Define "A Later Age"
Women who become pregnant when they are 45 or older are considered to be above the "normal" age range of pregnant women. However, the "normal" age range is in the process of changing now, as more and more women are opting to get their careers going before they try to start a family. 

The Risks
If one looks at the raw statistics, the rates of many of the complications of pregnancy go up in older women. Preeclampsia (a common pregnancy syndrome, characterized by high blood pressure), premature delivery, maternal, fetal, and newborn death, and placenta previa (the incorrect placement of the placenta inside the uterus) are more common, to name a few. 

From a practical perspective, there is more than overall statistics to look at. First, the rates of most complications are rather low. Therefore, an increase may not be much to get all worked up about. Even an increase double or triple the rate of the 25 year old population still means the absolute risk is low. For example, if the rate of something is one in a million at 25, and the risk is (gasp) ten times that at 45, then the risk is one out of 100,000. Not something to loose sleep over. Secondly, the reason more older women have complications during pregnancy is not all due to age. It is closely related to the increased rates of complications and diseases and problems as we age. Older women are simply more likely to have a medical problem to begin with. Pregnancy is a major strain on the heart and blood vessels, and in turn, on all the organs in the body. Nearly any pre-existing condition will be worsened during pregnancy and make a more difficult pregnancy. 

Like many age-related correlations in medicine, the risk depends on things that happen to us over time, not just age itself. Older mothers are more likely to have had other children. Some of the complications, like the placement of the placenta over the cervix, are more likely in women who have had many prior pregnancies. An older mom is one who has had more time to have had gynecological procedures, problems, and diseases that may change her organs in ways that make complications more likely. Older women tend to release more than one egg a month, leading to higher rates of twins. Twin pregnancies increase the risk of complications, in younger and older moms. In short, it is more important to look at the woman's medical history, and the pregnancy itself, rather than at the woman's age. 

Most importantly, is the practical significance even if one has a complication. With good pre-natal care and appropriate medical intervention, most complications can be corrected. Most pregnancies will end with a healthy baby. 

Some critics discourage older women from having kids, because they may die before the children are grown. With increased life expectancies today, you are more likely to live until this child reaches adulthood, than a 25 year old mom was, a century ago. 

Talk to Your Doctor
You should plan ahead when starting a family. Talk to your doctor about your specific health status to determine if your high-risk status would be merely due to your age or if there would be other complicating factors.  

REFERENCES
a listing of scientific articles and texts used.
 

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