i think this question depends totally on your job, not your age. I had my first child at 25, and went back to work part time with him at 3 months old. I worked in a day nursery. Although at that time in a responsible role, pay was not good.
By the time my 2nd child came along, I had to leave because i couldnt afford the child care fees , which were far more than my wages, even if I worked full time.
Iworked part time as bank staff if my MIL could look after the children, but by the time baby n3 came there was no question that i could work.
baby 4 arrived, and once baby was of nursery age, i returned to work part time, and then took on a more 'part time' senior role once the last child was at school full time.(part time in brackets due to the full time nature of the paperwork, which i did at home)
I ended up with two part time jobs, looked after 4 kids and did the housework ,( and voluntary stuff) while my husband was the main wage earner.
This is the curse of today's woman, who end up still taking on board the main bulk of child care, and work very hard for little pay. Even though I love my choice of career when your kids are small money and time is very important,and in short supply.
today i have four teenagers, and i am now still working part time, but in order to earn more and further my career and income I am a part time uni student.( BTW the teens do seem to need you more mentally than when when they were younger, which is more exhausting than when they were little.)
I will soon, return to full time work, and most of my earnings will go on paying back my student loan, and support each of my kids as they in turn go to uni. my husband, in order to have a better chance of keeping his employment choices, in a very uncertain world, is also going to uni, so that when he reaches the magic age of 50 , if made redundant he will be able to get a job, with a higher pay scale to support the four kids in uni, and the roof over our heads.
What does really scare me, is that i have never paid a pension during my working life, mainly because my pay was so small, and i have heard that i should , once i return to full time work , pay nearly £500 a month towards the a basic pension. I find this very scary!
The idea that we all have such choices in having our kids early or late is really not the main point, we still earn less than men, we still have no support with childcare, equality is still a dream for a large portion of todays woman in the workplace.