After Kate Cox learned her fetus had Trisomy 18, a genetic disorder that almost always results in miscarriage or stillbirth, the Dallas-area mother of two realized: “It isn’t a matter of if I will have to say goodbye to her, but when,” the 31-year-old wrote in a Dallas Morning News essay.
Cox, with a high-risk pregnancy that could jeopardize her future fertility, soon found herself ensnared in the national debate over reproductive rights. She petitioned a judge to get an abortion in Texas — where the procedure is banned in most cases — under a narrow exception that allows abortions when the mother’s health is put seriously at risk. While a lower court ruled last week to allow the exception, the Texas Supreme Court reversed the decision on Monday, arguing that the condition does not “pose the heightened risks to the mother the exception encompasses.”
Cox has since fled the state to have the procedure elsewhere.
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The legal battle has garnered national attention, reflecting concerns among medical experts and reproductive rights groups when Roe v. Wade was overturned in 2022 that medical decisions would be made in courtrooms rather than doctor’s offices. It has also put a spotlight on one of several reasons a person might choose to end a pregnancy — a rare fetal chromosomal condition that can be discovered during pregnancy.
Trisomy 18, also known as Edwards syndrome, is a disorder in which a fetus has three copies of chromosome 18 rather than two. Because genes direct development, “almost all the organs have abnormalities,” said Mary Norton, a professor of obstetrics, gynecology and reproductive sciences at the University of California at San Francisco. There is some variation, but brain, kidney, limb and especially heart abnormalities are common, she said.
About 50 percent of babies carried to term with Trisomy 18 are born alive, according to studies cited by the Minnesota Department of Health; among them, an estimated 90 to 95 percent do not survive beyond their first year. Most die within 10 to 15 days, often from cardiac arrest or respiratory failure, according to the amicus brief filed by the American College of Obstetricians and Gynecologists.
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With Trisomy 18, there is a “slight increased risk of maternal complications,” Norton said, such as high blood pressure, and if a patient already has a high-risk pregnancy, that’s a part of the discussion about how to proceed. A California study of deliveries between 2005 and 2008 found Trisomy 18 pregnancies were 2.5 times more likely to be delivered by Caesarean section and 10 times more likely to be delivered at less than 32 weeks.
Kirsten Palmer, head of the Maternal Fetal Medicine unit at Monash Medical Centre in Australia, also pointed to the added risk of “significant mental health issues, such as depression.” Higher rates of excessive amniotic fluid as well as higher rates of small antepartum hemorrhages, or bleeding from the genital tract, can also occur, she said in an email.
Cox’s decision and her doctor’s judgment “should not be interfered with by politicians lacking medical expertise especially given the potential cost to Ms. Cox’s life, health, and fertility,” ACOG wrote in its brief.
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Cox had been to the emergency room at least three times during her pregnancy, The Washington Post reported, with “severe cramping, diarrhea, and leaking unidentifiable fluid.” Cox has had two prior C-sections and would have probably needed a third if she carried the pregnancy to term, according to the complaint — which doctors said could have affected her ability to have more children.
Kathryn Gray, a doctor who studies fetal anomalies at the University of Washington Medical Center, said it would be difficult for the law to reflect all the complexities that can exist in a pregnancy. “As a high-risk obstetrician, I think you appreciate a large number of things that can happen to patients.”
Trisomy 18 is “unpredictable and random” and not the result of the parents’ actions before or during pregnancy, according to the Cleveland Clinic.
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Risk grows with maternal age, though it can occur at any time. Palmer said that at 25 years old “there is about a 1:2200 chance of having a baby with trisomy 18 detected early in pregnancy,” while at 40, there is a 1 in 150 chance.
Trisomy 18 is seen in an estimated 1 out of 2,500 pregnancies, but most such fetuses don’t survive full term.
Most fetuses with Trisomy 18, including Cox’s, have what’s called “full Edwards syndrome,” meaning all of their cells have an extra chromosome. This version is usually more severe because “there’s the most extra genetic material, and it causes very disordered development,” Norton said.
Fetuses can also have an extra chromosome in some cells (Mosaic Edwards syndrome) or only a section of the extra chromosome 18 present in their cells (Partial Edwards syndrome). A fetus with Partial Edwards syndrome may be “slightly less likely” to be miscarried or stillborn, “but still, they have pretty serious problems,” while Mosaic has more variability in severity, Norton said.
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Signs of Trisomy 18 can show up at the end of the first trimester in a cell-free DNA screening. Diagnostic testing to confirm the condition includes chorionic villus sampling, which involves collecting a small sample of placenta at about 11 to 14 weeks, or, starting at about 15 weeks, having an amniocentesis, where amniotic fluid is tested, Gray said.
By week 20, such a condition would probably be visible in ultrasound, where you could see major heart and brain defects and growth problems, such as intestines developing outside the body, Norton said.
In Norton’s experience, most people having an ultrasound or getting the screening are excited about their pregnancy. They want pictures of the baby and look forward to learning the baby’s sex, she said, “and you have to give them this terrible news. And it’s really just horrifying.”
Still, Norton, who is based in California, where abortion is legal until viability, says she is “fortunate to live someplace where I can talk with patients about what makes the most sense for them and their family.”
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