9.14 Abnormalities Of Placenta, Umbilical Cord, Membranes & Amniotic Fluid

Question 1

Abnormalities of shape - lobulated placenta

Answer 1

• Bilobular placenta = two or three large separate, distinguishable lobes (nearly equal size)
• If the lobes are linked by membranes = bipartite / tripatita - velamentous insertion
• Placenta fenestrate = abnormality involving the presence of a localized area where the villous tissue is absent and the chorionic plate is present or there is a hole in the placenta.

Question 2

Abnormalities of shape - Placenta membranacea (diffusa)

Answer 2

• The entire placenta is extremely thin
• The chorionic surface is almost completely covered by villi
• Associated with APH, Placenta previa, PTB and placental insufficiency.

Question 3

Abnormalities of shape - placenta succenturiata

Answer 3

• An additional lobe is present
• Blood vessels from the main placenta reach the
  separate lobe via the membranes that join them
• Tearing of these vessels = APH

Question 4

Abnormalities of shape - multiple pregnancies

Answer 4

• Monochorionic twins = one shared placentae (with one or two amniotic sacs)
• Dichorionic twins = two separate placenta’s

Question 5

Abnormal in size - Large
Define
Causes

Answer 5

Definition: placenta more than 600g

Causes of large placenta:
- Maternal DM
- Maternal Syphilis (untreated)
- Multiple gestations
- Hydrops fetalis (oedematous & pale)

Question 6

Abnormalities of size - small
Define
Causes

Answer 6

Definition: placenta less than 400g

Causes of small placenta:
- Prematurity
- Placental insufficiency (esp due to HPT disorders)
- Nutritional deficiency (low protein)
- Cigarette smoking
- Heroin use
- Alcoholism
- Chronic urinary tract infections
- Chronic systemic maternal disease
- IUGR

Question 7

Abnormalities of maternal surface

Answer 7

1. Abruptio Placenta = Sudden detachment of placenta from uterus while the fetus is still in situ, can result in a large retroplacental clot
2. Pale surface = immaturity, anaemia, APH, syphilis
3. Infarctions = Fresh – dark red / older – yellow-white, common in EOPET, DM
4. Calcifications = can be normal aging
5. MAP = placenta that has invaded beyond the endometrium and into deeper structures (myometrium, serosa, surrounding structures).

Question 8

Abnormal insertions of umbilical cord

Answer 8

• Battledore placenta = umbilical cord inserted on edge of placenta
• Velamentous insertion UC inserts onto the membranes instead of the chorionic plate

Question 9

Abnormal cord length

Answer 9

• Mean cord length = 37cm
• Congenital absence of UC = Achordia = rare, high fetal mortality rate
• Very Short = <30cm = may cause Abruptio, malpresentation, delayed second stage, inversion of the uterus, APH
• Very Long = > 70cm = entangles around fetus = high risk for fetal distress and fetal loss due to cord entanglement (true knots)

Question 10

Abnormalities of umbilical blood vessels

Answer 10

• Normal = 1 x Umbilical vein and 2x umbilical arteries
• Absence of one Artery = 1% of pregnancies and 7-14% of twin pregnancies
• Higher incidence in T13 and T18, DM and thalidomide exposure
• Can be associated with other structural conditions (Meckels diverticulum, Oesophageal atresia.

Question 11

Other abnormalities of umbilical cord

Answer 11

• Varicose veins = usually harmless
• Knots = true or false. True – occur early in gestation and tighten causing occlusion of vessels which can result in fetal death. False knots are loops to accommodate the length, they do not tighten and are not of clinical significance.
• Torsion = seldom occurs with polyhydramnios
• Abnormal thickness = due to change of Wharton’s Jelly. Very thin = placental insufficiency and oligohydramnios.
• Cysts = may be small, false cysts. No clinical significance.

