The number of women aged over 40 becoming pregnant is at a record level, figures from the Office for National Statistics show.
Pregnancy rates for over 40s have risen
The conception rate for the over 40s in England and Wales rose by 6% between 2005 and 2006, and now stands at 12.2 pregnancies per 1,000 women.
The overall pregnancy rate rose by 3% over the same period, the ONS said.
But teenagers are having fewer babies, with a slight fall in pregnancies among 13 to 15-year-olds.
There were an estimated 866,800 conceptions in 2006, a rise of 25,000 from the previous year.
The most likely age for motherhood was 25 to 29, with a rate of 129 pregnancies for every 1,000 women in this age group.
Four out of five women who became pregnant went on to give birth.
More than half of the pregnancies happened outside marriage, although the figures only cover those where the parents were unmarried at the time of the birth, and both appeared on the birth certificate.
More women are putting off motherhood until their 40s, partly due to advances in fertility techniques which help those who are unable to conceive naturally at that point.
While they and their unborn babies do face slightly increased risks during pregnancy and childbirth, studies have suggested that they are just as able as younger mothers to look after children.
The government wants to halve the number of conceptions in under-18s by 2010, based on a figure set in 1998.
Juliet Hillier, from Brook, the sexual health charity for young people, said she was expecting the downward trend in teenage pregnancy to continue.
"There are four main strands we need across the country to really bring teenage pregnancy levels down - a high quality clinical service, a high quality outreach service, you need really good sexual education in schools and a strong lead from local authorities.
"Quite a lot has happened in the last few years and we know what building bricks need to be in place."
Read a selection of your comments on this story:
I gave birth to my daughter at the end of October last year, I was 42. I already have a daughter aged 12. For me, I had been divorced for a number of years and met my new partner and we decided to have a baby. I think a lot of older women are having babies after meeting new partners following divorce.
I tried to get pregnant for over five years with my first and then fell pregnant at 38 and gave birth at 39. Again for our second child we tried for five years and were waiting for day 1 so that I could start IVF only to find I was pregnant and then gave birth at 44. We didn't even consider the possibility that I would fall pregnant again and so imagine our surprise when at 45 I found I was pregnant again and I gave birth at 46. All three are healthy happy kids and I love being a mum. I don't think it is age that determines how good a mother you will be but attitude!
I had my first baby at 40 and was surprised both at how easy it was to get pregnant (6 months) and the total lack of complications leading to a natural and healthy birth. The reason I left it so late was that I had a busy career, was very independent and did not meet the ideal partner with whom to share such an important part of my life until I reached my late thirties.
Vic, Dubai, UAE
I am now 43 and am still open to having more children. I do realise that having a pregnancy at my current age is more difficult but not fraught with as much danger as some statistics would lead us to believe. However, a woman's fertility rate does fall dramatically after 35 and so it takes longer to fall pregnant and this is something that women must take into account when delaying having children.
I had my son when I was 36 followed by a daughter when I was 40. I had been in a long term relationship without having children so ended up marrying late when I finally found Mr. Right. We wanted to have kids right away as we were both getting older. I did a lot of travelling when I was younger and concentrated on my career. I never seemed to have enough money and my then boyfriend didn't seem to have a steady income either. I just had to wait until I felt stable in my relationship, the finances never really improved but being in a relationship finally with someone who wanted to start a family as much as I did was what we both needed. I've never regretted my decision to wait, the kids keep me young!
Penny, Kingston, ON Canada
I had both my children when I was over 40. They are both fit and healthy and I had no trouble during pregancy nor in giving birth naturally. I didn't have an epidural with either. From my point of view, it would have been a huge mistake to have had children when I was in my 20s. Older mothers are more experienced in life and it's insulting to say, with some apparent surprise, that they are just as able younger mothers to deal with children. Older mothers are more likely to have greater reserves of patience and tolerance. They've usually done most of the things they wanted to do in life and can bring that experience to their children's upbringing. Older mothers have usually much of the idealism of youth with the realism of age.
Charani, Yeovil, SOM
I have many friends in the 35-45 age range, but do not know a single person who has "chosen" to delay having children. In my experience the causes of later pregnancies include taking a long time to meet someone with whom to have children and in some cases taking quite a while to conceive. Many women over 40 may well be having their second, third or more'th' child - I know several women who have had a desire for one last baby when their older children are moving through school. But as to choosing to delay pregnancy then going through fertility, well, maybe in the city, but I doubt anyone would deliberately put themselves in that position, would they?
Mrs HD, Herefordshire