Baby Sims cannot be created in Create-A-Sim, but instead are the result of a male Sim and a female Sim choosing the Try for Baby option while on a bed. In rare cases (less rare if a parent Sim has Fertility Treatment), WooHoo itself will result in a baby. A baby becomes a toddler after three Sim days. If desired, an adult Sim can call the adoption service to put the baby up for adoption. Pregnancy will be covered in a separate article.
As with adult Sims, baby Sims have needs. Here is a list of how to satisfy those needs:
At least one adult Sim must be on a lot with a baby. If all adults attempt to leave the lot, the game will force you to either stay or call a babysitter for §75. Babies can only sleep in cribs, not beds, so be sure to get one. Don't let your baby's social meter get too low, or it will get a negative Lonely moodlet. Be careful to tend to your baby's needs before your adult Sims go to bed, because otherwise, the baby might wake up and start crying in the middle of the night, disrupting your adult Sims' sleep (the crying is likely to wake adults even if they are in a different room.)