Comparison of fetal and neonatal growth curves in detecting growth restriction.

OBJECTIVE: To evaluate the outcome of intrauterine growth restriction (IUGR) infants with abnormal pulsatility index of the umbilical artery according to the neonatal birth weight/gestational age standards and the intrauterine growth charts.

METHODS: We analyzed 53 pregnancies with severe IUGR classified as group 2 (22 IUGR: abnormal pulsatility index and normal fetal heart rate) and group 3 (31 IUGR: abnormal pulsatility index and fetal heart rate). Neonatal birth weight/gestational age distribution, body size measurements, maternal characteristics and obstetric outcome, and neonatal major and minor morbidity and mortality were compared with those obtained in 79 singleton pregnancies with normal fetal growth and pulsatility index, matched for gestational age (appropriate for gestational age [AGA] group). Differences were analyzed with the chi(2) test and the Student t test. Differences between means corrected for gestational age in the different groups were assessed by analysis of covariance test. A P<.05 was considered significant.

RESULTS: At delivery, using the neonatal standards, 25 of 53 (47%) IUGR showed a birth weight above the 10th percentile (IUGR(AGA)), whereas in 28, birth weight was below the 10th percentile (IUGR small for gestational age [SGA]-IUGR(SGA)). All body size measurements were significantly higher in AGA than in IUGR(AGA) and IUGR(SGA). Forty-nine of 79 (62%) AGA and 49 of 53 (92%) IUGR were admitted to the neonatal intensive care unit (P<.001). One of 79 (1%) AGA and 6 of 53 (11%) IUGR newborns died within 28 days (P<.02). Major and minor morbidity was not different.

CONCLUSION: This study shows that neonatal outcome is similar in IUGR of the same clinical severity, whether or not they could be defined AGA or SGA according to the neonatal standards. Neonatal curves are misleading in detecting low birth weight infants and should be used only when obstetric data are unavailable.

LEVEL OF EVIDENCE: II.