Why You Never Saw Howard And Bernadette's Kids On The Big Bang Theory

While Howard and Bernadette got married and became parents to Halley and Neil Michael, the kids weren’t actually shown on-screen until the series finale of “The Big Bang Theory.” There were two reasons for that, according to executive producer Steve Holland, the first reason is very touching, while the other is practical.
When Halley was born, she let out a cry off-screen that sounded like the distinctive voice of Howard’s mother, who passed away during Season 8. During her time on the show Mrs. Wolowitz was only portrayed in voice-overs, so having Halley’s character heard but almost never seen was done as a tribute to her grandmother.
The other reason we only ever see the kids once was due to a production decision to keep babies off the set, mostly because Holland always felt bad for infants who were shoved in front of a camera. Fans do finally get to see the kids in the series finale, an idea that Holland said came from series creator Chuck Lorre.