孕激素能抑制排卵,但单独用其避孕可并发出血和月经紊乱,因此人们将雌、孕激素联合使用。为减少甾体激素对心血管和代谢的影响,必须降低甾体激素的总剂量,但很低剂量的复方口服避孕药不能完全控制月经周期,还可能引起由于雌孕激素失衡所发生的副作用,为使服药周期与自然周期更接近,人们发展了双相和三相的避孕药。其配伍(见表)。双相避孕药为雌孕激素复方,后者的剂量逐次有所增加。三相避孕药为雌激素与逐周增加剂量的孕激素相配伍(见表)。双相和三相避孕药符合理想避孕药的标准,即抑制排卵,中度阻滞垂体功能,促使子宫内膜增殖和宫颈粘液变化。双相避孕药的进步是在整个周期增加甾体激素的剂量,减少了单相复方避孕药所引起的点滴出血和出血的发生率及闭经。三相避孕药除上述作用外还在中期增加剂量以使可能出现的黄体高峰受到阻断。此外这种 Progestin can inhibit ovulation, but contraceptives alone can be complicated by bleeding and menstrual disorders, so people will be combined with estrogen and progesterone. In order to reduce the cardiovascular and metabolic effects of steroid hormones, the total dose of steroid hormones must be reduced, but very low doses of compound oral contraceptive pills can not completely control the menstrual cycle and may also cause side effects due to the imbalance of estrogen and progesterone. In order to bring the medication cycle closer to the natural cycle, two-phase and three-phase contraceptives have been developed. Its compatibility (see table). Biphasic contraceptives for estrogen and progesterone compound, the latter dose gradually increased. Three-phase contraceptives for estrogen and week-by-week increase in the dose of progesterone compatibility (see table). Two-phase and three-phase contraceptives are in line with the ideal standard of contraception, that is, inhibit ovulation, moderate pituitary function, promote endometrial proliferation and cervical mucus changes. Progress in bipolar contraceptives is to increase the dose of steroid hormones throughout the cycle, reducing the incidence of bleeding and bleeding caused by single-phase compound contraceptives and amenorrhea. Three-phase contraceptives in addition to the above-mentioned role in the mid-term dose increase in order to make possible the luteal peak was blocked. In addition to this