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Fetal lung development can be tested by sampling the amount of surfactant in the amniotic fluid obtained via amniocentesis. [9] Several tests are available, including the lecithin-sphingomyelin ratio (" L/S ratio "), the presence of phosphatidylglycerol (PG), and the surfactant/albumin (S/A) ratio . [ 9 ]
The lecithin–sphingomyelin ratio is a marker of fetal lung maturity. The outward flow of pulmonary secretions from the fetal lungs into the amniotic fluid maintains the level of lecithin and sphingomyelin equally until 32–33 weeks gestation, when the lecithin concentration begins to increase significantly while sphingomyelin remains nearly the same.
An amniocentesis is a procedure in which a sample of amniotic fluid is aspirated using a needle that is inserted into the abdomen guided by ultrasound. [1] The sample is then tested, and can help doctors diagnose genetic disorders, birth defects, or other fetal health problems.
Amniotic fluid is removed from the mother by an amniocentesis procedure, where a long needle is inserted through the abdomen into the amniotic sac, using ultrasound guidance such that the fetus is not harmed. Amniocentesis is a low risk procedure, with risk of pregnancy loss between 1 in 1,500 – 1 in 700 procedures.
In order to listen to the lungs from the back the patient is asked to move their arms forward to prevent the scapulae (shoulder blades) from obstructing the upper lung fields. These fields are intended to correlate with the lung lobes and are thus tested on the anterior (front) and posterior (back) chest walls.
There are several posited ways that have been positioned to cause amniotic fluid embolism. The first of which involves the thought that a combination or one of the following that include a difficult labor, a placenta that is abnormal and trauma to the abdomen through a caesarean section or other surgical tools dissipates the barrier that exists from the maternal fluid to the fetal fluid.
Medical diagnosis of pulmonary hypoplasia in utero may use imaging, usually ultrasound or MRI. [12] [13] The extent of hypoplasia is a very important prognostic factor. [14]One study of 147 fetuses (49 normal, 98 with abnormalities) found that a simple measurement, the ratio of chest length to trunk length, was a useful predictor of postnatal respiratory distress. [15]
Amniotic fluid levels are an important consideration when debating expectant management vs clinical intervention, as low levels, or oligohydramnios, can result in lung and limb abnormalities. [10] Additionally, labor and infection are less likely to occur when there are sufficient levels of amniotic fluid remaining in the uterus. [ 8 ]