MATURITY OF FETAL LUNGS TESTED BY PRODUCTION OF STABLE MICROBUBBLES IN AMNIOTIC FLUID

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Abstract
Lung surfactant in amniotic fluid, and hence the maturity of the fetal lungs, can be assessed by observation of stable microbubbles (less than 15 m diameter). Bubbles are formed by agitation with a Pasteur pipette and examined in hanging drops under the 10 power of a microscope. Either after a count of bubbles, or after a general survey of hanging drops, the fluid is given a stable microbubble rating. A 'strong’rating indicates that the idiopathic respiratory distress syndrome will not occur after delivery, and that the lecithin/sphingomyelin ratio will indicate maturity. Complete absence of stable microbubbles suggests a high risk of respiratory trouble for the newborn infant, as does a weak or lower rating in the 30 to 37 week gestational age group. The test takes 5 to 10 minutes to perform, is cheap and easy, is not affected by blood, but may be affected by meconium. If a 'strong’rating is found, measurement of the L/S ratio can safely be omitted.