Your pets probably don't understand that in nine months a new baby will be joining your family, but dogs and cats do detect differences in mood, posture, behavior, and body chemistry that clue them that an enormous change is happening.
Your dog or cat will pick up other signs, too: Our four legged friends are masters at reading our body language, so they'll notice when your movements start to get more and more awkward. Pets are also highly attuned to changes in your daily routine - say, if you're not taking your dog for runs as often as you used to, if you're spending more time on the couch, or if family members are treating you with extra care.
It's common for dogs to go on alert and become overprotective of their expecting owner from the very beginning of her pregnancy. Behaviorists have witnessed dogs growl, bark, or even block doors with their bodies to prevent other family members - even the baby's father - from coming into the same room as the mom-to-be.
Cats on the other hand are less socially involved, therefore less likely to go through these sorts of behavioral changes. Cat owners have reported a wide range of responses from uninterested to more loving and protective behaviors. But keep giving your cat attention and love during your pregnancy, as neglected cats may become more aggressive or act out by urinating where they're not supposed to, like in your bed or laundry basket.
To help prevent problem behaviors, try to stick to your pre-pregnancy routine as much as you can, and ask family members and friends to help when you're not up for a run in the park or a long brushing session. I advise clients to develop a plan for their pet while they're in the hospital, just like they'd develop a birth plan. Line up a caretaker for your pets and write down your pets' schedules for that person.
To help your dog understand that you still love him, be careful of the messages you send through your body language. Pregnant women often unconsciously place their hands over their stomachs, and dogs read this closed-arm posture as saying "I'm unavailable" or "step back." Open-armed postures, on the other hand, send dogs the message to "come here."
If your dog or cat starts seriously misbehaving during your pregnancy, or if you don't have experience preparing pets for a new baby, it's a good idea to get help from a professional trainer. Many offer "baby readiness" classes or individual training sessions to help pets adjust.
If you stay on top of any potential behavior problems, having pets during your pregnancy and afterward can be a wonderful thing for you and your baby. Studies have shown that spending time with a domesticated animal can improve mood, reduce depression, lower blood pressure, and even help you live longer. So enjoy!