Is aspartame safe during pregnancy?

For most pregnant women the regulators' answer is yes, within the acceptable daily intake, and for women with phenylketonuria (PKU) it is no. No randomized trial has given aspartame to pregnant women, so the answer rests on a risk assessment and on birth cohorts. The European Food Safety Authority found no risk to the developing fetus from the phenylalanine in aspartame at its acceptable daily intake of 40 mg per kg of body weight, with the exception of women with PKU. Large cohorts link a daily diet drink in pregnancy to more preterm births and heavier children. Those links are observational, inconsistent between studies, and not about aspartame alone.

Not for everyone. Women with PKU should avoid aspartame, in pregnancy and outside it. Aspartame is a source of phenylalanine, which women with PKU must keep low. In one 1992 study, a single 12-oz can of diet cola supplied 184 mg of aspartame, of which 104 mg was phenylalanine. In the Maternal PKU Study of 382 women and 572 pregnancies, the best birth outcomes came when the mother's blood phenylalanine was held at 120 to 360 micromol/L by 8 to 10 weeks of pregnancy and kept there.

What the trials found

No trial in pregnancy

We found no randomized trial that tested aspartame in pregnant women. The strongest general evidence is a 2019 systematic review with meta-analyses of 56 studies in healthy adults and children. It found no differences for most health outcomes between people who used non-sugar sweeteners and those who did not. The certainty of that evidence was very low to moderate, and pregnancy was not analyzed separately. In a 24-week randomized trial from 1989, 108 adults took 75 mg/kg of aspartame a day in capsules, almost twice the European acceptable intake. There were no persistent changes in standard laboratory tests or in blood phenylalanine, methanol or formate. None of the 108 was pregnant.

Sweeteners are common in pregnancy. In the ROLO trial of 571 pregnant women in Ireland, one third ate or drank low-calorie sweeteners in every trimester. The main sources were low-calorie fruit drinks, diet cola and low-calorie yogurts. Advice to follow a low glycemic index diet raised the share who used them in the second trimester. That trial measured intake. It did not test whether sweeteners changed any outcome.

Preterm birth

In the Danish National Birth Cohort of 59,334 pregnant women, those who drank at least one artificially sweetened soda a day had 38% higher odds of preterm delivery than those who drank none (odds ratio 1.38, 95% CI 1.15 to 1.65). The authors asked for confirmation. A Norwegian cohort of 60,761 pregnant women tried, and found a much smaller link for more than one drink a day (odds ratio 1.11, 95% CI 1.00 to 1.24), with a larger one for sugar-sweetened drinks. In the Norwegian data, body weight, smoking and education are possible confounders.

Gestational diabetes

In a Chilean cohort of 1,472 pregnant women, any use of non-nutritive sweeteners was linked to 58% higher odds of gestational diabetes (odds ratio 1.58, 95% CI 1.10 to 2.26). The main sweetener there was sucralose, which is not aspartame.

The child's weight

In the Canadian CHILD cohort of 3,033 mothers and infants, daily artificially sweetened drinks in pregnancy were linked to twice the odds of overweight at 1 year (odds ratio 2.19, 95% CI 1.23 to 3.88). Only 5.1% of the mothers drank them daily. In the Danish cohort, children of mothers who drank at least one a day had 26% higher odds of overweight at 18 years (odds ratio 1.26, 95% CI 1.12 to 1.42), after adjusting for both parents' body weight and breastfeeding. Among 918 Danish women with gestational diabetes, daily drinks were linked to a higher risk of a large baby (risk ratio 1.57, 95% CI 1.05 to 2.35) and of overweight at age 7 (risk ratio 1.93, 95% CI 1.24 to 3.01).

In the US Project Viva cohort of 1,683 children, mothers in the highest quarter of intake averaged about one serving a day. Their children had a BMI z-score 0.20 higher in infancy and 0.21 higher in mid-childhood. By early adolescence the gap, 0.14 (95% CI minus 0.07 to 0.35), no longer reached significance.

Unsettled. A 2020 systematic review of 21 cohort studies found mixed and null results for artificially sweetened drinks in pregnancy and the child's body size from 6 months to 18 years. Every study above is observational. Women who drink diet drinks daily may differ in weight, diabetes and diet in ways the adjustments do not fully capture, and none of these cohorts measured aspartame on its own.

For the rest of what is known about aspartame, see the aspartame page.

Who should be careful

Women with PKU, as above. Phenylalanine control has to start early in pregnancy, and a systematic review that built a food pyramid for adults with PKU puts aspartame among the foods banned from the diet.

