Sweet Beginnings: The Impact of Sugar-Sweetened Beverages on Newborn's Health

During pregnancy, maternal health behaviors impact the environmental exposure for embryos and fetuses both directly and interactively through epigenetics that can influence disease later in life. A large body of research has examined nutrition during the gestational period largely focusing on inadequate caloric or nutrient content. However, emerging evidence suggests that excessive energy supply, and in particular, in the form of added sugars and processed carbohydrates, may also increase disease susceptibility.

Although excessive consumption of added sugars has been consistently linked to obesity and related diseases across several age groups, much of the evidence is observational and cross-sectional, or limited to animal models in short-term clinical trials. Morever, few studies have focused on the effects of exposure in utero from the mother’s diet. Evaluating the causal influence of in utero exposure to a sugar-rich diet and health empirically is challenging - in large part because maternal dietary preferences and intake during pregnancy are not random. For example, maternal dietary intake will be correlated with mother’s own health and genetic risk factors. Thus a correlation between maternal sugar consumption and infant health may be due to the prenatal diet or due to shared health and genetic profiles. Evidence has linked maternal weight and obesity, which are a function of maternal dietary intake, to several birth outcomes, including infant birth weight and mode of delivery. Moreover, maternal pre-pregnancy weight is highly correlated with gestational weight gain during pregnancy, which also independently predicts infant weight, including a higher probability of birth weight over 4000 grams (macrosomia). Thus, the evidence to date has not disentangled these relationships between maternal diet, health, and weight and infant’s health and weight in a way that allows for convincing causal inference. To this end, experts have called for natural experiments and quasi-experimental methods that leverage some source of exogenous variation in exposure to a sugar-rich diet.

In this study, we leverage a unique natural experiment that provides plausibly exogenous variation in exposure to sugar-rich diet while in utero to establish causal evidence on its impact on infant health. In particular, combining rich dietary data among pregnant women and national vital statistics on several health measures, we exploit the sugar-sweetened beverages’ (SSBs) tax implemented in Mexico in January 2014 which we argue induced variation in exposure to SSBs in utero. We examine infant health measures, including birth weight, length for gestational age, and general health status (APGAR) among infants whose mothers were pregnant before the tax to those whose mothers were pregnant after the tax. Our preliminary findings suggest a small decline in infant birth weight following the tax, but no changes in the percent of macrosomic births (greater than 4000 grams), length for gestational age, or APGAR. We also find some evidence of heterogenous effects.