The Patient Equation

4Ava—Tracking Fertility, on the Road Toward Understanding All of Women's Health

It seems like a simple problem. There are just five days in a typical monthly cycle that a woman is able to get pregnant. Identifying those days can be the holy grail for a couple trying to conceive, but, historically, the tools available to make an accurate prediction have been deeply flawed. There's the calendar method, where a woman uses past cycles to predict the length of her current one, with roughly 30% odds of identifying the right days—not much better than chance. There's the temperature method, which, for best results, involves taking a rectal temperature reading first thing in the morning and watching for a 0.4-degree increase—an increase that tends to come at the very end of the fertile window, often too late to act on. And there's the cervical mucus method, which requires a woman to interpret subtle changes (as at least one website puts it¹) from tacky to cloudy to slippery.

No matter the approach, a complex, multivariate process is being reduced to just one set of measurements, just one source of data. Add to that the inconvenience of collecting that data and the potential difficulties in interpretation, and we're left with a real lack of useful and accurate information. Use whichever method you want, you're still not able to be particularly confident that you're identifying the optimal days to try for conception.

From a patient equation perspective, ovulation—while informed by multiple ...