For everyone else the limit is the acceptable daily intake. WHO experts kept it at 0 to 40 mg/kg in 2023, which they put at about 9 to 14 cans of diet soft drink a day for a 154 lb (70 kg) adult. In the same year IARC rated aspartame possibly carcinogenic, Group 2B, on limited evidence. In the United States, where the acceptable intake is set at 50 mg/kg, a modeling study found that mean intake and the 95th percentile both sat below it. That study names pregnant women among the 62.6% of the population who consume aspartame.

What expert bodies say

The European Food Safety Authority, in its 2013 full reassessment, found no risk to the developing fetus from phenylalanine derived from aspartame at the acceptable daily intake of 40 mg/kg, except in women with PKU. The WHO 2023 guideline advises against using non-sugar sweeteners, aspartame included, to control body weight, and applies that advice to everyone except people with pre-existing diabetes. That guideline is about weight, not about safety in pregnancy, and the WHO release did not mention pregnancy.

How we searched

What would change this answer

• A randomized trial of reducing sweeteners in pregnancy. One, the SweetPea trial, is registered and recruiting, and tests cutting non-nutritive sweeteners in pregnancy and breastfeeding.
• A cohort that measures aspartame itself, separately from sucralose and other sweeteners, rather than diet drinks as a group.
• A meta-analysis of the pregnancy cohorts that reports absolute rates, so a relative link can be turned into a number of extra cases.

Sources

1. ev-aspg-01 · Meta-analysis or systematic review · systematic review and meta-analyses of randomized and non-randomized controlled trials and observational studies · n = 56 studies (35 observational)
   Most health outcomes did not seem to have differences between the NSS exposed and unexposed groups.
   
   Who: generally healthy or overweight/obese adults and children; NSS within the acceptable daily intake for at least 7 days
   Effect: most outcomes no difference between NSS exposed and unexposed; very low to moderate certainty
   Certainty: Not about pregnant women; general population. Pregnancy was not analyzed separately.
   BMJ, 2019 · checked 2026-10-07 · we read the abstract
2. ev-aspg-02 · Randomized controlled trial(s) · randomized, double-blind, placebo-controlled, parallel-group · n = 108
   Safety of long-term administration of 75 mg/kg of aspartame per day was evaluated with the use of a randomized, double-blind, placebo-controlled, parallel-group design in 108 male and female volunteers aged 18 to 62 years. ... No persistent changes over time were noted in either group in vital signs; body weight; results of standard laboratory tests; fasting blood levels of aspartame's constituent amino acids (aspartic acid and phenylalanine), other amino acids, and methanol; or blood formate levels and 24-hour urinary excretion of formate.
   
   Who: male and female volunteers aged 18 to 62 years, 24 weeks
   Effect: no persistent changes vs placebo in laboratory tests, phenylalanine, methanol or formate
   Certainty: Not pregnant; 1989; capsules; the dose is almost twice the EFSA ADI of 40 mg/kg.
   Arch Intern Med, 1989 · checked 2026-10-07 · we read the abstract
3. ev-aspg-03 · Randomized controlled trial(s) · secondary analysis of a randomized controlled trial · n = 571
   One-third of all pregnant women consumed LCS across each trimester of pregnancy.
   
   Who: pregnant women randomized to low-GI dietary advice or usual antenatal care; 3-day food diary each trimester
   Effect: about one third consumers each trimester; more consumers in trimester 2 in the intervention group (p < 0.001); main sources low-calorie fruit drinks, diet cola, low-calorie yogurts
   Certainty: About intake, not health consequences; individual sweeteners not distinguished.
   Eur J Clin Nutr, 2022 · checked 2026-10-07 · we read the abstract
4. ev-aspg-04 · Observational data · prospective cohort · n = 59334
   In comparison with women with no intake of artificially sweetened carbonated soft drinks, the adjusted odds ratio for women who consumed ge 1 serving of artificially sweetened carbonated soft drinks/d was 1.38 (95% CI: 1.15, 1.65).
   
   Who: pregnant women, Danish National Birth Cohort 1996-2002; intake by FFQ in midpregnancy
   Effect: >=1 serving/d artificially sweetened carbonated soft drinks: adjusted OR 1.38 (95% CI 1.15 to 1.65); >=4 servings/d: OR 1.78 (1.19 to 2.66)
   Certainty: Observational; drinks, not aspartame separately; the authors ask for confirmation.
   Am J Clin Nutr, 2010 · checked 2026-10-07 · we read the abstract
5. ev-aspg-05 · Observational data · prospective cohort · n = 60761
   A high intake of AS beverages was associated with preterm delivery; the adjusted OR for those drinking >1 serving/d was 1.11 (95% CI: 1.00, 1.24).
   
