O&g: Abnormalities Of The Cord And Amniotic Fluid

1 umbilical vein

2 umbilical arteries

Supported in Wharton jelly except near fetal insertion, where an epithelial covering is substituted

•length & diameter

•cord coiling

•abnormalities of cord insertion

•abnormalities of vessel number: single umbilical artery, four vessel cord

•cord abnormalities capable of impeding blood flow

•torsion and strictures

•hematoma

•cysts

50-60cm, ave 55cm

Cord length <35cm

May lead to fetal distress, placental abruption, prolonged labour

Cord length >80cm

Higher occurrence of nuchal cord, cord around body, cord knot, cord prolapse and cord compression

IUGR

Macrosomia

Number of complete coils divided by the cord length in cm

<10th percentile - hypocoiled

10th - 90th percentile - normocoiled

>90th percentile - hypercoiled

Fetal demise, IUGR & Intrapartum hypoxia

Trisomies, single umbilical artery

At or near the center of the fetal surface of placenta

1. Marginal insertion (Battledore placenta): cord insertion at placenta margin. 7% at term. Cord could be pulled off during delivery of the placenta

2. Furcate insertion: rare. Umbilical vessels separate from the cord substance before their insertion into the placenta

3. Velamentous insertion: 1.1% of cases. Umbilical vessels separate in the membranes at a distance from the placental margin. Surrounded only by a fold of amnion. More frequently seen in twins

4. Vasa praevia: associated with velamentous insertion when some of the fetal vessels in the membranes cross he region of the cervical os below the presenting fetal part. 1 in 5200 pregnancies. 1/2 is associated with Velamentous insertion & 1/2 with marginal cord insertions and bilobed or succenturiate placentas

•bilobed, succenturiate or low-lying placenta (risk of 80%)

•multifetal pregnancy

•pregnancy resulting from IVF

•color Doppler examination (low sensitivity with ultrasound)

•perinatal diagnosis: associated with increased survival

•antenatal diagnosis: associated with decreased fetal mortality compared with discovery at delivery

•hemorrhage: antepartum or Intrapartum

•detecting fetal blood

-Apt test (alkali denaturation test)

-Wright stain (to visualize nucleated RBC which is normally present in cord blood but not maternal blood)

If diagnosed prenatally

•elective C/S (early enough to avoid emergency but late enough to avoid prematurity)

•baby requires aggressive resuscitation + blood transfusion

If Intrapartum vaginal bleeding

•Speculum examination

•Apt

•immediate C/S if fetal bleeding is confirmed

Due to atrophy of the previously existing umbilical artery

•0.63% in live births

•1.92% in perinatal deaths

•3% in twins

Diabetes

Epilepsy

PET (pre-eclamptic toxaemia)

APH

Oligohydramnios

Hydramnios

Chromosomal abnormalities

Aneuploides

Tracheo-oesophageal fistula

Renal a genesis

Imperforate anus

Vertebral defects

34% are growth restricted

17% deliver preterm

Anastomosis between the two umbilical arteries within 3cm of placental insertion site. Acts a pressure equalizing system b/w the two umbilical arteries

When the umbilical artery fails to split and the two share a fused lumen. May involve the entire length or may be partial

False knots

True knots

Result from kinking of the vessels to accommodate length of cord and are die to redundancies of umbilical vessels/Wharton's jelly

Incidence of 1-2%

More common in monoamniotic twins

Active fetal movements create true knots

Risk of still births is increased 5-10 folds in those with true knots.

FHR abnormalities are common during labor but cord blood PH values are normal

When loops of cord coils around the fetus.

More likely with longer cords

Loops of umbilical cord around the fetal neck.

Contractions may compress the nuchal cord and cause FHR decelerations

Incidence:

1 loop of nuchal cord 20-34%

2 loops of nuchal cord 2.5-5%

3 loops of nuchal cord 0.2-0.5%

Single is safer than multiple umbilical cord loops around the fetal neck

Type A nuchal cord:

Encircles the fetal neck in a sliding manner (less dangerous). End of the cord connected to the placenta crosses over the end connected to the baby. Unlocked nuchal cord

Type B nuchal cord:

Encircles the neck in a locking manner (very dangerous). End of the cord connected to the placenta crosses under the end connected to the baby. Locked nuchal cord

At time of birth, look for cord around the neck.

