Drinking diet drinks in pregnancy raises overweight risk in children, study finds

A long-term Danish study finds that artificial sweeteners consumed during pregnancy may shape children’s weight trajectories years later—raising fresh questions about the safety of ‘diet’ drinks for expectant mothers.

​​​​​​​Accepted manuscript: Consumption of Artificial Sweeteners during Pregnancy and the risk of Overweight in the Offspring. ​​​​​​​Image Credit: Motortion Films / Shutterstock

In a recent study published in the British Journal of Nutrition, researchers in Denmark assessed whether maternal intake of artificially sweetened beverages (ASB) or sugar-sweetened beverages (SSB) during pregnancy is associated with overweight in offspring from birth through adolescence.

Background

Did you know that childhood obesity has more than doubled in the past 30 years? Excess weight in early life raises the risk of diabetes, heart disease, and other chronic conditions later on. Many expectant mothers opt for ASB to avoid weight gain, assuming these are a safer choice. However, emerging evidence suggests that artificial sweeteners may disrupt metabolism, alter gut bacteria, or increase sweet cravings, even in the womb. While studies show conflicting results, some link artificial sweeteners to obesity in offspring. Given the widespread use of these products during pregnancy, further research is needed to clarify their long-term effects.

About the Study

The present nationwide longitudinal cohort study used data from the Danish National Birth Cohort (DNBC), which enrolled 101,042 pregnant women between 1996 and 2002. Women were followed through pregnancy and their children up to 18 years of age. Data were collected via interviews during gestational weeks (GW) 12 and 30, and postpartum at 6 and 18 months. A food frequency questionnaire was completed at GW 25 to capture the frequency of ASB and SSB intake. Beverage consumption was categorized as none, <1(250ml)/week, 1-6/week, or ≥1/day.

Outcomes included large for gestational age (LGA) birth weight and overweight status at ages 5 and 12 months, as well as at 7, 11, 14, and 18 years. Weight and height measurements were collected from general practitioners, parents, or adolescents. Overweight was defined using body mass index (BMI) cut-offs based on sex and age-specific standard deviations.

Women with diabetes and those with missing data were excluded. Analyses adjusted for maternal age, pre-pregnancy BMI, physical activity, smoking, dietary quality (including SSB intake via the Healthy Eating Index, which may influence results), paternal BMI, socioeconomic status, and breastfeeding duration. Multiple logistic and linear regressions were used to estimate odds ratios (ORs) and z-score differences. All statistical analyses were performed using R software.

Study Results

Of the original cohort, 66,668 women had valid data on ASB intake, and 66,568 had data on SSB intake. Women consuming ≥1 ASB/day were generally younger, had higher pre-pregnancy BMI, more often smoked, and had lower socioeconomic status. In contrast, those consuming less than 1 serving per week had higher physical activity and longer breastfeeding durations.

At birth and in infancy (5 and 12 months), maternal ASB consumption was not associated with an increased risk of overweight or LGA babies. However, from age 7 onwards, a consistent pattern emerged. Children of mothers consuming 1-6 ASB/week or ≥1 ASB/day had significantly higher odds of being overweight at 7, 11, 14, and 18 years compared to those with no ASB intake. After adjusting for confounders, the risk remained significant, with an adjusted OR of 1.26 (95% confidence interval (Cl): 1.12-1.42) at 18 years for ≥1/day ASB group versus no intake. This represents a modest increase in absolute risk, consistent with a dose-dependent relationship (higher intake = greater risk).

Conversely, SSB intake was associated with a lower risk of overweight in offspring at 11 and 18 years. However, mothers who consumed SSB were more likely to have healthier baseline characteristics, including lower pre-pregnancy BMI and higher socioeconomic status, which the authors note could partially—but not fully—explain these findings. For example, children of mothers who consumed ≥1 SSB/day had an adjusted OR of 0.72 (95% CI: 0.60-0.86) for overweight at 18 years compared to non-consumers. These findings were further supported by differences in BMI z-scores: offspring exposed to ≥1 ASB per day had higher BMI z-scores, while those exposed to ≥1 SSB per day had lower z-scores.

Subgroup analyses adjusted for total energy intake, rather than the Healthy Eating Index, showed only minor changes in ASB-related results, suggesting that the association is not solely due to higher calorie consumption. Substitution models replacing ASB with SSB further indicated a lower risk of overweight, suggesting a possible role of artificial sweeteners themselves.

Importantly, the impact of ASB only became evident from age 7 onwards. No significant difference was observed in infancy, suggesting that early weight differences may emerge as children begin making their own food choices. This timeline supports the idea that prenatal ASB exposure may prime long-term taste preferences or metabolic responses. However, the study could not rule out residual confounding from unmeasured factors, such as postnatal dietary habits.

Notably, the authors raised concerns that mothers consuming ASB during pregnancy might continue doing so postpartum, potentially exposing infants to artificial sweeteners through breastfeeding. Additionally, there was a substantial data gap between 12 months and 7 years—a critical period for early weight gain—limiting insights into when ASB-related effects first manifest.

Conclusions

To summarize, in this large-scale cohort, daily intake of ASB during pregnancy was associated with a modest but consistent increase in the risk of overweight in children and adolescents, especially from age 7 onward. SSB, in contrast, was unexpectedly associated with a lower risk of overweight in older children, though the authors stress that this association is speculative and may reflect socioeconomic or lifestyle differences rather than a direct protective effect of SSB.

These results challenge current dietary advice for pregnant women with overweight or diabetes, who are often encouraged to substitute sugar with artificial sweeteners. While the absolute risk increase linked to ASB is small, even modest effects at the population level could have significant public health implications.

Given the study’s limitations—including unresolved questions about postnatal exposure and the data gap in early childhood—these findings underline the need to re-evaluate recommendations and to investigate safer alternatives for managing gestational weight gain.