Seeing Through a Pregnant Seeing Through a Pregnant MotherMother: : The Balance between The Balance between Downright Hazards and Upright Downright Hazards and Upright

BenefitsBenefitsDr. Chai Ming Cheng

Obstetrician and Gynaecologist

Scenarios…Scenarios…36-year-old pregnant

lawyer at 34 weeks POAK/C bronchial asthmaFever, cough, SOB for 3/7O/E: Tachypnoeic,

crepitation and ronchiCXR TRO pneumonia but

strongly refused by her

Scenarios…Scenarios…16-year-old girl complaining of

abdominal distension for the past 5 month.

Ass. with nausea, vomiting. She has no BO for the past four days

O/E: distended abdomen, soft but tense

AXR TRO Intestinal obstruction

ContentContentIntroductionIonizing Radiation

◦X-ray◦CT-scan◦Nuclear Medicine

MRISGH O&G Radiology ConsentsTake Home Messages

IntroductionIntroductionImaging studies are important

adjuncts in the diagnostic evaluation of acute and chronic conditions

Confusion about the safety in pregnancy results in unnecessary avoidance of useful diagnostic tests

Health care providers should weight the risks and benefits

IONIZING RADIATIONIONIZING RADIATION

Electromagnetic SpectrumElectromagnetic Spectrum

X-ray – DiagnosisX-ray – Diagnosis

X-ray – DiagnosisX-ray – Diagnosis

X-ray - DiagnosisX-ray - Diagnosis

Ionizing RadiationIonizing RadiationAbsorbed dose

◦Amount of energy deposited per kilogram of tissue

◦1 Rad = 10 mGyAccepted background cumulative

dose of ionizing radiation = 5 Rad (50 mGy)

Ionizing RadiationIonizing RadiationBackground radiation to fetus

during entire pregnancy = 1mGy (0.5-1.6 mGy)◦Cosmic Rays◦Radioactive substance from buiding

materials◦Radiation emitting from

TV/handphoneSingle CXR ≈ 10 days natural

exposure to background radiation

Radiation Radiation EffectsEffects

DeterminisDeterministictic

EffectsEffectsStochasticStochastic

EffectsEffects Damage to multiple

cells Effects are seen

above a threshold dose

Severity increased with radiation dose

Eg: malformations

(teratogenic), mental or growth

retardation, death

Damage to single cell

No dose threshold Eg:

childhood cancer (carcinogenic),

mutagenic

Deterministic EffectsDeterministic EffectsCommonest teratogenic effects

of exposure to high dose radiation are CNS changes

Greatest risk of microcephaly or mental retardation is during10-17 week of gestation (no proven risk <10wk, >27wk)

Deterministic EffectsDeterministic EffectsBackground risks:

◦Miscarriage: 15%◦Growth Restriction: 4%◦Major Malformation: 3%

NO increased risk from raidation dose < 5 Rad

Stochastic EffectsStochastic EffectsLifetime risk of developing cancer is

estimated to be < 1 in 10,000 per 1mGy (vs Natural risk of 1 in 500)

Exposure to 50 mGy radiation◦Childhood leukaemia: Additional risk of

<1-3 per 1,000,000/year (background risk 40 per 1,000,000)

20 years after Chernobyl Disaster◦No evidence of increase risk of solid

cancer or leukaemia

Stochastic EffectsStochastic EffectsRisk of inducing hereditary ds

(congenital defects) is negligible◦0.012% if exposed to 25 mGy (vs 1-3% Natural risk)

Japanese atomic bomb survivors◦NO increase incidence of genetic

disorders

IV contrast media in CT-IV contrast media in CT-scanscanMost commonly used: Iodinated mediaLow Risks

◦Nausea, vomiting, flushing, pain at injection site

◦Anaphylactoid reactionsCross placenta but no reported

teratogenic or mutagenic effectsTheoretical risk of free iodide on fetal

thyroid gland◦To check neonatal TFT in 1st wk of life

Nuclear Medicine ImagingNuclear Medicine ImagingPerformed by “tagging” a chemical

agent with a radioisotopeEg: V/Q scan, bone scan, renal scanTechnetium 99m

◦Most commonly used ◦Radiation exposure dose < 5 mGy◦Half life: 6 hrs◦Safe in pregnancy

Iodine (I131) is contraindicated in pregnancy

MRIMRI

MRIMRIMagnet used in MRI is measured

according to SI unit of Tesla (T)Generally range 0.5-3.0 T (Earth’s

magnetic field: 0.0005 T)Advantages:

◦ Image deep soft tissue structures◦ Not operator dependent◦ Does not use ionizing radiation◦ No evidence of actual harm

Terotogenesis Tissue heating Acoustic damage *

*Reeves et al, Neonatal Cochlear Function: Measurement after Exposure to Acoustic Noise during in Utero MR Imaging. Radiology, Dec 2010 Vol 257 Issue 3

ContraindicationsContraindicationsMagnetically sensitive

equipments◦Cardiac pacemaker◦Implantable defibrillators◦Intraocular metals◦Cochlear implants◦Intracranial aneurysm clips

MRI is not advisable in the 1st trimester

Contrast Enhancement in Contrast Enhancement in MRIMRIGadolinium-based agents

◦Use in pregnancy is controversial◦Water soluble, cross the placenta into fetal

circulation and amniotic fluid◦Prospective study on pregnant women who

received gadolinium in 1st trimester reported no adverse perinatal or neonatal outcomes

◦Thus, use should be limited to situation in which the benefits clearly outweigh the possible risks

(De Santis M, Straface G, Cavaliere AF, Carducci B, Caruso A. Gadolinium periconceptional exposure: pregnancy and neonatal outcome.

Acta Obstet Gynecol Scand 2007;86: 99-101.)

KKM RADIOLOGY KKM RADIOLOGY CONSENTSCONSENTS

(Please Find the Consents in SGH O&G Website)http://www.sgh-og.com/downloads/kkm-radiology-consents-for-pregnancy/

Take Home MessagesTake Home MessagesMRI is safe during pregnancyRadiation exposure through

Radiography, CT scan or Nuclear Medicine imaging is very low to cause harm to fetus

Concern on ionising radiation should not prevent or delay medically indicated radiological procedures

Clinicians should weigh the risks and benefits of any radiographic study

ReferencesReferences1. ACOG , Guidelines for Diagnostic Imaging During Pregnancy and

Lactation. Committee Opinion Number 656, Feb 20162. The American College of Radiology, Practice Guideline for Imaging

Pregnant or Potentially Pregnant Adolescents and Women with Inizing Radiation. 2008

3. SOGC Clinical Practice Guideline No. 306. The Use of Magnetic Resonance Imaging in the Obstetric Patient. April 2014

4. Review Safety of Diagnostic Imaging in pregnancy. The Obstetrician and Gynaecologist. 2010

5. Medicines and Healthcare Products Regulatory Agency, Safety Guidelines for Magnetic Resonance Imaging Equipment in Clinical Use. March 2015

6. The College of Radiographers and The Royal Colelge of Radiologists. Pregnancy and Work in Diagnostic Imaging Departments. 2nd Edition 2009

7. Health Protection Agency, The Royal College of Radiologists and The College of Radiographers. Protection of Pregnant Patients dueing Diagnostic Medical Exposures to Ionising Radiation. March 2009

THANK YOUTHANK YOU