A comprehensive guide to early pregnancy screening: part 1

Early pregnancy care is extremely important in determining the health of both mother and baby and various tests can be carried out to establish any potential health issues during the baby’s development. In the first article of a two-part series esteemed consultant in obstetrics and maternal and fetal medicine.Dr Panicos Shangaris explains these tests and explains how these tests work and which potential health issues they can identify.  

What are the recommended screening tests during the early stages of pregnancy to assess the health of both the mother and the developing foetus?

Early pregnancy is an extremely important time for screening tests to ensure the health of both the mother and the developing foetus. Some recommended tests are as follows:

Pregnancy Confirmation Test

The first step is a pregnancy test, which is usually a urine or blood test. This test will confirm the pregnancy.

Dating Ultrasound

An early ultrasound may be performed to confirm the pregnancy location (to rule out an ectopic pregnancy), determine if there are multiple pregnancies and to confirm the gestational age and due date.

Blood Tests

A full blood count (FBC) will be used to detect if the expectant mother has anaemia. It determines both the blood type and Rh factor and if the mother is Rh-negative, she may need treatment to prevent Rh sensitisation.

If the mother’s immunisation status is unknown, tests for immunity to rubella (German measles) and chickenpox (varicella) are done. A test for syphilis, hepatitis B, and HIV may also be performed.

Urine Test

A urine test checks for urinary tract infections, kidney disease, and diabetes.

Screening for Gestational Diabetes

High-risk women (such as those who are overweight or have a family history of diabetes) may be screened early for gestational diabetes.

Genetic Screening

Depending on the woman's family history or ethnic background, certain genetic screenings may be recommended, such as carrier screening for conditions like cystic fibrosis or spinal muscular atrophy. Non-invasive prenatal testing (NIPT) can be done as early as 10 weeks to screen for Down syndrome and other chromosomal abnormalities.

Early Genetic Diagnostic Tests

For pregnancies at higher risk of genetic or chromosomal conditions, invasive diagnostic tests like chorionic villus sampling (CVS) may be performed in the first trimester. This test can diagnose certain conditions, but expectant mothers must be wary because it carries a small risk of miscarriage.

Screening for Infectious Diseases

In addition to those previously mentioned, women may be screened for other infectious diseases such as tuberculosis and sexually transmitted infections, including gonorrhoea and chlamydia, based on their risk factors.

These tests provide valuable information about both the mother’s and the developing foetus’s health. These tests must be discussed in detail with the healthcare provider, as the necessity can vary greatly depending on individual health histories, risk factors, and personal preferences.

What is the purpose of prenatal genetic screening tests, and what conditions do they typically screen for?

Prenatal genetic screening tests provide information about the likelihood of the foetus having certain genetic conditions. They are optional and can give expectant parents valuable information about the health of their developing baby. However, these tests do not provide definitive answers, they only have the ability to estimate the chances of a baby having certain genetic disorders.

The following conditions are commonly tested for through testing:

Down Syndrome (Trisomy 21)

Down syndrome is caused by an extra copy of chromosome 21. It's associated with intellectual disability and characteristic physical features. It may lead to heart defects and other health problems.

Edwards Syndrome (Trisomy 18) and Patau Syndrome (Trisomy 13)

These conditions develop due to an extra copy of chromosome 18 or 13, respectively. They are associated with severe intellectual disability and physical problems, and most babies with these conditions do not survive beyond infancy.

Open Neural Tube Defects, such as Spina Bifida

The spine, spinal cord, or brain defects occur when the neural tube doesn't close properly. This can lead to varying degrees of disability, including physical and intellectual.

Certain inherited genetic disorders

Depending on the parents’ family history or ethnicity, the foetus may be at greater risk of developing certain diseases, such as cystic fibrosis, Tay-Sachs disease, or sickle cell disease, therefore specific tests can be carried out according to the disease which of which the baby is at higher risk.

Different tests are available through the various stages of pregnancy.

First Trimester Screening:

This screening normally takes place between 11 and 14 weeks. It involves a blood test and an ultrasound examination called the nuchal translucency screening, which measures the thickness of space at the back of the baby's neck. This screening test can estimate the baby's risk of Down syndrome and trisomies 13 and 18.

Non-Invasive Prenatal Testing (NIPT)

Usually done after 10 weeks, this blood test analyses fragments of the baby's DNA in the mother's blood to screen for Down syndrome, trisomy 18, trisomy 13, and sex chromosome abnormalities.

Second Trimester Screening (Quad Screen)

This test usually takes place between 15 and 20 weeks and screens for four substances in a woman's blood to estimate the risk of Down syndrome.

As previously mentioned, it is important to remember that screening tests do not provide a diagnosis; they only provide a risk assessment. If screening tests indicate a higher risk, diagnostic tests such as amniocentesis can be performed to diagnose or rule out specific genetic conditions.

It is essential for every pregnant woman to have a detailed discussion with her healthcare provider to understand the benefits, risks, and limitations of these screenings and to decide which tests, if any, are right for her. The decision to have genetic screening is personal and should be based on the individual's values, concerns, and needs.

If you are pregnant and would like to book an appointment with Dr Shangaris, do not hesitate to do so by visiting his Top Doctors profile today.