TRANSVERSE
DIAMETER ( CM )
FREQUENCY PERCENTAGE ( % )
CUMMULATIVE PERCENTAGE
( % ) 2.0 –
3.9
49 17.0% 17.0%
4.0 – 4.9
176 60.9% 77.9%
5.0 – 5.9
53 18.3% 96.2%
> 5.9 11 100.0%
100.0%
FIG. 4. PIE CHART SHOWING FREQUENCY DISTRIBUTION OF UTERINE TRANSVERSE DIAMETER MEASUREMENTS
49
176 53
11
2.0 - 3.9 4.0 - 4.9 5.0 - 5.9 > 5.9
In the relationship between subjects’ height and uterine length, AP diameter and width, there were gradual increases, with the maximum mean 7.5cm, 4.57cm and 5.27cm respectively seen in the maximum height group of 176cm – 180cm, (where p < 0. 01). There was slight reduction in mean uterine length of 151-155cm and 171-175cm subject`s height classes and same trend is also observed in mean uterine width of the 156 – 160cm subjects’ height class and the mean uterine AP diameter of the 171 – 175cm subjects’ height class. (Table 5)
This deviation is minimal and does not alter the significant correlation between subjects’ height and uterine dimensions as shown in table 5.
TABLE 5
RELATIONSHIP OF HEIGHT TO UTERINE DIMENSIONS (MEAN OF LENGTH, AP AND WIDTH)
HEIGHT (CM)
MEAN LENGTH (CM)
MEAN AP (CM)
MEAN WIDTH (CM) 140-
145
6.6 3.44 4.2
146 - 150
6.9 3.53 4.40
151 - 155
6.7 3.60 4.54
156 - 160
6.9 3.62 4.45
161 - 165
7.1 3.64 4.54
166 - 170
7.4 3.92 4.76
171 - 175
7.3 3.82 4.85
176 - 180
7.5 4.57 5.27
In the relationship between subjects weight and uterine dimensions, the subjects’ weight ranged from 45 – 120kg, with the mean weight of 65.1kg. Majority of subjects were in the 51 – 60kg weight group. There was an increase in the dimensions of the uterus, as the weight of subject increased, which was maximal at the 111 – 120kg weight group, (where p < 0.01). Thus, there was significant correlation between subjects’
weight and uterine dimensions. Table 6
TABLE 6
RELATIONSHIP BETWEEN SUBJECTS’ WEIGHT AND UTERINE DIMENSIONS (MEAN OF LENGTH, AP AND WIDTH)
WEIGHT (KG)
MEAN LENGTH (CM)
MEAN AP (CM)
MEAN WIDTH (CM)
43 – 50 6.6 3.5 4.3
51 – 60 6.9 3.6 4.5
61 – 70 7.2 3.8 4.7
71 – 80 7.0 3.7 4.6
81 – 90 7.4 3.9 4.8
91 – 100 7.3 3.8 4.7
101 – 110
7.8 3.6 4.4
111 – 120
7.8 4.4 5.7
In the relationship between parity of subjects with uterine dimensions, the subjects’ parity ranged from 0 – 12. The maximum uterine length, AP diameter and width of 8.2cm, 4.8cm and 5.4cm respectively are achieved at the maximum parity class of 9 – 12, (where p<0.001).
The table 7 shows that with increasing parity, there is a corresponding increase in uterine dimensions. Thus, there is a highly significant correlation between parity of subjects and uterine dimensions.
