Comparing the pelvis of Tibetan and Chinese Han women in rural areas of China: two population-based studies using coarsened exact matching

Abstract

This study aims to investigate the difference of pelvic size and shape between Tibetan and Chinese Han women. Data on pelvic dimension measures including interspinous diameter (IS), intercrestal diameter (IC), external conjugate (EC) and transverse outlet (TO) were acquired from two population-based studies amongst Tibetan women in Lhasa, and Chinese Han women in Shaanxi province in China. After coarsened exact matching, there was no statistical difference between any characteristics amongst Tibetan and Chinese Han women (p>.05). The generalised estimating equation models showed Tibetan women had significantly lower IS and IC means than Chinese Han women (IS: 24.39 cm vs. 24.77 cm, p<.001; IC: 26.35 cm vs. 26.93 cm, p<.001) but statistically higher in TO mean (9.12 cm vs. 9.03 cm, p<.001). This study showed Tibetan women have smaller pelvis compared to Chinese Han women. This should offer a useful literature on the comparison of pelvis between Tibetan and Chinese Han women although the difference is small.

Impact Statement

• What is already known on this subject? Previous studies in China indicated different populations have different dimensions of pelvis, with the pelvis of Uighur women being bigger than Chinese Han women, and that of Zhuang and Tu women being smaller than Chinese Han women. Little research reports the specific size of Tibetan women’s pelvis. Living at high altitude, the Tibetan population have differentiated demographics and show local adaptions, such as unelevated haemoglobin, and significant catch-up growth for infants compared with Chinese Han infants. Therefore, there is a strong rationale for better understanding pelvic characteristics amongst this population.

• What the results of this study add? This study showed Tibetan women have smaller pelvises compared to Chinese Han women. Tibetan women have a smaller interspinous diameter and intercrestal diameter than Chinese Han women, which leads to relatively narrow hip.

• What the implications are of these findings for clinical practice and/or further research? This study provides useful comparative information on pelvic features between Tibetan and Chinese Han women although the findings of differences were small. In addition, during the formulation of women’s health policy, the results of this study can provide data to support the selection of appropriate indicators of obstetrics and gynaecology for different populations of pregnant women during antenatal care and delivery.

Keywords:

• Pelvis
• Tibetan women
• Chinese Han women
• coarsened exact matching
• population-based study

Acknowledgements

We express our appreciation to all participants in our study for their participation and co-operation, to the professors and students of Center of Medical Science, Xi’an Jiaotong University, to the gynecology and obstetrics doctors of maternal and child health care hospital in Tibet and Shaanxi, and to the county hospital doctors and MCH staff of township hospitals for their co-operation and organisation in the data collection.

Disclosure statement

The authors declare no conflict of interest.

Data availability statement

The datasets generated for the current study are available from the corresponding author on reasonable request.

Additional information

Funding

This work was supported by the National Science Foundation of China under Grant No. 30771835; the China Medical Board of New York under Grant No. 02-778; Birth Defect Control and Prevention Project of Shaanxi Health Commission under Grant No. Sxwsjswzfcght2016-013; and the 65th Batch of China Postdoctoral Science Foundation Grant under Grant No. 2019M653684.