I would like to get pregnant, but a doctor told me I need to lose weight first. Why?

Obesity & Pregnancy. Obesity is a significant risk factor for you (ovulation disorders, pregnancy complications) & baby. Obesity can increase likelihood of infertility & during pregnancy can cause HBP, diabetes, toxemia, c-section. Baby is more likely to be small or bigger than normal & be born prematurely. The heavier you are the greater the risk. If your BMI is 50 than anesthesia is life threatening for c-section.
Increased complicati. Obesity is a very significant risk factor for you and your baby.
Improves chance. Even 5% weight loss improves your chance of getting pregnant. The primary obstacle for overweight women is ovulation.Fat cells produce estrogen. The problem is that if you get too much estrogen your body reacts as if it is on birth control. Ovulation may not occur or it may be inadequate. An inadequate ovulation contributes to luteal phase defect and weight loss will improve the above.