Risks of conciving after the age of 45

There are several risks that are more pronounced at a later age , I gave the three main risks but at the site mentioned there are many more: 

The risk of bearing a child with certain chromosomal disorders increases as a woman ages. The most common of these disorders is Down syndrome, a combination of mental retardation and physical abnormalities caused by the presence of an extra chromosome 21 (humans have 23 pairs of chromosomes). At age 25, a woman has about a 1-in-1,250 chance of having a baby with Down syndrome;   and at 45, a 1-in-30 chance.

This specific risk is 41 times higher!!

Most miscarriages occur in the first trimester for women of all ages. The rate of miscarriage in older women is significantly greater than that in younger women. A 2000 Danish study found that about 9 percent of recognized pregnancies for women aged 20 to 24 ended in miscarriage. The risk rose to about 20 percent at age 35 to 39, and more than 50 percent by age 42. The increased incidence of chromosomal abnormalities contributes to the agerelated risk of miscarriage.

This specific risk is 5.5 times higher!!

Besides the increased risk of diabetes and high blood pressure, women over 35 have an increased risk of placental problems. The most common placental problem is placenta previa, in which the placenta covers part or all of the opening of the cervix. The University of California at Davis study found that first-time mothers over age 40 were up to 8 times as likely as women in their 20s to have this complication. Placenta previa can cause severe bleeding during delivery, which can endanger mother and baby, but complications often can be prevented with a cesarean delivery.

This specific risk is 8 times higher!!

http://www.marchofdimes.com/professionals/681_1155.asp

Most of the persons will be nearing menopause after 45 and will find it rather difficult to conceive in the natural way, though I am not suggesting that it is impossible or has not happened.

Elderly gravida has a higher chance of Ist trimester abortion.

The chances of giving birth to a mongoloid child increase many fold in addition to other congenital anomalies.

There is increased incidence of perinatal complications.

perinatal infant mortality is also high.

Besides this there are host of other social problems depending upon which part of the earth you hail from.

Although I had my last child at age 46 - concieved with my own eggs - the chance of getting pregnant at this age is slim largely due to egg quality decline.  As has been mentioned there is increased risk of chromosome abnormalities and although doctors will quote statistics as 1/30 etc. if you look at the percentage risk the real risk is actually still very small.  In my case my risk for having a child with Down's Syndrome was only 4% which was an acceptable level of risk for me.  ALso, there are several diagnostic tests such as CVS or amnio which can be done at the early stages of pregnancy (as early as 10 weeks) and along with the FISH test, can diagnose most age related chromosome problems so decisions can be made.  Fortunately, my tests all came back normal.

As for complications of pregnancy - a healthy woman in her 40's is no more at risk than any other woman going through pregnancy.  Often as we get older other health issues such as over weight, poor eating habits etc. can factor in and introduce problems which are exacerbated during pregnancy such as gestational diabetes.... however, just because you are in your 40's does not put you specifically at risk for these.  One thing which has been shown to be age related is the ability of the placenta to continue to do its work if you go over due ..... so it is a good idea to be monitored closely and consider induction if you go over or at least get stress tests for the fetus.