Guidance

Antenatal screening: special circumstances

Updated 6 July 2018

Special circumstances include women with relevant medical conditions or treatment who book for antenatal care.

1. Adoption

If either biological parent is adopted, they may not have accurate information on their true family origins. In low prevalence (LP) areas, these individuals should be treated as high risk and the woman should have full laboratory screening.

2. Blood transfusion

Individuals who have had a recent blood transfusion present misleading data on screening tests and will not show a true haemoglobinopathy result. During booking for antenatal care the healthcare professional (HCP) should ask all women if they have ever had a blood transfusion. If they have, the HCP should record:

• reason for transfusion
• date of last transfusion
• where the transfusion(s) took place

This information is also relevant when screening the baby’s biological father and should be conveyed to the laboratory on the blood test or family origin questionnaire (FOQ) form.

3. Bone marrow transplant

If either biological parent has had a bone marrow transplant (BMT) or stem cell transplant, the haemoglobinopathy screen results will usually reflect the genotype of the BMT donor. This means the genetic risk to the fetus will not be clearly identified.

If the biological mother has had a BMT, the baby’s biological father must be tested to ensure this is not a high risk pregnancy. If confirmation of the biological mother’s or father’s status is required, then a DNA test will be needed, and a hair follicle sample, rather than blood or saliva, is recommended. Follow-up should be based on both parental results.

4. Women with a major haemoglobin disorder

Pregnant women who have a major haemoglobin disorder are considered high risk and should always be booked for joint obstetric/haematologist care antenatally, not for midwifery-led care. The HCP responsible for following up screening results should make sure joint care is initiated by obstetrician and haematologist.

Occasionally, antenatal screening may identify women with previously undiagnosed sickle cell disease (Hb SC; Hb S/Beta+ Thalassaemia). However, most women with sickle cell disease and all women with thalassaemia major will know they have a condition before they become pregnant.

HCPs need to be aware that:

• there is a higher risk of having a baby with sickle cell disease or thalassaemia major (2 in 4 or 50% chance) if the baby’s father is a carrier
• the woman should be offered an appointment for counselling regarding care of her condition during pregnancy, as well as for genetic counselling and screening of the baby’s biological father
• if the woman is being transfused, blood tests may show normal or carrier status, and a careful booking history is required to identify the fact that the woman has a major haemoglobin disorder
• even if the woman has had a bone marrow transplant she will be ‘cured’ of the condition but can still pass a haemoglobinopathy gene on to her children
• women with a major haemoglobin disorder need specialist care during pregnancy and increased clinic visits may be indicated
• a hospital delivery should always be booked for women with a major haemoglobin disorder as they and their babies need close monitoring

There is guidance on care of pregnant women with sickle cell disease or thalassaemia major on the Royal College of Obstetricians and Gynaecologists’ website, and in units 3 and 4 of the sickle cell and thalassaemia screening e-learning module.

5. Women who book late in pregnancy or present un-booked in labour

Women who book very late in pregnancy, or who present at the maternity unit un-booked in labour, must be offered screening for a haemoglobinopathy. Screening could be in either the intra or post-partum period if the woman is in labour.

Results should be obtained within 3 working days. The offer of paternal screening should be conducted in the same way as routine antenatal screening early in pregnancy.

The focus is not reproductive choice, or the option to have prenatal diagnosis in this pregnancy. But it is important for the woman to know her genotype:

• for her personal health
• in preparation for newborn screening
• for future pregnancies

6. Screening results following miscarriage or termination of pregnancy

If a woman is screened antenatally and then has a miscarriage or abortion, screening services must still:

• inform her of screening results
• provide her with an information leaflet about her carrier status (where relevant)
• offer counselling and paternal screening, if she is a carrier

7. Women with a haemoglobinopathy who do not attend or cancel counselling appointment

Some women may not attend antenatal genetic counselling following a positive or inconclusive screening result. There must be a local policy to make sure these women are sent information about:

• their haemoglobinopathy screening result
• their specific carrier status (as appropriate)
• how to contact the relevant HCP for counselling at a later date, if the woman changes her mind

Primary care services and the community midwife should also be informed of the woman’s result, non-attendance for genetic counselling and screening of the baby’s biological father.

8. Couples with assisted pregnancies

8.1 Fertility treatment with sperm or egg donation or surrogacy

If a woman has had fertility treatment, it is important to establish the source of both egg and sperm to assess the potential risk of the baby inheriting a major haemoglobin disorder. If both egg and sperm are from the baby’s biological parents, the risk to the baby can be assessed as for any other carrier woman/couple.

If either the sperm or the egg has been donated to the couple, it is not possible to do a risk assessment of the pregnancy based on the parental screening results. If the donor sperm and/or egg have been screened for a haemoglobinopathy and the results are available, then this can be discussed with the couple.

If pregnancy has been achieved through a donor egg then the screening results on the woman will not be informative. Even if she is not the baby’s biological parent, it is best practice to always test the pregnant woman for a haemoglobinopathy to ensure optimal maternal care during pregnancy. The baby’s biological father must also be tested, irrespective of the woman’s result and, if screen positive, the fertility clinic should be contacted to obtain the biological mother’s haemoglobinopathy results.

