Final Amnio Results - 34 weeks Today

I just received a call from my doctor's office with the final results of the second test on the amniocentesis. It concluded the original test results that the lungs are not yet mature. The test they performed is called an L/S ratio (Lecithin Sphingomyelin Ratio). For those in the medical field or just want to learn more here is an explanation of this test.

The ability of the fetus to survive outside of the uterus is greatly dependent on proper pulmonary function. Pulmonary surfactant is needed to reduce the surface tension of the air-liquid interface of the alveolar lining, so that alveoli don't collapse upon expiration. Infants born with a deficiency of pulmonary surfactant are at increased risk of developing respiratory distress syndrome (RDS). Neonatal RDS is characterized by increased work of breathing, fetal acidosis, the need for supplemental oxygen, and surfactant replacement therapy. The incidence of RDS is dependent on gestational age, with more RDS occurring in younger fetuses. For instance, the risk of RDS is 0% at 40 weeks, 2% at 36 weeks, and 8 to 23% at 34 weeks, depending on birth weight. RDS can occur at term, especially with Rh isoimmunization and maternal diabetes. The fetal risk of RDS can be estimated by performing a fetal lung maturity profile.

Surfactant is a complex mixture of lipids, proteins, and carbohydrates. Most of the lipids are phospholipids including lecithin (L), sphingomyelin (S), disaturated lecithin, phosphatidyl inositol (PI), and phosphatidyl glycerol (PG). All of these phospholipids are manufactured by the fetal lung, possess surface tension activity, and are secreted into the amniotic fluid. Lecithin is present in the lung in the highest concentration. Lecithin must be stabilized by PI and/or PG to have maximal surface tension reducing activity. The relative concentrations of these phospholipids determine the state of fetal lung maturity. The L/S ratio and percentages of PI, PG, and disaturated lecithin are determined by two dimensional thin layer chromatography and reflectance densitometry.
In early pregnancy, the concentration of lecithin is very small, while that of sphingomyelin is much greater. Lecithin begins to be secreted into amniotic fluid by the developing fetal lung between 24 and 26 weeks of gestation. At 30 to 32 weeks, lecithin concentration remains relatively low, less than or equal to sphingomyelin. PI concentration is also low at this time and PG is nonexistent. Around 32 to 33 weeks gestation, lecithin and sphingomyelin concentrations are about equal. Subsequently, lecithin begins to increase, with an abrupt rise at 35 weeks. Lecithin continues to steadily increase until term. Sphingomyelin concentrations level off at 32 weeks and begin to decrease. PI increases in parallel with lecithin until 35 weeks and subsequently declines. PG becomes detectable at 36 weeks. In the mature lung, lecithin comprises 50 to 80% of the total surfactant lipid. Fetal lung maturity occurs during the 2 to 3 weeks period when the L/S ratio increases to 2.0 or more, PI decreases, and PG becomes detectable. Because PG appears later in gestation, it is a good indicator of maturity (positive predictive value >95%).

Results are interpreted as follows.

My number came back at 1.8 and they want to see it at 2.4 or more. So we are going to proceed with another round of steroids. One tonight and another 24 hours later. We will then do another amniocentesis on Thursday (Christmas Eve) and see if the lungs have matured enough to start the process of delivery. Until then I will stay at St. Mary's and they will be doing NST's every 8 hours and doppler ultrasound and fluid checks every 2-3 days. The specialists have a portable ultrasound machine that Dr. Balaskis's brings from the office to do the tests. So unless things change with the baby in terms of NST's or ultrasounds we will look at inducing on Thursday. They doctor's did say that they will not let me go anymore than two more weeks so at the very latest we will be inducing on New Year's Eve. That leaves us with a good possibility of a Christmas Day or New Year's Day baby.

I will continue to post with any new changes, but as of right now I will just be hanging out at St. Mary's Hospital catching up on my rest.

Thank you to everyone for your thoughts and prayers. It is really a great feeling to know that so many people are praying for this baby. We know that the baby is in God's hands.