Lecithin-sphingomyelin ratios in amniotic fluid in normal and abnormal pregnancy, Am J Obstet Gynecol. 1973 Feb 15;115(4):539-546.)
Dipalmitoylphosphatidylcholine (DPPC), that is, lecithin, and phingomyelin are surfactant components. Before 34 weeks, both are present in amnionic fluid in similar concentrations. At 32 to 34 weeks, the concentration of lecithin relative to sphingomyelin begins to rise (Fig. 34-1). The risk of neonatal RDS is slight whenever the concentration of lecithin is at least twice that of sphingomyelin-LIS ratio >2 (Gluck, 1971). Previously, RDS was thought to develop despite an LIS ratio > 2 in newborns of women with diabetes. Some recommend that phosphatidygycerol, another surfactant phospholipid, be documented in amnionic fluid of these women. Based on current evidence, it is unclear if either diabetes, per se, or its level of control causes false-positive phospholipid test results for fetal lung maturity (De Luca, 2009).
Of biophysical tests, the luorescence poariation test is an automated assay that measures the surfactant-to-albumin ratio in uncentriuged amnionic luid and gives results in less than an hour. Investigators found the TDx-FLM to be equal or superior to the LIS ratio, foam stability index, or phosphatidylglycerol assessment. his included testing in diabetic pregnancies (Karcher, 2005; Varner, 2013). he modified TDx-FLM Ilis used by many hospitals as their primary test of pulmonary maturity. Thresholds vary by gestational age (Bennasar, 2009). he oam stabiliy or shake test relies on the ability of surfactant in amnionic luid, when mixed appropriately with ethanol, to generate stable foam at the air-liquid interface (Clements, 1972). Problems include errors caused by slight contamination and frequent false-negative test results. Of other tests, the Lumadex-FSI test, luorescent poariation (microviscomery), and amnionic luid absorbance at 650-nm waveength have all been used with variable success.
The lamelar body count is a rapid, simple, and accurate method of assessing fetal lung maturity and is comparable to TDx-FLM and LIS ratio accuracy (Karcher, 2005; Varner, 2013).
This newborn bowel disorder has clinical findings that include abdominal distention, emesis, ileus, bilious gastric aspirates,
The Preterm Newborn 639 and bloody stools. here is often radiological evidence of bacteria. Other classic imaging findings include hepatobiliary gas and pneumoperitoneum. Bowel perforation may prompt resection. Necrotizing enterocolitis (NEC) is seen primarily in low-birthweight newborns but occasionally is encountered in mature neonates. Various hypothesized causes include peri natal hypotension, hypoxia, sepsis, umbilical catheterization, exchange transfusions, blood transfusions, and the feeding of cow milk and hypertonic solutions (Neu, 2010). he patho physiology is thought to be multifactorial, and genetic disposi tion, intestinal immaturity, imbalance in microvascular tone, abnormal microbial colonization in the intestine, exposure to enteral feeds, and highly immunoreactive intestinal mucosa play potential roles (Caplan, 2017; Neu, 2010).