Cohort studyindependent cross-checkabstract only checked★ key study I-MEAT-06 in-depth review

Too much vitamin A in early pregnancy linked to birth defects

Teratogenicity of high vitamin A intake.

Overview

Rothman KJ et al.. N Engl J Med 1995 · PMID 7477116 · DOI 10.1056/NEJM199511233332101

Above 15,000 IU/day: 3.5-fold more defects of head/face structures.

Does the study support the specific claim? No · Methodological quality: moderate

Study explained simply

What did the researchers want to find out?: Vitamin A and birth defects.
How was the study done?: Prospective study.
How many people, animals or samples were studied?: 22,748 pregnant women.
What was actually found?: High vitamin A teratogenic.
How large was the observed effect?: PR 3.5 (1.7-7.3).
What do the results mean in everyday life?: Pregnant women should avoid very high vitamin A sources such as liver.
What are the study's limitations?: Self-reported diet.
What does it say about Elawady's specific claim?: Contradicts free liver intake in pregnancy.
Do the results apply to Germany and Europe?: High.
What can explicitly not be concluded from this study?: Exact safe liver portion.

Is high vitamin A intake teratogenic?

Study design: Cohort study – Prospective study of pregnant women with dietary interviews (first trimester).
Population: Pregnant women undergoing AFP screening or amniocentesis
Country: USA
Period: Oct 1984 - June 1987
Sample size: 22,748 women; 339 babies with defects (121 cranial-neural-crest)
Inclusion and exclusion criteria: Not detailed in abstract.

Results: >15,000 IU/day food+supplements vs <=5,000: prevalence ratio 3.5 (1.7-7.3); supplements >10,000 IU/day vs <=5,000: 4.8 (2.2-10.5); apparent threshold near 10,000 IU/day supplemental; risk concentrated before week 7.
Absolute risks: Estimated 1 in 57 infants of women taking >10,000 IU/day supplements had a malformation attributable to the supplement.
Authors' conclusion: High dietary intake of preformed vitamin A appears teratogenic.

Strong relative effects; wide CIs.

Contradicts unrestricted liver allowance (C-MEAT-03) for pregnancy.

n/a

High.

Basis for pregnancy advice on preformed vitamin A.

Multidimensional assessment
Multidimensional assessment
Authenticity of the source	verified
Methodological quality	moderate
Risk of bias	some concerns
Precision of results	low
Directness	indirect
Reproducibility	partly replicated
Consistency with the overall evidence	mixed
Regional transferability	high
Adequacy of the interpretation (by the archive)	not applicable

Liver-specific dose.