When to plan a family with a career?

I have done a fair amount of off hand research on this topic and here are the most common reasons of having a baby -

1. Unplanned pregnancy - "Hush. It was a mistake!!"
2. Biological clock - "I crossed 30 and time was running out."
3. It was my dream - "I was born to be a mother"

There are two points to be noted here -

1. In none of the cases, did anyone ever state that pressure from family was the reason for having a baby. Well, that does make sense. No matter how much pressure family puts, they can't be in the bedroom and force you during the act! Also, I only spoke to well educated women (mix of both with corporate careers and full time home makers). So, most of them could hold their own under family pressure.
2. The women in Category 3 (It was my dream - "I was born to be a mother") were very very few. In fact, there was only one woman among almost 45 women I spoke with who stated that she really wanted to be a mother. She bravely went through two miscarriages followed by a series of hormonal treatments to get pregnant. She is now a proud mother of two and at the time of writing this post, quit her job where she had a promising career in a leading MNC. 

I am mulling this question because I am 30 and I am scared about how my life will change after the baby. I like kids but I am not sure if I can cope with the changes in my currently blessed life that I am living. 

The reasons for not having a baby were numerous. Most of them could be interpreted as procrastination. 

1. Stronghold in career - "One more promotion!"

2. Uncertainty in life - "We can barely afford our current lifestyle or there is no location certainty"

3. Lack of infrastructure - "Who will take care of the baby if I want to get back to work?"

4. Status Quo - "Umm..We are not ready"

5. Planned delay - "There's a lot of time before 30" 

30 seemed like a magic number. Women under 30 stated #5 as the most common reason. The ones above 30 were almost equally divided in the first four categories. 

Interestingly, no one stated changes in body figure as a reason!

Disclaimer: This was just an off-hand survey. The responses are assumed to be correct as they were results of heart to heart conversations. No notes were taken. No records were kept. The research does not include women who mentioned they would never have a baby in the future or are trying to conceive with medical help.