[Reference values range of the fetal oxygen saturation and its dispersal during labor without cardiotocographic evidence for fetal distress]

Abstract

The objective of this study is to establish the reference values range of the fetal oxygen saturation during the first and the second period of labor and their dispersal according to the extent of cervical dillatation in cases with normal FHR--absence of fetal hypoxia and asphyxia of the newborn.

Material and methods: This is a prospective study which involves 94 women with normal FHR. All of the newborns are with umbilical artery pH values greater than 7.15 and 5 min Apgar score greater than 7; there was no necessity for any reanimation procedures, assisted ventilation or intensive care treatment. The fetal oxygen saturation (SpO2) is monitored by fetal pulseoxymeter Nellcor N 400, fetal sensors FS - 14. Cardiotocographic monitoring is carried out simultaneously. Blood is obtained from the fetal scalp during labor for blood gas and pH analysis, and umbilical artery pH as well as the Apgar score of the newborn are determined.

Results: The average monitoring time during the first period of labor is 107.19+/-29.49 min. with reliability of the recordings 86.54+/-6.10%. The average monitoring time for the second period of labor is 36.72+/-8.31 min. with reliability of the recordings 75.42 +/-9.61%. The mean SpO2 values are 48.71+/-5.52% during the first period and 47.30+/-4.62% during the second period of labor. The reference SpO2 values ranging between the 25-th and 75-th percentile in fetuses with normal FHR are 46-52 % for the first and 44-50 % for the second period. The results for fetal SpO2 during the different stages of cervical dillatation are as follows: for 4-5 cm - 49.49+/-5.12%, for 6-7 cm - 48.76+/-5.42%, for 8-9 cm - 48.39+/-5.49%.

Conclusions: The fetal SpO2 dispersal during cervical dillatation of 4-5, 6-7 and 8-9cm accordingly demonstrates a nonsignificant decrease of SpO2 for the different groups (p>0.05). The fetal SpO2 dispersal between the first and the second period of labor also demonstrates decrease of SpO2 values and shows a minor statistically significant difference (p < 0.05 - Repeated measures ANOVA), which is considered to be within the normal range and does not reflect on the newborn's well-being.