Changes in the threshold of fetal lung maturity testing and neonatal outcome of infants delivered electively before 39 weeks gestation: implications and cost-effectiveness.

OBJECTIVE: To compare the neonatal outcome of infants delivered before 39 weeks' gestation following documentation of fetal lung maturity before and after the lamellar body count (LBC) threshold was increased from 30,000 to 50,000 LB/ul. We discuss the algorithm employed for testing fetal lung maturity, the cost of testing and potential savings.

MATERIAL AND METHODS: We studied the outcome of infants delivered electively before 39 weeks' gestation after fetal lung maturity was documented by amniotic fluid analysis. We compared the outcome of neonates born before and after the LBC threshold was increased.

RESULTS: Our cohort included 527 neonates who were divided into two groups: 264 who underwent fetal lung maturity studies before the change in LBC threshold and 263 who underwent testing after the change. In the first group, 158 neonates met the criteria of LBC >30,000 LB/ul and were delivered without further testing. The second group included 154 neonates who were mature by LBC >50,000 LB/ul and were delivered. Seven of the neonates born in the first group required admission to the neonatal intensive care unit (NICU), whereas in the second group only two neonates required admission (P = 0.02). Additionally, 16 neonates in the first group required respiratory assistance compared with six in the second group (P = 0.04). The overall neonatal complication rate was significantly higher in the first group (P = 0.001).

CONCLUSION: Changing the LBC threshold resulted in a significant decrease in neonatal morbidity. Employing the algorithm, we described for testing fetal lung maturity is cost effective, and more importantly, represents sound evidence-based medical management.