Imaging in Pregnancy

Question 1

What are the concerns with X-ray in pregnancy?

Answer 1

• Away from the pelvis - negligible, if any, harm.
• Of the pregnant uterus - possible but unsubstantiated increase of childhood cancer in the baby.

Question 2

Is there any evidence of harm in using MRI in pregnant women?

Answer 2

No

Question 3

What is the main concern surrounding USS in pregnant women?

Answer 3

• There is no direct harm; the main concern is false positive.
  
  • For example, finding ovarian cysts of unknown significance that can lead to anxiety or even unneccessary intervention.

Question 4

What is the lower segment of the uterus?

Answer 4

The lower part of the uterus that develops from the uper part of the cervix usually from about 25 weeks or sooner if there is premature labour.

Question 5

What are you looking for when you carry out imaging of the uterus?

Answer 5

• Uterine anomalies
  
  • Bicornuate uterus
• Uterine tumours
  
  • Fibroids (fibromyomata)
• Cervix
  
  • Length is a predictor for onset of labour
  • Especially important if very premature / late miscarriage
• Uterine artery blood supply
  
  • A predictor for pre-eclampsia

Question 6

What is shown in the image, pointed out by the yellow arrow?

Answer 6

• 5-6cm uterine fibroid
• Can increase the chance of PPH
• Worst case - can affect the blood flow to the placenta

Question 7

What are you looking for when imaging the placenta?

Answer 7

• Location of the placenta
  
  • Major and minor placenta praevia
• Location of cord vessels
  
  • Vasa praevia
• Abnormal placentation
  
  • Accreta
  • Percreta

Question 8

What is placenta praevia?

Answer 8

• When the placenta inserts into the lower uterine segment.
• Covers the internal cervical os = major.
  
  • ​Prevents the baby being born normally.
• Doesn’t cover the internal cervical os = minor.
  
  • ​Normal birth can sometimes occus.
• Major PP in earlier pregnancy can become minor PP in later pregnancy as the lower segment develops.

Question 9

Describe vasa praevia.

Answer 9

• Normally the cord arises directly from the placenta, but if the vessels joining the placenta to the umbilical cord run through the membranes,

AND

• also pass through the lower segment across the internal cervical os, in labour the baby can come through its own blood supply on the way out.
• Uncommon, but difficult to spot and can be disastrous.

Question 10

Describe placenta accreta / percreta.

Answer 10

• The placental trophoblast invades through the endometrium (called decidua in pregnancy) and into or through the myometrium.
• Becoming more common as associated with repeat C-section.
• Can be life threatening for both mother and baby.
• Usually results in hysterectomy at the time of C-section (due to the massive blood supply of pregnancy, can be difficult and result in major haemorrhage).
• While still uncommon, it is one of the major reasons to avoid C-section unless absolutely necessary.

Question 11

What are you looking for when carrying out imaging in early pregnancy?

Answer 11

• Is the baby alive?
  
  • Up to 7 weeks - no certainty.
  • Even at full term, especially with maternal obesity or twins, it can still be difficult.
• Up to 13 weeks:
  
  • Location - intra-uterine / ectopic
  • Number of fetuses and type if multiple
  • Size of the fetus (and therefore gestation)
  • Some anatomical structures

Question 12

What are you looking for when carrying out imaging in later pregnancy?

Answer 12

• Alive or not?
• Fetal anomaly screening (18 to 21 weeks)
• Growth
• Wellbeing
• Presentation
  
  • Cephalic or breech or transverse or oblique
• Position of head in labour

Question 13

What are you looking for on imaging at 18-22 weeks of pregnancy?

Answer 13

• Screening test for fetal anomaly
• List of anatomical structures to check, including:
  
  • Head / cerebral hemispheres and lateral ventricles
  • Cerebellum
  • Fetal face
  • Limbs
  • Hands and feet
  • Heart
  • Diaphragm
  • Kidneys and bladder
  • Spine

Question 14

What are the outcomes of ectopic pregnancy?

Answer 14

• This ectopic has not yet started to bleed.
• Ectopic pregnancies rarely rupture; they often miscarry from the end of the tube and the blood trickles away.
• The point where it is thought that it has ruptures is when the woman has lost so much into her abdomen that she decompensates and feints.

Question 15

How are growth an wellbeing established on fetal scans?

Answer 15

• Growth measurements
  
  • Abdominal and head circumference / femur length
• Estimated fetal weight
• Serial estimation
• Error of measurement
• Liquor volume
  
  • (Liquor is fetal urine)
  • This is only useful if it is profoundly abnormal
• Fetal blood flow measurements
• Umbilical artery doppler
  
  • More resistance to blood flow through the placenta, the lower the amount of flow during fetal diastole.
  • Absent or reversed flow is most serious.
  • Low resistance placenta is a healthy placenta.
• Other fetal blood flow measurements
  
  • Middle cerebral artery
    
    • Fetal anaemia or hypoxia
  • Ductus venosus
    
    • Reversal of wave form in pre-terminal hypoxia