Is diet soda safe during pregnancy?

What does the evidence say about diet soda during pregnancy?

1. Four artificial sweeteners studied in pregnant women all crossed the placenta and were present in the fetal circulation and amniotic fluid, with fetal-to-maternal plasma ratios between 0.57 and 0.80. 1
2. A meta-analysis of 11 studies covering 138,007 women found that consuming at least one serving a day of artificial sweeteners during pregnancy was associated with an 18 percent increase in the risk of preterm delivery. 2
3. The certainty of that evidence was graded low to very low by the authors, who called for higher-quality research, so the association is a signal rather than a settled finding. 2
4. A 12 oz cola contributes roughly 46 mg of caffeine, which counts toward the 200 mg daily limit most experts suggest during pregnancy. 3
5. The same meta-analysis linked daily prenatal sweetener intake with a birth weight increase of about 24 grams and a gestational age decrease of about 0.11 weeks, both small in absolute terms. 2

Is diet soda safe in each trimester?

• First trimester. Diet soda brings two separate things: sweeteners and, in colas, caffeine. A 12 oz cola carries about 46 mg of caffeine, so several cans move you meaningfully toward the 200 mg daily ceiling. If diet soda is what you can keep down during early nausea, that is a real consideration to weigh with your provider rather than a rule to break.
• Second trimester. The preterm delivery signal in the research attaches to daily intake, roughly one serving a day or more, not to the occasional can. If you are drinking several a day out of habit, the middle trimester is a comfortable moment to reduce the count rather than quit outright.
• Third trimester. Preterm delivery is the outcome the meta-analysis pointed at, which makes the third trimester the period this evidence is really about. The certainty of that evidence was graded low to very low, so this is a reason to moderate rather than to panic about cans you already drank.