Dr Rashbrook, a child psychiatrist from Sussex who has three grown-up children from a previous marriage, became pregnant seven months ago after years of attempts using donor eggs.
"People have accused me of craving a baby, of wanting something small and warm to cuddle - like a cat," she said in her first interview, "and they have implied that as a child psychiatrist I should have known better.
"But this is not about craving or wanting a baby at any price. It is about wanting a child with the man I love in the knowledge of everything that will entail. Being a parent is hard work, and I know that."
Dr Rashbrook married John Farrant, 60, a higher-education management consultant, in 2003. He has no children. She is believed to have become pregnant with the help of an egg donor in Russia under the clinical supervision of Severino Antinori, the maverick Italian fertility doctor.
The treatment has become unavailable in Italy, where she had previous attempts, because of a change in the law, and an unofficial age limit of 50 ruled out such procedures in the UK. Dr Rashbrook's children, aged 26, 22 and 17, were not told in advance of their mother's decision to try for a pregnancy. However, they are reported to be fully supportive of their mother.
"I have been through it before, so I have some idea what to expect and even though John has never has children, I have absolute confidence in him as a father," said Dr Rashbrook yesterday.
She fiercely defended her right to pregnancy, despite severe criticism from some quarters of the media. "I have never, for one second, regretted our decision to have a baby together," she said, "although all the media attention has been extremely upsetting for our families.
"We have received many letters and cards of support and only one critical one - which was unsigned. They have been deeply moving, especially the one from the obstetrician who delivered my three other children, which read: 'You will make the best mum in the world, forget the age thing.'
"I don't feel too old to have a baby or to cope with the demands of what lies beyond. I feel very much as I did when I had my other three children. To me, there is little difference.
"I have always looked very young for my age, and we are not the kind of couple who wanted to drift into a quiet retirement.
"I am not aware of people staring at us, and we have been treated just like any other couple expecting a baby when we go for antenatal appointments, so it has felt very normal."
John Farrant also spoke yesterday, shedding light on the prospect of late-life, first-time fatherhood. "When we embarked on IVF we never really believed that it would happen," he said. "We used to call it 'The Project'.
"The probability of our ever having a baby together was so low that when the pregnancy was finally confirmed, it took some getting used to. I think my exact words when the pregnancy was confirmed were 'Oh my God', because when we first started it seemed such an impossibility.
"In some ways, it is a daunting, slightly terrifying prospect becoming parents at our age, but underlying that is a feeling of absolute delight and joy. It just feels terribly exciting."
The child, Dr Rashbrook said, will offer a completeness in their relationship. "From the time we had first been together - more than eight years now - there has always seemed to be a baby-shaped space between us. I wanted to give John the child he'd never had, and I didn't see my age as a huge obstacle."Reuse content