Introduction

The female breast is one of the organs in the human body that has diverse shapes, varying due to factors such as age, physical condition, pregnancy status, and ethnicity. Global studies on breast anthropometry are consistently striving to describe features and find correlations between various breast anthropometric indexes [1,2,3], often characterized by country and ethnicity [4].

From the initial breast anthropometry research published by Penn (1955) to the present, it is clear that accurately and objectively assessing breast anthropometric indexes is still controverted, with no standardized, unified procedure [5]. Most authors are interested in a similar set of indexes to determine the “ideal breast,” focusing on breast volume, non-ptosis (non-sagging) breasts, and the appropriate position of the nipple-areola complex [2, 5,6,7]. This also represents the ultimate goal of breast cosmetic and reconstructive surgery.

The purpose of this study is to provide information on the distinct mean anthropometric values of young Vietnamese women’s breasts aged 18–25, with a normal body mass index (BMI) ranging from 18.5 to 25 kg/m2, who have never given birth. Moreover, we evaluate the correlation of anthropometric indexes with breast volume, compare the breast anthropometric indexes of young Vietnamese women with other women’s groups worldwide, and identify some unique distinguishing points. The results obtained from this study contribute to building a set of breast anthropometric indexes for Vietnamese women, providing significant value to breast and cosmetic surgeons in guiding and developing breast surgery plans for young Vietnamese women.

Objective and methods

The research was approved by the ethics committee of Hanoi Medical University. All volunteers participating in the research signed a consent form. The study involved a random selection of 128 female volunteers, a total of 256 breasts, aged 18 to 25 years, nulliparous, with no chest deformity, no local or systemic disease, normal physical development, and a body mass index ranging from 18.5 to 25 kg/m2.

Research tools included a measuring tape with 1 mm graduations, a caliper with 1 mm accuracy, a straight ruler with 1 mm gradations, a compass to measure the chest size, a digital camera, and a data collection form.

Volunteers were measured standing upright, their heads straight such that the external ear hole aligns with the midpoint of the shoulder. Landmarks on the chest were marked, including the suprasternal notch, mid-clavicular point, nipple, inframammary line, lowest point of the inframammary line, inner limit of the breast, and outer limit of the breast.

The study considered the following indexes (Table 1).

Table 1 List of indexes and variables
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Breast volume for each side was calculated using Qiao’s formula [1], based on LR, MR, IR, and MP measurements, breast volume V = 3.14/3 * MP2 * (LR + MR + IR − MP) ml. Body mass index was calculated using the formula: BMI (kg/m2) = weight (kg)/height2 (m2).

Data analysis: the results were presented as mean ± standard deviation (mean ± SD), minimum (min), and maximum (max) value. Normal distribution was tested with the Kolmogorov-Simirnov test; mean comparison between breasts was performed with the paired-samples T test, Wilcoxon signed ranks test, and one-sample statistics; and Spearman analysis was used to find correlations between variables, using SPSS 26.0 software for data analysis. Confidence interval was 95%, and statistical significance was defined as p < 0.05.

Results

The study was conducted on 128 young women, with an average age of 18.6 ± 0.6 (18–21) years. The mean weight was 50.8 ± 4.8 (41–66) kg, and the mean height was 155.7 ± 5.2 (145–173.2) cm. The mean body mass index (BMI) of the research group was determined to be 21 ± 1.6 (18.5–24.8) (kg/m2). The average distance from the suprasternal notch to the nipple (SN) was 18.4 ± 1.7 (15–23.8) cm on the right side and 18.5 ± 1.7 (15.2–23.2) cm on the left side. The mean distance from the midclavicular point to the nipple (CN) was 17.3 ± 1.9 (14–27) cm on the right side and 17.4 ± 2 (13.5–28) cm on the left side. The mean nipple-to-nipple distance (NN) was 19.1 ± 2.1 (14.2–26.8) cm (Fig. 1). The mean upper chest circumference (CC1), internippler chest circumference (CC2), and inframamarium chest circumference (CC3) were 80.6 ± 1.1 (72–91.1) cm, 82.5 ± 5.5 (63–95.8) cm, and 71.5 ± 4.2 (61.5–84) cm respectively (Fig. 2A). The mean chest depth was 16.3 ± 2.4 (8.5–20.8) cm.