TABLE 7
RELATIONSHIP BETWEEN PARITY AND UTERINE DIMENSIONS (MEAN OF LENGTH, AP AND WIDTH)
PARITY MEAN LENGTH (CM)
MEAN AP DIAMETER (CM)
MEAN WIDTH (CM)
0 – 2 6.7 3.6 4.4
3 – 5 7.2 3.8 4.7
6 – 8 7.6 4.0 4.9
9 – 12
8.2 4.8 5.4
TABLE 8
RELATIONSHIP BETWEEN AGE AND FREQUENCY WITH UTERINE DIMENSIONS (MEAN OF LENGTH, AP AND WIDTH)
AGE (YEARS)
FREQUENCY MEAN LENGTH (CM)
MEAN AP (CM)
MEAN WIDTH (CM)
16 – 20 42 6.70 3.45 4.31
20 – 25 68 6.75 3.54 4.45
26 – 30 72 7.03 3.59 4.52
31 – 35 42 7.30 3.87 4.56
36 – 40 33 7.12 3.72 4.67
41 – 45 32 7.40 4.02 4.75
A comparison of uterine dimensions obtained in the present study with established values for Caucasian women is shown in table 9.
TABLE 9
COMPARISON OF UTERINE DIMENSIONS OBTAINED IN THE PRESENT STUDY WITH ESTABLISHED VALUES FOR CAUCASIAN
WOMEN
PRESENT STUDY
ROBBINS AND COTRAN (1979)
MEMINN
(1994) MOORE (1992) UTERINE LENGTH
(CM) 7.02 0.9 8 8 7 – 8
RANSVERSE DIAMETER
(WIDTH) (CM) 4.5 0.66 5 – 6.5 5 5 – 7
ANTERO-POSTERIOR DIAMETER (THICKNESS) (CM)
3.6 0.69 3 3 2 - 3
Statistical analysis showed significant positive correlation (where P<0.01 and r <0.001), between age and each pair of anthropometric variables:
height, weight, parity and the uterine dimensions: length, thickness and width.
DISCUSSION
This study presented values of uterine dimensions in premenopausal Benin City women obtained by real time transabdominal sonography.
Real time transabdominal sonography was used in this study mainly to minimize inconveniences to the subjects. In the assessment of normal uterine sizes, transvaginal sonography can also be used but it is not readily available in our center and may have affected recruitment of subject mainly on cultural bias.
Transvaginal and Transabdominal sonography are well-established modalities for sonographic evaluation of uterine dimensions. Literature review showed favorable comparison of data obtained by transabdominal sonography and transvaginal sonography. 38, 48, 49
The mean uterine dimensions (length=7.02 0.9cm, AP diameter=3.6 0.69cm and width=4.5 0.66cm) of premenopausal women in Benin City do not remarkably differ from established values (length=8cm, AP diameter=3cm and width=5–6.5cm) for Caucasian women,28 although the technique used to obtain those established values from Caucasian women were not mentioned or specified in the study.
The study also showed the correlation of uterine dimensions with anthropometric variables (subjects’ weight and height). This shows that there was significant correlation between subjects’ height and uterine dimensions. However, this is not correlating well with under mentioned
of 151 – 155cm and 171 – 175cm subjects’ height classes due to the fact that these classes had lesser number of parity than their preceding subjects’ as per height classes. It showed favorable comparison with my study data. A significant reduction in the uterine dimension was noticed in the 71 – 80kg and 91 – 100kg weight groups in this study. This may have been caused by reduced parity in these groups. Also, significant reduction in the uterine dimensions was noted in the height group of 151cm – 155cm. This has been attributed to body mass and number of parity in that group. These were statistically significant (P<0.01) as the uterine dimensions increased with height and weight. This can be explained as a function of increase in body mass of the subject that correspondingly causes increase in uterine size, which can be related to physical body growth in the subject.
The dimensions of premenopausal uterus are greater in the multiparous than in the nulliparous women in this study. This is probably due to physiological uterine enlargements associated with reproductive functions.
Parity is found to be the most important factor in determining the uterine size in the premenopausal subjects.8,21 In fact, there was an increase in the uterine size as the parity increased in the parous group, as established in the present study (Table 7). In a study carried out by Nzeh et al, on ultrasound study on measurement of normal uterine size in premenopausal women, parity and age were reported to be the most variable factors that affect uterine size.
Correlation with age and parity was established, in confirmation of previous documentation on this correlation among the black women,
which showed that there is marked increase in the growth of the uterus at puberty. 23 During fetal life, the size of the uterus initially increases at slow rate until the end of first trimester, after which it increases in size at a faster rate due to the increased production of maternal oestrogen.
