Which form of contraception is least effective for a patient who is 5'6 and weighs 205 pounds?

Ortho Evra is a type of hormonal contraceptive that comes in the form of a transdermal patch. Its effectiveness can be significantly impacted by a person's weight, particularly in those who are heavier. Studies have shown that individuals with a higher body mass index (BMI) may not absorb the hormones effectively from the patch, which can lead to a decreased contraceptive efficacy. For women who weigh over a certain threshold, typically around 198 pounds, the patch may not provide sufficient hormonal dosage to prevent ovulation effectively, making it less reliable as a contraceptive method compared to other forms.

In contrast, oral contraceptives and methods like the NuvaRing deliver hormones directly into the bloodstream and are less likely to be affected by a patient's weight to the same degree as the patch. The diaphragm, a barrier method, does not involve hormones at all and its efficacy is related to correct and consistent use, making it less dependent on body weight. Therefore, given the impact of body weight on the efficacy of the Ortho Evra patch, it is identified as the least effective option for this specific patient profile.