Prenatal & preconception genetic testing through the years: the past, present, and future

Prenatal & preconception genetic testing through the years: the past, present, and future
Pregnancy is one of the most transformative times in a person’s lifetime, yet it’s often filled with uncertainties and fear. Reproductive genetics aims to give meaningful knowledge before and during pregnancy so it’s not such a “black box” experience. Here, we dive into what questions genetic testing have been able to answer over the years and chart a trajectory where things are heading next.
Written by Dave Gennert, PhD candidate, and Christina Ren, MS, CGC
Orchid offers advanced genetic testing for couples who want their child to have the best shot of a healthy life. “Genetics for Humans” is where we unpack how genetics impacts our everyday lives and the latest tools to help you build a healthier family.

Over the past century, the technology available for genetic testing before and during pregnancy has greatly advanced. While what’s possible today with Orchid seems something out of science fiction, the reality is that science of prenatal testing has been continuously evolving for several decades. In the span of just 60 years, we went from only being able to tell pregnant women the gender of their baby after doing an invasive procedure to today. Through advanced genetic testing with Orchid, it’s now possible to predict how a couple’s combined genetics can influence their future child’s genetic predisposition to common conditions.

Let’s look at a brief timeline of key milestones that have enabled parents-to-be better prepare for their pregnancy and know what lies ahead.

1955 – Amniocentesis: Collecting floating skin cells from the baby during pregnancy

Prenatal diagnosis first started with procedures like amniocentesis which involves the use of a needle that goes through the pregnant woman’s abdomen to sample the fluid that surrounds the baby. This fluid is known as “amniotic fluid” and contains skin cells that have shed from the baby — just like how we shed our skin cells when showering. Fun fact: amniotic fluid is mostly the baby’s pee. Crazy, right?

1955 was the first time scientists used amniocentesis to find out a baby’s sex during pregnancy. The way they first determined this was by looking for “Barr bodies,” which are dense packets of DNA found only in female cells. If Barr bodies were found in the cells collected, the baby was a female!

1966 – Prenatal karyotyping: Taking a picture of the baby’s chromosomes

Starting in the late 1950s, certain genetic conditions were found to be caused by an incorrect number of chromosomes in the cells of affected individuals. For example, Down syndrome was observed in people with an extra chromosome 21, and Turner syndrome was found in women whose cells were missing an X chromosome.

“Karyotyping” is a way to see the number of chromosomes in a cell. It tells us if there are whole extra or missing chromosomes. Research published in 1966 was the first to report karyotyping being used to check the baby for chromosome abnormalities during pregnancy. This was done by looking at the cells collected through amniocentesis.

So, the advent of amniocentesis and karyotyping meant that doctors could diagnose the sex and chromosomal abnormalities during pregnancy to answers questions like, “does my baby have Down syndrome?”

1983 – Chorionic villus sampling (CVS): Analyzing placental tissue

Similar to amniocentesis, cells originating from the baby are collected by CVS using a needle. In CVS, the tissue collected is from the placenta. The benefit of CVS is that it can be safely offered earlier in the pregnancy during the first trimester. In comparison, amniocentesis is offered during the second trimester, after 16 weeks of pregnancy.

Same deal as with amniocentesis — placental tissue collected by CVS can screen for chromosomal abnormalities in the baby during pregnancy.

1990 – Embryo testing for single-gene disorders: Genetic testing enters the IVF clinic

In 1978, the world’s first baby conceived through in vitro fertilization (IVF) was born. Since the ability to create embryos outside the body, scientists began ways to safely test the genetic makeup of these embryos before transferring into the uterus.

A series of discoveries in 1989 and 1990 paved the way for diagnosing genetic disorders caused by single genes in embryos. These diseases, such as cystic fibrosis and Duchenne muscular dystrophy, are often caused by specific mutations in one particular place in the genome. In the late 1980s, researchers began discovering the specific genes and their mutations that cause these genetic disorders.

This type of test is now commonly referred to as preimplantation genetic testing for monogenic conditions (PGT-M). It’s used only for individuals or couples with a known single gene disorder such as cystic fibrosis or Huntington’s disease.

In 1990, one group of scientists found that they could diagnose cystic fibrosis in embryos by looking for a specific mutation in the embryos’ DNA. In 1992, the first healthy girl was born after embryo testing for cystic fibrosis.

1992 – Embryo testing for chromosome count: Screening for chromosome number abnormalities

In 1992, researchers developed a new method for determining the number of chromosomes in a single cell which was applied on embryo genetic testing. Over time, the technology that enables preimplantation genetic testing for aneuploidy (PGT-A) has evolved to allow for increased detection and reporting of chromosomal abnormalities at a finer granular level.

At its core, embryos with extra or missing chromosomes were more likely to miscarry and less likely to lead to a healthy baby. Today, this type of test is often used during IVF treatment in hopes of increasing the chance of a successful pregnancy.

1997 – Cell-free DNA: Maternal blood test to investigate baby’s DNA during pregnancy

In 1997, a breakthrough report found that scientists could detect pieces of the baby’s DNA circulating in the mother’s bloodstream during pregnancy. This meant that it was possible to prenatally screen for chromosomal abnormalities without the use of procedures like aminocentesis or CVS.

Cell-free fetal DNA (or non-invasive prenatal tests, NIPT) became commercially available in 2011. Today, it is recognized by the American College of Obstetricians and Gynecologists as a universal screening option for all pregnant women and is routinely ordered by doctors.

2012 – Genome sequencing: Finding the causes of mysterious diseases

The age of genome sequencing, ushered in by the Human Genome Project’s publication of the human genome in 2003, revolutionized the diagnosis of disease. Technologies were developed to more quickly and cheaply sequence DNA, and more research identified parts of the genome not only responsible for causing disease, but also for increasing someone’s predisposition to developing a number of diseases.

In the last decade, scientists have used these new technologies to search for answers when other prenatal diagnostic tests come up short. If prenatal ultrasounds reveal abnormalities in a developing baby, and the parents are not themselves carriers of any known genetic disorder, sequencing the baby’s genome may provide a way to find a diagnosis.

Over 85% of disease-causing mutations appear within genes, which are the parts of the genome that provide instructions for how the body’s cells make and use proteins. The “protein-coding” region of the genome is known as the “exome.” Sequencing either the exome or entire genome may reveal mutations that can cause a genetic disorder in a baby.

Today – Advanced genetic testing before pregnancy: Predicting genetic susceptibility to common conditions

Prenatal testing of the mid-20th century relied on invasive procedures during pregnancy that provide limited information. Technology has since progressed to deliver more meaningful genetic information at earlier stages in pregnancy.

The next step in advancing what genetics can tell us is in predicting how a couple’s combined genetics can influence their future child’s genetic predisposition to common conditions — diseases such as heart disease, diabetes, cancer, and Alzheimer’s that we all likely know of someone whose health has been significantly impacted by.

Advanced genetic testing, like what Orchid now offers, provides hopeful parents meaningful information as early in their reproductive journey as possible. Orchid’s technology integrates the findings from the past 30 years in genomic science to help answer questions that matter most to couples. As the science evolves to provide a fuller picture of the genome’s contribution to disease risk, such testing will also evolve to provide the most complete view of a child’s genetic health.

Orchid offers advanced genetic testing for couples planning on building their family. We use advanced tools and smart, caring humans to help you give your future children the best shot of a healthy life. Conceive with greater confidence and peace of mind

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