Verify the Safety and Effectiveness of the Cerclage Pessary in the Prevention and Treatment of High-risk Preterm Pregnancy
Phase: NA
Conditions: High Risk Pregnancy
Sponsor: QH Medical Technology Ltd.

Protocol ID: QH-20170928
Verify the safety and effectiveness of the cerclage
pessary in the prevention and treatment of high-risk
preterm pregnancy
Version:3.0 (June 12，2018)

1. General information
Sponsor: QH Medical Technology Ltd.
Investigators and Clinical Research Organizations:
Primary investigator：Juntao Liu1
Other investigators：Jinsong Gao1，Yan Jiang3，Xiaowei Liu3，Luming Sun4，Yuan Wei2，
Pengbo Yuan2，Yangyu Zhao2, Gang Zou4.
1:Peking Union Medical College Hospital；2:Peking University Third Hospital；3:Beijing
Obstetrics and Gynecology Hospital, Capital Medical University；4:Shanghai First Maternity
and Infant Hospital
（In no particular order，listed in the alphabetical order order of the last name）
2. Rationale
2.1. Justification of the relevance of the trial.
Preterm birth complicates 13% of all pregnancies worldwide and is the most important
cause of neonatal morbidity and mortality.1 Although disability-free survival rates have
increased over the years as a result of improved facilities and treatments, preterm
birth is still accountable for 75% of all perinatal deaths and >50% of morbidities. 2,3
Women with a history of a preterm delivery have a distinctly increased risk to deliver
preterm in a subsequent pregnancy. This risk ranges from 11,1% with one previous
preterm delivery up to 28% for two previous preterm deliveries.4 This also applies to
women with a history of a second trimester fetal-loss after 20 weeks of gestation who
show an increased risk of 12% for preterm birth in a subsequent pregnancy.5 Yet
another independent risk factor for PTB is a previous cervical surgery; after a single
surgical conisation the risk of PTB increases almost 5 fold and after two even10-fold.6
One treatment option for prevention of preterm birth is a cervical pessary. A cervical
pessary is a silicone ring with a smaller diameter to be fitted around the cervix and a
larger diameter to fix the device against the pelvic floor. This effectively rotates the
cervix toward the posterior vaginal wall and corrects the cervical angle.7
A prospective-randomised trial by Goya et. al 7 proved a significant reduction of the
preterm delivery rate in singleton pregnancies with cervical shortening (≤25 mm,
18-22 weeks of gestation) after placement of a pessary compared to expectant
management. In a cohort analysis by Alfirevic et al.8 of asymptomatic women with a
singleton pregnancy and a history of preterm birth and a short sonographic cervix the
placement of a cervical pessary proved to be as effective as cerclage or treatment
with 200 mg vaginal progesterone in reducing the preterm birth rate.
A pilot study investigating the effect of pessary treatment in asymptomatic women
with a singleton pregnancy and a history of at least one cold knife conisation and a
short sonographic cervix suggest a beneficial effect on the prolongation of the
pregnancy.6
In the one Cochrane review 9 available concerning pessary therapy the authors detail
a significant decrease in the incidence of spontaneous pretermbirth in women with a
short cervix when compared with expectant management: PTB less than 37 weeks’

