Overall, consuming artificial sweeteners during pregnancy was not associated with increased infant birth weight or BMI at birth or at ages 6 months, 1 year, 3 years, and 7 years compared to no consumption.

The association between artificial sweetener consumption during pregnancy and childhood BMI

Consuming 1 or more servings of artificial sweeteners per day was associated with a higher birth weight compared to no consumption, but the effect size was very small and only marginally passed the threshold of statistical significance.

The overall quality of the evidence was rated as very low, due primarily to methodological limitations and heterogeneity among studies.

Does artificial sweetener intake during pregnancy promote childhood obesity? Original paper