To explore the causes of heart rate variability (HRV) in elderly pregnant women and its influence on their perinatal outcomes.

From June 2020 to May 2022, a total of 70 elderly pregnant women and 70 non-elderly pregnant women in the same period who visited Shanghai First Maternity and Infant Hospital were selected in this study, and were respectively enrolled in study group and control group. Statistical methods such as independent samples t-test and chi-square test were used to statistically analyze the following indicators of pregnant women between two groups: HRV, HRV analysis metrics [standard deviation of normal-to-normal intervals (SDNN), five-minute R-R interval means (SDANN), root mean square of successive difference (RMSSD), percentage of normal to normal intervals differing by more than 50 ms (PNN50)], echocardiography indicators [left atrium end-systolic diameter (LAD), left ventricular end-diastolic diameter (LVDD), inter-ventricular septal thickness (IVST), left ventricular posterior wall thickness (LVPWT), right ventricular end-diastolic diameter (RVDD), left ventricular ejection fraction (LVEF), early mitral inflow velocity (E), late mitral inflow velocity (A), diastolic velocity during early diastolic filling (Em), late diastolic velocity during atrial contraction (Am)], adverse pregnancy outcomes (miscarriage, stillbirth, preterm labor, cesarean section delivery and postpartum hemorrhage, etc.), neonatal abnormalities (neonatal asphyxia, low birth weight, etc.). This study received ethics approval from the Ethics Committee of Shanghai First Maternity and Infant Hospital (20200305). Written informed consent was obtained from all the participants.

①There were no significant differences in gestational age, pre-pregnancy body mass index (BMI) and parity between two groups (P>0.05), but there was significant difference in gestational age between two groups (P<0.05). ②The SDNN [(103.7±10.4) ms], SDANN [(110.6±10.6) ms], RMSSD [(24.7±5.4) ms], PNN50 [(15.5±3.3)%], and delta index (35.6±6.8) of pregnant women in control group were higher than those of study group (93.6±9.5) ms, (99.7±9.7) ms, (19.7±3.6) ms, (11.7±3.1)%, and 27.7±6.5, and the differences were statistically (t=6.02, 6.35, 6.48, 7.08, 7.03; P<0.05). In addition, the HRV of pregnant women in study group (17.8%, 16/70) was higher than that of control group (5.6%, 5/70) and the difference was statistically significant (χ²=6.52, P=0.011). ③ The LAD [(33.6±2.2) mm], LVDD [(47.8±2.4) mm], A [(84.0±8.0) cm/s], and Am [(11.7±3.1) cm/s] in study group were greater than those of control group (31.7±2.6) mm, (45.4±2.6) mm, (62.7±6.4) cm/s, (9.6±2.7) cm/s, and the differences were statistically significant (t=4.66, 5.38, 17.38, 4.26, all P<0.0, 01), and there were no statistically significant differences when comparing the IVST, LVPWT, RVDD, and LVEF between two groups (P>0.05). ④Pearson correlation analysis showed that SDNN, STANN, RMSSD, PNN50 and triangle index were negatively correlated with LAD, LVDD, A and Am, respectively (P<0.05), and positively correlated with E and Em, respectively (P<0.05). ⑤ The incidence of adverse pregnancy outcomes (61.4%, 43/70)]and neonatal abnormality (22.9%, 16/70) in study group were higher than those in control group (22.9%, 16/70) and (4.3%, 3/70), and the differences between two groups were statistically significant (χ²=30.51, 10.29, all P<0.001).

Elder pregnant women have significantly reduced HRV, mainly because of left ventricular diastolic dysfunction, resulting in reduced cardiac reserve function. Lower HRV will increase the risk of adverse pregnancy outcomes and adverse neonatal outcomes.