Birth Control

Birth Control is a passive collectible added in Revelations Chapter One.

Effects

 * Familiars and orbitals are consumed for 0.20 damage up. Some familiars also grant special effects to the player.

Familiar Modifiers

 * BFFS!: Grants Isaac the Magic Mushroom collectible.
 * Baby-Bender: Grants Isaac homing tears.
 * Child Leash: Sets Isaac's speed to 1, regardless of other speed modifiers.
 * Duct Tape: Isaac stops immediately when no movement control is pressed.
 * Extension Cord: Lasers fire out of Isaac's head at the nearest enemy.

Random Loot

 * Distant Admiration, Friend Zone, Halo of Flies, Forever Alone, Smart Fly, Best Bud, ???'s Only Friend, Lost Fly, Big Fan, Obsessed Fan, Papa Fly, and Angry Fly will spawn a random amount of blue flies. (2 to 7)
 * Sissy Longlegs, Daddy Longlegs, and Juicy Sack will spawn a random amount of blue spiders. (2 to 6)
 * Acid Baby: Spawns a random amount of pills. (4 to 6)
 * Little C.H.A.D.: Spawns a random amount of red hearts. (5 to 9) Each red heart has a 33% chance to be a half red heart.
 * Mystery Sack: Spawns a random amount of pickups. (4 to 7) These pickups are completely random, they can be anything from coins, chests, hearts, keys, bombs, or even, though rarely, collectibles.
 * The Relic: Spawns a random amount of soul hearts. (4 to 7) Each soul heart has a 33% chance to be a half soul heart.
 * Rune Bag: Spawns a random amount of runes. (4 to 6)
 * Sack of Pennies: Spawns a random amount of pennies. (5 to 9) Each penny has a 20% chance to be a lucky penny.
 * Sack of Sacks: Spawns a random amount of sacks. (3 to 5)

Familiars

 * Angelic Prism: Grants Isaac a passive angelic prism effect. Tears fired will be duplicated immediately as if Isaac shot tears through the familiar, complete with visual changes to the tears.
 * Bandage Baby: Every 10th tear Isaac fires will instead be one of Bandage Baby's bandage balls.
 * Brother Bobby: Grants Isaac a +1 tears up.
 * Censer: Grants Isaac a passive censer effect. The slowing aura normally centered on the familiar is now centered on Isaac.
 * Depression: Grants Isaac the Aquarius collectible.
 * Dry Baby: Grants Isaac the Missing Page 2 collectible.
 * Envy's Enmity: Grants additional damage ups the more damage Isaac takes. The first hit adds 0.2 damage, the second hit adds 0.4 damage, and the third hit adds 0.8 damage. This resets after leaving the room.
 * Farting Baby: Grants Isaac the The Black Bean collectible.
 * Fate's Reward: Grants Isaac the Fate collectible.
 * GB Bug: Grants Isaac the Missing No. collectible.
 * Ghost Baby: Grants Isaac spectral tears.
 * Harlequin Baby: Grants Isaac the The Wiz collectible.
 * Lil Brimstone: Grants Isaac the Brimstone collectible.
 * Lil Frost Rider: Grants Isaac the Ice Tray collectible.
 * Lil Loki: Grants Isaac the Loki's Horns collectible.
 * Lil Monstro: Grants Isaac the Monstro's Lung collectible.
 * Little Gish: Grants Isaac slowing tears.
 * Little Steven: Grants Isaac homing tears.
 * Milk!: Grants Isaac the Chocolate Milk collectible.
 * Multidimensional Baby: Grants Isaac a passive multidimensional baby effect. Tears fired will be duplicated immediately as if Isaac shot tears through the familiar, complete with the visual changes the familiar applies to the tears.
 * Robo-Baby: Grants Isaac the Technology collectible.
 * Robo-Baby 2.0: Grants Isaac the Technology 2 collectible.
 * Rotten Baby: Grants Isaac the The Mulligan collectible.
 * Sister Maggy: Grants Isaac a +1 tears up.
 * Succubus: Grants Isaac a passive succubus effect. The damaging dark aura normally centered on the familiar is now centered on Isaac. This also effectively acts as a permanent 1.5 damage multiplier.
 * Seraphim: Grants Isaac the Sacred Heart collectible.