"Jennifer and Marc are delighted, thrilled and over the moon," Fields told the magazine.
Lopez' publicists and agent did not return telephone calls from The Associated Press early Friday.
Ending months of speculation, Lopez confirmed her pregnancy at a Miami concert in November. Her father, David Lopez, told Telefutura's "Escandalo TV" earlier this month that the 39-year-old singer was expecting twins.
Lopez and Anthony, 38, married in 2004. The twins are her first children, and his third and fourth.
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