Research advances of common gynaecological diseases in twin cohorts

Twin study is an economical and effective method to analyse genetic and environmental factors in complex diseases. It is extensively used to explore the aetiology of many diseases. The heritability of diseases has been analysed by comparing the phenotypes of monozygotic twins and dizygotic twins in a classical twin study. With the development of molecular biology, the combination of twin study and omics is becoming an emerging and promising method. The study of twin pairs with inconsistent disease phenotypes is a powerful improvement to the traditional case-control study. In the area of gynaecology, Western countries have used the twin study to analyse the aetiological characteristics of several common gynaecological diseases in the Caucasian population, including pelvic floor disease, uterine leiomyoma, endometriosis, polycystic ovary syndrome, and some other diseases. The main findings include the following: in stress urinary incontinence and pelvic organ prolapse, environmental factors contribute more than genetic factors; genetic factors have a greater impact on the incidence of uterine fibroids than environmental factors; the random environmental effects have a great impact on endometriosis, amongst which infertility is closely related to endometriosis; genetic factors are important in the aetiology of polycystic ovary syndrome; and female orgasmic disorders have a genetic basis, etc. However, no twin study of gynaecological diseases in Asian populations has been conducted. The Chinese National Twin Registry has recruited more than 20 000 pairs of female twins. In combination with molecular biological methods, we believe that a breakthrough in understanding common gynaecological diseases in China will occur and provide better clinical guidance. The main difficulties in the future will be the expansion and long-term maintenance of the twin cohort.