Abnormalities of placenta and cord obg

Has a velamentous insertion of the cord (the umbilical cord inserts abnormally into the fetal membranes, instead of the center of the placenta) Has placenta previa (a low-lying placenta that covers part or all of the cervix) or certain other placental abnormalities.

1. ABNORMALITIES OF PLACENTA AND CORD

2. ABNORMALITIES OF PLACENTA AND CORD ABNORMALITIES OF PLACENTA AND CORD There is a marked variation in the morphology including size, shape and weight of the placenta. Variation of the cord is also quite common. Only those of clinical importance are described.

3. PLACENTA SUCCENTURIATA Morphology : One (usual) or more small lobes of placenta, size of a cotyledon, may be placed at varying distances from the main placental margin. A leash of vessels connecting the main to the small lobe traverse through the membranes. The accessory lobe is developed from the activated villi on the chorionic laeve . In cases of absence of communicating blood vessels, it is called placenta spuria . The incidence of placenta succenturiata is about 3%.

4. Diagnosis Diagnosis is made following inspection of the placenta after its expulsion. ( 1) With intact lobe —the features have already been described ( 2) With missing lobe : ( a) there is a gap in the chorion and ( b) torn ends of blood vessels are found on the margin of the gap.

5. Clinical significance If the succenturiate lobe is retained , following birth of the placenta , it may lead to: ( 1) Postpartum hemorrhage which may be primary or secondary ( 2) Subinvolution ( 3) Uterine sepsis ( 4) Polyp formation.

6. TREATMENT Whenever the diagnosis of missing lobe is made , exploration of the uterus and removal of the lobe under general anesthesia is to be done.

7. PLACENTA EXTRACHORIALIS Two types are described: ( 1) Circumvallate placenta ( 2) Placenta marginata

8. Development The placenta of such type is due to the smaller chorionic plate than the basal plate. Recurrent marginal hemorrhage as diagnosed on serial ultrasound is thought to be the cause . The chorionic plate does not extend to the placental margin. The membranes (amnion and chorion) are folded, rolled back upon itself to form a ring which is reflected centrally. This leaves a rim of bare placental tissue.

9. Morphology Circumvallate placenta — ( 1) The fetal surface is divided into a central depressed zone surrounded by a thickened white ring which is usually complete. The ring is situated at varying distances from the margin of the placenta. The ring is composed of a double fold of amnion and chorion with degenerated decidua ( vera ) and fibrin in between. ( 2) Vessels radiate from the cord insertion as far as the ring and then disappear from view ( 3) The peripheral zone outside the ring is thicker and the edge is elevated and rounded.

10. Placenta marginata Placenta marginata —A thin fibrous ring is present at the margin of the chorionic plate where the fetal vessels appear to terminate.

11. Clinical significance There is increased chance of: ( 1) Abortion ( 2) Hydrorrhea gravidarum ( excessive watery vaginal discharge) ( 3) Antepartum hemorrhage ( 4) Growth retardation of the baby ( 5) Preterm delivery ( 6) Retained placenta or membranes.

12. PLACENTA MEMBRANECEA The placenta is unduly large and thin. The placenta not only develops from the chorion frondosum but also from the chorion laeve so that the whole of the ovum is practically covered by the placenta.

13. Clinical significance : ( 1) Encroachment of some part over the lower segment leads to placenta previa . (2) Imperfect separation in the third stage leads to postpartum hemorrhage. ( 3) Chance of retained placenta is more and manual removal becomes difficult.

14. BATTLEDORE PLACENTA The cord is attached to the margin of the placenta . If associated with low implantation of the placenta, there is chance of cord compression in vaginal delivery leading to fetal anoxia or even death; otherwise, it has got little clinical significance.

15. VELAMENTOUS PLACENTA The cord is attached to the membranes . The branching vessels traverse between the membranes for a varying distance before they reach and supply the placenta. If the leash of blood vessels happens to traverse through the membranes overlying the internal os , in front of the presenting part, the condition is called vasa previa . Rupture of the membranes involving the overlying vessels leads to vaginal bleeding. As it is entirely fetal blood, this may result in fetal exsanguination and even death.

16. MANAGEMENT In the presence of fetal bleeding, urgent delivery is essential either vaginally or by cesarean section. The infant’s hemoglobin should be estimated and if necessary, blood transfusion be carried out. If the baby is dead, vaginal delivery is awaited.

17. ABNORMAL LENGTH The cord may be unduly long (300 cm) or absent ( acordia ). Short cord : The short cord may be true (less than 20 cm or 8") or commonly relative due to entanglement of the cord round any fetal part. In exceptional circumstances, the cord may be absent and the placenta may be attached to the liver as in exomphalos .

18. Clinical significance In either variety , it may cause : ( 1) Failure of external version ( 2) Prevent descent of the presenting part especially during labor (3) Separation of a normally situated placenta ( 4) Favor malpresentation ( 5) Fetal distress in labor.

19. Long cord The clinical significance due to the presence of a long cord is that there is an increased chance of: (1) Cord prolapse. ( 2) Cord entanglement round the neck or the body. The condition may produce sufficient compression on the cord vessels so as to produce fetal distress or rarely death. ( 3) True knot is rare . Even with true knot the fetal vessels are protected from compression, by the Wharton’s jelly. False knots are the result of accumulation of Wharton’s jelly or due to varices.

20. SINGLE UMBILICAL ARTERY Single umbilical artery is present in about 1–2% of cases. It may be due to failure of development of one artery or due to its atrophy in later months. It is more common in twins and in babies born of women with diabetes, epilepsy, oligohydramnios, hydramnios , preeclampsia and antepartum hemorrhage. It is frequently associated with congenital malformation of the fetus (20–25%). Renal and genital anomalies , Trisomy 18 are common . There is increased chance of abortion, fetal aneuploidy , prematurity, IUGR and increased perinatal mortality.