2. Hormone replacement protocol: The patient is given beta estradiol 2mg three times a day (Estrofem - Novo Nordisk) from the first day of the menstrual cycle. This prevents indigenous follicle development on the one hand, but is sufficient to prepare the endometrium. When the endometrium is at least 7 mm thick vaginal suppositories of progesterone are administered 100 mg tid (Endometrin - Lapidot) for 48 hours after which the embryos are transferred. If the endometrium fails to reach 7 mm, additional estrogen is added. Since there is no corpus luteum in this protocol, estradiol and progesterone supplementation must be given until the placenta produces these hormones in sufficient quantities. We maintain hormonal support until 11.6 weeks of gestation in cycles where pregnancy is attained.