Assessment of fetal retardation via ponderal index and weight percentiles

Intrauterine growth retarded fetuses could not realize their genetic potent ial due to intrauterine malnutrition and could thus not reach an appropriat e length or weight according to their gestational age. New born infants bel ow the 10(th) percentile are termed "small for gestational age" (SCA). Howe ver, this definition does not account for asymmetrically retarded infants w ho's birth weight is above the 10(th) percentile, but who are underweight f or their length. In contrast the fetal Ponderal Index (PI) regards both fet al length and weight. New born infants with a PI < 10(th) percentile are cl assified as "low Ponderal Index" (LPI). From pediatric studies it is well k nown that LPI infants are more likely threatened by hypoglyclemia, hypother mia, hypocalcemia and meconium aspiration pneumonitis. Long term follow-up studies showed a retarded physical and mental development of these infants. Purpose: The current study followed the question if intrauterine growth ret arded fetuses, esp. LPI infants are also at higher risk during labour. The data of 3687 new born infants were retrospectively analyzed. Study Design: According to their birth weight and length they were characte rized as SCA, LPI, SGA/LPI or "appropriate for gestational age" AGA. The AG A infants together with the LGA infants were used as control group. Results: No significant differences in respect to birth modalities (i.e. va ginal delivery, cesarean section, operative vaginal delivery) could be dete cted between SGA-, LPI- and AGA infants. However, concerning the indication which formed the basis for an operative delivery, we found significant dif ferences. In 31% of all operatively delivered LPI new born, 47% of the SGA infants and 52% of the SGA/LPI group the indication for the operative manag ement was based on fetal problems. This indication accounted for only 16% o f the operatively delivered infants in the control group. Regarding the fet al outcome, specified by the fetal acid base status, Apgar index, frequency of transfer to the neonatal intensive care unit, and perinatal mortality, no differences between LPI, SGA and SGA/LPI infants could be detected. Conclusion: We conclude that the current strategies of monitoring labour, e .g. by continuous CTG scanning, are sufficient to detect and master fetal p roblems. The detection of a "low Ponderal index" did not add any informatio n concerning the management of labour.