Fig. 1
figure 1

Breast anthropometric results for the following indexes: distance from the clavicle to the nipple, distance from the sternal notch to the nipple, distance between two nipples, areola width, and breast base width

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Fig. 2
figure 2

Breast anthropometric results for the following indexes. A Chest circumference at the armpit, chest circumference at the nipple, and chest circumference at the inframammary fold. B Medial mammary radius, lateral mammary radius, and nipple-inframammary fold length

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The mean distance from the nipple to the lateral mammary radius (LR) was 9.7 ± 1.6 (5.1–14.2) cm on the right side and 9.7 ± 1.6 (4.1–14.3) cm on the left side. The mean distance from the nipple to the medial mammary radius (MR) was 8.9 ± 1.2 (6.3–12.5) cm on the right side and 9.2 ± 1.3 (6.2–12.1) cm on the left side. The mean nipple-inframammary fold length (IR) was 6.8 ± 1.2 (4.2–9.8) cm on the right side and 6.8 ± 1.2 (4–11) cm on the left side. The mean mammary projection (MP) was 4.2 ± 1.1 (2.1–6.7) cm on the right side and 4.3 ± 1.1 (2.2–6.9) cm on the left side (Fig. 2). The mean breast volume (V) was 437.1 ± 266.8 (95.5–1244.7) ml on the right side and 457 ± 259.7 (93.7–1315.6) ml on the left side. The mean areola diameters on the right and left sides were 3.4 ± 0.6 cm and 3.4 ± 0.7 cm, respectively.

The mean breast width (WB) was 13.5 ± 1.4 (10–17) cm on the right side and 13.6 ± 1.4 (10.2–17) cm on the left side. The mean areola diameter (AD) was 3.4 ± 0.6 (2–5.1) cm on the right side and 3.4 ± 0.7 (2.2–6.8) cm on the left side. The mean thickness of the upper breast tissue (TU) was 5.3 ± 0.9 (3–7.6) cm on the right side and 5.4 ± 0.8 (3.1–8) cm on the left side. The mean thickness of the lower breast tissue (TL) was 4.4 ± 1 (2.6–7.2) cm on the right side and 4.4 ± 0.9 (2.4–8) cm on the left side (Table 2).

Table 2 General characteristics of breast anthropometric indexes (n = 256)
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There is no difference between the left and right breast in the mean values SN, LR, IR, AD, and TI (p > 0.05). The mean value CN L are greater than CN R, MR R is greater than MR L, MP L is greater than MP R, left breast volume is greater than right breast volume, and WB L is greater than WB R are statistically significant (p < 0.05), with these indexes tending to be higher on the left side than the right. Comparisons of the average values between the two breasts for these indexes are presented in Table 3.

Table 3 Comparative anthropometric features of the left and right breasts (n = 128)
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In analyzing the breast volume value of the research group, it was found that 5 out of 128 (accounting for 4%) volunteers have equal breast volumes. The remaining individuals in the group have different breast volumes, with 73 out of 128 (57%) volunteers having a larger left breast volume and 50 out of 128 (39%) having a larger right breast volume.

The Kolmogorov-Siminov test for evaluating the normal distribution of variables found that the normally distributed variables are SN R, SN L, NN, CC1, CC2, LR R, LR L, MR R, MR L, IR L, WB R, WB L, TU R, TU L, TL R, MP R, MP L, H, BMI, HR, and HL. The non-normally distributed variables are age, CN R, CN L, CC3, IR R, AD R, AD L, TL L, W, volume P, and volume T.

There is no correlation between the height value (H), the distance from the left suprasternal notch to the left nipple (SN L), and the distance between the two nipples (NN) with the breast volume. The 8 indexes that strongly correlate (r > 0.5) with breast volume are, respectively, mammary projection (r = 0.963), medial mammary radius (r = 0.807), lower breast tissue thickness (r = 0.805), lateral mammary radius (r = 0.71), distance from the right suprasternal notch to the right nipple (r = 0.63), breast circumference at the nipple (r = 0.614), breast base width (r = 0.597), and midclavicular point to nipple distance (r = 0.571) (Table 4).

Table 4 Correlation between breast volume and factors affecting breast volume
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Clinical application

Patient height (H) and mid-clavicular point to nipple distance (CN)

With an average height of the study subjects being 155.7 ± 5.2 cm, the average nipple-midclavicular distance is 17.3 ± 1.9 cm. Therefore, the nipple-areola complex is placed in a proportionate position relative to the body height, a position corresponding to the “ideal nipple plane” across the midpoint of the arm of the nipple-areola complex according to Westreich Melvyn [7], creating aesthetically pleasing results.

