/** Standard menstrual-cycle length. */
export declare const DEFAULT_CYCLE_LENGTH = 28;
/** Luteal phase is biologically near-constant at ~14 days. */
export declare const LUTEAL_PHASE_DAYS = 14;
/** Sperm survive up to ~5 days before ovulation. */
export declare const FERTILE_DAYS_BEFORE = 5;
/** The oocyte is viable ~1 day after ovulation. */
export declare const FERTILE_DAYS_AFTER = 1;
export interface CycleInput {
    /** First day of the most recent period. */
    lastPeriodStart: Date;
    /** Average cycle length in days. Defaults to 28. */
    cycleLength?: number;
    /** Period (bleed) length in days. Optional — used for the period range. */
    periodLength?: number;
}
export interface DateRange {
    start: Date;
    end: Date;
}
export interface CyclePrediction {
    /** Start date of the next period. */
    nextPeriod: Date;
    /** Estimated ovulation date. */
    ovulation: Date;
    /** Fertile window (5 days before ovulation → 1 day after). */
    fertileWindow: DateRange;
    /** Start dates of the next few periods (length = `occurrences`). */
    upcomingPeriods: Date[];
    /**
     * The current period's bleed range (first day → last day), or `null` when no
     * `periodLength` was given.
     */
    periodRange: DateRange | null;
}
/**
 * Predict ovulation, the fertile window and upcoming periods from the last
 * period's start date. `occurrences` controls how many future periods to
 * list (default 3).
 */
export declare function predictCycle(input: CycleInput, occurrences?: number): CyclePrediction;
//# sourceMappingURL=cycle.d.ts.map