Search strategy

Database searches were performed by a medical librarian (S.C.) in December 23, 2014, and updated September 5, 2017, using subject headings and text words to retrieve articles related to the following concepts: breast reduction or mammoplasty and breastfeeding or lactation. Individual case reports were excluded from the searches. No other restrictions were applied. All databases were searched from their inception to September 5, 2017, without language restriction.

Databases that were searched included: OVID Medline, OVID Embase, OVID all EBM Review databases (including the Cochrane Database of Systematic Reviews), Proquest Dissertations & Theses, EBSCO CINAHL, and Scopus. Search strategies were adjusted accordingly for each database (see S1 Text which lists all search strategies). Google Scholar was also searched with “breastfeed” and "breast reduction"; the first 15 pages of results were reviewed.

References of all included studies were reviewed. Foreign language studies were translated using Google translate. No authors were contacted for further information.

Study selection

Studies were included if they provided the number of women successful at breastfeeding or lactation after breast reduction surgery, and if they reported either the total number of women who had children following breast reduction surgery or the total number of women who attempted to breastfeed following surgery. Successful breastfeeding was based on the definition used in each reviewed study.

Two independent reviewers (R.K. and C.K.) assessed all identified studies. First, titles and abstracts were evaluated to identify possible studies for inclusion. An article was then reviewed in full if its title and/or abstract were determined to be relevant. Disagreements were resolved with consensus between the two reviewers. Percent agreement in study selection was computed.

Data extraction

The following data were extracted from all included studies:

Study characteristics: (1) study citation: title, publication year, journal title, volume, pages, first three authors, last author, and language; (2) study location: country, state/province, and city (in cases when studies did not specify the location, the location of the authors was used as the study location); (3) definition of successful breastfeeding: number of weeks breastfeeding and exclusive or any breastfeeding. If a study did not provide a definition of breastfeeding, we considered it as “any” breastfeeding. If a study had several time points, we selected the definition closest to the WHO definition of breastfeeding success (six months), unless otherwise noted; and (4) study methods: type of study, focus of study (breastfeeding or other), sample size estimation, location of participant recruitment (plastic surgeon office, hospital or other), control group and study group drawn from the same population, outcome assessors (participant or study authors), blinding of outcome assessors, length of follow up period, statistics used, and whether confounding variables were considered.

Participant characteristics: (1) number of participants: number of women available for recruitment into the study, number of women who agreed to participate, number of women with children, and number of women who attempted breastfeeding; (2) average Body Mass Index (BMI); (3) average age at surgery; (4) percentage of women informed about the impact of breast reduction on breastfeeding prior to surgery; (5) breastfeeding supports; (6) reasons for not attempting to breastfeed; and (7) reasons for not breastfeeding successfully.

Breast reduction surgery characteristics: (1) name of breast reduction technique; (2) average tissue removed per breast in grams; (3) pedicle location, meaning the location of parenchyma left connected to the nipple areola complex; (4) preservation of column of parenchyma between the nipple areola complex and the chest wall (subareolar parenchyma), with none meaning the column of subareolar parenchyma was fully transected and there was no intact connection between the nipple areola complex and the chest wall; portion meaning part of this column was preserved intact; and entire meaning the entire column of subareolar parenchyma was preserved unaltered; and (5) width of pedicle.

Study results: (1) number of women successful at breastfeeding; (2) whether characteristics between women successful and not successful at breastfeeding were examined (e.g. BMI); (3) percent of women satisfied with the surgery; and (4) study conclusion.

Author profession was obtained through information in the study or Google search and was classified as plastic surgeon, plastic surgery affiliation, other, or unknown.

Two reviewers (R.K. and G.M.A.) developed a data extraction sheet and extracted data from the first four studies together to calibrate the data extraction between reviewers. Subsequently, two reviewers (R.K. and E.B.) independently extracted data on pedicle characteristics and two reviewers (R.K. and L.K.) independently extracted all other variables. Disagreements were resolved through consensus between the two reviewers. Percent agreement in data extraction was computed.

