[Considerations and observations on management of premature labor]

As the structural conditions of an obstetric ward obviously influence the mortality rates of premature infants, the actual obstetric management of premature births was to be studied more thoroughly in relation to the size of the clinics in a given area of North Rhine-Westphalia.

The data records of about 142 clinics, which included 622,778 births in the years 1990-1996, were available (Perinatal Investigation Eastern Westphalia-Lippe). Each file comprised the performance data of an individual clinic (anonymous) per year. In total, the yearly records of 1,003 clinics were known: 2 wards registered no premature births in 1 calendar year. The following variables (each per clinic per year) were used: number of newborns, number of infants who died perinatally, number of neonates who died on the 1st to 7th day after birth, number of premature infants < or = 32nd week of gestation and number of premature infants born between the 33rd and 37th weeks of gestation. A second, analogous database registered, in identical order, only those newborns who had been delivered by Caesarean section. As both databases were directly accessible by computer, the percentages of vaginally delivered premature infants could be calculated for each clinic (per year). Non-parameteic tests were used for the statistical analysis. The easily comprehensible graphic presentation of all data by correlation diagrams was considered particularly important:

The percentages of premature births are not randomly distributed in the 1,001 clinics of Westphalia-Lippe; the median is 12.9, the 10th percentile 9.4 and the 90th percentile 18.5% (mean: 13.6 +/- 4.7%). With increasing numbers of births this rate increases (non-linearly) as well (p << 0.001) but without any general 'centralization.' The same applies to premature births < or = 32nd week of gestation. The proportion of Caesarean sections due to prematurity (< or = 37th week of gestation) is about 34% in Westphalia-Lippe; immature preterm infants (< or = 32nd week of gestation) are delivered by Caesarean section in approximately 60% (median). The lower the percentage of premature infants per clinic, the higher is (surprisingly) the rate of vaginally delivered premature babies (p << 0.001). The same applies to very immature preterm infants. The lower the number of births in a clinic (its 'size'), the higher the percentage of immature preterm infants (< or = 32nd week of gestation) delivered vaginally (p << 0.001). As for premature births in general (< or = 37th week of gestation): the higher the percentage of vaginally delivered premature infants per clinic, the lower the mortality rate between the 1st and 7th days of life. However, immature preterm infants (, or = 32nd week of gestation) show no significant correlation between way of delivery and mortality rate from the 1st to the 7th day of life.

To date, an effective centralization of premature births has not been carried out in the area of Eastern Westphalia-Lippe which comprises half North Rhine-Westphalia: small and very small wards have approximately 12% of premature births. These wards obviously prefer vaginal delivery even in cases of very immature preterm infants, which has a rather favourable effect on mortality rates. Immaturity as the sole indication for Caesarean section has to be reconsidered.