Empirical estimation of the normative blood pressure in infants <28 weeks gestation using a massive data approach

To determine the expected systolic, mean and diastolic blood pressures at birth and respective rates of change during the first 72 h of life in infants born at <28 weeks estimated gestational age (EGA) with a favorable short-term outcome, defined as survival to 14 days with grade II or less intraventricular hemorrhage (IVH).

Systolic, mean and diastolic blood pressures were continuously sampled at 0.5 Hz via umbilical artery catheter from birth through 72 h. The raw data were aligned by postnatal hour and underwent error correction. For each infant, the mean values of systolic, mean and diastolic blood pressure were calculated for each postnatal hour. The slope and intercept of best-fit line for each of the three blood pressure parameters was then calculated. Infants that received inotropic medications, died in the first 14 days of life, or had IVH grade III or IV were excluded.

Using 11.9 million valid data points from 35 infants (mean EGA=25.7 ± 1.5 weeks, mean birth weight=865 ± 201 g), we found independent associations of African-American race (P<0.01) and a complete course of antenatal steroids (P<0.01) with higher blood pressures at birth and a slower rate of increase. Acute chorioamnionitis was independently associated (P=0.02) with lower blood pressures at birth and a faster rate of increase. EGA and birth weight were not independently predictive of blood pressure parameters.

We found that (i) the estimated mean blood pressure at birth is ~33 mmHg in a cohort of very preterm infants, (ii) blood pressure gradually increases with postnatal age, (iii) systolic blood pressure increases at a faster rate than diastolic blood pressure, (iv) race, antenatal steroid exposure and chorioamnionitis are independent modulators of blood pressure whereas EGA and birth weight are not.