Background: the age at formation of circadian rhythm of BP is not known in man

Subjects: 13 healthy PI (27+3 to 33+0 weeks of gestation, birth weight 690 to 1910 g. age at study 6 to 79 days, weight at study 1200 to 3670g)

Intervention: 19 BP profiles for 24 hrs by oscillometrical recordings every 15 min

Results: Mean arterial BP was 48 (38-68) mmHg. The ABPM-FIT program found significant BP and HR rhythms with periods length of 4.24 hrs Times at peaks and troughs showed great intra- and interindividual differences and were not influenced by activity or post partal age. The reproducebility of rhythms were low.

Conclusion: a rhythmic pattern was present in BP and HR in PI from the first week of life However, rhythms were not yet synchronized by light-dark cycle.