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Randomization and abortion

July 30, 2020

Randomization is a proven technique for controlling bias in drug trials. Alas, it is something that is much harder to do with many of the other things we want to study about people. Ideally, to study the effects of drinking, we would take a group of people turning 21, and randomly assign them either to the subset that will be teetotalers or the subset that will drink, and follow them for the next ten years. Or fifty. There’s just no practical ways to do that. And it might seem as difficult to take a group of pregnant women wanting abortion, and randomly assign them to a subset that gets that and a subset denied that. Except there, some researchers realized they could come pretty close, by looking at women who were denied an abortion because they missed the cut-off date, and compare them to women who were under it. And the results — published in a book — are not surprising:

Women in the study who received the abortion they sought were more likely to be in a relationship they described as “very good.” (After two years, the figure was forty-seven per cent, vs. twenty-eight per cent for the women turned away.) If they had been involved with a physically abusive man at the time of the unwanted pregnancy, they were less likely to still be experiencing violence, for the simple reason that they were less likely to be in contact with him. (Several of the participants interviewed for the book talk about not wanting to be tethered to a terrible partner by having a child together.) Women who got the abortion were more likely to become pregnant intentionally in the next five years than women who did not. They were less likely to be on public assistance and to report that they did not have enough money to pay for food, housing, and transportation.

The obvious criticism is that what divided the two groups was not quite random. Those who made their cut-off date may have differed in some important regards from those who did not. Perhaps they were more conscientious. Or less bothered morally with their choice. And perhaps their extra dose of diligence and lesser tendency to dithering was what mattered to their future lives, rather than their having the abortion they wanted. There is a power to true randomness for revealing the nature of things that near-randomness doesn’t quite meet.

PBS has an article on the use of fetal tissue in medical research, including vaccine development.

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