Being pursued in countries in Africa, in Thailand and the Dominican Republic, the studies are likened by the journal to the infamous Tuskegee experiment which, between 1932 and 1972, left 399 black men in Alabama untreated for syphilis so researchers could follow the disease's course.
These studies, backed by both the National Institutes of Health and the Centers for Disease Control, seek to find cheaper alternatives to the treatment given in richer countries to pregnant women with Aids: heavy doses of the drug AZT.
The use of AZT on infected women in pregnancy has been spectacularly successful. Research has shown that without AZT, roughly 25 per cent of women with Aids who give birth will produce babies with Aids. If women are treated with AZT, however, the rate falls to 8 per cent.
The problem in the Third World, however, is cost. AZT is an expensive drug and a course of treatment for each person costs $1,000. The researchers are trying to discover if lesser amounts can still help.
This research, however, is controversial: while half the women in each study are receiving AZT in varying dosages, half of them are not. In other words: the researchers are knowingly condemning some of the yet-to-be- born infants - as many as 1,000, according to critics - to death by Aids.
Defending the work, the NIH said in a statement: "We continue to believe that these studies, as designed, are not only appropriate but essential to finding a way as quickly as possible to prevent the potential infection of millions of infants worldwide with HIV."
Defenders of the programme say that were the researchers not present in these countries none of the women involved would have had access to AZT anyway.
The Washington-based advocacy group, Public Citizen, is attempting to have the studies suspended. "We have turned our backs on these mothers and their babies," said its director, Dr Peter Lurie.