Rhesus, low birthweight and placental insufficiency Flashcards
What is rhesus?
- The name rhesus refers to various types of rhesus antigens on the surface of red blood cells.
- The antigens on the red blood cells vary between individuals.
- The rhesus antigens are separate to the ABO blood group system.
What can happen within a rhesus group?
Within the rhesus group, many different types of antigens can be present or absent, depending on the person’s blood type.
The most relevant antigen within the rhesus blood group system is the rhesus-D antigen
What do we mean when we refer to someone’s rhesus status in pregnancy?
When we refer to someone’s rhesus status in relation to pregnancy (e.g. “she is rhesus-negative”), we are usually referring to whether they have the rhesus-D antigen present on their red blood cell surface.
What happens when a woman is rhesus- D negative?
possibility that her child will be rhesus positive.
- It is likely at some point in the pregnancy (i.e. childbirth) that the blood from the baby will find a way into the mother’s bloodstream. - - When this happens, the baby’s red blood cells display the rhesus-D antigen. The mother’s immune system will recognise this rhesus-D antigen as foreign, and produce antibodies to the rhesus-D antigen.
- The mother has then become sensitised to rhesus-D antigens.
When does the sensitisation process in rhesus cause problems
- Generally not in 1st pregnancy
- During subsequent pregnancies, the mother’s anti-rhesus-D antibodies can cross the placenta into the fetus.
- If that fetus is rhesus-D positive, these antibodies attach themselves to the red blood cells of the fetus and causes the immune system of the fetus to attack them, causing the destruction of the red blood cells (haemolysis).
- The red blood cell destruction caused by antibodies from the mother is called haemolytic disease of the newborn.
What is the management for Rhesus?
Prevention of sensitisation is the mainstay of management. This involves giving intramuscular anti-D injections to rhesus-D negative women. There is no way to reverse the sensitisation process once it has occurred, which is why prophylaxis is so essential.
How does the anti- D medication work?
by attaching itself to the rhesus-D antigens on the fetal red blood cells in the mothers circulation, causing them to be destroyed. This prevents the mother’s immune system recognising the antigen and creating it’s own antibodies to the antigen. It acts as a prevention for the mother becoming sensitised to the rhesus-D antigen.
When are Anti-D injections routinely given?
- 28 weeks gestation
- Birth (if the baby’s blood group is found to be rhesus-positive)
- Anti-D is given within 72 hours of a sensitisation event.
Where are Anti-D injections given?
Anti-D injections should also be given at any time where sensitisation may occur, such as:
Antepartum haemorrhage
Amniocentesis procedures
Abdominal trauma
What happens after 20 weeks gestation?
Kleinhauer test is performed to see how much fetal blood has passed into the mother’s blood, to determine whether further doses of anti-D are required.
What does the Kleihauer test check?
- The Kleihauer test checks how much fetal blood has passed into the mother’s blood during a sensitisation event.
- This test is used after any sensitising event past 20 weeks gestation, to assess whether further doses of anti-D is required.
How does the Kleihauer test work?
The Kleihauer test involves adding acid to a sample of the mother’s blood. Fetal haemoglobin is naturally more resistant to acid, so that they are protected against the acidosis that occurs around childbirth. Therefore, fetal haemoglobin persists in response to the added acid, while the mothers haemoglobin is destroyed. The number of cells still containing haemoglobin (the remaining fetal cells) can then be calculated
What is rhesus disease a cause of?
haemolysis manifest in the first 24 hours of life due to rhesus incompatibility between mother and baby. It is the result of a mother being rhesus negative and having antibodies produced towards a rhesus positive baby.
When does Rhesus disease most commonly occur?
It occurs after the mother has been sensitised by either a mismatched blood transfusion, or from foetal blood entering her circulation during miscarriage, abortion, placental bleeding, amniocentesis or external cephalic version. Most commonly it occurs at the end of a previous pregnancy during labour and delivery.
How does haemolysis in Rhesus occur?
The mother reacts to fetal blood by producing antibodies of anti-Rh D type, which cross the placenta during pregnancy and cause haemolysis of the fetal red cells
When is Rhesus sensitisation more likely?
Sensitisation is more likely if the mother and foetus are ABO compatible, as this ensures that fetal cells persist in the maternal circulation for a more potent immune reaction to be stimulated.
What does the severity of the condition caused by Rhesus incompatibility vary from>
varies from the baby born with mild jaundice and anaemia to the development of hydrops fetalis in utero. The latter is usually fatal.
Which Rhesus antigen is the most important?
Note that Rhesus D antigen is the most important and its absence is used to categorise Rhesus negative. However antibodies to other Rhesus antigens may develop (Rh C, Rh E), and can cause Rhesus immunisation.
When should anti-rhesus (anti-D) immunoglobulin be giveN?
after delivery to all Rh-negative women where the baby’s blood group cannot be determined (e.g. if macerated stillbirth). Also anti-D should be given to Rh-negative mothers following the birth of a Rh-positive infant, immediately or within 72 hours
When is antenatal prophylaxis with anti-D given?
antenatal prophylaxis with anti-D: NICE now recommends that routine anti-D prophylaxis is offered to all non-sensitised pregnant women who are RhD negative
can be given as:
- two doses of anti-D immunoglobulin of 500 IU (one at 28 weeks and one at 34 weeks gestation)
- as two doses of anti-D immunoglobulin of 1000-1650 IU (one at 28 weeks and one at 34 weeks gestation
- a single dose of 1500 IU either at 28 weeks or between 28 and 30 weeks gestation
In what other situations could anti-D be used?
