The mean weekly increment of amniotic fluid TDx-FLM II ratio is constant during the latter part of pregnancy

Objective: The purpose of this study was to determine the mean weekly increment in amniotic fluid TDx-FLM II ratio during the latter part of pregnancy. Study design: All women who underwent >1 amniocentesis for the determination of fetal lung maturity between 1998 and 2004 were identified retrospectively. Clinical information and TDx-FLM II ratios were collected from the participant's chart and analyzed. Results: The gestational age of all participants at the first TDx-FLM II test was 31.2 to 37.5 weeks (mean, 34.7 ± 1.4 weeks of gestation). The median interval between the 2 tests was 7 days (range, 5-36 days). We found that the mean weekly increment of TDx-FLM II was 14.4 ± 9.9 mg/g (surfactant to albumin) and remained constant across the gestational ages. Conclusion: The mean weekly increment of TDx-FLM II is 14.4 ± 9.9 mg/g and is constant during the latter part of pregnancy. This information, combined with the gestational age, should be useful in treating women with an initial immature test.