The goal of this national registry-based study is to investigate the prevalence of reconstructive breast surgery and risk factors for surgical complications in women who have had weight loss surgery previously. The main questions it aims to answer are:

1. What is the perceived need for breast implants after weight loss surgery, described as the proportion who have breast implants, and what characteristics, in terms of demographics and surgical details, do the operated women have?
2. In women who have breast enlargement or breast enlargement combined with a lift, are there any differences between the women who have had weight loss surgery and other women regarding complications after the operation and characteristics of the surgery, for example skin incision and choice of implant (for example texture, shape, size)?
3. In women who have delayed breast reconstruction after breast cancer, that is have had their breast/s reconstructed in a separate operation, are there any differences between the women who have had weight loss surgery and other women regarding complications after the operation and characteristics of the surgery, for example in technique used (autologous versus implant-based, choice of implant, such as texture, shape and size), and timing of the surgery? Immediate breast reconstruction is defined as performed at the same time as the mastectomy, and delayed as an operation performed later in a separate operation.
4. In women who have immediate breast reconstruction after breast cancer?, that is have a breast reconstruction at the same time as the mastectomy, are there any differences between the women who have had weight loss surgery and other women regarding complications after the operation and characteristics of the surgery, for example in technique used (autologous versus implant-based, choice of implant, such as texture, shape and size), and timing of the surgery? Immediate breast reconstruction is defined as performed at the same time as the mastectomy, and delayed as an operation performed later in a separate operation.
5. In women who have risk reducing mastectomies, are there any differences between he women who have had weight loss surgery and other women regarding complications after the operation and characteristics of the surgery, for example in technique used (autologous versus implant-based, choice of implant, such as texture, shape and size), and timing of the surgery? Immediate breast reconstruction is defined as performed at the same time as the mastectomy, and delayed as an operation performed later in a separate operation.
6. Are there any identifiable risk factors for complications after breast reconstructive surgery, specific to the women who have had weight loss surgery and other women?

Researchers will compare the patients to women who have the same type of reconstructive breast surgery but have not had bariatric surgery previously.

The study will use prospectively collected data from seven registers: The Scandinavian Obesity Surgery Register (SOReg), The Swedish Breast Implant Register (BRIMP), the Swedish National Quality Register for Breast Cancer (NKBC), the Swedish National Diabetes Register (NDR), Statistics Sweden (SCB), the Swedish inpatient register, and the Swedish National Prescribed Drug Register.

Inclusion Criteria:

Inclusion in Soreg and thereafter inclusion in either BRIMP or NKBC

Exclusion Criteria:

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Women who have weight loss surgery and then have breast reconstruction.