Study design and participants
In this retrospective cohort study, twin pregnancies were matched with
the degree of cervical dilation at diagnosis. The patients in our study
had comprised all twins with asymptomatic cervical dilation 1-6cm and/or
with prolapsed membranes up to the external os at 18–26 weeks of
gestation from December 2015 to December 2022 at four
Medical Institutions:
Women’s Hospital, Zhejiang
University School of Medicine;
Huzhou
Maternity and Child Health Care Hospital; Shaoxing Maternity and Child
Health Care Hospital; and The First People’s Hospital of Fuyang. The
study was approved by the institutional Review Boards at each
participating institution.
In case group, cerclage procedures were performed under a combination of
the McDonald and Shirodkar’s techniques. Specific operations are as
follows:
Firstly, using the McDonald’s technique with 1-0 non-absorbable sutures,
under spinal anesthesia, the suture was not tightened,.A cervical
balloon dilator (Aiyuan) was introduced to the cervical canal with
gentle pressure to replace the membranes into the uterus before
suturing, and the balloon at the top of the catheter was filled with
10-20 ml saline. Secondary, with the Shirodkar technique, a Mersilene
tape was inserted above the junction of the cervix with dissection of
the bladder and rectum and tried to place the tape as close to the
internal cervical os as possible. Thirdly, remove the balloon slowly
after drainng the saline, tightened the Mersilene tape first, then
tighted the 1-0 non-absorbable suture.
A control group were matched one-to-one with the case group, according
to the cervical dilation at diagnosis of ± 2 cm, GA of ±3 weeks at
presentation of diagnosis and maternal age of ±5 years. We used
case–control matching in Statistical Packages of Social Sciences (SPSS)
for Windows, version 25.0 (SPSS, Chicago, IL, USA). Cerclage procedures
were performed under McDonald’s techniques.
The decision to perform which cerclage technique was based on individual
physician and patient preferences, and antenatal steroids were offered
to all women ≥ 24 weeks of gestation. The exclusion criteria were
included as follows: history of multi-fetal pregnancy reduction to twins
at >14 weeks, fetuses with structural or chromosomal
abnormalities, medically indicated PTB (twin-twin transfusion syndrome,
severe preeclampsia, placental abruption, PPROM, or placenta previa),
and cerclages placed for other indications (history-indicated cerclage
or ultrasound-indicated cerclage). Patients who did not deliver in the
four hospitals or were lost to follow-up by telephone were also
excluded.