It is measured from the 12 o'clock position to the 6 o'clock position. To calculate a single deepest pocket, the sonographer scans each of the four quadrants of the abdomen looking for the deepest pocket of amniotic fluid that does not include any fetal body parts or an umbilical cord. Randomized control trials have shown that use of AFI can cause an increased number of false positive diagnosis of oligohydramnios and recommend using the measurement of a single deepest pocket (SDP) of amniotic fluid to diagnose oligohydramnios instead. An AFI 25 cm is considered polyhydramnios. In this method, the sonographer measures the amniotic fluid in each of the four quadrants of the abdomen (right upper quadrant, left upper quadrant, right lower quadrant, left lower quadrant) and adds the values together. The first is by using an amniotic fluid index (AFI). There are two methods that can be used to make the diagnosis. Diagnosis ĭiagnosis of oligohydramnios is made by conducting a transabdominal ultrasound of the abdomen. Other common clinical presentations include fetal malpresentation, undue prominence of fetal parts, premature rupture of membranes, and reduced amount of amniotic fluid. For this reason, discrepancies between fundal height measurements and gestational age can be a clinical indication of amniotic fluid abnormality and should be evaluated by ultrasound. The volume of amniotic fluid typically increases until 36 weeks and starts decreasing after 40 weeks in post-term gestations. Amnion nodosum failure of secretion by the cells of the amnion covering the placentaĭiagnosis Clinical Manifestation.Intrauterine growth restriction (IUGR) associated with placental insufficiency.Congenital abnormalities such as renal agenesis and cystic renal disease are associated with impaired urine production, and posterior urethral valves or urethral atresia which are associated with obstruction of the lower urinary tract.Chromosomal abnormalities such as Down syndrome which are associated with gastrointestinal abnormalities.Infections such as the TORCH infections (toxoplasma gondii, rubella, cytomegalovirus, herpes simplex virus) and parvovirus B19.Maternal dehydration, especially in the hotter summer months.When the fetal kidneys are not able to produce adequate amounts of urine, this leads to reduced amniotic fluid or oligohydramnios. Medications such as angiotensin converting enzyme inhibitors (lisinopril), prostaglandin synthetase inhibitors ( NSAIDs, anti-inflammatory steroids), and trastuzumab decrease blood flow to the kidneys of the fetus.Decreased blood flow to the fetus causes impaired urine production which leads to reduced amniotic fluid and oligohydramnios. These conditions decrease the blood flow to vital organs such as the placenta which supplies blood, oxygen, and nutrients to the developing fetus. Conditions such as preeclampsia, chronic hypertension, collagen vascular disease, nephropathy, and thrombophilia cause uteroplacental insufficiency.The development of oligohydramnios may be idiopathic or have a maternal, fetal, or placental cause. By the second trimester, the fetal kidneys start to produce urine which becomes the main source of the amniotic fluid for the remainder of the pregnancy. In the first trimester, the main sources of amniotic fluid are fetal lung secretions, transportation of maternal plasma across the fetal membranes, and the surface of the placenta. The amount of amniotic fluid available is based on how much fluid is produced and how much is removed from the amniotic sac. The opposite of oligohydramnios is polyhydramnios, or an excess of amniotic fluid. The prognosis of the fetus is dependent on the etiology, gestational age at diagnosis, and the severity of the oligohydramnios. Low amniotic fluid can be attributed to a maternal, fetal, placental or idiopathic cause and can result in poor fetal outcomes including death. Amniotic fluid is necessary to allow for normal fetal movement, lung development, and cushioning from uterine compression. It is typically diagnosed by ultrasound when the amniotic fluid index (AFI) measures less than 5 cm or when the single deepest pocket (SDP) of amniotic fluid measures less than 2 cm. Oligohydramnios is a medical condition in pregnancy characterized by a deficiency of amniotic fluid, the fluid that surrounds the fetus in the abdomen, in the amniotic sac.
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