gestation (22% versus 59 %; RR 0.36, 95% CI 0.27 to 0.49) and PTB less than
34
weeks´gestation (6% and 27% resp. RR 0.24; 95% CI 0.13 to 0.43). However, the
need for further trials in different settings and with different risk factors is obvious.
This study aims to investigate the effect of a prophylactic treatment with a cervical
pessary in women at high risk of PTB due to a history of at least one previous preterm
delivery and/or a history of late abortion.
2.2. Description of the study population.
Women with a singleton pregnancy at 12 – 18 weeks of gestation and a history of at
least one previous preterm delivery before 34+0 weeks and/or a history of late
abortion attending the reference hospital and who do not fulfil the exclusion criteria
the study will be proposed. The patients will be informed of the intended therapeutic
effect and possible side effects. If they agree and after obtaining their informed
consent, they will be randomised according to either usual management with rescue
cerclage placement only when (and as soon as possible) a cervical shortening below
25 mm occurs (=control group) or cervical pessary placement (= pessary group).
Pessaries or cerclage shall be placed up to 37+0 weeks of gestation. Serial cervical
length measurements shall be conducted every 4 weeks in order to diagnose cervical
shortening as soon as possible in the control group.
2.3. Name and description of the device under investigation.
The Arabin cervical pessary, which is CE-certified for preventing SPB (CE 0482 / EN
ISO 13485: 2003 annex III of the council directive 93/42 EEC).
See annex I.
2.4. Statement that testing will be performed according to protocol, GCP and
applicable legal requirements.
The Clinical Trial will be conducted following the protocol, the GCP, and all legal
requirements.
3. Objective
This study aims to investigate the benefit of a prophylactic cervical pessary treatment
in women at high risk of PTB due to a history of at least one previous preterm delivery
before 34+0 weeks and/or a history of late abortion.
4. Design

4.1. Specific description of primary and secondary variables.
4.1.1. Primary outcome:
o
Child's birth and survival
4.1.2. Secondary outcomes:
o
Offspring
o
Time to birth
o
Preterm birth before 37 weeks: rate of delivery before 36+6 weeks
o
Preterm birth before 34 weeks: rate of delivery before 33+6 weeks
o
Preterm birth before 32 weeks: rate of delivery before 31+6 weeks
o
Preterm birth before 30 weeks: rate of delivery before 29+6 weeks
o
Preterm birth before 28 weeks: rate of delivery before 27+6 weeks
o
Birth weight: median weight (g) of the newborns at birth
o
Fetal or neonatal death: rate of intrauterine demise or neonatal death
during the first 24 hours
o
Neonatal morbidity: rate of major adverse neonatal outcomes before
discharge from the hospital

Intraventricular Haemorrhage (IVH): grades III-IV

Retinopathy of prematurity

Respiratory Distress Syndrome (RDS): grades II-IV,

Need for ventilation > 72 h

Necrotising enterocolitis

Proven or suspected sepsis, antibiotics (>5 days)

Need (Duration in days) for neonatal special care (NICU)
o
Harm from intervention
o
Mother:
o
Maternal death
o
Significant maternal adverse events (rate):

Heavy bleeding: bleeding that requires a medical intervention

Cervical tear: cervical rupture due to the pessary placement

Uterine rupture: rupture of the uterus due to contractions or surgery
o
Physical or psychological intolerance to pessary: discomfort or pain due to
the pessary that makes daily life uncomfortable (number of cases)
o
Rupture of membranes before 32 weeks: rate of rupture of amniotic
membranes before 31+6 weeks
o
Infection/inflammation
o
Hospitalisation
for
threatened
preterm
labour
before
32
weeks:
requirement of hospitalisation due to preterm contractions that need
medical treatment to try to stop them before 31+6 weeks (rate)


Mean hospital stay duration: number of days of admittance at the
hospital

Use of tocolytic treatment: Type of tocolytic, days of treatment,
dose
4.2. Description of the trial design.
Open Multicentre Randomized Controlled Trial, in parallel groups, based on treatment
with progesterone comparing the placement of a prophylactic cervical pessary with
usual management in singleton pregnancies at high-risk of PTB due to a history of at
least one previous preterm delivery and/or a history of late abortion.
4.3. Flowchart.
4.4. Description of the medical device and the treatment regimen.
The cervical pessary is a vaginal device (silicone ring) that is used to treat pregnant
women for preventing spontaneous preterm birth. This device can be easily placed
around the uterine cervix without pain (see annex I).
Women with a singleton pregnancy at 12+0 – 18+0 weeks of gestation and a history
of at least one previous preterm delivery before 34+0 weeks and/or a history of late
abortion attending the reference hospital for a preventive examination will be informed
of the ongoing trial. The patient will be advised of the intended therapeutic effect and
possible side effects. If they agree and after obtaining their informed consent, they will
be randomised according to either progesterone (=control group) or cervical pessary
placement up to 37+0 weeks (= pessary group).
High-Risk-Singleton pregnancy
At 12+0-18+0 weeks of
gestation
History of PTB(20-34weeks)
History of late abortion
progesterone

