ABSTRACT
OBJECTIVES: Maternal anemia is common hematologic disorders during pregnancy. Although mild maternal anemia is not associated with fetal anemia, neonatal morbidity including fetal anemia are common with severe maternal anemia during pregnancies. We aim to analyze each variable of FHR using linear and nonlinear methods to detect maternal anemia during pregnancies. METHODS: Seventy antepartal anemic pregnant women(Hb<10.0g/dL) and the contrast group, 70 normal pregnant women were selected among the women who underwent nonstress test(NST) during 3rd trimester in Hanyang University Hospital. The calculated FHR parameters(NST time=20 min) from collected FHR data(40-50min) were made by HYFM II data file. To assess the difference between the anemic and normal pregnancy group, the parameters such as baseline FHR, variability (AMP, MMR), acceleration and deceleration(15bpm-15seconds), gestational age at the time of NST, loss of record, the number of fetal movement, FHR were evaluated. We compared the canonical correlation between each groups using variables of NST. The overall complexity of each FHR time series was quantified by its approximate entropy(ApEn), measure of regularity derived from nonlinear dynamics, "chaos theory". Finally we extract the value of ApEn and were compared between two groups, normal and anemic pregnant women. RESULTS: There were significant decrease of FHR variability(amplitude and mean minute interval) in anemic group. Canonical correlation ensemble was significantly high in 36th-37th and 38th-39th gestational weeks in anemic group(p-value=0.03048 and 0.03421). The value of ApEn was significantly low(0.68+0.26) in anemic group comparing with normal pregnant group(0.95+0.08), respectively. CONCLUSIONS: This study shows that FHR of maternal anemia is different from that of normal pregnant women, and that subtle behavioral differences could be demonstrated in uterus using computerized FHR analysis. The anemic women during pregnancy have more linear and less complicated FHR than the normal pregnancy group. ApEn, which is bound to be used as an index of fetal well-being would be used as an evaluating tool of intrauterine fetal function in the near future.