I have just read this entire thread and I can't believe how judgy and nasty some posters are (thinking dog with a bone).
To categorise all overweight women as a time-bomb of health problems when ttc and pregnant is a simple and limited view. So many factors are involved and although, statistically there may be extra risks associated with pregnancy in overweight and obese women, it does not mean that being thin = no problems.
I have had three miscarriages and I recall reading, after the first one that being overweight may have been a factor. I was devastated to think I might have caused the miscarriage because I had a BMI of 30. However, my doctor was able to reassure me that it was highly unlikely that it caused my miscarriage and in fact it was a chromosomal issue related to my advanced maternal age.
I know some people consider me to be irresponsible to ttc at my age as there a risks associated with advanced maternal age, but it won't stop me. Frankly no one has the right to interfere with my decisions about my fertility, that's entirely up to me.
It has been a long hard road with the miscarriages, but I have actually reduced my BMI since the last miscarriage to about 28.3, but haven't conceived since(I last miscarried in May '12). Clearly my weight isn't contributing to fertility issues, it is my age.
If infertility is due to lack of ovulation, and that is caused by being overweight, then perhaps one has to consider weight as a factor, but if you are ovulating, then it is unlikely that weight is contributing to problems conceiving.
Good luck to everyone ttc, I hope everyone gets their longed-for babies soon. Everyone here would clearly love a baby and size makes no difference to your capacity to love a child.