The baby stage (幼児期 yōjiki), known as the first Babytchi stage (ベビーっち bebītchi) in vintage Japanese media, is the beginning of the Tamagotchi's life, after hatching from its egg. Under normal circumstances, it will evolve into the child stage. Starting from the Tamagotchi Connection, this is when the Tamagotchi's gender is first identified.
Once hatched from its egg, all of the baby's Hungry and Happy hearts will be empty, and will empty rapidly during its time in this stage. The baby will also poop, take a 5 minute nap, and get ill. From the Tamagotchi Connection onward, it will also call for training by crying and requiring praising. After one hour, the baby will evolve to the Child Stage.
On most of the vintage releases, babies cannot gain weight and usually remain at 5 lb. The Angel and the Mesutchi and Osutchi have exemptions to this rule - on the former weight is replaced with Angel Power, and on the latter babies from the second generation onward can gain and lose weight.
On the Morino and from the second generation onwards on the Mesutchi and Osutchi, the baby stage lasts for 24 hours. To accomodate for this, the babies on those devices are much less needy than the others.
From the Version 1 until the release of the Version 5, the Baby would appear crying on the screen, and its lifespan would not begin until the user gives it a name.
Death cannot normally happen in the stage; even if the baby suffers extreme neglect, it will evolve into the Child Stage before the effects of neglect could invoke death.
On the classic Tamagotchi, the user could deliberately invoke death by feeding the baby snacks nonstop. Additionally, the 24 hour span that the baby stage can last for on the Morino and the Mesutchi/Osutchi (including factors such as predators on the former and evolution to Debutchi on the latter) gives babies on those releases the opportunity to die from neglect.
Babies from Marriage
Once an adult marries and has children, there will be a period of time in which the player will raise both parent and child. In the time, the baby could poop and get ill, but the adult does all of the baby's feeding. If the adult dies, the baby will die with them.
On the Mesutchi and Osutchi, babies resulting from marriage would stay in this stage for one full day, and evolve into the child stage the following day. What baby is born from the parents correlates directly to the TMP level of the two parents; two parents of the same TMP level would result in a baby with a higher TMP level, while two parents of different TMP levels would result in a baby with a lower TMP level.
From the Tamagotchi Connection until the Version 5, the baby character will live with the adult for a minimum of 24 hours, and babies born via connection will be the same gender. After the 24 hours, the parent would leave the following midnight, and the user could name the new baby once it awoke in the morning. Unlike the Mesutchi and Osutchi, the new baby will act exactly like one from the first generation and evolve in one hour.
On the Chou Jinsei Enjoi Tamagotchi Plus and Ura Jinsei Enjoy Tamagotchi Plus, there are two babies for each of the three families, and the baby resulting from marriage is determined by the family of the two adults. This was carried over to the Version 5 and its variations.
From the Version 5 onward, the baby's life begins immediately after the adult of the previous generations marries, with the Tamagotchi Music Star being the sole exception.
Certain baby characters can only be born under certain conditions, while regular babies born under special circumstances can evolve into special characters.
- From the Version 1 until the Version 5, if Ojitchi and Otokitchi marry, the resulting baby would always be male and evolve into Oyajitchi after one hour, skipping the Child and Teen stages entirely. This appears again on the Tamagotchi Plus Color and TamaTown Tama-Go, except now a female baby could be born that evolves into Grippatchi. On the Hexagontchi, the special adults born this way are Tensaitchi Jr. and Tensaikotchi Jr.
- The special babies Hatenatchi and Bikkuritchi are obtained on the Entama and Uratama respectively, and only appear when one of the special Dating Cards are used.
- On the Version 5 and Version 5 Celebrity / Royal Famitama, Iwatchi can only be born if two toys from different regions marry or if the user chooses to marry Sunnytchi or Jeweltchi on the Dating Channel on English language editions. Babies of special families will reach adulthood in an hour (for example: in the Mametchi Family, the male and female Mimifuwatchis will evolve into Mametchi and Chamametchi).