If it is lose enough for the cord to be slipped over the baby's head

If the cord is too tight, then it has to be clamped and cut before the baby is born

This necessitates baby's birth rapidly, since it is no longer getting oxygen from the mother via placenta

Extreme focal deficiency in Wharton Jelly

May be found along the course of the cord

True cysts:

•epithelium lined

•remnants of the allantois

•coexist with patent urachus

False cysts:

•due to degeneration of Wharton's jelly

•single cyst may resolve completely

•multiple cysts may be associated with miscarriage

Funic presentation/procubitus

Note: membranes are ruptured

Occult cord prolapse: descent of the umbilical cord alongside the presenting part

Overt cord prolapse: umbilical cord past the presenting part

When one or more loops of umbilical cord is between the fetal presenting part and the cervix without rupture of membranes

•prematurity

•abnormal presentations (breech, brow, face, transverse)

•multiple gestation

•placenta praevia

•polyhydramnios

•premature rupture of membranes

•excessive length of cord

•maternal factors: multiparity, pelvic tumours, abnormal birth canal

•iatrogenic factor: artificial rupture of membranes with an unengaged presentation

1. Cord compression preventing venous return to the fetus

2. Umbilical arterial vasospasn secondary to exposure to vaginal fluids and/or air

•malpresentations + poorly applied cephalic presentations - ultrasound at the onset of labour

•during labour for patients at risk, continuously monitor for abnormalities of FHR

•avoid amniotomy until the presenting part is well applied to the cervix

•at the time of spontaneous membrane rupture a prompt, careful pelvic examination should be carried out

•if cervix is fully or almost fully dilated and head is down, use vacuum

•immediate CS

•head down or knee chest position

•lift foot off the bed

•500ml of N/S in bladder

•assistant may lift fetal head digitally and hold it

•manual replacement of the cord is not recommended

•to prevent vasospasm - minimal handling of the loops of cord lying outside the vagina and cobmver them in surgical packs soaked in warm saline

1. Physical properties

•colourless

•specific gravity: 1010-1020

•reaction: neutral or slightly alkaline (pH 7-7.5)

•volume: reaches maximum volume at 36 weeks (1-1.5 litre) and gradually diminishes to 500-1000ml at term. Completely changed every 3 hours

2. Chemical composition

•water 98-99%

•solids: 1-2%; half organic (carbs like glucose & fructose, proteins & hormones) and half inorganic (constituents similar to those found in maternal plasma like Na & Cl)

Maternal: filtrate from maternal plasma

Fetal:

1. Secretion from the amniotic epithelium

2. Fetal urine

3. Diffusion from the umbilical cord vessels

4. Transudation through fetal skin

5. Secretion from bronchial mucosa, buccal mucosa and salivary glands

Maternal: transudation into maternal circulation

Fetal: swallowing

A. During pregnancy

1. Protection of the fetus

2. Keeps the fetal temperature constant

. Allows free fetal movements

4. Prevents adhesions between the amnion and fetal skin

5. Nutrition

3. Allows free fetal movements4. Prevents adhesions between the amnion and fetal skin5. Nutrition6. Acts as a medium for fetal excretion7. Forms a closed sac around the fetus preventing ascent of infection, from the cervix or vagina

6. Acts as a medium for fetal excretion

7. Forms a closed sac around the fetus preventing ascent of infection, from the cervix or vagina

B. During labour

1. Helps dilatation of the cervix

2. It prevents direct compression of the placenta between the uterine wall and fetus during uterine contraction thus avoiding fetal asphyxia

3. When the membranes rupture, the fluid washes the birth canal from above downward thus removing any infectious material

1. Clinical assessment: unreliable

2. Objective assessment: depends on ultrasound

•deepest vertical pool

•amniotic fluid index: it is a total of the DVPs in each of the four quadrants of the uterus. It is a more sensitive indicator of AFV throughout pregnancy

10-25cm = normal

<10cm = reduced volume

<5cm = oligohydramnios

>25cm = polyhydramnios

Excessive amniotic fluid, more than 2 litres

By ultrasound, the vertical diameter of the largest pocket of amniotic fluid measures 8cm or more, or the amniotic fluid index (AFI) is 25cm or more.