Quality assessment

We used the risk of bias assessment in Sobhy et al’s systematic review as a template [13].

For studies without control groups, we used the following criteria to assess the risk of bias: adequacy of sample size, representativeness of the population, measurement, and outcome assessment. We considered sample size to be adequate if the study had 20 or more women with children, and inadequate if the study had fewer than 20 women with children. We considered a study adequate in terms of representativeness if no subsets of patients were excluded, and inadequate if a subset was excluded or it was unclear from the description provided. We deemed measurement to be adequate when the study provided a definition of breastfeeding success, and inadequate when a study did not provide a definition of breastfeeding success. We determined outcome assessment to be adequate when a study followed breastfeeding for at least six months, and inadequate when a study followed breastfeeding for less than six months. If ≥3 criteria were met, the study was deemed to have a low risk of bias. Otherwise, it was considered to have a high risk of bias.

For studies with control groups, we used the Newcastle-Ottawa scale to determine the risk of bias in selection, comparability of cohorts, and outcome assessment [14]. Studies that had four stars for selection, two stars for comparability, and three stars for ascertainment of the outcome were deemed to have a low risk of bias. Studies with two or greater stars for selection, one for comparability, and two for outcome ascertainment were considered to have a medium risk of bias. All other studies were considered to have a high risk of bias.

Data extraction

Characteristics of included studies are provided in Table 1 (see S2 Table for additional study details). Agreement between the two reviewers for data extraction on pedicle characteristics was 89%; the agreement for the remaining data extraction was 95%.

The selected studies were published between 1957 and 2013. The studies were located worldwide: 50% in Europe, 25% in North American, and 25% in other locations. Eleven studies had control groups. Twenty-two studies provided a definition of breastfeeding success; it ranged from 1 week to 24 weeks of breastfeeding. In 46 studies, we were able to determine the profession of the first author. In 42 of these studies, the first author was a plastic surgeon or had a plastic surgery affiliation [16,17,19,21–27,29–32,34,36–39,41,43,45–59,61–66].

Nine studies provided BMI; in 6 studies, the average BMI was ≥ 25, in the remainder of the studies the average BMI was <25. Two studies provided the disclosure that women received from surgeons on the impact of the surgery on future breastfeeding [40,60]. The disclosure was variable. It is unclear if the variability is due to different breastfeeding techniques, as the breast reduction techniques were not disclosed. Five studies (N = 86) provided reasons why women did not attempt to breastfeed, with the lack of support and encouragement being the predominant reason (72%) (S3 Table). Seven studies (N = 120) provided reasons for unsuccessful breastfeeding, with 55% of women reporting insufficient milk and 16% of women reporting reluctance and the lack of support (S3 Table).

In the 51 studies, there were 102 reported breast reduction techniques (see S4 Table for characteristics of each breast reduction technique). When the data were grouped based on the preservation of the column of subareolar parenchyma, 10 techniques had full preservation, 35 had a portion, 19 did not preserve any, and 38 did not have the preservation information. Ten studies provided the width of the pedicle; in all cases, it was ≥5 centimeters. In total, among the 102 reported techniques, there were 31 distinct breast reduction techniques.

Twenty-seven studies provided the satisfaction rate with breast reduction surgery; the median satisfaction rate among these studies was 92%. In 31 studies, the authors offered a conclusion of whether or not breast reduction surgery impacted breastfeeding; in 27 of these studies, the authors concluded breast reduction surgery did not impact breastfeeding [16–18,21,23,28–32,34,36–38,40,41,43,45–49,51,55,57,59,66].

Quality assessment

Fig 2 shows the probability of bias for studies with and without control groups (see S5 Table for risk of bias calculation for each study). For studies without control groups, six had a low probability of bias and 34 had a high probability of bias. For studies with control groups, one had a medium probability of bias, and ten had a high probability of bias.

The authors would like to thank the University of Alberta Libraries Interlibrary Loan Service for retrieval of studies.