You probably remember how Target used purchase histories to predict pregnancies among their customer base (although, don't forget the false positives). Janet Vertesi, an assistant professor of sociology at Princeton University, made sure that sort of data didn't exist during her nine months.
First, Vertesi made sure there were absolutely no mentions of her pregnancy on social media, which is one of the biggest ways marketers collect information. She called and emailed family directly to tell them the good news, while also asking them not to put anything on Facebook. She even unfriended her uncle after he sent a congratulatory Facebook message.
She also made sure to only use cash when buying anything related to her pregnancy, so no information could be shared through her credit cards or store-loyalty cards. For items she did want to buy online, Vertesi created an Amazon account linked to an email address on a personal server, had all packages delivered to a local locker and made sure only to use Amazon gift cards she bought with cash.
The best part was that her modified activity—like purchasing $500 worth of Amazon gift cards in cash from the local Rite Aid—set off other (in real life) triggers.