Small for dates: evaluation of different diagnostic methods.

Ninety-four high-risk pregnancies were studied weekly in a prospective and longitudinal study. Uterine height, biparietal diameter (BPD), cranial perimeter (CrP) and abdominal perimeter (AbP) were measured. Amniotic fluid volume (AFV) was assessed. Of the sample selected, 58 neonates were appropriate for gestational age and 36 were small-for-date (17 symmetrical and 19 asymmetrical). The sensitivity values in diagnosis of small-for-dates were: 67% for BPD, 42% for CrP, 94% for AbP, 56% for Uterine Height and 28% for AFV. The specificity for the five variables ranged from about 91% to 100%. If we consider symmetrical and asymmetrical retardation separately, the sensitivity values for the former were: 94%, 77%, 100%, 77% and 24% for BPD, CrP, AbP, Uterine Height and AFV respectively. For symmetrical retardation, the sensitivity values were: 43%, 11%, 90%, 37% and 32% for BPD, CrP, AbP, Uterine Height and AFV respectively. The fetal cranial measurements were the only ones to demonstrate a different pattern of evolution in symmetrical and asymmetrical small-for-dates. This is therefore a useful measurement in making a differential diagnosis between both retardations. The earliest diagnoses were made in the symmetrical small-for-date group.