First off, what exactly does "Trisomy 18" mean? It means that there are three of the 18th chromosome on every cell in the body. This is for "full Trisomy 18." Even more rare is "mosaic Trisomy 18" which means that not every cell has the third 18th chromosome.
You can easily find scientific explanations of Trisomies online. Here is an easy to understand definition. D.V., a genetic counselor that we have talked with explained it this way: "All of our chromosomes contain information vital to survival, so when
there is too much information (as with a trisomy when there is an entire
extra copy of the chromosome) or too little information it affects
development. I often use the analogy of a recipe (e.g. a cake
that calls for two eggs, but three are used, with some ingredients
being extra or missing having varying effects on the outcome)."
Support Organization for Trisomy 18, 13, and Related Disorders (known as SOFT) - resources, publications, articles, family support, etc: http://www.trisomy.org/
Trisomy Talk - lots of good info. plus webinars with important topics: http://trisomytalk.com/
Prenatal Partners for Life - : http://www.prenatalpartnersforlife.org/
Now I Lay Me Down To Sleep - free remembrance photography: www.nowilaymedowntosleep.org
Hope for Trisomy - http://www.hopefortrisomy13and18.org/
Living with Trisomy 13 - www.livingwithtri13.org
Hope for Trisomy: http://www.hopefortrisomy13and18.org
Noah's Never Ending Rainbow: http://noahsneverendingrainbow.org/
Trisomy 18 Mommies (for parents of Trisomy 13 children too): http://www.facebook.com/groups/T18Mommies/
TrisomyTalk - www.facebook.com/TrisomyTalk
Hope for Trisomy - www.facebook.com/TrisomyNewsFeed
Trisomy Tea - www.facebook.com/groups/TrisomyTea
SOFT sells "The Book" on Trisomies 13 & 18 called: Care of the Infant and Child with Trisomy 18 or Trisomy 13 This book is available in paperback or as an e-book.
Gift of a Lifetime booklet by Tammy Tate on perinatal
care, ideas if you receive the news while pregnant that there's
something wrong with your baby: http://www.heartlink.org/pdf/giftofalifetime.pdf
(You can purchase the booklet here.)
Guiliana (mosaic Trisomy 18): http://www.g-giftoflife.blogspot.com/
Julia (Trisomy 18): http://jennychildress.blogspot.com/
Faith (Trisomy 18 and monosomy 21): http://littlefaithtobigfaith.blogspot.com/
Lily (Trisomy 18): http://iseeloveblog.blogspot.com/
Aaron (Trisomy 18): http://compatiblewithjoy-trisomy18.blogspot.com/
Hannah (Trisomy 18): http://kwantfamilycorner.blogspot.com/
Alegria (Trisomy 13): http://alegriaelizabeth.blogspot.com/
Caleb (Trisomy 18): http://calebsjourneyfromgod.blogspot.com/
Note: a quick Google search will reveal quite a number of other Trisomy blogs. This is just my list, of those that I read the most often.