The transformation the player undergoes courtesy of Maria comes fully equipped with all the trimmings. This includes a fully functional womb; a character who is carelessly promiscuous with men (or presumably futanaris) will find themselves getting pregnant. A character needs to make regular use of condoms and birth control pills from the Drug Mart if they want to avoid becoming pregnant.
Characters have a Fertility rating, which is affected by such things as Transformations, using the "Bag of Special Tea" from the Drug Dealer, and taking the Fertility Statue from the Lab. A high Fertility rating impairs the effectiveness of condoms and birth control.
They also have a rating of Multiple Pregnacy Chance; this details the likelihood that a given pregnancy will instead produce identical twins, fraternal twins, or triplets. This starts at 1%, but is increased by Fertility; the Cat Transformation includes the "Litter" racial trait, which gives +20% to this score and means the character's Multiple Pregnancy Chance will never drop below 20%. The planned Dog Transformation will also include this trait, but the Werewolf Transformation lacks it.
Being pregnant with multiples is functionally identical to being pregnant with singletons - characters who are pregnant with triplets while having a Strength score under 50 will be bedridden by the weight of their womb, and so cannot take any actions until they give birth.
Using the Black Dildo from Nipples And Dimes can result in a unique "Monstrous Pregnancy", where the character experiences a far faster than normal pregnancy that results in the birth of a monster offspring.
Babies have a 50% chance of being male and a 50% chance of being female; the odds of this are calculated at conception. Characters who have at least 50% of the Succubus Transformation will always give birth to girls.
The various Transformations can affect a character's unborn children. The Dragon Transformation, Sex Doll Transformation, and Robot Transformation all render it impossible for a character to become pregnant; Dragons will lay a clutch of unfertilised eggs once a month, but these cannot be fertilised without another dragon. Other Transformations will change the race of the character's unborn children if the character is over 50% transformed while pregnant. This is confirmed to exist for Catgirl, Cowgirl and Succubus characters; it is unknown if Futanari, Giantess, or Wings transformations also apply to offspring.
A Pregnancy Fetish is one of the possible Traits and Sexual Traits that a character can develop. Currently, it is planned to make the "Pregnancy Lover" ending available, but it is not implemented; one of the Random Events is a "Brood Mother" dream that gives 1 point towards this sexual trait, but no other methods of acquiring it are possible.