Question 12

Abnormal insertion on chorionic plates
Define
Two types

Answer 12

• Trophoblasts normally penetrates the decidua at right angles
• Occasionally the surface of the chorionic plate is reduced = smaller than the decidual plate = the trophoblasts penetrates the decidua and further in a lateral direction.
• Results in the capillaries to be small and friable = insufficient oxygen supply preventing proper intervillous space development
  The villi become necrotic and fibrin is deposited = pale ring around the chorionic plate

Two types:
- Placenta circummarginate
- Placenta circumvallate

Question 13

Discolouration of membranes

Answer 13

• Red or Rust = haemorrhage
• Green = meconium – fresh meconium can be wiped away easily. Longer exposure leads to phagocytosis of pigments and can not be wiped off

Question 14

Amnion nodosum (abnormality of membrane)

Answer 14

• Yellow, opaque nodules in the amnion on the fetal surface of the placentae
• Consists of a mixture of vermis, fibrin, desquamated epithelial cells and lanugo hair
• Clinically associated with oligohydramnios

Question 15

Chorio-amniotic membrane separation

Answer 15

• Chorion and amnion are normally separate in T1 – thereafter they fuse
• Spontaneous separation can occur = extremely rare, following an amniocentesis or fetal surgery
• Complications include = miscarriage, PTB, PPROM and IUGR
• Also associated with Downs Syndrome
• Disruption after 16w = extra-amniotic pregnancy

Question 16

Placental cysts

Answer 16

• Usually situated subchorionically, but occasionally on fetal surface
• Vary in size = 0,5-10cm
• Usually contain watery fluid
• Have no clinical significance

Question 17

Segmental constrictions of arteries

Answer 17

• Occasionally observed on fetal surface of placenta
• More common in HPT disease

Question 18

Thrombosis of chorionic vessels

Answer 18

• May be present as a result from underlying placental infarct or following prolonged exposure to meconium
• Meconium elicits a chemical inflammatory reaction in the amnion = may cause thrombosis of the chorionic blood vessel
• More prevalent in DM patients

Question 19

Amnion bands

Answer 19

• Rare
• Thin threads or bands of the amnion run across the amniotic cavity
• May arise after early and prolonged rupture of membranes
• Bands ma coil around fetus = causing congenital deformities of limbs, amputation of a limb as a result of vascular occlusion and subsequent distal necrosis
• Other causes included: abdominal trauma, CVS, early amniocentesis, IUCD, teratogenic drugs and connective tissue disorders

Question 20

Oligohydramnios
Define
Clinical presentation
Causes
Complications

Answer 20

• Definition = Less than 600ml, AFI < 5cm or DVP < 3cm
• Clinical presentation = Small for gestational age / small SF, Easily palpable fetal parts, firm fetus
• Causes = placental insufficiency, congenital abnormalities, postdates, PPROM
• Complications = Fetal death, PTB, fetal distress, cord compression, uterine dysfunction during labour, fetal lung hypoplasia, amniotic bands, pressure deformaties
• Mx = Determine the cause, assess the placental function and cervical length, assess for PET, consider IOL.

Question 21

Polyhyframnios
Define
Clinical presentation
Causes
Complications

Answer 21

• Definition = excessive amniotic fluid, DVP > 8cm
• Clinical presentation = large SF, difficult to feel fetal parts, Patient may be SOB, discomfort, nausea and vomiting
• Causes = DM, fetal congenital abnormalities, infections (TORCH), multiple gestation, fetal hydrops, congenital malformations, idiopathic
• Complications = PTB, PPROM, Abruptio placenta, cord prolapse, abnormal lie/presentation, PPH, increased operative deliveries, Respiratory distress, prematurity,
• Mx = based on the severity and gestational age. Determine the cause, treat any complications, can do an amnio-drainage if severe, controlled ROM.

Question 22

Abnormalities in colour of amniotic fluid

Answer 22

Green = fresh meconium
Brown = previous meconium
Yellow = bilirubin due to fetal hemolysis (Rh-iso-immunization)
Blood = Abruptio