Visit-to-visit blood pressure variability and risk of adverse birth outcomes in pregnancies in East China

To investigate the potential associations between visit-to-visit blood pressure variability (VVV) and adverse birth outcomes in pregnancies, 48,209 pregnant women without proteinuria or chronic hypertension before 20 weeks of gestation who delivered live singletons between January 2014 and November 2019 in Taizhou or Taicang cities were recruited. VVV was estimated as the standard deviation and coefficient of variation of blood pressure [i.e., systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP)] measured from 20 weeks of gestation onwards. Pregnant women were classified into four groups according to the corresponding quartiles for each VVV index. It was found that VVV was significantly higher in women with small for gestational age (SGA) or low birth weight (LBW) infants than in their counterparts. Graded associations between VVV categories and poor birth outcomes were observed. In particular, when comparing the women with the highest to the lowest quartiles of standard deviation and coefficient variation of DBP, the odds ratios (95% confidence interval) for SGA was 1.15 (1.06-1.26) and 1.14 (1.05-1.25), respectively. Interestingly, the addition of DBP-VVV to established risk factors improved risk prediction of SGA; DBP-VVV demonstrated modestly superior predictive performance to VVV obtained from SBP or MAP. Similar results were found even among normotensive pregnancies. Our findings indicated that VVV during pregnancy, especially DBP-VVV, was independently associated with poor birth outcomes of pregnancies in East China. The inclusion of DBP-VVV with established risk factors may help in identifying pregnancies at high risk of SGA. Validations are needed.