pregnancy Rupture of membranes Intrauterine growth restriction (IUGR) associated with placental insufficiency Amnion nodosum; failure of secretion by the cells of the amnion covering the placenta Placental Placental abruption Twin-twin transfusion Placental thrombosis or infarction Diagnosis Clinical Manifestation The volume of amniotic fluid typically increases until 36 weeks and starts decreasing after 40 weeks in post-term gestations. 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. Other common clinical presentations include fetal malpresentation, undue prominence of fetal parts, premature rupture of membranes, and reduced amount of amniotic fluid. Diagnosis Diagnosis of oligohydramnios is made by conducting a transabdominal ultrasound of the abdomen. There are two methods that can be used to make the diagnosis. The first is by using an amniotic fluid index (AFI). 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. For reference, a normal AFI is 5–25 cm. An AFI <5 cm is considered oligohydramnios and an AFI >25 cm is considered polyhydramnios. 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. 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. It is measured from the 12 o'clock position to the 6 o'clock position. For reference, a normal SDP is 2–8 cm. A SDP <2 cm is considered oligohydramnios and a SDP >8 cm is considered polyhydramnios. The use of a SDP for diagnosis of oligohydramnios is associated with less false positives and thus less unnecessary interventions without an increase in adverse perinatal outcomes. In a multiple gestation pregnancy, measuring a single deepest pocket is the most accurate determination of adequate amniotic fluid levels. Management After initial diagnosis of oligohydramnios has been made, the next step is to perform a thorough history and physical exam, followed by diagnostic testing if indicated. Retaking a maternal and family history and performing a physical exam can point to maternal conditions