If you have such strong feelings about this... are you sure this is the relationship for you? Perhaps finding someone that does not already have children would be a better fit for you. 

Feral kids with her.

the only thing hubby said to his sisters is with his exwife it was all csections, getting pregnant was a mistake

and she fought with the drs and nurses and told them to cut the baby out of her. No medical reasons, she was just too privileged too inconvenienced to deal with a vaginal birth.

our first was vaginal and hubby seeing me crying and in pain pushing bubs out was a new experience to him and seeing me right after acting like I hadn't given birth barely 20mins prior was astonishing to him. There were no comparisons from hubby

sd's however love to criticize my 2 kids aged 3 & 4. My kids have reddish blonde hair and very fair skinned as they are half white while skids are dark brown skinned 100% asians.

my kids have curly hair, eldest sd will say her younger sister had curly hair but it became straight when older snd so will both of mine. 
 

my daughter has blonde hair, eldesr sd will say her younger sistet had blonde hair when younger and it turned black when older and so will mine. 
 

i refuse to be around sd

Well first births never go to plan, it's better to make a birth flow chart than a rigid birth plan.

Pregnancies vary a lot too, once you find yourself pregnant he'll see how different it is. You have to tell him you don't want to hear about BMs experience,you can talk about pregnancy and birth just not HER pregnancy and birth.

From what I heard (in the beginning against my will) BM had a horrible pregnancy with SD, miserable, lots of complications, a c section and SD was a sickly baby. I felt great being pregnant, stayed very active, had a mostly normal birth, vaginal, recovered very quick and our BD had no issues whatsoever. I defied all of DHs preconceptions and he often said I made it look easy. Well it's easy when you aren't a whining complainer like BM.

I'm pregnant with my 2nd now and BMs pregnancy couldn't be farther from his mind.

By my math, your SO is 21, so I'm assuming you are too.  Slow down here. If you are so bothered by his other child, find a man that doesn't have any, shouldn't be too hard at your age.  Going into it already angry about things he has said before you are even pregnant isn't a good sign.

There is no shame in knowing this guy's past experiences and baggage is not making this a good relationship for you.  

My MIL said my daughter looks like my stepdaughters, who look like their mother.  My BIL said my daughter is part DH and part BM, it was a name slip but still.  Unfortunately you will probably hear stupid sh*t from alot of places comparing the skids/BM experience with yours.  If you already anticipate this will be your future and it annoys you, dont settle and think you will just cope with it.  

If I could go back in time I would have exited while dating when he threw the second red flag about his personality and done the single mom sperm donor thing.  I would have a lot more money right now and not have to deal with his family or psychotic son and personality disordered BM. 

Honestly... this doesn't sound like the right relationship for you.  He does have experience with someone being pregnant and the birth process..  he has had a child.  It will not be a brand new experience for him and he is likely to say things that he learned from his first rodeo.

Now, I'm NOT saying that if he were to have a baby with you that it would not be important.. or special... it won't ever be his first.. that has happened for him... but it would be his first with you.  I'm not saying you need to accept him waxing poetic about how much his first baby mom was glowing in her 5th month.. but if you have such a visceral reaction.. to him.. and per your prior post.. to issues surrounding his child?  

Steplife isn't for you.

10 months.. is way too early to be thinking about this really... do not get pregnant.  in fact.. I would go find yourself someone who doesn't already have a child so that you don't have to endure all the worries that you are forecasting with this guy.  

Given that his child was born when he was 16, I seriously doubt he knows very much about pregnancy and childbirth beyond what he sees on TV ...

Some men are just dumb when it comes to stuff like this. It sounds like he's concerned for you, and is basing his fears on his experience but obviously you don't want to hear about it. If you do feel this strong a reaction to the comparisons maybe you shouldn't have kids with the man. Often the comparisons get worse, friends and family get on board with them too. 

I actually listened with interest about dh bm pregnancy, as I didn't have the hate for her I do now. By all accounts it was a negative experience from conception to birth and thereafter. So I guess that helped me. Having that child split them up,the stress, anxiety and realising they were 2 completely different ppl and parents. I just noticed that your partners child is also very young, did they split up quite soon after birth? You're adament you don't want to hear what went down there, but if you did you might learn some things, even find a few red flags about your own partner, or not? I certainly realised what kind of wet weekend my dh was gonna be lol, but often best to discover that before you get pregnant 

I think you both need to slow your roll on this. You're early-20s. I remember being engaged/married in my early 20s and saying how I was going to have a water birth, no epidural, use cloth diapers, exclusively breastfeed, etc. We weren't actively trying to have kids, but my brain was actively planning to have kids.

Within two years, I was divorced. Now that I'm 32, remarried, and actively trying to get pregnant (total aside: got excellent news from DH's fertility doc yesterday!), my entire outlook on birth and pregnancy has changed from what it was a decade ago. A decade ago, I was idealistic. I didn't think about what insurance would cover, how I'd be able to travel for work and breastfeed exclusively when I could be gone for a week at a time, the time and energy it would take to work full-time and clean cloth diapers, prepare all my own baby food, etc. 

Now that I'm ACTUALLY thinking about these things, I HAVE asked my DH for his experience. We've had discussions about it. I've asked if he had found certain items useful or not, how he felt in the delivery room, how he reacted as a first-time dad with little sleep. I'm getting the benefit of his first-hand experience, and it's GREAT!

Now, I'm not saying him offering his opinions without you asking is appropriate. However, if you are planning on having kids WITH him - as in, you're a couple - I DO think these sorts of things need to be a DISCUSSION. He shouldn't decide whether you have an epidural, but he has a right to feel uneasy about you being adament about a home birth when a home birth isn't right for every pregnancy and could put you and future baby in danger.

Yes, it's YOUR body and YOUR pregnancy. But you are HIS partner carrying HIS child. DH and I have had several talks about fears and feelings around pregnancy (especially since this has been an emotionally-charged road for us), and I've learned that DH has worries and fears about pregnancy and health, but he doesn't really have an outlet to express it without being invited to express it first.

So, what do you do going forward? First, I'd stop talking about future birth plans until you two are actively trying to conceive. What you want now and what want later may be different, so you're just inviting conflict for no reason. If you want to talk about pregnancy, approach it from "I like the idea of home births, here's why, what's your opinion on home births in general?" You might find that by having a discussion about the topic might bring about a change of heart for one or both of you, or expose some feelings/concerns in your partner that you didn't k ow existed.

You have every right to dictate how your delivery and pregnancy go. You don't, however, have a right to tell your partner how he should feel or respond. You can ask that he not bring up BM. You can tell him what the birth plan is and that's final. But you can't make him okay with it, and you can't prevent him from expressing his opinion on how he thinks that plan will impact you, him, and your mutual child. It's unfair to put him in a position where he has no voice over something that affects him, too.

You need to find someone else that doesn't have kids.  There are a lot of red flags here and you don't think he is properly parenting.  You are young so just go and don't stay for th sh^& show.