However, pregnancy tests can be taken as early as five days before the expected start of your period. (pregnancy-info.net)
There is one major aerosol event (Katmai) at the very start of the period but none after. (skepticalscience.com)
Regardless of the period, 3 - month returns following the start of a period of steady tightening were on average negative and more volatile, as markets initially reacted negatively to the start of a tightening cycle. (blackrockblog.com)