Free Oxford Handbook of Midwifery by Janet Medforth, Sue Battersby, Maggie Evans, Beverley Marsh, Angela Walker

at first contact and 10.5g/dL at 28 weeks’ gestation.
In order to correctly assess for anaemia the impact of gestational age
on plasma volume should be considered. Use of haemoglobin level as a sole indicator of anaemia is not recommended.
Serum ferritin is the most sensitive single screening test to detect adequate iron stores. Using a cut-off point of 30micrograms/L a sensitivity of 90% has been reported. 1
1 National Institute for Health and Clinical Excellence (2008). Antenatal care: Routine care for the healthy pregnant mother. Clinical guideline 62. London: NICE. Available at: M www.nice.org. uk/cg62.
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CHAPTER 4 Antenatal care
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ABO blood group and rhesus factor: anti-D prophylaxis for the Rh-negative mother
At the initial appointment as well as obtaining a full medical and obstetric history from the woman, venous blood is obtained so that blood group, Rh factor, and the presence of red cell antibodies can be determined. This test will identify women who are Rh-negative and who therefore require further antibody testing during pregnancy.
Recording the blood group is necessary for future reference if the mother needs a blood transfusion around the time of birth. Group O is the most common blood type in the UK; 85% of individuals will also have the Rh factor and will therefore be Rh-positive.
What is the Rh factor?
The Rh factor is a complex protein antigen carried on the surface of the red blood cell. It is inherited from three pairs of genes called cde/
CDE. It is the pair named D that makes an individual Rh-positive and is
likely to cause Rh iso-immunization.
Rh-negative women who carry an RhD positive fetus may produce antibodies to the fetal RhD antigens after a feto-maternal haemorrhage. These antibodies may cross the placenta in future pregnancies causing haemolytic disease of the newborn (HDN) if the fetus is RhD-positive.
HDN can range in severity from stillbirth, severe disabilities, or death, to anaemia and jaundice in the neonate. To prevent this occurring,
Rh-negative women who have experienced a suspected or known sensitizing event during pregnancy are given an intramuscular injection of anti-D immunoglobulin (anti-D Ig) to prevent antibody production.
The anti-D Ig works by coating the fetal red cells that have escaped into the mother’s circulation so that they cannot be recognized by her immune system. This prevents maternal antibody formation, and thus protects the RhD-positive fetus of any subsequent pregnancy.
What is a sensitizing event?
Very occasionally Rh-negative women may produce antibodies as a result of a mismatched blood transfusion, but fetal red cells from the RhD- positive fetus can cross the placenta and enter the woman’s circulation at any time during the pregnancy, particularly if events cause bleeding from the placental site.
3The most important cause of RhD immunization is during pregnancy where there has been no overt sensitizing event. Sensitizing events include:
Threatened abortion, and abortion after 12 weeks’ gestation
Chorion villus sampling
Threatened abortion, spontaneous abortion, termination of pregnancy
Amniocentesis
Antepartum haemorrhage
Abdominal trauma
Hypertension
ABO BLOOD GROUP AND RHESUS FACTOR
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Eclampsia
Traumatic delivery, including caesarean section
Placental separation during the third stage of labour
Manual removal of the placenta.
In the Rh-negative woman these events should be followed by prophylactic administration of anti-D immunoglobulin. NICE has reviewed the advice that recommends that all Rh-negative women receive prophylactic anti-D. 1
The treatment regimen may vary according to local costs. For instance being able to offer a one visit option, staff costs of administration and the cost of the immunoglobulin.
The options are 500IU, at 28 and 34 weeks’ gestation.
1000–1650IU at 28 and 34 weeks’ gestation.
A single dose of 1500IU at 28–30 weeks as well as cover for sensitizing events.
If a