- anti-D should also be given in management of an ectopic pregnancy in a Rh-negative woman
- anti-D should also be given to all Rh-negative women following any other potentially sensitising episode (e.g. surgical termination of pregnancy, abortion, stillbirth)
Who is Anti-D no longer necessary for?
Anti-D Ig is no longer necessary in women with threatened miscarriage with a viable fetus and cessation of bleeding before 12 weeks’ gestation (1)
What does NICE state with respect to use of Anti-D rhesus prophylaxis in ectopic pregnancy and miscarriage?
offer anti-D rhesus prophylaxis at a dose of 250 IU (50 micrograms) to all rhesus negative women who have a surgical procedure to manage an ectopic pregnancy or a miscarriage
Which women do we not offer anti-D rhesus prophylaxis to?
- receive solely medical management for an ectopic pregnancy or miscarriage or
have a threatened miscarriage or
have a complete miscarriage or
have a pregnancy of unknown location
do not use a Kleihauer test for quantifying feto-maternal haemorrhage
What are some causes of low birthweight?
Low birth weight may be due to premature birth, before 37 weeks - preterm infant - or poor fetal growth - small for dates infant. Some babies may be born both preterm and small for dates.
What is very low birthweight defined as?
Very low birth weight is defined as being less than 1.5 kg but more than 1 kg.
Extremely - less than 1kg
What is the definition of failure to thrive?
Failure to thrive refers to poor physical growth and development in a child
What is the definition of low birthweight?
Low birth weight is defined as all babies weighing 2500g or less at birth. It may be used as a blanket term including very and extremely low birth weight.
What is faltering growth defined in the 2017 NICE guidelines?
faltering growth in children as a fall in weight across:
- One or more centile spaces if their birthweight was below the 9th centile
- Two or more centile spaces if their birthweight was between the 9th and 91st centile
- Three or more centile spaces if their birthweight was above the 91st centile
What are centile spaces?
Centile spaces are the distance between two centile lines on a growth chart. The distance between the 75th and 50th centile lines is a centile space. A weight that falls this distance is a drop across one centile space.
Examples of centile lines?
For example, if the initial weight of a child is plotted halfway between the 9th and 25th centile lines and several months later is plotted halfway between the 2nd and 9th centile lines, they have dropped a full centile space.
What are some causes of Failure to thrive?
Inadequate nutritional intake
Difficulty feeding
Malabsorption
Increased energy requirements
Inability to process nutrition
What are some causes of inadequate nutritional intake
- Maternal malabsorption if breastfeeding
- Iron deficiency anaemia
- Family or parental problems
- Neglect
- Availability of food (i.e. poverty)
What are some causes of difficulty feeding?
- Poor suck, for example due to cerebral palsy
- Cleft lip or palate
- Genetic conditions with an abnormal facial structure
- Pyloric stenosis
What are the causes of malabsorption?
What are the causes of increased energy requirements?
- Hyperthyroidism
- Chronic disease, for example congenital heart disease and cystic fibrosis
- Malignancy
- Chronic infections, for example HIV or immunodeficiency
What is the inability to process nutrients properly?
Inborn errors of metabolism
Type 1 diabetes
What is involved in the assessment of low birthweight?
The aim of assessment is to establish the cause of the failure to thrive. This involves taking a full history, examining the child and completing relevant investigations.
What are the key areas needed to be assessed in the assessment of low birthweight?
- Pregnancy, birth, developmental and social history
- Feeding or eating history
- Observe feeding
- Mums physical and mental health
- Parent-child interactions
- Height, weight and BMI (if older than 2 years) and plotting these on a growth chart
- Calculate the mid-parental height centile
What does a feeding history involve for low birthweight?
A feeding history involves asking about breast or bottle feeding, feeding times, volume and frequency and any difficulties with feeding. An eating history involves asking about food choices, food aversion, meal time routines and appetite in children. Asking the parent to keep a food diary can be helpful.
How is BMI nad Mid parental height calculated?
BMI is calculated as: (weight in kg) / (height in meters)2.
Mid parental height is calculated as: (height of mum + height of dad) / 2.
What outcomes from the assessment that would suggest inadequate nutrition or a growth disorder are?
Height more than 2 centile spaces below the mid-parental height centile
BMI below the 2nd centile
What are the investigations for low birthweight?
NICE guidelines from 2017 on faltering growth recommend the following initial investigations:
Urine dipstick, for urinary tract infection
Coeliac screen (anti-TTG or anti-EMA antibodies)
Further investigations are usually not necessary where there are no other clinical concerns. Focused investigations should be considered where additional signs or symptoms suggest an underlying diagnosis, such as cystic fibrosis or pyloric stenosis.
What is the management for low birthweight?
Management depends on the cause and may involve input from the multidisciplinary team. All children with faltering growth should have regular reviews to monitor weight gain. Reviews that are too frequent can increase parental anxiety.
Where difficulty with breastfeeding is the cause, there are lots of ways for the mother to get support, including midwives, health visitors, peers groups and “lactation consultants”. Supplementing with formula milk is likely to successfully improve growth, however it often results in breastfeeding stopping
Other management for low birthweight?
Where inadequate nutrition is the cause there are several management options based on individual circumstances:
Encouraging regular structured mealtimes and snacks
Reduce milk consumption to improve appetite for other foods
Review by a dietician
Additional energy dense foods to boost calories
Nutritional supplements drinks
Where other measures fail and there are serious concerns the multidisciplinary team may consider enteral tube feeding. This needs to have clear goals and a defined end point.
