Changes in Vascular Function from Preconception to Postpartum Among Mongolian Women

Abstract

Background: Pregnancy is associated with physiological changes to meet the metabolic demands of the growing fetus. To understand adverse pregnancy outcomes it is important to establish vascular changes throughout pregnancy. We examined longitudinal changes in vascular measurements from prepregnancy through postpartum. Materials and Methods: Seventy women planning to conceive in Ulaanbaatar, Mongolia enrolled in this prospective study. Within 6 months, 44 (63%) had conceived; of which 36 (82%) delivered. Ten (28%) developed complex pregnancies and were analyzed separately. Vascular measures included central systolic blood pressure (cSBP), central diastolic blood pressure (cDBP), augmentation index corrected for heart rate of 75 beats/minute (AIx-75), and pulse wave velocity (PWV). Measurements were performed at prepregnancy, second trimester (22-24 weeks), third trimester (34-36 weeks), and 2 months postpartum. Missing values (n = 0-6 per time period) were replaced by multiple imputation. A repeated measures analysis of variance analyzed changes within individual women over the four time points adjusted for age, parity, and body mass index. Results: We observed significant reductions from prepregnancy to second trimester for mean Alx-75 (17.1%-12.6%; p = 0.006) and cSBP (91.7-86.8 mmHg; p = 0.03) but not for cDBP or PWV. Both mean AIx-75 and cSBP increased in third trimester. In the postpartum, cSBP returned to prepregnancy levels, whereas AIx-75 exceeded prepregnancy levels, although this fell short of significance (p = 0.09). Similar vascular patterns were observed in women with complex pregnancies for AIx-75; however, PWV increased from the second trimester and remained higher through postpartum, although not significant. Conclusion: In Mongolian women, we observed a decrease in AIx-75 and cSBP from prepregnancy through second trimester, which resolved postpartum. These results provide an understanding of changes across pregnancies in an Asian country. Future studies should assess vascular changes across pregnancies to determine if it can predict conditions such as pre-eclampsia.

Keywords: Mongolia; pregnancy; prepregnancy; vascular health.

FIG. 1.

Participant flowchart. Participants in the gray shaded boxes are included in the current analysis.

FIG. 2.

Vascular changes from prepregnancy to postpartum. Each data point is predicted from a linear mixed model at for parous women at mean BMI (22 kg/m²). (A) cSBP; (B) cDBP; (C) AIx-75%; (D) PWV. ^aValue is from a linear mixed model adjusting for age, parity, and BMI comparing the second trimester mean cSBP (A), cDBP (B), AIx-75 (C), and PWV (D) to the prepregnancy mean cSBP (A), cDBP (B), AIx-75 (C), and PWV (D). ^bp-Value is from a linear mixed model adjusting for age, parity, and BMI comparing the postpartum mean cSBP (A), cDBP (B), AIx-75 (C), and PWV (D) to the prepregnancy mean cSBP (A), cDBP (B), AIx-75 (C), and PWV (D). ^cGlobal test p-value from a linear mixed model adjusting for age, parity, and BMI testing whether the means of cSBP (A), cDBP (B), AIx-75 (C), and PWV (D) are different for at least one time point. Each data point is predicted from a linear mixed model at for parous women at mean BMI (22 kg/m²). AIx-75, augmentation index adjusted to a heart rate of 75 beats per minute; BMI, body mass index; cDBP, central diastolic blood pressure; cSBP, central systolic blood pressure; PWV, pulse wave velocity.

FIG. 3.

Vascular changes from pre-pregnancy to postpartum by pregnancy complications. (A) AIx-75; (B) pulse wave velocity.

FIG. 4.

Linear regression between age and vascular change during pre-pregnancy, pregnancy, and postpartum in noncomplex pregnancies. (A) cSBP; (B) cDBP; (C) AIx-75; (D) PWV. se, standard error.