What would you do if an essential medical supply you used every day disappeared from store shelves and the inventories of online retailers overnight? Even in an era of 24/7 news coverage and social media, it turns out that this can happen to thousands of Americans while remaining all but invisible to the rest of the population.

It was in the middle of February, weeks before lockdowns and other social distancing measures were put in place around the United States, when customers first noticed the shortage of Clearblue fertility test strips, which suddenly became unavailable from major online retailers, including Amazon, Walmart, and CVS. These test strips are used with a device that allows women to track their menstrual cycles accurately and determine when they are most fertile. Clearblue is ostensibly aimed at couples trying to conceive children. But for thousands of mostly American Catholics, the monitor is used with the opposite intention: to avoid pregnancy by Church-approved means.

Natural family planning is arguably as old as the human race. Women have always been at least imprecisely aware that their likelihood of becoming pregnant rises and falls in accordance with a natural cycle. There are references to intentional period abstinence in the works of St. Augustine and in ancient Chinese medical documents. In the modern era, what users refer to colloquially as "NFP" or, waggishly, as "Vatican roulette," began with the publication of The Rhythm of Sterility and Fertility in Women by Dr. Leo Latz in 1932. Though some traditionalist Catholics remain critical of natural family planning, its licitness has been confirmed by Rome regularly at least since the reign of Pope Leo XIII.

In the early 20th century, most couples engaged in NFP used the so-called rhythm method, which involved the consultation of charts and the use of rulers, protractors, or slide rules. In more recent years the Creighton method, developed at the Catholic university in Nebraska, has become widespread. Creighton NFP requires analysis of cervical mucus, a technique that, in addition to being labor intensive, requires extensive instruction and remains open to human error.

Which is why in the late 1990s researchers at Marquette University in Wisconsin began to develop a new method based upon hormonal monitoring technology that had recently become available for couples attempting to increase their chances of conceiving. The advantages of this new technique were twofold: in addition to requiring less instruction, using devices such as the Clearblue fertility monitor left less room for user mistakes. Dr. Richard Fehring, one of the architects of the Marquette method, explained to The Week: "The urinary hormonal markers are more accurate and objective than other typical indicators of fertility."

While there are no reliable figures on the number of non-Catholics using the Marquette method, Fehring believes that its appeal could be widespread. "This is not a Catholic Church issue," he said. "It is a health and family planning issue." He points out that unlike NFP, synthetic birth control causes negative side effects for many women and poses numerous health concerns, including increased risks for certain types of cancer.

Fehring and his research associates are currently conducting two studies that would allow Marquette protocols to be followed with alternative, and much less expensive, technologies. While it is technically possible at present to apply Marquette techniques with non-Clearblue urine LH test strips, no users with who spoke with The Week had been trained in using these alternative products. This leaves Clearblue as an effective monopoly holder over this customer base.

This is not because the Swiss pharmaceutical company sought to acquire one. In fact, due to FDA regulations, Clearblue cannot publicly acknowledge that it is selling a product used by thousands of customers in the opposite manner for which it has been approved. "Hormone monitors are generally not cleared in the U.S. by the FDA for these purposes because it's a very costly and prolonged procedure to go through," Christina Valenzuela, a Boston Cross-Check NFP instructor, explained.

The disappearance of fertility test strips from online retailers and many store shelves was as surprising as it was sudden. "My wife and I had started having a conversation about getting a fertility monitor just as the pandemic became mainstream in the U.S.," said Asher Gelzer-Govatos, a graduate student in St. Louis. "We decided to order a monitor, and my wife got as far as putting one in her Amazon cart, when she realized that all the refill strips were sold out."

Many couples have turned to third-party sellers, who are charging as much as $60 or even $150 for a product normally listed at $30. Others have sought instruction in other NFP methods, including Creighton and Billings, an alternative mucus-based technique. Shawna Van Uden, a Canadian Billings NFP instructor, said that she has received numerous requests for emergency consultations from Marquette users.

Leah Libresco Sargeant, a writer in Princeton, N.J., recently switched to the Marquette method after giving birth to her daughter, Beatrice. "I was just at the end of my first box when the shortage hit," she said. "A friend of mine who also uses Marquette sent me an extra box of hers."

It is not entirely clear why the shortage emerged. At the beginning of April, Lesley Foster, a spokeswoman for ClearBlue said, "We are aware of some product not being available at all retailers as buying patterns are out of the ordinary at the moment." Foster said that coronavirus had not affected the supply of the test sticks, which are manufactured in China. "I can confirm that we have not had any manufacturing issues related to the current pandemic that have affected product supply. The Clearblue Fertility Monitor test sticks are currently available in CVS physical stores nationwide. We recognize, however, that many people want to avoid shopping in physical stores at the moment, so our immediate response has been to work on getting the product listed in as many online retailers as possible. We expect them to start having product available in the coming days."

Foster's reassurances about in-store availability were difficult to verify. CVS has removed the product from its online directory, which made evaluating inventory at individual stores difficult. In conversations with dozens of Marquette users across the country, The Week was unable to confirm a single in-store purchase.

Several weeks later, the test strips remain unavailable on Amazon, Walmart.com, and CVS's online platform. "There is no supply shortage of this product in the U.S.," Foster said again last week. "The product is still available nationwide in most CVS stores. Since COVID-19 has presented challenges for consumers to get into stores, we realize this option is not accessible for everyone right now. We are trying to get the item relisted [online], but there is a strict prioritization of medical, cleaning, and other essential goods on those sites in the wake of COVID-19, so other priorities have extended the timeline to get this accomplished. There will also be a ramp-up period where the inventory is gradually increased to meet demand, so it is unfortunately likely to be a month before the situation can be fully remedied."

Since the shortage began, Clearblue users have turned to one another for support. Valenzuela, the NFP instructor who is also a member of a lay Dominican group, created a Google Form that has allowed women in need to request strips from those who have a surplus. Valenzuela said that she became aware of the shortage in early February "when Amazon's availability started getting spotty." Some of her own clients even offered to purchase sticks for women who could not afford them on the black market.

Valenzuela's is one of dozens of underground networks for exchanging sticks that have emerged on Facebook and NFP message boards. "I am incredibly blessed with the generosity of many clients who have offered to purchase test sticks for anyone who has trouble affording them, or send sticks for free to others who can't find them," she said.

Carey Helmick in Alexandria, Va., said that she and her husband managed to accumulate a surplus of sticks before the shortage after seeing them available for a lower-than-average price on Amazon. "They were still on my shelf because I only use a handful each month, so I hadn't even been looking for more." Then in early April a friend alerted her to the shortage on a Facebook page for Catholic women. "We ended up giving a box to a nearby friend who asked if we had any extras," Helmick said. "They gave us some bread flour."

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