Speaking in a statement ahead of the anniversary, the bishops said: "In this jubilee year of Poland's baptism, we urge all people of goodwill, believers and nonbelievers, to take action to ensure full legal protection of unborn lives."
Abortion is currently illegal in Poland in most cases but there are exceptions if the pregnancy poses a threat to the woman's life, if it results from a crime like incest or rape or if the foetus is damaged.
Protesters say that a total ban would lead to women dying and it would force people to travel to other countries for abortions.
Around 90% of Poles identify as Catholic. In 2015 the ruling Law and Justice party won both presidential and parliamentary elections, partly thanks to support from the Church.
Earlier in April, the Prime Minister Beata Szydlo (pictured) suggested she was in favour of a Catholic Church proposal to outlaw terminations.
She stood for election on a platform to "restore Catholic values" to the nation her party is not currently preparing legislation on abortion.
At the beginning of April bishops' read out the call against abortion in churches and people walked out of churches, protests were held and participants carried coat hangers as symbols of illegal, life-threatening abortions.
The anniversary of Catholicism will be celebrated this week with prayers at the 10th century Gothic Cathedral of Gniezno and a parliament session.
Ceremonies planned by the Church alongside the government will also emphasise Poland's Catholic identity and later in July Pope Francis will visit the country for World Youth Day celebrations.
