BOSTON, AUG. 19 -- Spermicides do not appear to increase the risk for certain birth defects even when used before pregnancy, during conception or in early pregnancy, two research teams reported today.

Separate studies published in The New England Journal of Medicine found no link between spermicides used in various forms of contraception and some birth defects.

Dr. Allen Mitchell of Boston University, who conducted one study, said the research "together with previous studies may offer a great deal of reassurance about the safety of spermicides."

Researchers focused on Down's syndrome, an abnormality of the penis, abnormally short arms or legs, tumors and brain and spinal defects, all of which previous research suggested were most likely associated with spermicide use.

The Boston team examined the cases of 1,138 infants born with the defects and 3,442 babies born with other defects between January 1983 and June 1986 in relation to whether their mothers had used spermicides.

"The results of this study suggest that the risks of five specific birth defects . . . are not increased by exposure to spermicide contraceptives in the first four months of pregnancy, at the time of conception or at any time before conception," the researchers said.

In the second study, Columbia University scientists compared the cases of women who had babies with Down's syndrome or a similar genetic abnormality known as trisomy to those who had healthy babies, and reported no association with spermicide use.