Graphic protesters of an aborted 10-week-old foetus were used
Protesters on both sides of the abortion referendum faced off outside the Dáil earlier.
Pro-choice campaigners tried to block graphic posters from view.
One of the protests said a rosary for Ireland, chanting: "Jesus, protect and save the unborn".
Graphic abortion protesters of a 10-week-old aborted foetus were raised.
Protesters trying to block the graphic abortion posters outside the Dáil. In response they raised them higher. One of a number of protests today pic.twitter.com/T6dHU4aYYn— Sean Defoe (@SeanDefoe) May 4, 2018
Dr Jean Engela, from the Irish Centre for Bio-Ethical Reform (ICBR), defended them
"It's accurate, it's scientifically correct, it's a medical depiction of a clinical procedure.
"It has to form an essential part of any reasoned, informed discussion on abortion - otherwise it's censorship".
However protesters said it was shameful they had been put outside maternity hospitals this week.
"Women were walking in and out of that hospital.
"They could have been raped, they could have been miscarrying, they could have just received their diagnosis of fatal foetal abnormalities.
"These people don't know or care about the real-life experiences of women".
On Monday, the Rotunda Hospital warned that the posters had caused "a lot of upset and distress for patients, many of whom attend the hospital for a number of different reasons and not just for the happy occasion of giving birth to a new baby."
After the posters were re-erected on Thursday night, a group calling themselves "Radical Queers Resist" decided to take action.
They said the images, which show foetuses at various stages of development, are distressing to women - and covered them up with LGBT Pride flags.
We won’t back down until they do. Images are being blocked, pride flags are on their way. Stay safe everyone, avoid this area if you need to! - N pic.twitter.com/IPMGZfo6e8— Radical Queers Resist (@RadQueersResist) May 3, 2018
This woman was among those who tried to cover up the posters last night - and said they will do it again if necessary:
"We just decided that we weren't content for this to go on, on our streets; for them to have these images which are harmful and distressing outside maternity hospitals," she said.
"Women going in might be getting diagnoses of fatal foetal abnormalities, they might be going through miscarriages, they might be going through unwanted pregnancies or through wanted pregnancies.
“It is all quite distressing to see these images when you are going through things."
The LoveBoth campaign handed in a letter to Health Minister Simon Harris, formally challenging him to a debate.
Cora Sherlock from LoveBoth said the graphic ICBR posters were not needed.
"We're very clear about the ICBR - we're not affiliated with them at all - our line has been consistent.
"We don't condone the indiscriminate showing of graphic imagery, and that will be our position going forward in this campaign".
More launches are expected over the weekend, with just three weeks left to polling day.
Additional reporting: Michael Staines and Jack Quann