If the pregnant woman is assigned to the pessary group and after having excluded a
vaginal infection the pessary will be inserted directly. This procedure does not need
anaesthesia and it does not need to be done in a surgery room. After the insertion of
the pessary the correct fit of the pessary is verified by transvaginal ultrasound and in
case it does not fit perfectly, it can easily be adjusted.
In the control-group, the pregnant women be treated with progesterone. Utrogestan is
one of the normal drugs in China to prevent spontaneous preterm birth, the
Utrogestan used in this study is from Laboratories Besins International. For the
enrollment, pregnant women in the control group were treated by 200 mg QN, it is
used for 34 gestational weeks.
The pessary will be removed at 37+0 weeks of gestation, or before if any unexpected
event occurs (see 4.6). After insertion of the pessary the obstetrical management
during the remainder of the pregnancy will be usual management.
Further surveillance of the pregnancy will not be influenced by the participation on the
study.
4.6. Completion and interruption criteria of the study or the subjects.
The pessary will be removed at 37+0 weeks of pregnancy. The indications to remove
them before this time will be: active bleeding stronger than period bleeding, persistent
contractions after tocolysis and premature rupture of the membranes after 34+0
weeks.
After removing the pessary, the obstetrical management will be done as usual and will
not be influenced by the study.
4.10. Selection and withdrawal of subjects
4.10. 1 Inclusion criteria.
o
Women with a singleton pregnancy and a history of at least one previous preterm
delivery before 34+0 weeks and/or a history of late abortion
o
12+0 -18+0 weeks of gestation
o
Minimal age of 18 years
o
Informed consent signature
4.10. 2 Exclusion criteria.
o
The previous preterm delivery is iatrogenic proterm labor
o
Major fetal abnormalities (requiring surgery or leading to infant death or severe
handicap)
o
The pregnant woman with severe cervical erosion, cervical polyp, hemorrhage
and the doctors think she could not use cerclage pessary

o
The pregnant woman with uterine cervicitis
o
The pregnant woman that has been confirmed premature birth
o
Cerclage prior to randomisation
o
Uterine malformation
o
Placenta previa totalis
o
Active vaginal bleeding at the moment of randomization
o
Spontaneous rupture of membranes at the time of randomization
o
Silicone allergy
o
Painful regular uterine contractions
o
Thepregnant woman have the indication of operation cervical cerclage
o
Current participation in an other RCT
4.10. 3. Withdrawal criteria.
If a participant may voluntarily withdraw from treatment or if it is necessary to remove
the pessary due to the conditions described before, the patients will be followed as
usual until delivery (intention-to-treat analysis).
Replacement of patients is not applicable in this trial.
4.10. 4. Rescue treatment criteria.
According the current guide
and
expert advice,
when
the routine
follow-up
examination, the rescue cervical cerclage may be adopted when the secondary
cervical shortening occurs.
4.11. Treatment of Subjects
4.11.1. Treatments to be administered.
The pessary will be inserted during a preventive examination in pregnancy in the
examination room. This procedure does not need anaesthesia and it does not need to
be done in a surgery room. After the insertion of the pessary the correct fit of the
pessary is verified by transvaginal ultrasound and in case it does not fit perfectly, it
can easily be adjusted. pregnant women in the control group were treated by 200 mg
QN, it is used for 34 gestational weeks. The pessary or cerclage will be removed at
37+0 weeks of gestation, or before if any unexpected event occurs (see 4.6).
After insertion of the pessary the obstetrical management during the pregnancy will be
usual management.
Further surveillance of the pregnancy will not be influenced by the participation on the
study.
5. Assessment of Safety

