There are an estimated 82.5 million mothers of all ages in the United States, and the number of stay-at-home mothers was 5.4 million in 2003, statistics released by the Census Bureau on Tuesday showed.

Each year, about 4 million women have babies, of whom about 425,000 are teens aging between 15 and 19 years old and more than 100,000 are 40 or over.

US women today can expect to have two children on the average in their lifetime, and about 10 percent of them end their childbearing years with four or more children, compared with 36 percent in 1976.

The odds of a woman delivering twins is 1-in-32, and her odds of having triplets or other multiple births is approximately 1-in-540.

Among American mothers with infant children in 2002, according to the figures, 55 percent were in the labor force, down from a record 59 percent in 1998.

The Census Bureau released the figures to mark Mother's Day, which falls on the second Sunday of May.