Immediately after delivery, the size of the uterus decreases as a result of ceasation of maternal oestrogen. During a woman’s life time, the changes in morphology result from changes in the muscular layer of the uterus, particularly in the body portion of the uterus. It is known that growth criteria (height, weight and other body indices) are influenced by race, hereditary, environment and nutrition. Table 8 shows an age related increase in the uterine measurements during the reproductive years with the maximum mean uterine dimensions (length, AP diameter and width) obtained in the 26 – 30 years age group. The mean length, AP diameter and mean width of the subjects’ weight class of 71 – 80kg showed a slight reduction, compared to the preceding 61 – 70kg weight class due to fewer number of parity in the former. This might be due to the fact that there is increase growth of the uterus during the reproductive years, with possible decline attributed to atrophy, due to old age and ceasation of hormonal stimulation. 4, 9 however, the 36-40 years age group showed a deviation from this trend. The mean uterine dimensions (length and AP diameter) were lower than the preceding age groups. This might be due to the fact that this age group has fewer number of parity than the preceding age groups.
There are other studies that showed morphological changes in accordance with phases of menstrual cycle, caused by hormonal influences.5,20
These changes can affect uterine size on ultrasound examination5,9, hence cognisance should be taken in the evaluation of patients at different phases of the menstrual cycle.
Studies have shown that the size of the uterus enlarges towards the end of the menstrual cycle and is thinnest during the menstruation.5,9,26,27
This present study has presented mean uterine dimensions in Benin City and its environs at the pre-ovulatory phase of their menstrual cycle, with mean uterine length as 7.02 ± 0.9cm,and range of 4.6cm – 11.2cm;
the mean anteroposterior diameter (thickness) of 3.6cm ± 0.69 and range of 1.7cm – 5.7cm, while the mean transverse diameter (width) was 4.55cm ± 0.66cm, with a range of 2.4cm – 6.6cm. The comparison reveals that the measurements of uterine dimension obtained in the present study is fairly similar to established values for Caucasian women.
The findings from this study can have potential gynaecological application. In essence, the uterine dimensions obtained in the present study are fairly similar to established values for the Caucasian women. 6,
9, 21, 24
CONCLUSION
The mean values of anteroposterior diameter, length and width of the uterus have been evaluated and presented. They showed similar measurement relationship in studies carried out in Caucasians. The effect of weight, parity, height and age have been examined and showed a positive correlation, i.e. corresponding increase in the size of the uterus as the subjects’ weight, height, age and parity increases in premenopausal women.
This study has suggested baseline for the mean dimensions of the uterus at pre-ovulatory phase of menstrual cycle, of premenopausal women in Benin City and its environs. It also suggest that deviation from these obtained values during the pre-ovulatory phase of menstrual cycle may be taken to mean uterine pathology or that the dimensions obtained were probably taken during the secretory phase of the menstrual cycle.
SUMMARY
Sonographic evaluation of normal uterine dimensions among 289 premenopausal women in Benin City was done, with Medison Sonoace 1500 ultrasound scanner, and curvilinear real-time probe of 3.5MHz transducer frequency. Suprapubic approach was used with subjects lying in comfortable supine position. Uterine size was determined by three measurements obtained by electronic caliper directly from the image for each of the following parameters: Transverse diameter (width) measured on the transverse scan, longitudinal diameter measured on sagittal scan and the anteroposterior measurement on sagittal scan.
Height and weight of the subjects were measured, using the appropriate scale. From this study the mean uterine dimensions in Benin City and its environ are: mean uterine length as 7.02 ± 0.9cm and the range of 4.6cm – 11.2cm; the mean anteroposterior diameter (thickness) was 3.6
± 0.69cm and range of 1.7cm – 5.7cm; while the mean transverse diameter (width) was 4.55 ± 0.66cm, with a range of 2.4cm – 6.6cm.
These values of uterine dimensions compared favourably with established values in Caucasian women.
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