Month Three:  

No Energy

Her energy levels can be extremely low at this time, so don't expect that she will want to have sex with you every night.

Blood volume is increasing, so her heart has more work to do.

Month Four:

She's clearly pregnant.... 

By the end of the fourth month, it's clear for all to see that your partner is pregnant.  Every woman is different and each pregnancy shows in different ways.  It can depend on the location of the placenta and many believe that boys and girls create different shapes.

During the second trimester, most women tend to feel much better than during the first or last trimesters.  The strains of helping the baby and placenta grow have passed whilst the weight that she needs to carry around is not yet too overwhelming.

Having said that, your partner may be plagued by new problems created by the hormones, such as aching joints, running nose and skin problems.

The abdominal muscles may ache periodically due to the stretching caused by the growing baby.