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Pregnancy is a period of rapid development, and parents naturally want to understand what may influence their baby's health. Diet, stress, sleep and other aspects of daily life are often discussed in this context. However, when a concern about the baby's development is identified during pregnancy, it is important not to assume that it is simply the result of something the mother did or did not do.
Fetal development is complex, and genetic factors can be an important part of the picture. This is where advances in prenatal genomic testing are helping doctors understand some fetal abnormalities in greater detail.
Global recommendations published in 2026 by the European Society of Human Genetics (ESHG) and the International Society for Prenatal Diagnosis (ISPD) provide updated guidance on the use of diagnostic genomic sequencing during pregnancy. The recommendations focus on pregnancies where ultrasound or other clinical information raises the possibility of an underlying genetic condition. They are intended to help healthcare teams decide when genomic sequencing is appropriate and how its results should be interpreted.
When does genomic testing become relevant?
Genomic sequencing is not recommended as a routine test for every pregnancy.
According to the new recommendations, it can be considered when a fetus has a major single abnormality or abnormalities affecting multiple organ systems that suggest a possible genetic cause. It may also be considered in selected situations where there is a previous undiagnosed pregnancy or child with similar abnormalities, certain patterns of multiple minor abnormalities, or recurrent unexplained stillbirths accompanied by a similar pattern of fetal abnormalities.
This distinction is important for parents. The availability of a sophisticated genetic test does not mean that every pregnancy requires one. In pregnancies where there are no ultrasound abnormalities, the recommendations do not support prenatal genomic sequencing as a screening test. The paper notes that the diagnostic yield in asymptomatic fetuses is around 1%, while the potential for misinterpretation and the risks associated with invasive sampling need to be considered.
An ultrasound finding may raise a question, not always answer it
Ultrasound remains an important part of assessing fetal development. However, seeing an abnormality does not always explain why it has occurred.
The 2026 recommendations highlight the importance of accurate fetal phenotyping essentially, documenting what is seen in the fetus when genomic results are being interpreted. This is because the clinical features observed during pregnancy can help doctors determine whether a genetic variant identified through sequencing is relevant to the fetal condition.
There is also an important limitation fetal features can change as pregnancy progresses. Some conditions may become more apparent later in pregnancy, particularly certain neurological conditions. For this reason, the recommendations emphasise continued ultrasound monitoring, as changes in the fetal phenotype can sometimes help doctors reassess the significance of a genetic finding.
Does this mean lifestyle does not matter?
The supplied recommendations do not assess whether diet, stress, exercise or other maternal lifestyle factors influence fetal development. Therefore, they cannot be used to establish such a relationship.
What they do highlight is that when a fetal abnormality is detected, the explanation may involve factors that cannot be understood simply by looking at the mother's lifestyle. A genetic cause may be considered when the pattern of fetal findings suggests one.
This is particularly important for parents who may blame themselves after an unexpected finding during pregnancy. A fetal abnormality should not automatically be attributed to a particular food, activity, stressful period or other aspect of the mother's daily life. Determining the underlying cause requires appropriate clinical assessment.
Why testing both parents can be important
The updated recommendations identify trio testing analysing the fetus and both biological parents as the preferred strategy for prenatal genomic sequencing. According to the guidance, this approach can offer a higher diagnostic yield and a shorter turnaround time.
The interpretation also requires information about the parents and family. Parental health and reproductive history, as well as relevant information about siblings, should be collected and communicated to the team interpreting the genomic results. This information can help doctors understand whether a genetic finding fits the fetal condition and how it may have been inherited.
A genetic test does not always provide a complete answer
Genomic sequencing can provide valuable information, but it is not a guarantee of a diagnosis.
The recommendations note that more than half of cases can remain inconclusive. Genetic knowledge is also evolving, which means that the interpretation of a genetic variant can change as new information becomes available. Future developments discussed in the recommendations include technologies such as RNA sequencing, long-read sequencing, optical genome mapping and epigenetic signature analysis.
This is why a genomic result should not be viewed in isolation. It needs to be considered alongside the fetal findings, family history and other investigations.
Genetic counselling is an essential part of the process
Receiving information about a possible genetic condition during pregnancy can be difficult for parents. The recommendations therefore emphasise genetic counselling before and after testing.
Families should understand why the test is being offered, what it can and cannot identify, the possible results and what those results could mean for the pregnancy and the family. The guidance also stresses that testing and decision-making should take the family's needs and values into account.
Prenatal genomic medicine is therefore not simply about sequencing a genome and receiving a report. It involves deciding when testing is appropriate, understanding what is seen on ultrasound, interpreting genetic findings in that context and communicating the information clearly to parents.
For expectant parents, the key message is one of perspective. A baby's development is not something that can be explained by a single lifestyle factor or a single test. When a concern is identified during pregnancy, the right approach is to investigate it carefully rather than assume its cause.
As genomic medicine develops, the aim is not to test every pregnancy, but to use the right test for the right clinical situation. The 2026 global recommendations provide a framework for doing this while keeping accurate diagnosis, appropriate interpretation and informed decision-making at the centre of prenatal care.
(Dr Shrinidhi Nathany, Consultant Molecular Hematology & Oncology, Fortis Memorial Research Institute, Gurgaon)
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