Or a maximum vertical pool of >7cm

Mild: largest vertical pocket diameter 8-11cm

Moderate: largest vertical pocket diameter 12-15cm

Severe: largest vertical pocket diameter >/= 16cm

1-3.5% of all pregnancies

•Fetal malformation

-GIT: esophageal/duodenal atresia, tracheoesophageal fistula

-CNS: anencephaly (decreased swallowing, exposed meninges, no ADH)

•twin to twin transfusion - fetal polyuria (recipient twin)

•hydrops fetalis: congestive heart failure, severe anaemia or hypoproteinemia - placental transudation

•diabetes mellitus (osmotic diuresis)

•idiopathic

Acute polyhydramnios:

Very rare. Usually occurs in early pregnancy (16 weeks) and is almost always associated with uniovular (monozygotic) twins. Large amount of fluid accumulates in a few days. Leads to abortion or preterm labour.

Chronic polyhydramnios:

Commoner than acute. Usually in late pregnancy, the fluid accumulates slowly

Symptoms:

•dyspnoea

•oedema

•abdominal distension

•preterm labour

Abdominal examination

•uterus is larger than expected

•difficult to palpate fetal parts

•difficult to hear fetal heart sound

•ballotable fetus

Ultrasound

•excessive amniotic fluid

•fetal abnormalities

•assess fetal wellbeing: BPP & Doppler

Fetal karyotyping

I.

A) During pregnancy

1. Abortion (as a result of overdistension of the uterus)

2. Preterm labour

3. Premature rupture of membranes

4. Cord prolapse

5. Placental abruption

6. Malpresentation

7. Non-engagement of the presenting part

8. Pressure symptoms: as dyspnoea, palpitation and oedema of lower limbs

B) During labour

1. Early rupture of membranes

2. Prolapse of arm, cord or both

3. Abruptio placenta due to rapid escape of liquor with premature separation of the placenta

4. Splanchnic shock occurs if the fluid escapes rapidly, so the pressure exerted by the uterus on the splanchnic vessels drops suddenly leading to pooling of blood in the splanchnic area and shock

5. Postpartum hemorrhage due to: uterine atony due to overdistension of the uterus, retained placenta, prolonged labour

C) During puerperium: subinvolution

False.

They are ineffective

Diminished amniotic fluid less than 500ml.

By USS the vertical depth of the largest pocket of amniotic fluid measures 2cm or less, or the amniotic fluid index is 5cm or less

0.5% of all pregnancies

Midgestation (poor prognosis)

Third trimester

1. Fetal causes

•renal cause (57%)

-renal agenesis (Potter's syndrome)

-polycystic kidney

-urethral obstruction (atresia/posterior urethral valve)

•fetal growth restriction

•fetal death

•post term pregnancy

•preterm premature rupture of membranes

2. Maternal causes

•uteroplacental insufficiency

•preeclampsia

3. Placental causes

•twin to twin transfusion (donor twin)

4. Drug causes

•Prostaglandin synthetase inhibitors such as NSAIDs

5. Idiopathic

1. The fundal level is lower than the GA

2. Breech presentation is common

3. The fetal parts are easily felt and the fetus is almost immobile

4. The FSH are clearly heard

1. Ultrasound

•confirms diagnosis: DVP </=2cm or AFI </=5cm

•detects a cause: fetal growth restrictions, congenital anomalies

•malpresentation

•assesses fetal wellbeing: BPP and Doppler

2. Evaluation of fetal wellbeing (serial): fetal kick count - NST - BPP - Doppler

3. Fetal karyotyping

•amniotic adhesions or bands - amputations/death

•pressure deformities (club feet)

•pulmonary hypoplasia

-thoracic compression

-no breathing movement

•flattened face

•postural deformities

•treat the cause (PPROM, pre-eclampsia)

•assess fetal wellbeing (US/CTG/Doppler/BPP)

•vesicoamniotic shunting (urethral obstruction)

•amnioinfusion