McCarthy, 41, recently told her 11-year-old son, Evan about sex, which she termed 'bird and bees talk', reported The Us magazine.
"I just had the birds and the bees talk. He watched that recent video of that dad driving his wife to the hospital who was going to have a baby.
"She is screaming bloody murder and he was like, 'What's going on? What's going on?' And I'm like, 'This woman is having a baby.' And he was so tortured by it that I had to sit down and give him the birds and the bees talk," she recalled.
McCarthy, who is set to wed Blue Bloods star Donnie Wahlberg soon, admitted it was difficult but being the kind of single mother she has been, she has more responsibilities.
Evan is McCarthy's son with ex-husband actor John Mallory Asher. The couple tied the knot in 1999 and got divorced in 2005.