   Who: pregnant women, Norwegian Mother and Child Cohort Study; FFQ in midpregnancy
   Effect: AS beverages >1 serving/d: adjusted OR 1.11 (95% CI 1.00 to 1.24); SS beverages >1 serving/d: OR 1.25 (1.08 to 1.45)
   Certainty: Replication of the Danish signal gave a weaker effect; confounding (BMI, smoking, education).
   Am J Clin Nutr, 2012 · checked 2026-10-07 · we read the abstract
6. ev-aspg-06 · Observational data · prospective birth cohort · n = 3033
   Compared with no consumption, daily consumption of artificially sweetened beverages was associated with a 0.20-unit increase in infant BMI z score (adjusted 95% CI, 0.02-0.38) and a 2-fold higher risk of infant overweight at 1 year of age (adjusted odds ratio, 2.19; 95% CI, 1.23-3.88).
   
   Who: mother-infant dyads, CHILD Study 2009-2012; maternal FFQ in pregnancy; infant BMI at 1 year
   Effect: daily ASB vs none: infant BMI z +0.20 (95% CI 0.02 to 0.38); overweight adjusted OR 2.19 (1.23 to 3.88)
   Certainty: Only 5.1% of mothers drank daily; OR is odds, not risk.
   JAMA Pediatr, 2016 · checked 2026-10-07 · we read the abstract
7. ev-aspg-07 · Observational data · prospective cohort · n = 918 dyads
   Compared to never consumption, daily ASB intake during pregnancy was positively associated with offspring large-for-gestational age [adjusted relative risk (aRR) 1.57; 95% CI: 1.05, 2.35 at birth], BMIZ (adjusted β 0.59; 95% CI: 0.23, 0.96) and overweight/obesity (aRR 1.93; 95% CI; 1.24, 3.01) at 7 years.
   
   Who: women with gestational diabetes and their singleton children, Danish National Birth Cohort
   Effect: daily ASB vs never: LGA aRR 1.57 (95% CI 1.05 to 2.35); overweight/obesity at 7 y aRR 1.93 (1.24 to 3.01)
   Certainty: High-risk group (HCD); observational.
   Int J Epidemiol, 2017 · checked 2026-10-07 · we read the abstract
8. ev-aspg-08 · Observational data · longitudinal cohort · n = 72821
   We found increased odds of overweight in 7-, 11-, 14- and 18-year-old offspring whose mothers reported drinking ≥ 1 artificially sweetened beverage daily during pregnancy compared with no consumption (18 years: adjusted OR 1·26 (95 % CI 1·12, 1·42)).
   
   Who: Danish National Birth Cohort, 72,821 women with pregnancy FFQ; offspring followed to 18 years
   Effect: >=1 ASB/d vs none: overweight at 18 y adjusted OR 1.26 (95% CI 1.12 to 1.42)
   Certainty: Adjusted for maternal and paternal BMI, breastfeeding; residual confounding possible.
   Br J Nutr, 2025 · checked 2026-10-07 · we read the abstract
9. ev-aspg-09 · Observational data · prospective pre-birth cohort · n = 1683
   The highest quartile of NNS intake (Q4: 0.98 ± 0.91 servings/day) was associated with higher BMI z-score in infancy (β 0.20 units; 95% CI 0.02, 0.38), early childhood (0.21; 0.05, 0.37), mid-childhood (0.21; 0.02, 0.40), and early adolescence (0.14; -0.07, 0.35) compared with Q1 intake (Q1: 0.00 ± 0.00 servings/day).
   
   Who: mother-child pairs, Project Viva, Massachusetts 1999-2002; NNS intake in 1st and 2nd trimesters
   Effect: Q4 vs Q1: BMI z +0.20 (95% CI 0.02 to 0.38) in infancy; +0.21 (0.02 to 0.40) mid-childhood; +0.14 (-0.07 to 0.35) early adolescence
   Certainty: Q4 averages ~1 serving per day; observational.
   Int J Obes (Lond), 2022 · checked 2026-10-07 · we read the abstract
10. ev-aspg-10 · Observational data · systematic review of prospective cohort studies · n = 21 studies
    Mixed and null findings were observed for the relationship between total carbohydrates, n-3 polyunsaturated fatty acids, protein, sugar-sweetened beverages, and artificially sweetened beverages and offspring body size.
    
    Who: prospective cohorts of healthy pregnancy and offspring body size 6 months to 18 years
    Effect: mixed and null findings for artificially sweetened beverages
    Certainty: Review of cohorts, without meta-analysis; level C.
    Paediatr Perinat Epidemiol, 2020 · checked 2026-10-07 · we read the abstract
11. ev-aspg-11 · Observational data · secondary analysis of a prospective cohort · n = 1472
    The adjusted model showed a significant association between the consumption of any NNS and sucralose and the risk of GDM (OR for any NNS = 1.58; 95% CI: 1.10-2.26; P = 0.014; OR sucralose = 1.44; 95% CI 1.06-1.95; P = 0.020).
    
