Preconception blood pressure and risk of preterm birth: a large historical cohort study in a Chinese rural population.
OBJECTIVE
To examine the relationship between preconception blood pressure (BP) and the risk of preterm birth (PTB) using a historical cohort of reproductive-aged women and girls from a Chinese rural population.


METHODS
A historical cohort study established between 2010 and 2013 in People's Republic of China.


METHODS
Local family-planning service agencies and maternal-child care service centers.


METHODS
A total of 367,425 reproductive-aged women and girls who participated in the National Free Pre-pregnancy Checkups in 2010-2012 and subsequently had a live birth before October 2013.


METHODS
None.


METHODS
Incidence rates of PTB in reproductive-aged women and girls across preconception BP levels.


RESULTS
Preterm births were defined as babies born alive at 28 to 37 weeks of pregnancy. Compared with the participants with a systolic BP of <120 mm Hg, the multivariable-adjusted odds ratio (OR) for PTB was 0.99 (95% confidence interval [CI]: 0.95-1.03]), 1.21 (95% CI: 1.11-1.32), 1.47 (95% CI: 1.22-1.77), 1.80 (95% CI: 1.25-2.59), and 1.81 (95% CI: 1.20-2.73) for the participants with systolic BP of 120-129, 130-139, 140-149, 150-159, and ≥160 mm Hg, respectively. When the participants with normal BP were used as the reference, the adjusted OR for PTB was 1.04 (95% CI: 1.01-1.08), 1.38 (95% CI: 1.25-1.53), and 1.54 (95% CI: 1.21-1.97) for the participants with prehypertension, stage-1 hypertension, and stage-2 hypertension, respectively. In addition, isolated systolic and diastolic hypertension increased the risk of PTB by 55% and 30%, respectively.


CONCLUSIONS
Our results indicated a strong linear and independent relationship between BP levels and the risk of PTB in Chinese reproductive-aged women and girls. Maternal hypertension before pregnancy can significantly increase the risk of PTB.
National Research Institute for Family Planning, Beijing, People's Republic of China.
Ying
Y
Yang
National Research Institute for Family Planning, Beijing, People's Republic of China.
Yuan
Y
He
National Research Institute for Family Planning, Beijing, People's Republic of China; Graduate School of Peking Union Medical College, Beijing, People's Republic of China.
Qian
Q
Li
National Research Institute for Family Planning, Beijing, People's Republic of China.
Yuanyuan
Y
Wang
National Research Institute for Family Planning, Beijing, People's Republic of China.
Zuoqi
Z
Peng
National Research Institute for Family Planning, Beijing, People's Republic of China.
Jihong
J
Xu
National Research Institute for Family Planning, Beijing, People's Republic of China; Graduate School of Peking Union Medical College, Beijing, People's Republic of China. Electronic address: maxutougao@163.com.
Xu
X
Ma
D000293:Adolescent; D000328:Adult; D044466:Asian People; D001794:Blood Pressure; D002681:China / Q000453:epidemiology; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006973:Hypertension / Q000175:diagnosis* / Q000453:epidemiology*; D007231:Infant, Newborn; D008875:Middle Aged; D016742:Preconception Care / Q000639:trends*; D011247:Pregnancy; D047928:Premature Birth / Q000175:diagnosis* / Q000453:epidemiology*; D012307:Risk Factors; D012424:Rural Population / Q000639:trends*; D055815:Young Adult
Preterm birth; blood pressure; cohort study; pre-pregnancy