Alongside the image are messages saying: “You were like this at 11 weeks. All your organs were present. Your heart was already beating from the third week after conception. You were already sucking your thumb. And now you're here because your mother did not abort you.”
The campaign, launched by the pro-life organization ProVita Onlus, comes ahead of the 40th anniversary since abortion was legalized in Italy.
Posters started to appear in the Vatican area towards the end of last year, but the latest is the most explicit.
The move has sparked an outcry among pro-choice groups who have pledged to hold a protest under the poster on Via Gregorio VII and have called on Rome mayor Virginia Raggi to remove it.
Monica Cirinnà, the Democratic Party senator who drafted Italy's civil unions bill, wrote on Twitter: “It's shameful that posters against a State law and the right of women to choose have been allowed to appear on the streets of Rome. Raggi, remove it straightaway.”
ProVita has defended the campaign, saying the “hysterical” reaction is due to consciences having been rattled.
“The truth hurts, which sometimes makes people hysterical,” Enzo Pennetta, the organization's president, said in a statement.
Italy legalized abortion in May 1978 but with over 70 percent of medics across the country being conscientious objectors it is extremely difficult for women, especially those in the south, to access a safe procedure. Meanwhile those who terminate a pregnancy illegally face fines of between €5,000 and €10,000.