Management of the Rhesus Negative Mother

Dr Shantala VadeyarMD, FRCOG, DM

Advanced Obstetric Ultrasound (RCOG / RCR)Subspecialist Fetal & Maternal Medicine (RCOG)

Consultant Obstetrician, Fetal & Maternal Medicine

Kokilaben Dhirubhai Ambani Hospital, Mumbaiwww.totalpregnancycare.com

• Incidence of Rh neg individuals varies with race

• Caucasians (whites) 15%• Afro-Carribeans (blacks) 7-8%• Asians 5%• Chinese and Japanese 1%

Background

What is the Rhesus factor?

• It is a Red blood cell antigen

• Other Red cell antigens include -

• A, B – blood groups• Duffy, Kell, Kidd

Genetics of Rh factor

• C, D and E antigens• D antigen is the most

important and determines Rh positivity

• cDe is Rh positive• Two alleles –

heterozygotes or homozygotes

• Rh negative person has dd genotype

Rh positive Rh neg

Pathophysiology in pregnancy

• Rh negative mother• Carrying a Rh positive fetus• Some Rh positive RBCs cross over

into the maternal circulation• Since the mother has not been

exposed to these antigens, • She makes antibodies to this

“D” antigen

Pathophysiology of isoimmunisation

• These circulating “anti-D” antibodies enter fetus

• They will attack fetal RBCs that are rhesus positive

• This causes RBC destruction (hemolysis)

• This leads to fetal anemia• Fetus does not get

hyperbilirubimemia • Manifests as hydrops and

fetal loss

Management of Rh negative gravida

Coomb’s test

• Careful history• Previous pregnancy

losses• h/o blood transfusions• Check husband’s blood

group and Rh factor• Check anti-D antibodies • If no antibodies at

‘booking’, then repeat titres at 28, 36 weeks

Prophylactic Anti-D

• Prophylactic antenatal anti D at 28, 34 weeks 300 IU injection

• Following any episode of antepartum haemorrhage

• Miscarriage, Ectopic pregnancy

• Amniocentesis / CVS / FBS• Delivery – normal and LSCS

Anti – D:Mechanism of Action

• The Rh positive fetal RBCs that enter the maternal circulation are destroyed by the anti D

• Thus, the D antigen is not allowed to be presented to the maternal immune system

• Prevents ‘sensitisation’

Rh Sensitised PregnancyRh antibodies positive

Titres < 1:32

Titres 4 weekly till 24 wks and 2 wkly till term

Titres > 1:32

Serial fetal MCA Dopplers every 1-2 wks

Middle Cerebral Artery

MCA Doppler- Rhesus isoimmunisation

MCA Doppler- IUGR

Rh Sensitised Pregnancy - 2MCA Doppler VelocimteryPeak Systolic Velocity

MCA PSV 1.5 MoMs and above

Fetal Blood Sampling and consider IUT

If no facilities for FBS, amniocentesis

MCA PSV less than 1.5 Moms

Monitor MCA PSV 1-2 wkly

Fetal assessment of hemolysis– invasive procedures

• Amniocentesis and checking ODD 450 to check level of bilirubin in AF

• Fetal Blood Sampling and checking fetal Haemoglobin level

Amniotic fluid ODD 450

Intrauterine blood transfusion

Antenatal Steroids

• If preterm delivery <36 wks may be predicted, then antenatal steroids must be given to enhance fetal lung maturity

• 2 doses of betamethasone 12 mg• 24 hours apart• Careful blood sugar monitoring in

GDM• May also cause hyperacidity

Delivery

• Most commonly with Rh sensitised pregnancies – LSCS

• May try induction of labour• Continuous FHR monitoring• Early recourse to LSCS is any doubts• Neonatologists present at delivery

Neonatal Management

• Commonly need Phototherapy

• May need Exchange Transfusion

• Bone marrow suppressed if IUT

• Anemia – blood transfusion • Haematinics long term• Good long term outcome

Rhesus isoimmunisation-1• Mrs KC, age 38, P1, 15 yr

girl• Rh negative, booking

antibody screen• Anti D at 15 weeks- 11iu/ml• Scan at 20 weeks- MCA

Doppler normal• Repeat Anti D titres and

scans for MCA PSV every 2-3 weeks.

• 26 weeks- raised titres 20iu/ml and MCA PSV raised to 1.5MoMs

Rh isoimmunisation-2

• Amniocentesis ODD450- below action line

• 29, 30 weeks- MCA Doppler normal

• 30 weeks- repeat amniocentesis- slight increase in ODD 450 levels, but below action line

• 31 weeks- Steroids, MCA Dopplers every week- within 1.5 MoMs- normal

Delivery

• 32 weeks- amniocentesis- action line

• Options- Intrauterine transfusion v/s delivery

• 33+5 w- delivery- 2.2kg female

• Exchange transfusions and phototherapy postnatally- discharged 2 weeks

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