A new report reveals that 51 births in two hospitals in Ireland over an 18-month period were "concealed".
The study, based on research on births at a maternity hospital in Dublin and a general hospital in the west between July 2003 and December 2004, noted there were also women who hid pregnancy entirely and never presented to hospital.
Concealment of pregnancy was defined as where a woman presented for antenatal care after 20 weeks of pregnancy without disclosing the pregnancy to her social network.
UCD-based researcher Catherine Conlon found the average age of the 51 women who had concealed pregnancies was 21 years. All but four were single and almost half were not in a relationship with the child's father.
The report, entitled Concealed Pregnancy: A case-study approach from an Irish setting, was commissioned by the Crisis Pregnancy Agency and the HSE West and published in Athlone.
The report refers to the case of Ann Lovett, the 15-year-old Co Longford schoolgirl who was found dead after giving birth in a churchyard in Granard in 1984 after concealing her pregnancy.
"The abhorrence expressed at the plight of the young girl generated a pervasive sense that it should never happen again," it said.
"However, there continue to be reports in the media of bodies of newborn infants found or newborn infants anonymously left in public places," it added.
There were 24 such reports in one national newspaper between 1996 and 2005, it added.
Some 13 of the women gave in-depth interviews as part of the research. To protect their identities the names of the two hospitals studied were not given.
In the rural hospital the prevalence of concealed pregnancy was found to be one in every 403 births while in the city hospital it was one in every 625 births.
This compared to a rate of one in every 475 births in a study conducted in Germany in 2003.
The fact that more were concealed in the rural Irish hospital "would suggest that concealment of pregnancy is a more rural than urban phenomenon", the report said.
But it added that concealment was not unique to the Republic "but rather remains a feature of contemporary western societies".
In eight of the 51 cases the women presented for the first time when they were in labour. Forty-five were Irish, nine were "in denial to themselves" that they were pregnant, 31 presented late because they were concealing the pregnancy from others and 11 presented late because they were not aware they were pregnant.
The report says they tried to conceal their pregnancies by wearing tight clothing, dieting, burying themselves in their work and continuing to go out drinking at weekends.
Over half of the group said they concealed their pregnancy for fear of upsetting their parents.
Of the total number, some 17 were students and 27 were living with parents.