Effectiveness of fetal scalp blood sampling for the prevention of cesarean section in case of suspected fetal distress during labor (SCALP-trial); a randomized controlled multicenter study

Continuous cardiotocography (CTG) is used in the majority of pregnancies to
monitor fetal wellbeing. The method is associated with an increase in cesarean
sections (CS) without an improvement in long-term perinatal outcome(1). CS is
associated with a 4 fold higher risk of maternal mortality and severe morbidity
compared to a vaginal birth. Moreover a CS in the previous pregnancy carries a
risk of serious complications in the subsequent pregnancy.

In order to avoid unnecessary operative delivery in case of suspected fetal
distress, fetal blood sampling (FBS) can be used as an adjunctive test to CTG.
It is a procedure whereby a small amount of blood is taken from the fetal
scalp, to measure acid-base balance (pH, base deficit). FBS has been introduced
in the 1960's in an effort to identify those babies who are truly compromised
and need to be born immediately and to differentiate them from those who are
not truly compromised. There is limited evidence to support this assumption. In
a meta analysis of randomized comparisons between CTG and intermittend
auscultation during labor, it was shown that CTG increases the CS rate (OR
1.96, 95% CI 1.24-3.09). If FBS was applied to CTG this rise in CS appeared to
be less profound (OR 1.50, 95% CI 1.10-2.06).

CTG abnormalities occur rather frequently with an incidence of 30% during the
first stage of labor rising up to 90% during the second stage. The use of FBS
in the Netherlands varies widely across hospitals. A national survey (2008)
showed that all of the larger (teaching) hospitals use FBS, in approximately
14% of deliveries, whereas the non-teaching hospitals use FBS in only 3% of
deliveries.

FBS has been abandoned in the USA. This change in practice was claimed not to
be accompanied by an increase in CS rate for suspected fetal distress or in
indicators of perinatal asphyxia. However, in the USA FBS was already used
rather infrequently (0,5% to 2%), and the CS rate was and is quite high.
European guidelines do recommend the use of FBS, assuming it to prevent
unnecessary operative delivery despite the fact that its effectiveness is
unproven.

FBS is an invasive and cumbersome procedure with high failure rates (up to
20%). Moreover the FBS result only represents a moment in time and the test
often has to be repeated. Lactate analysis in FBS, instead of pH largely
overcomes these problems, but this has not translated into differences in mode
of birth or neonatal outcome. Complications caused by FBS occur with an
incidence of 0.4 -6%. The majority of these complications consists of fetal
bleeding and infection and seldom results in serious consequences for the
neonate.

Another adjunctive test to CTG is ST analysis of the fetal electrocardiogram
(STAN). This technique detects changes in the ST segment of the fetal ECG (ST
events), which are related to fetal hypoxia. The occurrence of these ST events
are interpreted together with CTG. One third of Dutch delivery wards already
uses this method and it is expected that in the near future this will further
increase to 50%. Meta analysis shows that STAN use lowers the FBS rate (RR
0*59, 95% CI 0*44-0*79)(11). However, it is still unclear if STAN makes FBS
redundant or not.

In the Netherlands approximately 25% of all CS during labor in term singleton
pregnancies is performed because of fetal distress (Perinatale Registratie
Nederland). This accounts for 3200 cases per year. If this study shows that FBS
leads to a reduction in CS of at least 10%, without a negative influence on
perinatal outcome, more than 320 CS could be prevented each year, thereby
improving maternal health and safety as well as reducing direct delivery costs.
If this study shows that FBS is not effective, the method can be abandoned.
Either way the results of this study will have great impact on obstetric
management in Europe and the USA; abolish or apply FBS consistently.

The primary aim of this study is to determine to what extent FBS is effective
in preventing unnecessary operative delivery for CTG-suspected fetal distress.
The secondary aims are to determine if FBS does not enhance poor perinatal
outcome. Tertiary objectives include the cost effectiveness and patients
experiences.

We propose an observational cohort study in women with continuous CTG
monitoring during labor, with randomization of women with CTG suspected fetal
distress (i.e. an abnormal CTG).
Eligible women will receive the patient study information at around 34 weeks of
gestation, in the outpatient clinic or the ward. After consent, women are
included in the study.
Included women will be monitored with continuous CTG with or without ST
analysis if the fetal ECG (STAN) during labor. The CTG is classified according
to the criteria of the International Federation of Gynecology and Obstetrics
modified for ST analysis (FIGO/STAN criteria). CTG patterns are classified as
normal, Intermediary, abnormal or pre-terminal.

ONLY if and when the CTG is classified as abnormal randomization is performed
through a computer generated sequence. Women are allocated to either FBS with
action based on its results (continue monitoring, repeat FBS or immediate
delivery) or no FBS (immediate delivery). See flowchart protocol appendix A.

The intervention (standard practice in teaching hospitals) is FBS in case of an
abnormal CTG (FIGO/STAN criteria) with further action based on its results
according to the following guidelines:

pH < 7,20: Abnormal, CS
pH 7,20-7,25: Borderline, repeat FBS * 30 minutes
pH > 7,25: Normal, continue fetal monitoring CTG/STAN, repeat FBS at the
discretion of the doctor.

With lactate analysis is FBS other cut-offs are used depending on the lactate
meter. See protocol page 18.

The burden for the women involved in this study is limited to taking note of
the background of fetal surveillance during labor, the equipoise of both
study-arms and a 18-item questionnaire which has to be filled out shortly after
the delivery.