For any woman out there who feels like she can't get her sleep to sync with that of her male partner, you're not alone. New research published in Science has an explanation for this phenomenon. 

The research discovered that while women tend to be morning people and are more active during the day it is the opposite for men who are more inclined to be night people. In addition women cope better with disruptions to their sleep and men are more likely to nap during the day. 

The research hasn't officially discovered a reason but I know that for all the moms reading this one thing is coming to mind:

One possible reason for the resilience to circadian disruption in females relates to their biological imperative. Resistance to the negative consequences of circadian disruption coupled with improved sleep, even when experiencing nocturnal disturbances, may facilitate their adaptation to frequent nocturnal awakenings over a sustained period, given their predominant role in nurturing offspring. The early-activity chronotypes seen in women before menopause also align with those in children.

Of course that's not to say dad shouldn't or don't manage offspring sleeplessness. It just suggests this might be natures way of helping moms cope with night nursings and going for long periods without consistent sleep patterns.

There is light at the end of the tunnel though for couples who find themselves awake an opposite times. Circadian rhythm differences in men and women tend to alleviate as they grow older so it's likely that in retirement you'll be a little more on the same schedule.