According to the results of Fig. 3, we derived a correlation of H = 9 × CN as a clinical reference for patients undergoing late breast ptosis surgery or for patients with breast hypertrophy combined with ptosis. We designed the distance from the lower edge of the sternal notch to the new nipple position as 17–17.5 cm for patients with a height of 155–160 cm; 18–18.5 cm for patients with a height of 160–165 cm. Along with this, the diameter of the new areola was designed to be 38–42 mm.

Fig. 3
figure 3

Relationship between midclavicular-nipple distance (CN) and patient’s height (H)

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Mammary projection (MP) and mid-clavicular point to nipple distance (CN)

A statistically significant correlation between MP and CN was observed, following a linear equation with CN = 1.0222 × MP + 12.968 (p < 0.05), R2 = 0.3227 (Fig. 4). With the CN ranging from 17 to 18 cm, the corresponding MP falls within the range of 4–5 cm. We also observed that, for the group of young Vietnamese women, a projection of 4–5 cm ensures an ideal aesthetic breast shape. This projection is also the desired goal to be applied for breast augmentation surgery for our patients.

Fig. 4
figure 4

Correlation between mammary projection (MP) and midclavicular-nipple distance (CN) and the regression equation showing the relationship between MP and CN (p < 0.05) R2 = 0.3227

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Reference anthropometric indexes in breast reconstruction surgery

Our study was conducted on normally developing young females, from which we could deduce the relationship between these anthropometric indexes. However, the application of these anthropometric indexes for surgical guidance depends on several other variables in the surgery that pure anthropometric indexes do not fully reflect. Currently, some breast anthropometric indexes in our study are used as a basis for hypertrophic breast reduction surgeries, mastopexy, and the post-surgery results are very noteworthy. Besides the indexes mentioned below, the lateral breast position varies greatly among patients, possibly from the anterior axillary line to the mid-axillary line, so the reference value of the LR index changes significantly (Fig. 5).

Fig. 5
figure 5

Ideal breast anthropometric indexes used as reference for surgery. The following dimensions are considered guidance for surgery: sternal notch to nipple: 18–19 cm (yellow); midclavicle to nipple: 17–18 cm (sky blue); medial mammary radius: 9–11 cm (indigo); nipple to IMF: 6–7 cm (red); areola diameter: 38–42 mm (green); breast projection: 4–5 mm (violet)

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Case presentation

Case 1 involved a 39-year-old female with a height of 156 cm and weight of 53 kg. She was preoperatively diagnosed with grade 3 hypertrophic breast ptosis according to Regnault classification [11]. The preoperative chest indexes were 25 cm for the right CN-N and 26.5 cm for the left CN-N, with an expanded areola diameter. A new CN-N distance of 17 cm was designed for the patient, incorporating a 4 cm areola diameter and a 15 cm distance from the lower point of the sternal notch to the upper edge of the new nipple-areola complex (NAC) (Fig. 6). Postoperatively, the position of the NAC was found to be appropriate to the body, located midway along the arm.

Fig. 6
figure 6

Images of hypertrophic breasts, severe ptosis operated based on anthropometric indexes. A Breast images and preoperative design, the new nipple-areola position is designed 15 cm from the midpoint of the sternum, the new areola diameter is 40 mm, and the new IR length is 6.5 cm. B Results 1 month after surgery

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Case 2 involved a 38-year-old female who requested breast augmentation without addressing ptosis (Fig. 7). Her preoperative indexes were as follows: MR 8.4 cm, LR 9.9 cm, IR 5.4 cm, MP 3.7 cm, and volume 286.6 ml. According to the reference, the expected breast dimensions were increased by 1.5 cm and the projection by 5 cm, resulting in the following expected values: MR 9.9 cm, LR 11.4 cm, IR 6.9 cm, MP 5 cm, and volume 607.1 ml. Consequently, a 320-ml breast implant was used, calculated by subtracting the preoperative volume (286.6 ml) from the expected volume (607.1 ml).

