The replacement of oestradiol and progesterone in very premature infants

The idea of replacing 17 beta -oestradiol (E2) and progesterone (P) in pret erm infants is based on the observation that during pregnancy E2 and P plas ma concentrations rise in the mother and the fetus by a factor of 100. Disr uption of the placental supply of these hormones is a physiological event f or an infant delivered at term. A preterm infant is deprived from this supp ly at an earlier developmental stage. In vitro and ill vivo data are discus sed, and they highlights the potential benefit of E2 and P on the developme nt of different organ systems. The postnatal replacement of E2 and P has th e aim of maintaining in utero plasma concentrations. In the first randomize d clinical study in 30 extremely preterm infants, E2 and P were replaced po stnatally for a total of 6 weeks. With a median intravenous replacement of 8.4 mu mol/kg/day of E2 (4.2-22.9) and 67.4 mu mol/kg/day of P (35.7-87.0), plasma levels of E2 and P were maintained within the intrauterine referenc e values of 7.3-22.0 nmol/L and 0.95-1.9 mu mol/L, respectively. Three- to sixfold higher dosages were needed via the transepidermal route. Trends tow ards an improved postnatal bone mineral accretion and a reduced incidence o f chronic lung disease were found. Further studies are warranted to clarify the potentially important role of E2 and P for the postnatal development o f an extremely preterm infant.