[Diurnal rhythm of fetal heart rate in third trimester of pregnancy].

Objective: To investigate the diurnal rhythms of fetal heart rate in third trimester of pregnancy. Methods: From June 2014 and October 2017, 97 cases of low-risk pregnancy women who received antenatal care and deliveried in Peking University Third Hospital were collected. Totally 130 cases of fetal heart rate and maternal holter monitoring data were analyzed. All cases were singleton pregnancy, cephalic position and had normal perinatal outcome. They were divided into three groups based on gestational age, 29 cases (22.3%,29/130) in pregnancy 28-33(+6) weeks, 37 cases (28.5%,37/130) in 34-36(+6) weeks, and 64 cases (49.2%, 64/130) in 37-40(+6) weeks. Fetal heart baseline (FHB) , fetal heart baseline variation (FHBV) , fetal heart rate acceleration area and maternal heart rate were acquired by computer, their diurnal rhythms and the differences among three groups were analyzed. Results: FHB、FHBV、fetal heart rate acceleration area and maternal heart rate all presented diurnal rhythms. (1) FHB rose in daytime and decreased at night with the minimum value at 2:00-5:00, and didn't decline further at night with the advancing of gestational age ( P =0.548). (2) FHBV was similar to FHB, which rose in daytime and decreased at night, but declined smaller at night with the advancing of gestational age, especially after 37 weeks ( P <0.01). (3) Fetal heart rate acceleration area reduced in daytime and enlarged at night, and enlarged more with the advancing of gestational age. (4) The diurnal rhythm of maternal heart rate was consistent with fetal heart rate. FHB lagged behind maternal heart rate for 1-2 hours when declining to the nocturnal nadir but been basically in sync with maternal heart rate when recovered. Conclusion: The basic characteristics of fetal heart rate in normal pregnancy exist obviously diurnal rhythms, and change in different trends with the advancing of gestational age.