I would like to thank the authors for their correspondence regarding the review article, “The importance of the cerebroplacental ratio in the evaluation of fetal well-being in SGA and AGA fetuses.” The question posed by Ghi and Frusca, as to whether the cerebroplacental ratio (CPR) is an alert bell or a crash sound, remains to be determined.

One of the dilemmas for the obstetrician is identifying the fetus at risk for adverse outcome during labor. Whereas it would seem inappropriate to deliver every fetus based on an abnormal CPR, the information is useful in several clinical scenarios.

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  The fetus who presents in the third trimester with no early prenatal assessment of gestational age in which there is a discrepancy between the last menstrual period and fetal biometry. In this scenario, an abnormal CPR may identify a small-for-gestational-age (SGA) fetus instead of one with an incorrect gestational age. When an abnormal CPR is present, more frequent serial growth and antepartum testing would be prudent.

  
  
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  Antepartum testing is performed for a number of clinical indications other than a risk for an SGA fetus. Often the nonstress test may not be sufficient, therefore necessitating evaluation of the amniotic fluid, umbilical artery resistance as well as fetal behavior using the biophysical profile. Although these tests are only predictive of adverse outcome when abnormal, the CPR may precede abnormal antepartum testing and therefore alert the clinician of an increased risk for adverse outcome during labor. Knowing this information may guide the management of labor and delivery.

Although the results are not in regarding whether the CPR is an alert bell or a crash sound, I would suggest the clinician consider the alert bell as a viable option until further studies designed to address this issue have been reported.

Arabin et al suggest that the CPR may be additive to the biophysical profile as referenced from their previous work published in 1993. I would agree that the CPR should not be interpreted in isolation.

Similar to the evolution of Doppler studies of the uterine artery, umbilical artery, ductus venosus, descending aorta, and the middle cerebral artery, the physician must evaluate all parameters in assessing the global well-being of the fetus at risk for adverse outcome. Although the CPR was introduced more than 20 years ago for the evaluation of fetuses who were SGA, its value has recently been demonstrated to identify the term SGA and appropriate-for-gestational-age fetus at risk for adverse perinatal and neonatal outcome.

From my perspective, this group of fetuses presents a clinical challenge, as discussed in the previous text, in which the CPR may be of value. Further studies are needed in which the CPR is obtained several days before delivery to determine its value as an assessment tool for the detection of the fetus at risk for adverse outcome during the labor process.