Fig. 7
figure 7

A Female patient, 38 years old, image before surgery. B Follow-up after 1 month of breast augmentation, axillary incision, under pectoralis major muscle, 320 ml implant. C Projection before surgery. D Projection 1 month after surgery

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Discussion

Our research design includes 19 variables, divided into three groups for convenience during the research process, data analysis, and research result evaluation. Group 1 includes general anthropometric indicators such as weight, height, and BMI. Group 2 includes indicators reflecting the correlation between the patient’s chest, body, and breasts: SN, CN, NN, CC1, CC2, CC3, and CH. Group 3 consists of anthropometric indicators that describe unique breast characteristics: LR, MR, IR, MP, V, WB, TU, TL, and AD.

Breast volume

In breast anthropometry studies, accurate breast volume assessment remains a difficult issue and is still debated. Many methods have been proposed by authors worldwide and are divided into two groups: direct breast volume measurement methods such as water displacement, mold filling, or indirect measurement through anthropometric indicators [8, 12]. According to a study by Choppin in 2016, the author evaluated 8 current methods of measuring breast volume. MRI breast volume measurement gives the highest accuracy results with an error of less than 10%, but the cost is high and it cannot be frequently applied on a large scale. Besides, breast volume measurement by anthropometry remains a method that provides high accuracy in methods with low cost, simplicity, convenience, easy application, and is preferred by both research participants and surgeons [13].

Previous anthropometric breast studies focused on young, nulliparous women, results such as Qiao’s study [1] on Chinese women aged 18–26 with an average breast volume of 310–330 ml, standard breast volume within the range of 250 ml to 350 ml. A study by Westreich [7] in 1997 on 50 Israel women aged 17 to 38, left breast volume was larger than right breast volume. Avsar’s study [8] on 385 Turkish women also showed that left breast volume was larger than right breast volume, with an average breast volume of 407.2 ± 263.6 ml. Similarly, in our study, the volume of the left breast is 457 ± 259.7 ml and the volume of the right breast is 437.1 ± 266.8 ml, statistically significant larger left breast volume (p = 0.002 < 0.05), and the average volume of both breasts is 447.1 ± 259.5 ml.

Weight and height

The correlation between breast volume and weight is still debated and has not been agreed upon. According to a study by Vandeput and Nelissen [2] in 2002, the authors pointed out that breast volume is independent of weight or torso width (similar to CC3). This study is equivalent to Katch’s research [14] in 1980, which also showed a weak correlation between height or weight and breast volume. However, recent studies all point out the significant correlation of weight to breast volume. Qiao [1] in 1997 showed a positive correlation between breast volume and weight, chest circumference, waist circumference, and hip circumference. In overweight women, breast volume increases by 20 ml per kilogram of weight. Avsar [8] in 2009 pointed out a positive correlation between breast volume and weight (p < 0.001), and a negative correlation with height (p = 0.712). Sa Jin Kim [15] in 2014 showed a clear positive correlation between breast volume, age, and weight variables (p < 0.001). In our study, breast volume has a medium positive correlation with weight with r = 0.406 and p < 0.001. Height has absolutely no correlation with breast volume with p = 0.978, which is similar and consistent with many previous breast anthropometry studies [7, 8].

Sternal notch to nipple, midclavicle to nipple, nipple to nipple

Set of indexes reflecting the position of the breast and areola complex on the chest wall includes SN, CN, NN, CC1, CC2, and CC3.

We evaluated the SN left, SN right, and NN together, reflecting the relative position of the breast and areola complex on the chest. In our study, the mean SN was 18.4 ± 1.7 cm, the right SN distance was 18.4 ± 1.7 cm, the left SN distance was 18.5 ± 1.7 cm, and there was no difference between the left and right sides in this index (p = 0.252 > 0.05). The mean NN distance in our study was 19.6 ± 5.6 cm. The NN distance is statistically smaller than the left and right SN distances. The three points comprising the sternal notch, left nipple, and right nipple form an isosceles triangle. The NN distance is on mean 0.6 cm shorter than the SN. The SN and CN distances in our study are the shortest compared to other global anthropometric studies of the breast (Table 5), the mean SN distance in Longo’s study [10] was the largest at 24.73 cm, and the mean CN was 24.96 cm. Longo’s research subjects ranged in age from 30 to 75, and this group had accompanying breast ptosis or hypertrophy, hence the large SN and CN distances. Our study was conducted on female volunteers who had never given birth, with almost no breast ptosis. The average SN distance in Longo’s study was a maximum of 24.73 cm, and the average CN was 24.96 cm. Longo’s study participants ranged in age from 30 to 75, and this group included individuals with ptosis or hypertrophy, resulting in larger SN and CN distances [10]. Our study was conducted on volunteers who were women who had never given birth, and therefore, almost none had ptosis.

