5. Family history
Updated 8 October 2024
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Taking a family history during pregnancy is important for establishing:
- if there is a family history of any of the conditions screened for during newborn blood spot (NBS) screening
- the need to refer parents for an obstetrician appointment
- the need to refer parents for genetic counselling
- an appropriate birth plan that is written in the mother’s notes
- a referral and care plan for the baby following birth (this is extremely important for a baby at risk of having an inherited metabolic disease (IMD)
- correct interpretation of NBS screening results
If there is a known family history (on either parent’s side) of one the conditions screened for, then the sample taker must note the condition in the comments box on the blood spot card.
For example, write ‘family history of phenylketonuria (PKU)’. This is so that the laboratory knows why the sample has been taken early.
1. When to take the sample
If there is a family history, early NBS samples are recommended for some conditions. The table below summarises when to take NBS samples:
| Condition | Early sample | Routine sample | Comment for NBS card |
|---|---|---|---|
| Sickle cell disease (SCD) | No specific day | Day 5 | Results of both parents |
| Cystic fibrosis (CF) | N/A | Day 5 | Family history of CF |
| Congenital hypothyroidism (CHT) | N/A | Day 5 | Family history of CHT |
| Phenylketonuria (PKU) | 48 to 72 hours after birth | Day 5 | Family history of PKU |
| Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) | 24 to 48 hours after birth | Day 5 | Family history of MCADD |
| Maple syrup urine disease (MSUD) | 12 to 24 hours after birth | Day 5 | Family history of MSUD |
| Isovaleric acidaemia (IVA) | 24 to 48 hours after birth | Day 5 | Family history of IVA |
| Glutaric aciduria type 1 (GA1) | 24 to 48 hours after birth | Day 5 | Family history of GA1 |
| Homocystinuria (HCU) | N/A | Day 5 | Family history of HCU |
Early samples should be followed by the routine day 5 sample for the other conditions. When taking the day 5 sample, write on the blood spot card that it is a second sample and the reason for the early sample.
2. Family history of SCD
Couples known to be at high risk (1 in 4) of having a baby with SCD or beta thalassaemia major might wish to know their child’s NBS result earlier than normal. To be a known ‘1 in 4’ high risk pregnancy, the haemoglobin results must be known for both parents.
Local policies should be in place to take an early NBS sample for SCD at the parents’ request. Some Trusts offer a liquid capillary blood specimen (not cord blood) which can be taken for analysis soon after birth. This is not part of the screening programme and does not replace newborn blood spot screening.
The blood sample must be analysed in a laboratory with expertise in haemoglobinopathy analysis in the newborn period. It is the responsibility of the laboratory undertaking the analysis to inform the newborn screening laboratory of the result. Further details are available in the Sickle cell and thalassaemia handbook for newborn laboratories.
The sample taker should write on the day 5 blood spot card that an early sample has been taken. The newborn screening laboratory will undertake the routine screen as usual and this test will act as a ‘failsafe’ and quality check. It is important that parents receive the test result as soon as possible to relieve anxiety. A liquid blood sample is a parallel test to the screening sample and not a substitute.
3. Family history of CF
We do not recommend early screening for babies with a family history of CF. Take the routine NBS sample on day 5 as normal.
4. Family history of CHT
We do not recommend early screening for babies with a family history of CHT as there is no benefit to the baby. This is because there is a surge in thyroid stimulating hormone (TSH) in the first few hours of life. Screening using this protocol is only accurate after the TSH level has decreased, usually after a few days. Take the routine NBS sample on day 5 as normal.
5. Family history of IMDs
It is important to test babies with a family history of an inherited metabolic disease (IMD) at the earliest opportunity (this applies to all the IMDs except HCU where there is not a need for urgent treatment).
Failure to diagnose and treat an IMD early can lead to serious illness and possible death. Fortunately, early diagnosis and treatment minimises the complications and most children once diagnosed lead healthy normal lives.
The midwife should discuss the pregnancy at an early stage with the local specialist metabolic team and genetic service to plan careful management of the birth to minimise the risk of a metabolic crisis.
Management at birth will depend on the presentation of any previous siblings diagnosed with an IMD. If a previous sibling became ill shortly after birth, consider transferring the mother before the birth to a centre with all the facilities for managing an affected baby.
5.1 Management
If the results indicate the baby might have one of the conditions, the specialist metabolic team will advise the family how to manage their baby’s condition.
PKU
Before results: the baby should be established on a normal milk intake (bottle or breast milk) until the results become available.
MSUD
Before results: guidelines for the prospective management of a baby at risk of MSUD at birth are available from BIMDG. Consider transferring the baby to a specialist metabolic centre as soon as possible.
IVA
Before results: guidelines on ‘Management of a baby at risk of an organic acidaemia at birth’ are available from BIMDG. Consider transferring the baby to a specialist metabolic centre as soon as possible.
HCU (pyridoxine unresponsive)
Before results: no special management of the baby is required.
MCADD and GA1
Before results: it is essential that the baby maintains a good milk intake. A full term baby should be fed at least every 4 hours and a preterm baby at least every 3 hours.
Babies are particularly at risk in the first 72 hours after birth when feeding is being established. Top up feeds of expressed breast or formula milk may be necessary in the first 48 to 72 hours until feeding is established. If oral feeds are not tolerated, or if the baby is unwell in any way, make an urgent referral to a metabolic paediatrician for review.
Guidelines for the prospective management of a baby at risk of MCADD at birth are available from the BIMDG.