Methods: We used repeated antenatal blood pressure
measurements [median (interquartile range) 10 (9–11) per
woman] for 10 327 women. Multilevel models were used
to derive longitudinal reference ranges for SBP and DBP
from 12 to 40 weeks gestation for the whole cohort, for
women with normal pregnancies (without essential
hypertension or preeclampsia who delivered an
appropriate-size-for-gestational age infant at term)
and for subgroups of normal pregnancies defined by
different levels of maternal prepregnancy BMI, smoking
and parity.