FIGO criteria for CTG analysis and fetal scalp blood sampling in subpartal monitoring

Aim: Evaluation of the correlation between a computerized analysis of the FIGO criteria for CTG analysis with fetal scalp blood pH analysis (FSB-pH).

Rationale: Studies have shown that monitoring of the fetus could be more reliable in combination with fetal scalp blood sampling. Many obstetricians, however, still feel insecure in deciding when to do a FSB. A monitoring system analyzing CTGs according to the FIGO criteria may help to ease this decision.

Methods: All deliveries between 2000–2002 which have at least one pH value collected by fetal scalp blood sampling and a corresponding CTG recording have been selected. Up to 5 fetal FSB-pH values were determined during each delivery. Overall 375 samples from 242 patients were evaluable. A 30-min period of all CTGs recorded prior to the FSB-pH was retrospectively analysed by Trium CTG Online. The calculated FIGO criteria were correlated with the corresponding categorized FSB-pH. Furthermore, short time variation (STV) was correlated with each FSB-pH.

Results: Computer-analysed overall FIGO criteria do correlate with fetal pH values (p=0,01). Out of 10 pH values ≤7,20 6 are recognized as pathological and 3 as suspicious. 29 pH Values between 7,21–7,24 are rated 16 times as ominous, 8 times as suspicious and 5 times as normal. But also only 107 out of 336 samples ≥7,25 were considered to be normal (32%), 135 suspicious and 94 pathological. No correlation was found between STV and fetal pH value (ρ=0,07).