1. Disorders of amniotic fluid &umbilical disorders

2. ●Oligohydramnios – AFI ≤5 cm ●Normal – AFI >5 cm and <24 cm
Amniotic fluid index 
 AFI measurement is calculated by first dividing the uterus into four quadrants using the linea nigra for the right and left divisions and the umbilicus for the upper and lower quadrants. The maximum vertical amniotic fluid pocket diameter in each quadrant not containing cord or fetal extremities is measured in centimeters; the sum of these measurements is the AFI.
●Oligohydramnios – AFI ≤5 cm
●Normal – AFI >5 cm and <24 cm
●Polyhydramnios – AFI ≥24 cm .

3. However, small variations in the thresholds used are common
However, small variations in the thresholds used are common. For example, polyhydramnios has been defined as AFI >18, >20, >24, and >25 cm . Currently, there is insufficient evidence to recommend any additional antenatal assessments because of borderline AFI (5.1 to 8 cm)

4. Plyhydramnios

5. ETIOLOGY 
: The most common cause of severe polyhydramnios are
fetal anomalies (often associated with an underlying genetic abnormality or syndrome), while maternal diabetes, multiple gestation, and idiopathic factors are more often associated with milder cases
After birth, an abnormality is diagnosed in up to 25 percent of cases considered idiopathic prenatally
Fetal infection, Bartter syndrome, anemia, and neuromuscular disorders account for some of these cases and should be considered in the differential diagnosis if a structural abnormality and maternal diabetes are excluded.

6. Polyhydramnios has been associated with fetal anomalies in most organ systems. The most common structural anomalies associated with polyhydramnios are those that interfere with fetal swallowing and/or absorption of fluid . Decreased swallowing may be due to a primary gastrointestinal obstruction (eg, duodenal, esophageal, or intestinal atresia), neuromuscular disorders (eg, anencephaly), or to secondary obstruction of the gastrointestinal
tract (eg, massive unilateral dysplastic kidneys)
The combination of intrauterine growth restriction and polyhydramnios is suggestive of trisomy 18; other sonographic markers of trisomy 18 are typically present . Excess amniotic fluid in this syndrome may be related to difficulty swallowing or to intestinal abnormalities. Other aneuploidies have also been associated with polyhydramnios, most commonly trisomy 21.

7. Increased urine production may occur in high fetal cardiac output states (eg, fetal anemia due to alloimmunization, parvovirus infection, fetomaternal hemorrhage, alpha-thalassemia, glucose-6-phosphatase deficiency) or, rarely, from entities such as fetal Bartter syndrome
In monochorionic multiple gestation, polyhydramnios/oligohydramnios sequence (is diagnostic of twin-twin transfusion syndrome (TTTS

8. oligohydramnios

9. Maternal
Medical or obstetrical conditions associated with uteroplacental insufficiency (eg, preeclampsia, chronic hypertension, collagen vascular disease, nephropathy, thrombophilia)
Medications (eg, angiotensin converting enzyme inhibitors, prostaglandin synthetase inhibitors, trastuzumab)

10. Placental
Abruption
Twin to twin transfusion (ie, twin polyhydramnios-oligohydramnios sequence)
Placental thrombosis or infarction

11. Fetal
Chromosomal abnormalities
Congenital abnormalities, especially those associated with impaired urine production
Growth restriction
Demise
Postterm pregnancy
Ruptured fetal membranes
Idiopathic

12. Umbilical cord abnormalities

13. UMBILICAL CORD — The umbilical cord is normally composed of two umbilical arteries and an umbilical vein supported by loose gelatinous tissue called Wharton's Jelly.
Appearance — The umbilical cord should have a smooth, white, opaque, shiny appearance with spiraling consisting of about three half spirals over a 5 cm length of cord. Abnormal coloring suggests infection , meconium, or the sequelae of fetal demise

14. Coiling 
 The umbilical cord has a characteristic twist or coil .
Coiling of the umbilical cord is thought to protect it from compression, kinking, and torsion, thus preventing disruption of the blood supply to the fetus. Coiling may also facilitate umbilical venous blood flow

15. Placental insertion — The umbilical cord normally inserts centrally or slightly eccentrically and directly into the placental disk. Fewer than 10 percent of insertions occur at the margin of the placenta (battledore placenta)
A velamentous cord insertion refers to a cord that inserts into the membranes rather than the placental disk

16. Length 
The average length at term is about 55 cm, with a wide normal range (35 to 77 cm)
short cords are associated with fetal inactivity related to fetal malformations, myopathic and neuropathic diseases, oligohydramnios, and some syndromes .
Long cords may be caused by a hyperactive fetus and have been associated with cord accidents, such as entanglement, knotting, and prolapse . Long cords are also associated with placental lesions indicative of intrauterine hypoxia such as delayed villous maturation, as well as fetal death, fetal growth restriction, and long term adverse neurologic outcome . In addition, the longer route that blood must travel to and from the fetal heart when the cord is very long may result in fetal heart failure.

17. Knots — False knots are tortuousities of the umbilical vessels that form bulges , they are not associated with any adverse outcome.
True knots occur in 1 percent of births and are generally single and loose .
However, tight or multiple true knots and knots associated with coiling or twisting of the cord increase the risk of intrauterine demise, particularly if the cord is long and during the second trimester when the fetus has a lot of room to move

18. Vessels — A single umbilical vein conducts blood from the placenta back to the fetus and is essential for fetal survival. The two umbilical arteries shunt blood from the fetus to the placenta.
the presence of a single umbilical artery or hypoplastic second umbilical artery is not lethal.
The number of umbilical vessels are best counted by cutting the cord in a relatively uniform region (away from bulges of false knots) at least 5 cm from the placental insertion since the two arteries sometimes fuse near the insertion .
Two vessel cords should be documented in the medical record and confirmed by histological examination.