Is obstetric and neonatal outcome worse in fetuses who fail to reach their own growth potential?

OBJECTIVES

To determine the perinatal outcome of fetuses who had birthweights less than that expected from early third trimester ultrasound scanning.

DESIGN

Retrospective estimation of centile fetal weight at early third trimester ultrasound scanning compared with actual centile birthweight corrected for gestational age, parity and sex.

SETTING

Teaching Hospital Obstetric Unit, London.

SUBJECTS

197 unselected women with singleton cephalic pregnancies who were delivered at term in our unit between October 1989 and May 1990.

MAIN OUTCOME MEASURES

CTG abnormality, need for fetal blood sampling in labour, meconium-staining of the amniotic fluid, mode of delivery, Apgar scores at 1 and 5 min, need for transfer of baby to neonatal unit, and need for neonatal intubation of the neonate at delivery.

RESULTS

An actual birthweight greater than 5% less than the birthweight estimated from ultrasound scanning identified 44 babies (22%) with an increased risk of CTG abnormalities (chi 2 = 8.38, P less than 0.0025; Odds ratio (OR) = 2.54; 95% CI 1.36 to 4.78) and need for operative delivery (chi 2 = 5.81, P less than 0.0125; OR = 1.94; 95% CI 1.15 to 3.27), when compared with the remainder of the sample. Overall 14 (32%) of this group had birthweights above the 50th centile. A group of 44 babies selected as being the smallest for gestational age, without reference to growth pattern, had a similar excess morbidity. (All this group had birthweights below the 39th centile).

CONCLUSIONS

This study supports the hypothesis that in-utero fetal growth pattern is as important for perinatal outcome as being small for gestational age per se.