Antenatal care received and its association with preterm birth in Greece.

A total population sample of singleton births to mothers with certain dates of last menstrual period (LMP) was identified from the Greek National Perinatal Survey of April 1983. Two groups of mothers were considered separately, 3116 primigravidae and 6524 multigravidae, with preterm birth rates of 5.9% and 8.4% respectively. Of all the antenatal care factors tested, primigravidae showed significant associations (unadjusted) with haematocrit level and with drugs taken during pregnancy. The logistic regression analysis which followed showed that the only factor independently associated with preterm delivery for that group of mothers was drugs taken during this period: women taking no drugs (including vitamins and iron) had the highest risk of preterm delivery. In contrast, multigravidae showed significant unadjusted associations with a great variety of parameters of antenatal care. Nevertheless, in the logistic regression analysis only three proved to have independent significant associations: drugs taken during pregnancy (reduced risk among mothers taking vitamins and iron), hospital admission during pregnancy (mainly for cervical cerclage) and the pattern of antenatal care during the first two trimesters (those attending the recommended number of times having least risk).