In the developing Asian nation, giving vitamin A supplements to pregnant women in the rural north didn't cut down on their chance of pregnancy-related death, or on infant deaths, according to a new study.
Still, the researchers say making sure pregnant women get enough vitamin A through diet or supplements is "an important public health goal" for other reasons.
But experts debate whether vitamin A supplements are helpful.
"At the moment I think there's very little evidence to support the supplementation of women with vitamin A," Anthony Costello, of the University College London Institute for Global Health, told Reuters Health.
"It seems likely that either it doesn't have an effect, or it only has an effect in populations where there are really serious levels of vitamin A deficiency," said Costello, who has studied vitamin A in the past but was not involved in the current research.
"For most women in the world, that probably doesn't apply."