Types of Genetic Testing in the First Trimester of Pregnancy

Pregnancy is an exciting yet delicate phase in every woman’s life. Ensuring the health of both mother and child is the top priority. One of the most effective ways to achieve this is through genetic testing during the first trimester. This testing helps identify potential genetic disorders or chromosomal abnormalities in the early days of pregnancy, providing parents with crucial insights into their baby’s health. Understanding the different types of genetic tests available in the first trimester can help expectant parents make well-informed decisions regarding their pregnancy journey.

Who Should Consider Genetic Testing in the First Trimester?

Genetic testing during the first trimester of pregnancy is typically recommended for certain groups of expectant parents who may have a higher risk of passing genetic disorders to their child. Genetic testing during the first trimester of pregnancy is typically recommended for certain groups of expectant parents who may have a higher risk of passing genetic disorders to their child. While every parent can consider genetic testing, it is especially recommended if you or your partner have a family history of genetic disorders, such as Down syndrome, cystic fibrosis, or sickle cell anaemia. These tests can help assess the risk to your baby.

Expecting women over the age of 35 or those who have had previous pregnancies affected by genetic abnormalities should also consider first-trimester prenatal screening. ¹ Additionally, couples from certain ethnic groups with a higher prevalence of genetic disorders might benefit from early screening.

In some cases, even if there are no apparent risk factors, doctors may recommend first-trimester prenatal screening to rule out any possible issues and ensure peace of mind.

Types of Genetic Testing Available in the First Trimester

Several screening methods are available during the first trimester of pregnancy to identify genetic conditions, including:

Double Marker Screening (bHCG and PAPP-A)

This genetic testing during the first trimester of pregnancy measures levels of beta human chorionic gonadotropin (bHCG) and pregnancy-associated plasma protein-A (PAPP-A) in the mother’s blood. This test helps assess the risk of chromosomal abnormalities, primarily Down syndrome (Trisomy 21).

Accuracy: Very high in combination with other screenings.

Benefit: Non-invasive and provides valuable information early in the pregnancy.

Double Marker + Preeclampsia Risk (bHCG, PAPP-A, PIGF)

In addition to measuring bHCG and PAPP-A levels, this test includes placental growth factor (PIGF) to assess the risk of preeclampsia. Preeclampsia is a pregnancy-related condition characterised by high blood pressure that, if untreated, can affect both the mother and baby.

Accuracy: High sensitivity in detecting preeclampsia risk alongside chromosomal risks.

Benefit: Offers a comprehensive risk assessment for both chromosomal abnormalities and preeclampsia, allowing for timely medical intervention.

First Trimester Combined Screening:

This screening assesses the risk of chromosomal abnormalities, such as Down syndrome (trisomy 21) and Edwards syndrome (trisomy 18), by combining maternal blood tests and an ultrasound examination. It’s typically conducted between the 11th and 13th weeks of pregnancy.

Components:

Blood Test: Measures levels of pregnancy-associated plasma protein-A (PAPP-A) and human chorionic gonadotropin (hCG).
Ultrasound: Evaluates nuchal translucency (NT), which is the fluid thickness at the back of the baby’s neck.

Accuracy: Approximately 85% detection rate for Down syndrome in singleton pregnancies.

Benefit: Non-invasive assessment that helps determine the need for further diagnostic testing.

Non-Invasive Prenatal Testing (NIPT)

One of the most popular and safe first-trimester prenatal screening methods is the Non-Invasive Prenatal Test (NIPT). This test analyses small fragments of fetal DNA circulating in the mother’s blood. It helps detect chromosomal abnormalities such as Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and Patau syndrome (Trisomy 13). The test is done as early as the 10th week and carries no risk to the mother or baby.

Accuracy: 99% for detecting Down syndrome².

Benefit: Safe and reliable, providing early detection without any invasive procedures.

Rhesus D Track

This test determines the Rh factor of the baby through a blood sample from the mother. If the mother is Rh-negative and the baby is Rh-positive, there is a chance of Rh incompatibility, which can lead to complications. This test helps in identifying Rh-negative women who may require treatment to prevent any adverse outcomes.

Accuracy: High accuracy for Rh determination.

Benefit: Helps manage issues with Rh incompatibility, safeguarding both maternal and fetal health.

First Trimester Diagnostic Tests

Below is a list of diagnostic tests available during the first trimester of pregnancy to detect genetic conditions.

Chorionic Villus Sampling (CVS):

Chorionic Villus Sampling (CVS) is a prenatal diagnostic test performed between the 10th and 12th weeks of pregnancy to detect chromosomal abnormalities and certain genetic disorders. It involves collecting a small sample of placental tissue, either through the cervix (transcervical) or the abdominal wall (transabdominal), under ultrasound guidance. This procedure enables collection of fetal tissue for further diagnostic testing.

A genetic workup is essential when there is a suspected genetic abnormality and may include the following tests:

Carrier Screening: A genetic test that identifies whether an individual carries a gene mutation for certain inherited disorders, even if they do not show symptoms. It helps assess the risk of passing the condition to their child.
Karyotyping: A technique that examines the number and structure of chromosomes to detect abnormalities such as deletions, duplications, or translocations, which can lead to genetic disorders.
Prenatal Sanger Sequencing: A precise DNA sequencing method used during pregnancy to identify specific genetic mutations in the fetus, helping to diagnose hereditary conditions before birth.
QF-PCR / FISH: Rapid molecular techniques used to detect common chromosomal aneuploidies and structural abnormalities, providing quick and reliable results in prenatal testing.
Microarray: A high-resolution method that identifies submicroscopic chromosomal imbalances such as copy number variations, offering greater sensitivity than conventional karyotyping.
MLPA: A technique used to detect specific deletions, duplications, or gene copy number changes that may be associated with genetic disorders.
Low-Pass Whole Genome Sequencing: A sequencing approach that provides an overview of the entire genome at low coverage, enabling the detection of large chromosomal abnormalities and structural variations.
Fetal Trio Exome Sequencing (Trio Exome): An advanced genetic test that examines the protein-coding regions of the genome (the exome) in the fetus, along with those of both parents. By comparing the trio (mother, father, and fetus), this test can detect disease-causing mutations. It is particularly useful in cases where fetal ultrasound shows structural anomalies, or when other genetic tests such as karyotyping and microarray return normal results but a genetic disorder is still suspected.

Benefits of Genetic Testing in the First Trimester

Genetic testing during the first trimester offers several benefits for the expecting parents:

Early Detection of Genetic Conditions: Detecting genetic disorders in the early stages of pregnancy allows for better planning and medical intervention, if necessary.
Informed Medical Decisions: Identifying potential problems early on helps your healthcare provider create a personalised care plan that ensures the best possible outcome for both mother and child.
Access to Early Treatment: Some genetic disorders can be treated in utero, and early screening increases the chances of starting necessary treatments before birth.

The first-trimester prenatal screening plays a crucial role in assessing your unborn baby’s health. Understanding the types of genetic testing available helps you take informed steps towards ensuring a healthy pregnancy. You should discuss with your healthcare provider to select the most appropriate genetic screenings depending on your unique situation and medical history.

Conclusion

For reliable genetic testing and comprehensive care, MedGenome offers advanced testing options such as a non-invasive prenatal test, carrier screening, and genetic counselling. Contact MedGenome to learn more about how we can support you during your pregnancy journey.