Table 5 Comparison between SN, CN, and NN indexes between countries
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Lateral mammary radius, medial mammary radius, nipple-inframammary length, areola diameter, breast volume

The mean nipple-inframammary fold length or IR distance in our study is 6.8 cm, and there is no difference in the nipple-inframammary fold length between the left and right breasts (p = 0.969 > 0.05) (Table 3). The IR distance in our study is equal to the IR in Qiao’s study [1] at 6.8 cm, longer than the IR in Sa Jin Kim’s study [15] with the right IR length at 5.9 cm, left IR length at 6.3 cm. In Longo’s study [10], the mean IR length was the longest and equaled 9.26 cm. In fact, Longo’s research group had a higher mean age of 51.3, the research group consisted of women with breast ptosis and hypertrophy, hence the long nipple- inframammary fold length. With a similar research subject group in terms of age, BMI Avsar’s study [8] had the longest nipple-inframammary fold length of 8.3 cm. Both our study and Avsar’s measured a random group of women, never been pregnant, and not ideal breast patients. In addition, when evaluating the breast volume in Avsar’s study [8], it was 407.2 ml, smaller than our study at 447.1 ml, the average medial, lateral radius, and projection were all shorter. This indicates Avsar’s research group had a high rate of ptosis or pseudo-ptosis, leading to an elongation of the nipple-inframammary fold length.

The areola diameter mean in our study was 3.4 ± 0.6 cm. When compared to Qiao’s study, we found the areola diameter equivalent to Qiao’s study at 3.3 cm was significant (p = 0.093 > 0.05). The areola diameter is much larger in Arabian women with an average AD of 4.5 cm and Italian women with an average AD of 4.79 cm (Table 6). The similarity in areola diameter with Qiao’s study is easily explained by the similarity in the research group of young, Asian women. In Longo’s study [10], the subjects were mostly women who had given birth, along with breast hypertrophy, ptosis leading to the expansion of the areola. This is a very significant index for cosmetic surgeons, applied for breast augmentation surgery through the periareola.

Table 6 Comparison of areola diameter with other global studies
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With the usual conical shape of the breast, the projection of the breast is a factor that strongly influences the volume of the breast. The breast projection is also the variable with the highest correlation coefficient with breast volume (r = 0.963, p < 0.01). The breast projections in Luiz Sa’s study [9] and Demiroz’s study [3] were all much larger than our study or other anthropometric studies. The difference lies in the anatomical landmark chosen to measure breast projection. Both authors (Luiz Sa and Demiroz) chose from the axillary line to measure projection; this distance includes a part of the chest wall length, chest muscle thickness, and breast projection; it will not accurately reflect the breast projection. We chose to measure breast projection from the inframammary line and perpendicular to the chest wall, only accurately evaluating the skin, subcutaneous tissue, and breast gland component. In our study, the mean breast projection distance was 4.3 cm. The mean breast projection of Chinese women in Qiao’s study [1] was 3.6 cm, and the mean breast projection of Korean women in Sa Jin Kim’s study [15] was 3.3 cm. The mean breast projection of Turkish women published by Avsar [8] was 4 cm, and Israeli women was 4.93 cm7 (Table 7).

Table 7 Comparison of LR, MR, IR, MP, and AD between countries
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The limitations in previous studies on breast anthropometry include the lack of standardization in measurement techniques and the tools used before, during, and after interventions. The second issue is accurately determining anatomical landmarks for breast anthropometry. For skeletal landmarks such as the sternal notch and the mid-clavicle point, the positions are relatively stable across measurements and patients. However, accurately determining soft tissue landmarks, such as the outermost and innermost points of the breast, can sometimes be unclear, leading to measurement errors.

Our study was conducted on young volunteers aged 18 to 25 years, who had never given birth, had no previous breast surgery, and had no pre-existing diseases. Although this may not represent all Vietnamese women of various ages, it can represent young women who have never given birth. This valuable anthropometric data of the breast can assist plastic surgeons, cosmetic surgeons, and breast surgeons in planning for reconstructive and cosmetic breast surgery.