Why is ‘Saheli’ considered an effective- contraceptive for women

Why is ‘Saheli’ considered an effective- contraceptive for women to space children?

‘Saheli’ is considered to be an effective and improved form of contraceptive for women due to following reasons:
(i) It is a non-steroidal preparation.
(ii) It is ‘once a week’ pill.
(iii) It has high contraceptive value.
(iv) It has little side effects.