Comparison of fetal heart rate parameters depending on gestational age in maternal complications

Abstract

This study was aimed to investigate and analyze the difference in fetal heart rate (FHR) indices depending on gestational age in normal and pathological pregnancies, especially with maternal complications. Non-stress test (NST) data were obtained using a computerized FHR analysis system at Hanyang University Hospital between 2003 and 2010, 236 cases with pregnancy-induced hypertension (PIH), 30 cases of gestational diabetes mellitus (GDM) and 102 cases of maternal anemia (MA) were selected. NST was performed between 28 and 42 weeks of gestation. Including normal group (472 cases), four groups were analyzed by gestational groups; 28-30 weeks, 31-32 weeks, 33-34 weeks, 35-36 weeks, 37-38 weeks, 39-40 weeks and 41-42 weeks. Neonatal outcomes and FHR parameters were analyzed. FHR parameters differed among groups. Fetal movements (FM), amplitude (AMP) and number of accelerations (10bpm-10seconds, Acc1010) were significantly lower in PIH group than normal group (FM; 1.34±1.94 vs 1.79±2.42, AMP; 16.50±5.65 vs 17.87±6.02, Acc1010; 0.89±1.42 vs 1.20±1.89). When FHR indices were compared in each group according to gestational age, the number of accelerations had statistically significant change in PIH and normal group (Acc1010 in both group and only PIH group in 15bpm-15seconds). Regression analysis and Chow test were performed to identify a difference in structural patterns. Mean baseline FHR decreased significantly during overall gestational age in PIH and normal group (P<0.05). Chow test result showed significant difference between regression curves of MA and normal group for AMP (F-value=3.68, P=0.0485). The regression curves of PIH and MA group for Acc1010 also differed significantly with the normal group (PIH vs normal; F-value=4.15, P=0.0477/ MA vs normal; F-value=6.21, P=0.0175). Other parameters and Chow test results did not show statistically significant differences but the regression patterns and correlation coefficients differed among groups by gestational age. To analyze complex factors affecting FHR, this study considered not only the maternal complications but the gestational age. The difference between the estimated regression curves and the correlation coefficient in this study suggested different degree of influence by gestational age in each group. Different pathological conditions might have influenced FHR maturation during the gestational period. The Change of FHR patterns during the gestational age also differed among groups with different maternal complications. The study result suggests the necessity to consider both the gestational age and the maternal complications, when the FHR patterns are to be interpreted.