There are all kinds of men in the world but generally, men are not happy who are "stay at home parents" just like most women do not respect this kind of man. It's biological, stereotypical or not. Besides, a man who is a stay-at-home dad is likely to be professionally and socially isolated from other men except for other stay-at-home dads, who, as they are the kind who want to be stay-at-home dads may not be the kind your stay-at-home dad wants to hang out with.
Ignore the real differences between men and women at your peril.
Here are some real differences: I stayed home to handle life in general when my husband worked over 80 hours a week, NEVER at home. Seriously, in six months, he was home 4 days. He arrived at 11:00pm, and left before 10pm the next day, when he was out of state or out of country again. When I worked out to sea (yes, I am a woman, and yes, I worked on the N. Atlantic Fishing Fleet as a researcher) he changed jobs to work at home full time. Medicine isn't the only field that demands family sacrafices; I was out to sea for a solid month at a time, home for a week, out to sea for 4-5 weeks, repeat. When I was home, I slept and vomitted from land sickness. Sometimes I would only be allowed 2 days off. On the boats, we slept the 8 hours out, then went to 20:4 shifts....20 hours awake doing physically demanding work in a dangerous environment followed by 4 hours of sleep. I do not know if residency demands more or less time commitment or energy, but I do know rarely are you dealing with salt water freezing on your clothing and all the surfaces surrounding you. If this is your passion and you have the ability to set up a solid support team, you can pursue it and do so effectively. Everyone will sacrafice, but sacrafice isn't the most terrible thing. Sometimes it makes people appreciate what they have all the more. I am grateful more than ever to have a husband who likes to brag to the other workaholics in his current company (most investment bankers, previously it was global consulting for a 3 letter firm) that his wife could outsurvive them in horrendous conditions and has the scars to prove it. Oh, and he does work in a trophy wife culture, and yet his co-worked admire his rough and tumble wife....and respect his latest plan to work from home while I enter school. Not med, but I am still a non trad and have worked jobsthat have taken me far, far from home, and are immensely dangerous.
We can chose to buy into stereotypes and continue to perpetuate them, or we can chose to pursue our own paths and define new standards for ourselves and our families. People are isolated because they chose not to pursue and develop community, male or female. There are plenty of stay at home mothers who also feel isolated and are not happy.
Your biological assumptions are based on euro-american culture...not all societies are patriarchial or embrace the belief in woman as primary caregivers. Unfortunatly, most of these populations have been marginalized. Fortunatly, I happen to come from a matriarchial culture and found a husband who embraced my need to be a competent and skilled professional, just as he is. We take turns taking the hits in our relationship rather than expecting that a Y chromosome excepts him from taking hits to his career or entitles him to less responsabilities.
To the OP, my best friend in HS had her child while in school. Here is her blog:
http://ayradyss.livejournal.com/
She is an amazing woman who I admire far more than she realizes. I have no doubts what so ever that her child received ample love, affection, and attention, if not always in quantity, at least in quality.
Also, having grown up with both parents working, often taking turn outs of town for months at a time (when your poor, your family works where it can) I can honestly say that I learned valuable lessons about independence, hard work, dedication, ambition, pursuit of dreams, and generosity to others. Yes, my poor father must have been socially and professionally isolated dragging his toddler daughter to fire fighting meetings and the occasional fire. He was a mechanic on call and a firefighter. His mates found it fascinating that a child could identify various woods and give burn rates better than most rookies, because I grew up learning it. Fire fighters are tough folk, and he was well admired and respected for being an excellent father and husband as well as a man to be counted on under fire.