neonatal mortality and perinatal mortality. Consistent with previous literature [47, 48], obese women were more likely to experience stillbirth, early neonatal mortality and perinatal mortality. Thus, it is necessary to emphasis-that women control their weight and reduce levels of overweight or obesity to reduce these adverse birth outcomes.

Similar to some previous studies [49, 50], overweight and obese women were more likely to have prolonged labor, which may lead to maternal and newborn death and disability [51]. It may also result in increased risk of cesarean delivery and maternal complication following ruptured membranes, trauma to the bladder, and ruptured uterus with consequent haemorrhage [52]. In this study, both underweight and overweight or obese women were less likely to experience preterm birth compared to normal-weight women. This is inconsistent with other studies conducted in Ireland [53], Spain [42], South Australia [54], and China [55]. A recent systematic review and meta-analysis also found underweight women have higher risk of preterm birth [17]. This contradictory finding in our study may be due to the small number of cases was extracted from the verbal autopsy record. Our study indicated that underweight women were at increased risk of stunting and wasting children. However, overweight or obesity plays a protective role against stunting and wasting among children

The key strength of this study was the availability of a large, nationally representative dataset providing the sufficient power to investigate the adverse birth and health outcome related to maternal BMI. The use of STROBE checklist strengthened our paper (Additional file 1: Table S2). However, we were unable to establish a causal relationship between the maternal BMI and birth and health outcomes as a result of cross sectional study design. Secondly, BMI should be measured either before pregnancy or in the first trimester; however, BDHS collected women height and weight information during interview and birth outcomes were recorded within last three years. Since BMI is not stable over time, which may lead to partially bias the association between exposure and outcomes. To address this limitation, we exclude women with substantial fluctuation of BMI. Furthermore, we see reassuringly that the direction and magnitude of effect of BMI as a function of time elapsed between the index of birth and survey is similar in women with adverse birth or health outcomes, and would if anything have led to underestimate of effect. These findings suggest that misclassification bias of BMI is likely to be small. A previous study published in Lancet also found the little misclassification bias of BMI in a similar study design [56]. Finally, information about a majority of the outcome variables (except diabetes and hypertension) were self-reported. However, the DHS has been collecting data in low-income settings by similar methods for more than two decades, and there has been a substantial improvement in the completeness and reliability of the dataset [57].

Our findings represent a clear picture of the adverse birth and health outcome that are related to maternal BMI. Higher risk of pregnancy complication, prolonged labor, cesarean delivery, diabetes, and hypertension was found among overweight or obese women. On the other hand, higher odds of stunting, and wasting were found among underweight women. Therefore, weight management is necessary to prevent adverse birth and health outcomes. Clinicians and other healthcare providers and policy maker should counsel women prior to or in early pregnancy on adverse threats of underweight, overweight, or obesity on their own and their infant’s health. Informed women could try to optimize their BMI before conception.