married_mother_pregnancy_effect

married_mother_pregnancy_effect = {
	add_trait_force_tooltip = pregnant
	if = {
		limit = {
			NOT = { exists = scope:spouse }
			exists = primary_spouse
		}
		primary_spouse = {
			save_scope_as = spouse
		}
	}
	if = {
		limit = { exists = scope:spouse }
		scope:spouse = {
			pregnancy_spouse_suspicion_chance_effect = yes
		}
	}
	hidden_effect = {
		if = {
			limit = {
				NOT = {
					any_owned_story = {
						type = story_peasant_affair
						var:peasant_character = {
							this = scope:real_father
						}
					}
				}
			}
			trigger_event = { #This parses whether the mother is planning to confess to a real_father, and checks if there are characters out there who should suspect that they might be the real father
				id = adultery.1101
				days = 20
			}
		}
	}
}

As written in game/common/scripted_effects/00_pregnancy_effects.txt.