Dose-response relationship between maternal blood pressure in pregnancy
and preterm birth: based on the monitoring data of 212,941 pregnant
women in China
Abstract
Objectives: To analyze the dose-response relationship between maternal
Blood pressure (BP) in different trimesters and preterm birth(PTB).
Design: A monitoring data (cohort) study. Setting and population: All
single-fetus pregnant women who delivered during 2014-2018 in 13
counties of 6 provinces in China. Methods: Through the Maternal and
Newborn Health Monitoring System in China, the monitoring data were
obtained, including essential maternal information, all previous
antenatal examination and pregnancy outcomes of all pregnant women lived
in the monitoring area. Main outcome measures: PTB(delivered between 28
and 37 weeks); Hypertensive disorders of pregnancy(HDP)(SBP ≥140mmHg
and/or DBP ≥90mmHg once); Hypotension (SBP<90mmHg and/or
DBP<60mmHg once). Results: A total of 212,941 single-fetus
pregnant women were included. The overall incidences of HDP and PTB were
7.07% and 4.04% respectively. Taking the group of normal BP as
reference, the odds ratios(OR) of PTB for the groups of HDP in 1st, 2nd
and 3rd trimesters was 3.23, 2.70 and 2.05
respectively(P<0.001). Hypotension in 3rd trimester was
associated with a 1.5-fold higher risk of PTB(P<0.001). ORs of
PTB had a nonlinearly U-shaped association with SBP and DBP in 1st, 2nd
and 3rd trimesters. Conclusions: The risks of PTB varied among pregnant
women with the same BP in different trimesters. An increase of BP within
the normal range during pregnancy could prevent PTB. Hypotension in 3rd
trimester was associated with a high risk of PTB. Funding: Funded by the
government of China (No.1311300011301). Key words: Maternal blood
pressure, preterm birth, dose-response relationship, restricted cubic
spline, hypertensive disorders of pregnancy, hypotension