Background: The purpose of this study was to compare electronic fetal heart rate monitoring (EFM) characteristics between Appropriate for Gestational Age (AGA ) and Small for Gestational Age (SGA) fetuses and to determine whether SGA fetuses have specific abnormalities.

Materials and Methods: Among children born from Apr 2002 to Mar 2003 in Arash hospital, we identified 300 singleton infants born after 36 weeks' gestation of uncomplicated pregnancies in whom second-trimester (24-27 weeks' gestation) EFM records were obtained. Individual components of fetal heart rate (FHR) pattern; baseline rate, baseline FHR variability, presence of acceleration and periodic and episodic deceleration , and birth characteristics were compared between AGA and SGA infants or between pregnancies with or without second-trimester decelerations. Statistical analysis was performed using Student t, Chi square and Fisher exact test.

Results: Among 300 infants, 261 (87%) were AGA and 39 (13%) were SGA; 65 had and 235 did not have second-trimester decelerations. Baseline FHR variability, second- trimester decelerations and intrapartum FHR decelerations were significantly higher in SGA fetuses than in AGA fetuses (P<0.05). Birth weight and gestational age were significantly lower in SGA fetuses than in AGA fetuses (P<0.05). There were no significant differences in baseline rate and acceleration ,maternal age and parity, Apgar score in 1 minute, meconium staining, mode of delivery, NICU admission, between SGA and AGA infants. Small for Gestational Age infants were more frequent in pregnancies with second-trimester decelerations compared with those without second-trimester deceleration (P<0.05). Baseline FHR variability in pregnancies with second-trimester decelerations was significantly higher than in pregnancies without second-trimester deceleration (P<0.05).

Conclusion: Periodic or episodic decelerations and increased FHR variability during late second-trimester EFM were associated with an increased risk of SGA infant