What is pre-pregnancy carrier screening and should potential parents consider it?

July 14, 2017 by Gina Ravenscroft, Nigel Laing And Royston Ong, The Conversation
Couples thinking about kids can be screened for genes that may cause disease in their offspring. Credit: Redd Angelo, Unsplash, CC BY-SA

The American College of Obstetricians and Gynecologists recently recommended obstetricians, gynaecologists and other related health care providers offer pre-pregnancy carrier screening for genetic diseases to all patients.

Pre-pregnancy carrier screening involves testing healthy adults for the presence of gene mutations that cause diseases that are not present in them, but if both parents have the same recessive gene, could eventuate in their children. This includes diseases such as cystic fibrosis and muscular dystrophies.

Who are genetic carriers?

If both partners in a couple carry the same recessive , then the couple have a one in four chance of a child with that disease. Carrier couples may therefore have multiple affected children. Some recessive diseases are relatively mild but others are severe, including many that cause death at or shortly after birth.

Newton Morton, one of the founders of genetic epidemiology, estimated from population data as long ago as 1956 that each of us is a carrier of three to five lethal recessive mutations and this has been confirmed by more recent research. This means we are all carriers of something, but most of us are generally unaware of our carrier status unless we have an affected child.

Pre-pregnancy carrier screening

Historically, pre-pregnancy carrier screening programs have been tailored for specific population groups who are more likely to have a recessive disease. For example, the recessive brain condition Tay-Sachs disease, which is usually fatal in early childhood, has a high incidence in the Ashkenazi-Jewish community.

In 1969 it was discovered the loss of an enzyme (called hexosaminidase A) causes the disease. This led to the development of tests allowing carriers for Tay-Sachs disease to be identified. The first pre-pregnancy carrier screening programs in the Ashkenazi population followed in the 1970s. Since then the incidence of Tay-Sachs disease has reduced by more than 90%.

Other such targeted pre-pregnancy carrier screening programs exist in other parts of the world. For example in Mediterranean countries where there is a high rate of the recessive blood disease thalassaemia, pre-pregnancy carrier screening was offered and this also resulted in a reduction in the incidence of the disease.

Today, the country with the most comprehensive pre-pregnancy carrier screening program is Israel. It introduced a national program in 2003 and by 2015, the program was screening approximately 60,000 people annually for nearly 100 recessive conditions. The Israeli program is tailored to the different ethnic groups in the country, but also includes diseases common in all ethnic groups such as spinal muscular atrophy.

Diagnostic laboratories around the world are now using technology that can sequence multiple individuals for hundreds of disorders at once. This technology is used to diagnose many different types of genetic diseases and is more effective than standard diagnostic testing. It has also been investigated for carrier screening and can detect carriers of multiple recessive disorders.

Autosomal recessive inheritance of harmful mutations. Credit: National Library of Medicine


When pre-pregnancy carrier screening programs are introduced, they reduce death and disease associated with the screened diseases. They can save families from experiencing the tragedy of a child affected by a significant genetic disease. They also reduce the burden of recessive disease within the population as a whole.

Each recessive disease is rare but there are hundreds of recessive diseases and so collectively they have wide-ranging social and economic impacts. A study of 50 severe recessive diseases found their collective incidence to be greater than that of Down syndrome (one in 600 compared to one in 1,100).

So pre-pregnancy carrier screening programs that include many , as now recommended by the American College, would maximise knowledge of genetic risk for couples.


When testing genes, some identified variations are definitely harmful while most are definitely harmless. But for some variations we can't be sure if they are harmful, and whether or not they will cause disease in any children.

And some mutations, called de novo mutations, arise spontaneously during the development of a child. These mutations cannot be detected by pre-pregnancy screening.

So while the risk of having an affected child is reduced by pre-pregnancy carrier screening, it is not eliminated.

There are no guarantees that pre-pregnancy screening will result in a healthy baby, but it will allow couples options to reduce the burden of disease associated with known disease-causing mutations.

Counselling is required before and after the test to explain the risks to couples.

There is little health risk from the test, no more than the risk associated with taking a blood sample. The cost may be prohibitive for many couples, though. While it depends on the number of genes screened, costs may be several hundred dollars per person.

Can and should we have testing in Australia?

A small number of targeted pre-pregnancy carrier programs have been in place in Australia for a number of years including for Ashkenazi populations, for individuals with a family history of various diseases, and in IVF clinics. In Victoria the Victorian Clinical Genetics Service offers private pre-pregnancy carrier screening.

Several Australian groups, such as the Australian Genomics Health Alliance, are researching ways to screen larger numbers of genes. It remains to be seen if Australian bodies will make similar recommendations to those in the US.

Explore further: ACOG recommends use of carrier screening before pregnancy

Related Stories

ACOG recommends use of carrier screening before pregnancy

February 27, 2017
(HealthDay)—The American College of Obstetricians and Gynecologists (ACOG) recommends use of carrier screening for all women, according to two Committee Opinions published in the March issue of Obstetrics & Gynecology.

What's missing from current methods for genetic screening of sperm donors?

April 26, 2016
U.S. sperm banks perform genetic testing to screen for and disqualify carriers of a limited number of recessive disease mutations, but more comprehensive and affordable DNA-based screening methods are now available that can ...

The future in your genes

October 4, 2013
Would be parents are opting for cystic fibrosis (CF) carrier screening tests to assess the chances of having a baby suffering with CF, a life-shortening genetic disorder with no cure.

Recommended for you

Though most prolapse surgeries regress over time, symptoms remain improved

April 17, 2018
An estimated one in three women in the U.S. has a pelvic floor disorder, a condition that often develops after bearing children and getting older. These disorders can lead to incontinence, painful intercourse and even the ...

Painkillers in pregnancy may affect baby's future fertility

April 16, 2018
Taking painkillers during pregnancy could affect the fertility of the unborn child in later life, research suggests.

Mom's marijuana winds up in breast milk

April 10, 2018
(HealthDay)—Breast-feeding has known benefits for both baby and mom, but if a new mom also smokes marijuana, does the drug turn up in her breast milk?

Like babies, eggs send signals when 'hungry'

April 9, 2018
In humans and other mammals, the female reproductive cells - the eggs or oocytes - need nourishment in order to grow and remain fertile. It is known that the egg gets its food from little arm-like feeding tubes (called filopodia) ...

New clues to restoring fertility in women with disabling ovary disorder

April 9, 2018
Groundbreaking research out of the University of Otago is showing potential to restore fertility in women suffering polycystic ovary syndrome.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.