Story highlights The new law is meant to help fix a shortage in organ donations in the Netherlands

"Presumed consent" is also the official policy in countries such as Spain and Belgium

(CNN) A new law would make all adults in the Netherlands organ donors -- unless they opt out of the system.

The law was narrowly approved by the Dutch Senate on Tuesday in a 38-36 vote. It passed the lower house of Parliament in 2016 by a slim 75-74 margin.

The law is expected to be implemented in 2020 after approval from King Willem-Alexander.

The new policy is meant to help fix a shortage in organ donations in the Netherlands, according to its drafter, Pia Dijkstra, a member of the House of Representatives.

Every person over 18 who is not registered will receive a letter asking whether they wish to donate their organs. Failure to respond to this letter -- or another six weeks later -- will result in that person being considered a donor by default.