Abstract: The invention relates to a multiphase combination-type sequential preparation for oral contraception consisting of 20-22 tablets each containing a gestagen and an oestrogen wherein a first phase consists of 5-8 tablets, each of which contains a low dose of gestagen and a relatively high dose of oestrogen, a second phase of 5-8 tablets each having a gestagen dose which is greater than that during the first phase and an oestrogen dose which is smaller than that in the first phase, and a third phase of 5-11 tablets each of which has a gestagen dose equal to or greater than that during the second phase and an oestrogen dose equal to or less than that in the second phase, and to a method of oral contraception using said preparation.

Abstract: The invention relates to novel prostaglandin analogues, characterized by the general formula: ##STR1## or a racemic mixture thereof, as well as esters, amides, salts and acyl derivatives of these compounds, in which C.sub.n H.sub.2n represent an alkylene (2-5 C) group,R, r.sub.1, r.sub.2, r.sub.3 represent hydrogen or alkyl (1-4 C),X represents oxygen or sulphur andZ represents F, Cl, Br or CF.sub.3and whereby the symbol .about. means the .alpha. or .beta. configuration.The compounds show a pronounced activity on the uterus and the ovary, owing to which they are very suited for initiating the partus or the termination of pregnancy.