The ability to love is not finite. Your heart expands to accept all you wish to have enter - and sometimes they wiggle in, anyway
. When a pet dies and you get a "replacement" - nothing *replaces* your beloved pet. Your heart just expands to accept a new one.
Human babies are a bit different because they need more attention for a longer period of time. New moms are exhausted, and time to yourself is limited. BUT, whereas your lap space may diminish a bit, you still have sides. When you're tending to the baby's needs, Snickers can sit beside you and get some skritches and lovin', too.
I'm a firm believer: let your dog (or cat) stay in your lap while you're pregnant. They can hear the baby's heartbeat through your belly, and they can feel it move. When the baby arrives, it's not such a stranger. Let Snickers check the baby out from head to toe to familiarize himself with the newcomer.
When the baby's crying, and you don't know why ... when you're up to your eyeballs in laundry and it's raining ... and Snickers wants to go out, or drops a ball at your feet ... if you're human, you'll get annoyed. But if you love him, you'll take a deep breath, bend over and get that ball, and give it a toss down the hallway.
You'll both do better for the diversion.
My "animals" are family members. Logically, I understand that humans take precedence, but emotionally - *emotionally* they are all equal and all get the time they need according to their needs.
You'll find a way, too.