If donor sperm has been used and the mother has a positive screening result then, where possible, the fertility clinic should be contacted to obtain the biological father’s haemoglobinopathy results.

In the case of surrogacy the fertility clinic should be contacted to obtain the haemoglobinopathy results of both biological parents.

If no screening results are available for either donor sperm or egg, then the process for dealing with this situation should be determined locally, with discussions between maternity services, specialist nurses and consultant haematologist.

9. Link between antenatal and newborn screening

The linked NHS sickle cell and thalassaemia screening programme is delivered across professional and organisational boundaries, so clear pathways and robust partnerships are required. The linked programme encourages practitioners to review results from antenatal testing before, during and after the newborn screening test is offered, and to check that the results are consistent.

At a minimum, all maternal carrier results, and all at-risk couple results should be linked to the appropriate newborn screening results. Use this form (Appendix 7) to make this link.

Maternal and paternal (where available) antenatal screening results should be recorded on the newborn screening blood spot card.

A linked service:

• makes sure every step of the screening process is informed by results from the previous step
• allows more accurate interpretation of the newborn screening results, avoiding unnecessary repeat testing, if both maternal and paternal results are known
• allows parents who have been screened antenatally to have prior information regarding the risk of their baby inheriting a condition, or being a carrier, and allows them to be prepared
• can help ensure everyone’s results are accessible throughout their lifetime, so appropriate information and care can be provided when and where needed.

A linked service does not always contribute to reducing parental anxiety. If the mother’s antenatal results show normal haemoglobin then the father will not generally have been tested. If the baby is subsequently found to be a carrier, the risk would not have been identified antenatally. Research shows that prior knowledge of carrier status gives parents a more positive newborn screening experience than discovering test results out of the blue^{[footnote 1]}.

The postnatal report given to all women following the birth of their baby should contain all antenatal screening results, including sickle cell and thalassaemia screening, for communication to primary care.

10. Guidance concerning possible non-paternity

All genetic tests undertaken during pregnancy and the newborn period will include the possible issue of non-paternity. This needs to be considered by all HCPs when offering screening tests, and when inviting the ‘baby’s father’ for testing. It should be highlighted to the mother that the correct person to be screened is the ‘baby’s biological father’ in order to assess the genetic inheritance in the baby correctly.

The role of HCPs, if there is any discrepancy, is to provide clarity and discretion around genetic screening test results, particularly as there is no consensus on the rate of non-paternity in the population^{[footnote 2]}. Obtaining this unsolicited information during screening creates an ethical dilemma about whether to pass the information on, and to whom. The revelation of non-paternity may be detrimental to established relationships and HCPs must be alert to the need for discretion in pursuing family studies and in discussing results with the mother/parents.

Non-paternity may be suspected when^{[footnote 3]}:

• a baby with a major haemoglobin disorder has a carrier mother but the ‘father’ is not a carrier
• a baby identified as a carrier has neither their mother nor their father identified as a carrier

However, even when screening results seem to suggest non-paternity, alternative explanations must also be considered.

For example:

• one parent may carry a variant that cannot be detected by routine screening methods such as an unstable variant or a silent form of beta thalassaemia.
• there may have been an error:
  • with labelling a sample
  • in the laboratory
  • in reporting the results
• a parent’s identity may have been stolen or used by another person
• the couple may have used assisted reproductive methods (artificial insemination by donor egg/sperm), which may not have been declared
• a very premature baby may not yet have developed any of their adult haemoglobin
• the baby may have developed a De Novo mutation, which although rare, is possible

Despite these possibilities, a risk of non-paternity remains and needs to be handled carefully if relationships and family units are not to be disrupted. When discussing results, the need for discretion is essential.

The HCP needs to be non-judgemental while considering the following actions:

1. Review the antenatal and newborn screening process to establish whether or not an error may have occurred at any stage of the pathway.
2. Explore the possibility of non-paternity with the mother, preferably on her own in private, without her partner present.
3. Agree with the baby’s mother how the situation will be dealt with if non-paternity is indeed a possibility.
4. Offer a re-test (in the first instance) to:
   • mother
   • baby
5. After discussion with the mother, if indicated, re-screen the father.
6. Carefully document results and communicate these only to those HCPs who need the information to support the family.

1. Kai, J Ulph, F Cullinan, T and Qureshi, N (2009) Communication of carrier status information following universal newborn screening for sickle cell disorders and cystic fibrosis: qualitative study of experience and practice. Health Technology Assessment 2009; Vol. 13: No. 57 ↩

2. Voracek M; Haubner T; Fisher ML (2008) Recent decline in nonpaternity rates: a cross-temporal meta-analysis. Psychological Rep. 2008 Dec; 103(3): 799-811 ↩

3. Turney L (2005) The Incidental Discovery of Non-paternity Through Genetic Carrier Screening: An Exploration of Lay Attitudes. Qualitative Health Research 2005; 15(5): 620 ↩