You might live to regret it later, if you don't take the opportunities to boost your career now.
Not when you get your BFP, or when the baby arrives, or even when you're baby starts nursery, but many years down the line. Obviously you won't regret having children, but you might regret not ensuring that the timing was as right for you as it was for your DH.
It's easy for DHs, they don't have to take all of this into account on the same level that us mothers do, although I know there are many DHs out there who stay at home, work part time etc.
Also, there are things like DC2 to consider..if you want more than one, and if you don't want a big age gap, you can add another couple of years on top of the calculation for how long you might be overlooked for promotion etc.
Are you planning to be a SAHM, or will you return part time/full time? If you only want one DC then the impact on your career will probably be less, similarly if you are a high flier who intends to return full time, then providing you can juggle it all, I imagine the impact on your career will be much less, and that it'll be quicker to pick up from where you left off.
One last thing..this site is full of people who have years of heartache ttc, and who wish they'd started trying earlier. I don't know how old are you, but age is also an important factor, too.
If you're mid thirties onward, and being is a mum is what you want more than anything, if it were me, I'd start trying and think about my career later. But if your in your twenties, the clock isn't ticking yet so loudly just yet!