Re: Cerebroplacental ratio in predicting adverse perinatal
outcome: a meta-analysis of individual participant data
Dear Sir:
We read with interest the study by Vollgraff Heidweiller-Schreurs et
al1 in which the authors compare the abilities of the
umbilical Doppler, middle cerebral Doppler and cerebroplacental ratio
(CPR) for the prediction of adverse perinatal outcome (APO). We would
like to congratulate the authors for this collaborative study and also
for the CPR IPD initiative. However, we disagree with the conclusions
and methodology upon which we would like to make several comments:
First, and foremost the main diagnostic performance of CPR relies on its
ability to detect compromised fetuses unable to stand the stress of
labor2. However, in absence of contractions, even
endangered fetuses, with abnormal Doppler, may be delivered with a good
APO and absence of acidosis. Second, CPR performance is strikingly
dependent on the interval to labor, decreasing importantly after 15
days. If we consider that, beyond the appropriate performance range,
Doppler techniques with different abilities may resemble equally
accurate, the interval information becomes of crucial
importance3. Third, as earlier published and
regardless of CPR, the possibility of APO varies depending on the kind
of labor onset. As a consequence, inductions with poor Bishop score are
more likely to present acidosis and APO than deliveries with spontaneous
onset and good obstetrics conditions4. All this
implies that in order to perform appropriate comparisons between
different Doppler techniques, cases with elective cesarean sections and
higher intervals to labor should be discarded while the type of labor
onset should be taken into account. However, as far as we are concerned
none of this was done. Last but not least, when preterm fetuses are
studied, admission to pediatric care units can be the result not only of
hypoxia, but also of prematurity. Consequently, considering that in this
scenario intrapartum and neonatal pH become the only accurate parameters
to establish a clear diagnosis of acidosis, these should be homogeneous
and obtained using similar pH thresholds among all cases studies.
Unfortunately, this information was not provided.
Overlapping ROC curves may be the result of a similar performance
between the studied parameters. However, considering the above-mentioned
aspects they might also be the result of biased comparisons performed
out of the appropriate performance ranges. While the findings of this
meta-analysis do not support the use of CPR out of a research protocol,
we would still like to consider that further research is needed to reach
such conclusion, and that CPR remains as a poor predictor, but still the
best individual predictor of APO.
José Morales-Roselló*/**, Gabriela Loscalzo*, Silvia Buongiorno*,
Vaidilė Jakaitė*, Alfredo Perales-Marín*/**
*Servicio de Obstetricia, Hospital Universitario y Politécnico La Fe,
Valencia, Spain, and **Departamento de Pediatría, Obstetricia y
Ginecología, Universidad de Valencia, Valencia, Spain.