Obesity is defined as any Body Mass Index of more than 18.5-24.9 and any woman with the BMI of above 25 will have certain problems conceiving a baby. The most common condition is what we call Polycystic Ovary Syndrome, which affects the ovulation in a woman. Also, once they conceive, the chances of miscarriage and development of other issues like hypertension or Diabetes is high in these women. For more information, visit care.com