Natural intercourse means a conjugal act which is suitable in itself for the procreation of offspring.  Though all contraceptive measures, including chemical and physical barriers, are intrinsically evil, the use of condoms or vaginal sheaths and coitus interruptus also prevent consummation. Other methods of artificial birth control/contraception do not prevent consummation because consummation is, in essence, the conjugal act with the deposit of the semen in the vagina. See canon 1061. (For Basic Course lesson 14. For Advanced Course lesson 24. Added 2019.)