    Who: pregnant women in primary care, Puente Alto, Chile (CHiMINCs-II); 24-h recalls
    Effect: any NNS: OR 1.58 (95% CI 1.10 to 2.26); sucralose OR 1.44 (1.06 to 1.95)
    Certainty: The main sweetener is sucralose, not aspartame; observational.
    Nutrition, 2024 · checked 2026-10-07 · we read the abstract
12. ev-aspg-12 · Observational data · multicentre non-randomized clinical study · n = 382 women, 572 pregnancies
    Optimal birth outcomes occurred when maternal blood Phe levels between 120 and 360 micromol/L were achieved by 8 to 10 weeks of gestation and maintained throughout pregnancy (trimester averages of 600 micromol/L).
    
    Who: women with hyperphenylalaninemia (PKU) on a phenylalanine-restricted diet, 1984-2002
    Effect: optimal outcomes with maternal Phe 120-360 micromol/L achieved by 8-10 weeks and maintained
    Certainty: Explains why aspartame (a source of phenylalanine) is prohibited for pregnant women with PKU.
    Pediatrics, 2003 · checked 2026-10-07 · we read the abstract
13. ev-aspg-13 · Position of an expert body · agency risk assessment · n = —
    With respect to pregnancy, the Panel noted that there was no risk to the developing foetus from exposure to phenylalanine derived from aspartame at the current ADI (with the exception of women suffering from PKU).
    
    Who: pregnant women
    Effect: no fetal risk at ADI 40 mg/kg bw/day; exception: women with phenylketonuria
    Certainty: EFSA 2013, full reevaluation; ADI 40 mg/kg.
    EFSA, full risk assessment of aspartame, press release 10 December 2013 · checked 2026-10-07 · we read the section
14. ev-aspg-14 · Position of an expert body · WHO guideline · n = —
    The recommendation applies to all people except individuals with pre-existing diabetes and includes all synthetic and naturally occurring or modified non-nutritive sweeteners that are not classified as sugars found in manufactured foods and beverages, or sold on their own to be added to foods and beverages by consumers.
    
    Who: all people except individuals with pre-existing diabetes
    Effect: recommends against NSS for weight control or NCD risk reduction (conditional)
    Certainty: About weight control, not safety in pregnancy; pregnancy is not mentioned in the release.
    WHO, WHO advises not to use non-sugar sweeteners for weight control in newly released guideline, 15 May 2023 · checked 2026-10-07 · we read the section
15. aspm-daily-r8-08 · Observational data · controlled challenge study · n = 6
    Six normal subjects each ingested a single 12-oz can of a diet cola (Diet Coke) providing 184 mg aspartame (APM), of which 104 mg is phenylalanine (Phe), and, on another occasion, a single 12-oz can of regular cola (Coke Classic).
    
    Who: normal subjects drinking one 12-oz can
    Effect: 184 mg aspartame per can, 104 mg phenylalanine
    Certainty: one brand, 1992 formulation
    Clin Pediatr (Phila), 1992 · checked 2026-09-29 · we read the abstract
16. aspm-daily-r8-11 · Observational data · systematic review of mixed designs with expert food pyramid · n = —
    the one red indicates foods that are banned from diet (aspartame and protein foods exceeding individual dietary phenylalanine tolerance).
    
    Who: adult patients with phenylketonuria
    Effect: aspartame placed in the banned category
    Certainty: recommendation, not effect size
    Clin Nutr, 2023 · checked 2026-09-29 · we read the abstract
17. aspm-daily-r8-14 · Position of an expert body · exposure modeling on NHANES · n = —
    Mean, 90th percentile, and 95th percentile aspartame intake estimates are below the acceptable daily intake (50 mg/kg/day) and are lower than estimates from previous decades. ... Aspartame exposure is highly prevalent (62.6%) in the US including sensitive populations such as pregnant women and children.
    
    Who: US population, NHANES with purchase data
    Effect: mean, P90, P95 below 50 mg/kg/day; prevalence 62.6%
    Certainty: modeled from purchases and recalls
    J Expo Sci Environ Epidemiol, 2025 · checked 2026-09-29 · we read the abstract
18. aspm-daily-r8-17 · Position of an expert body · agency risk assessment (JECFA) and hazard classification (IARC) · n = —
    IARC classified aspartame as possibly carcinogenic to humans (Group 2B) ... with a can of diet soft drink containing 200 or 300 mg of aspartame, an adult weighing 70kg would need to consume more than 9–14 cans per day to exceed the acceptable daily intake
    
    Who: general population
    Effect: ADI 0-40 mg/kg body weight; IARC Group 2B
    Certainty: position of bodies; IARC based on limited evidence for hepatocellular carcinoma
    WHO, Aspartame hazard and risk assessment results released, 2023 · checked 2026-09-29 · we read the section