Having been through it twice before, she was pretty prepared for her third child. What she wasn't prepared for, was the label she was given.
"I was a bit apprehensive. I worried, lots of people told me I was going to be so much more tired and I did worry that it was just gonna knock me sideways."
Jagger was speaking in an exclusive interview with http://www.huffingtonpost.co.uk/news/relationships/ href="http://www.huffingtonpost.co.uk/news/tess-daly/" target="_hplink">Tess Daly as part of AOL Original series, Being Mum.
The mother-of-three - Sisi, 22, and Amber, 19 and Ray, nine months - said unlike she thought, she still had a lot of energy being a new mum at 43 admitting "it hasn't really stopped" in her life.
While more mums are being described as 'geriatric' if they have babies over 35, we wanted to find out what it means.
The phrase 'geriatric' mum is commonly put on pregnant women's medical charts above the age of 35.
According to the NHS, older women and their babies face an increased risk of pregnancy-related complications and health problems at this age which needs to be alerted to staff.
The number of women giving birth over the ages of 35 and 40 has risen steadily during the last decade Rosemary Dodds, senior policy adviser at NCT told us.
She said: "There are many reasons for women choosing to have their children later on in life, including parents waiting until they are best placed to welcome their baby into a financially stable or family setting.
"Whilst births of first babies to older women are associated with more complications, they don’t need to be treated as high-risk unless specific problems develop. The majority of women in this age range are fit, healthy and likely to have a straightforward birth and healthy baby."
Although there might be risks associated with being an 'older mother', is using the phrase 'geriatric' really necessary?
She told HuffPost UK Parents: "Historically a geriatric mum is anyone over 35 - but that didn’t stop me being rather taken aback to be given this title at my very first antenatal appointment.
"As an older mum (we’ll stick with that title) myself I’ve heard all the cliches… but the bottom line is that most of us have babies later because of circumstance rather than deliberate choice, and being stigmatised for doing so is unhelpful to say the least.
"Fertility does start to decline at 35 (so it would be naive to think getting pregnant at, say, 40 will be a given) and the risks of conditions such as Down’s Syndrome do increase with age.
"But that’s not to say that older mums can’t have healthy and uncomplicated pregnancies."
In Rosen's experience, being an older mother was really not that different to her friends - she still had sleepless nights, exploding nappies and shared the same worries.
She added: "We might be shopping at M&S rather than Topshop, but I’m not sure that could be considered an indicator of our ability as parents or of our energy levels (at 50, with a seven-year-old, I’m more active than I’ve ever been)."
Carrie-Anne Rainey shared her story on HuffPost UK Parents Facebook: "I was 39 when I had my first and 41 when my second was born.
"All the midwives classed me as old, everyone double checked my age whenever they saw me. I am now coming up to 45 with a five-year-old and a three-year-old.
"I am the oldest mum picking up their kids (bar one) from school, I am older than my boys teachers, the headmaster and I am probably old enough to be the parent of some of the young parents picking up their kids. I do consider myself to be an older Mum especially as some of the parents at my son's school thought I was Grandma at first!"
But it became clear that being referred to as geriatric was a concern among many older mothers.
Jodie Hawkins said on Facebook: "I was 42 when I had my fourth baby and was mortified when I was put down as a geriatric mum on the paperwork."
And she wasn't the only one. Emma Lewis was also referred to as this: "I was 20, 24, 28 and 35. I had more energy at 20 but more patience at 35 - and did not like being called a 'geriatric mother' just because I was 35! I'm 37 now and in no way feel geri-bloody-atric!"
Jackie Turner said: "I was 42 when I had my youngest, other people, including medical professionals can be cruel and thoughtless in things they say."
However, Dr Jacque Gerrard Hon, Director England at The Royal College of Midwives said she would in no way endorse any older mum being called this.
She told HuffPost UK Parents: "I've never ever seen this on a mother's note. I have seen a comment saying "greater than 35 or over 40" simply flagging up the risk, because older mums do have slightly higher risks.
"If I was a supervisor on the ward and saw that, I would say it's inexcusable and shouldn't be allowed."
Dr Gerrard explained women over 35 having babies are more at risk of developing high blood pressure or pre-eclampsia, as well as having a higher risk of miscarriage.
She added: "Other medical complications can include gestational diabetes, ectopic pregnancy and placental problems."
Agreeing with Dr Gerrard, she said doctors need to be aware of the health of the mother and any potential risks to the baby.
Siobhan Freegard, founder of the UK's video parenting community Channel Mum agreed that older mums are unfairly criticised: "They can face accusations of lacking energy to care for their kids, of being irresponsible or even leaving it too late to become a parent."
But one thing people did agree on, was the positive aspects older mothers encounter.
Dr Gerrard explained the positives for older women include great life skills: "They've been in work, had relationships, great life experience and this will transfer onto bringing up a newborn child.
"They might also be better prepared from a health perspective and put themselves in an optimum healthy state to have a healthy pregnancy."
Hayman believes that some women may also be able to look at this as an advantage.
"As an older mother, you have maturity, patience, and perspective on the world. You recognise what you do isn't going make the world end, and you can solve problems better with life experience.
"There is a lot more confidence there in finding out how to solve problems and they feel they can go back to work because they've already built a career before they had children."
Alerting risks is fair enough and making sure older women are aware of these complications is also valid, but is seems obvious that for some women, choosing an age to having a baby really isn't that easy.
Jean Thomas told HuffPost UK Parents Facebook: "I had my son at 42 after being told, after a severe back problem where I lost the use of everything from the waist down, that the likelihood of me getting pregnant was non-existent.
"But despite this and being on the pill to try to regulate my periods, my little bundle of fun was determined. I had to wait a month to find out if I could carry him physically and then had to have scans every week but eventually got the all clear at 26 weeks.
"I did worry a bit about being an 'ancient mum' but my husband and I are both second marriage and had got a lot out of our system.
"He had travelled the world and did all the crazy things you do when you are young and now we could give our son our undivided attention.
"We were the oldest parents in the playground but we didn't care. We never missed any of the important moments in his life, his first step, his first word, his first solo bike ride. He is always made to feel loved and always has our attention."
Kate Russell is 37 and currently five months pregnant with her first child. Having only met her husband at 33, she said sometimes it's not practical to start a family before this age.
She said: "I seemed to be constantly seeing articles in the media about how you should have your children before the age of 30 and how your fertility drops off a cliff at 35. I realise that it can be tougher the older you get with fertility challenges, but the level of scaremongering out there is irresponsible."
Hayman from Family Lives added: "It's really down to making your own mind up and feeling what is right for you and your own priorities.
"Things have changed enormously in the past decade and having children older isn't that different anymore.
"You're not alone, there's a great body of experience out there for women who have children older."
To read older mothers share their stories and experiences, visit our Facebook thread here.