Preconception blood pressure and time to pregnancy among couples attempting to conceive their first pregnancy.

Abstract

BACKGROUND\nThe association of abnormal blood pressure levels (including hypertension and prehypertension) with reduced fecundability among young childbearing-age couples is not yet completely elucidated.\n\n\nOBJECTIVE\nTo investigate the association between abnormal preconception blood pressure level and time to pregnancy among couples attempting to conceive their first pregnancy.\n\n\nSTUDY DESIGN\nA total of 2,234,350 eligible couples (with no prior gravidity and whose female partners were aged between 20 and 49 years) participated in the National Free Pre-conception Check-up Projects from January 1, 2015 to December 31, 2016. Couples preconception blood pressure levels were measured, and time to pregnancy was recorded. Cox models for discrete survival time were used to estimate fecundability odds ratios and their corresponding 95% confidence intervals after adjusting for age, ethnicity, educational level, occupation, household registration, region, tobacco exposure, alcohol intake, body mass index, and duration of marriage of the couples, and fasting plasma glucose levels of the female partner.\n\n\nRESULTS\nCompared with normotensive females, those with hypertension (systolic blood pressure≥140 mmHg or diastolic blood pressure≥90 mmHg) had a 21% lower pregnancy rate (fecundability odds ratio = 0.79, 95% confidence interval: 0.78-0.81). A similar finding was found among males (fecundability odds ratio = 0.89, 95% confidence interval: 0.88-0.90). Prehypertension (120 mmHg ≤ systolic blood pressure<140 mmHg or 80 mmHg ≤ diastolic blood pressure<90 mmHg) in both male and female partners was slightly associated with reduced fecundability odds ratios. Compared with couples in which both partners were normotensive, the pregnancy rate was reduced by 27% (fecundability odds ratio = 0.73, 95% confidence interval: 0.69-0.77) among couples in which both partners had hypertension.\n\n\nCONCLUSION\nAbnormal preconception blood pressure levels were associated with prolonged time to pregnancy among couples attempting to conceive their first pregnancy, and the mechanism is worth further investigation.