There is a recognised phenomenon in which during pregnancy, the man (i.e. the father) actually shares or even substitutes the mother in terms of experiencing some of the symptoms associated with pregnancy.
This syndrome is known as "Couvade Syndrome".
It generally begins at the end of the first trimester and can increase in its severity up to the third trimester. Symptoms include nausea, vomiting, changes in appetite and even weight gain. There's a lot of information out there about this phenomenon and most of which actually come to the conclusion that this syndrome may have more of a 'physical' component than once thought.
Previously, it was the assumption that most if not all of these symptoms that make up the syndrome are purely psychosomatic (i.e. psychologically induced) seeing that there was no real physiological explanation for them. But the current school of thought seems to be shifting towards a more physical basis of which the exact cause is yet to be identified. Hormones are mainly to blame but which and how and why... well, that is yet to be known.
Interesting ain't it?
The father experiences "morning sickness" together with his pregnant wife.
In fact, it is documented in some cases that the father can even develop a 'baby belly' in which the abdomen becomes swollen resembling up to a 7 month pregnancy!
Now, i'm not sure if ill be one of the fathers that 'sympathises' with my wife's pregnancy to that extent.
Perhaps the weight gain i'm experiencing now and the occasional cravings are attributable to 'Couvade'.
then again maybe it's just my love for food! ;)