In the past, parents-to-be concerned with the genetic state of their gestating offspring had to test both the mother's and father's blood in order to determine what traits the child would likely inherit. But this method of genetic testing often leads to some socially awkward situations, as it's estimated that the incidence of "non paternity" is anywhere from 3 to 10% of babies; in other words, the guy who thought he was the father isn't actually the father (which explains why there are so many paternity episodes of Maury Povich). So, what to do? How about just ignore the man entirely?
Scientists at Stanford University have figured out a way to test for genetic defects by focusing entirely on the mother's DNA and inferring what traits the baby will inherit. Here's how it works, in terms as laymen as this non-scientist can put it: a woman's genome sequence can be determined by examining her red blood cells. Her future child's genome sequence is present in her plasma cells. And, obviously, Dad's DNA is in Dad's blood. In order to determine what's going on in the baby's genes without peeking at Dad's, scientists compared the woman's genome to her plasma. Genes that the baby would inherit from the mother were present in excess in plasma cells, and genes that the baby would likely inherit from the father were present in the plasma cells but not present in the mother's red blood cells. A less complicated way to tell if a pregnancy will survive! Hooray!
Not so fast. Unsurprisingly, there are some pretty serious ethical issues when it comes to fetal genetic testing. Critics worry that minimally invasive early pregnancy testing could lead to abortions for reasons that many would consider suspect — an extreme example: the child won't be tall enough, or the child will have the wrong color eyes (or gender, or a disability with wildly varying severity like Downs). But scientists say that this could be an empowering tool for parents-to-be, allowing them to determine early in pregnancy whether or not their baby will have a fatal genetic disorder and giving them the freedom to choose abortion if they'd prefer to not carry a nonviable pregnancy into the third trimester. Finding out sooner that a tragedy is imminent gives parents more options, makes a difficult decision less physically traumatic on the mother, and could theoretically help minimize emotional trauma for family members excited for the child's birth. On a less morbid note, genetic testing like this can help doctors detect a myriad of disorders, some of which can be treated more effectively with early detection.
Unfortunately, scientists haven't yet developed a test to accurately determine whether your baby will grow up to be the type of person who doesn't give up her seat to old people on the subway, or if your baby will one day be rude to wait staff. The prenatal jerk test is years, if not generations away.