Black children are twice as likely as white children to die in the first year of life, three times as likely to be poor, four times as likely not to live with either parent and five times as likely to be on welfare, according to a study released yesterday by the Children's Defense Fund.

The study, drawn from a variety of government statistics, portrays a widening schism between black and white children in America. It concludes that during the past five years black children have been "sliding backwards" and are increasingly suffering from "inequality that denies opportunity to millions of black children."

While focusing on black children, the study notes that white children also are facing greater hurdles than in the past five years.

It found that white households headed by females under age 25 now have a poverty rate of 72.1 percent and that 39.3 percent of all white female-headed families are in poverty.

The report said 16.9 percent of white families are poor and 12.3 percent of all teen-age births are to whites.

But the study noted that, for black children in single-parent families headed by women under age 25, the poverty rate is 85.2 percent.

The poverty rate for all families headed by black women is 63.7 percent.

The report also said there has been a dramatic decline in educational opportunities for black youth.

In 1977, black and white high school graduates were equally likely (50 percent for blacks and 51 percent for whites) to go on to college.

By 1982, 52 percent of white high school graduates were going to college, compared with 36 percent of black high school graduates.

"Poverty appears to be the key to low college attendance rates among blacks," the report said.

"These facts require urgent community and national responses," said Marian Wright Edelman, president of the Children's Defense Fund, a Washington-based organization that lobbies on children's issues and studies trends in child welfare.

Edelman charged that the growing disparity between white and black children is in part the result of Reagan administration policies that have "targeted poor children and families."

She said poor children cannot "escape poverty with governmental policies that snatch income, food and health care from the poor in order to pay for defense increases and tax breaks for the wealthy."

A spokesman for President Reagan said the White House would have no comment on the report.

The Children's Defense Fund study, "Black and White Children in America: Key Facts," said that, in 1982, more than 55 percent of black children were born out of wedlock. It said the current rate of out-of-wedlock births "essentially guarantee s the poverty of black children for the forseeable future."

The study also said: Black children are twice as likely as whites to be born prematurely, to suffer low birthweight, to have their mothers receive late or no prenatal care, to see a parent die, to live in substandard housing, to be unemployed as teens; to have no parents employed and to live in an institution.

Black children are three times as likely as white children to to have their mothers die in childbirth, to live in a female-headed family and to die of known child abuse.

Also yesterday, the National Association of Latino Elected and Appointed Officials reported that, over the past five years, the highest rate of child poverty in families headed by women has been among Hispanic children, a rate of 70.6 percent.