The objective of this article is to describe the conditions under which very premature babies were born in the Paris region between June 1 and December 31, 1998, that is to say those born prior to reaching 33 weeks of term (SA) and/or having a birth weight less than 1500 grams. The study looked at all pre-term births, including medical terminations of pregnancy (TOP), occurring in one of the 135 maternity units in the Paris region. Between June 1 and December 31, 1998, 1337 mothers gave birth to babies prior to reaching 33 weeks of term (SA) and/or having a birth weight less than 1500 grams in 84 maternity units in the Paris region, 263 of which had a medical termination of pregnancy (20%). These mothers were older than average for the region (25% were 35 years old or older); 4.3% of them do not have social insurance coverage. The remaining 1074 mothers (excluding TOP) gave birth to 1290 children, of which 202 were stillbirths, 46 died in the labor ward and 1042 were admitted to a neo-natal unit. Of the same group of 1074 mothers, 195 (18%) had a multiple pregnancy--175 twins, 19 triplets, and 1 quadruplet 60% of them (599 women) who had very premature or low birth weight babies (excluding TOPs) delivered them in a tertiary perinatal centre (TPC). This proportion varies according to two variables: 1) the community in which the family lives (40% in the Seine-et-Marne department, the eastern region of Paris and a district without TPCs, to 70% in the Hauts-de-Seine, a northern district), and 2) whether the pregnancy is single (58.8%), twin (72.6%) or triple (84.2%). In utero transfer accounts for 62.7% of the mothers who delivered in TPC, who were transferred prior to delivery. This type of study is useful for measuring the implementation of the regionalisation high-risk perinatal care and access to adequate services. It clearly demonstrates that inequities in access to care exist for women by district of residence.