Section 4E. No subscription certificate under an individual or group medical service agreement which shall be delivered or issued or renewed in the commonwealth shall be denied or cancelled or fail to be renewed, nor shall any excessive rates be charged or restrictions on the length of coverage be imposed, nor shall any other factor be altered in such a way as to constitute discrimination primarily because the insured person has had a suspected, alleged or confirmed exposure to the potential hazards and afflictions of diethylstilbestrol or compounds commonly referred to as DES. The practices prohibited under this section shall include not only those overtly discriminatory but also practices and devices which are fair in form but discriminatory in practice.