Danny Ghitis for The New York Times  Maria Seidman, right, head of a tech start-up, in her nursery in New York.

“He looks like a little pumpkin,” her brother-in-law remarked. “You should dress him up as a pumpkin for Halloween.”

“I think we can come up with a more creative costume than that,” Mrs. Stern recalls replying. “But that reminds me. ...”

With that, she reached for her laptop and fired off an e-mail to an associate about a Halloween party being planned by her New York business, Divalysscious Moms.

One should note: this was in July.

“There wasn’t even a thought in my mind about taking a maternity leave,” said Mrs. Stern, whose oldest child was 3 at the time. “It was like, Oliver was going to be born, and he was, and life was going to be continuing in — I don’t want to say madness — but the way that I do business.”