5.1. Procedures to record and report adverse events.
If a serious and unexpected adverse effect occurs during treatment, it will be notified to
the study Sponsor. The Department of Obstetrics and Gynecology of the Sponsor will fill
the side effects document to notify it to the Ethics Committee.
The patient affected by the adverse effect will be followed more intensively during the
first days and if nothing else occurs, she will return to the standard control.
5.2. Definitions.
Adverse Event (AE): Any untoward medical occurrence in a patient or clinical
investigation participants administered a medicinal product, which does not necessarily
have to have a causal relationship with this treatment (the study medication). An AE
can therefore be any unfavourable and unintended sign (including an abnormal
laboratory finding), symptom or disease temporally associated with the use of the study
medication/procedure, whether or not considered related to the study medication.
Adverse Reaction (AR): All untoward and unintended responses to a medicinal product
related to any dose. The phrase "responses to a medicinal product" means that a
causal relationship between a study medication and an AE is at least a reasonable
possibility, i.e., the relationship cannot be ruled out.
All cases judged by either the reporting medically qualified professional or the sponsor
as having a reasonable suspected causal relationship to the study medication /
procedure qualify as adverse reactions.
Serious Adverse Event (SAE): A serious adverse event is any untoward medical
occurrence that at any dose: Results in death; is life-threatening, NOTE: The term
"life-threatening" in the definition of "serious" refers to an event in which the participant
was at risk of death at the time of the event; it does not refer to an event which
hypothetically might have caused death if it were more severe; Requires inpatient
hospitalization or prolongation of existing hospitalization; Results in persistent or
significant disability/incapacity, or is a congenital anomaly/birth defect.
Other important medical events: Other events that may not result in death, are not life
threatening, or do not require hospitalization, may be considered a serious adverse
event when, based upon appropriate medical judgment, the event may jeopardize the
patient and may require medical or surgical intervention to prevent one of the outcomes
listed above.
To ensure no confusion or misunderstanding of the difference between the terms
"serious" and "severe", which are not synonymous, the following note of clarification is
provided:
The term "severe" is often used to describe the intensity (severity) of a specific event
(as in mild, moderate, or severe myocardial infarction); the event itself, however, may
be of relatively minor medical significance (such as severe headache).
This is not the

same as "serious," which is based on patient/event outcome or action criteria usually
associated with events that pose a threat to a participant's life or functioning as defined
in the bullet points above. Seriousness (not severity) serves as a guide for defining
regulatory reporting obligations.
Serious Adverse Reaction (SAR): An adverse event (expected or unexpected) that is
both serious and, in the opinion of the reporting investigator, believed with reasonable
probability to be due to one of the study treatments, based on the information provided.
Suspected Unexpected Serious Adverse Reaction: A serious adverse reaction, the
nature or severity of which is not consistent with the applicable product information (e.g.
Investigator’s Brochure for an unapproved investigational product or summary of
product characteristics for an approved product).
5.3. Procedures for immediate notification of serious or unexpected adverse
events.
All AEs occurring during the study /or observed by the investigator or reported by the
participant, whether or not attributed to study medication, will be recorded on the CRF.
The following information will be recorded: description, date of onset and end date,
severity, and assessment of relatedness to study medication, other suspect drug or
device and action taken. Follow-up information should be provided as necessary.
AEs considered related to the sanitary device, as judged by a medically qualified
investigator, will be followed until resolution or the event is considered stable. All related
AEs that result in a participant’s withdrawal from the study or are present at the end of
the study, should be followed up until a satisfactory resolution occurs.
It will be left to the investigator’s clinical judgment whether or not an AE is of sufficient
severity to require the participant’s removal from treatment. A participant may also
voluntarily withdraw from treatment due to what he or she perceives as an intolerable
AE. If either of these occurs, the participant must undergo an end of study assessment
and be given appropriate care under medical supervision until symptoms cease or the
condition becomes stable.
A medically qualified investigator will assess the relationship of AEs to the study
medication.
All SAEs must be reported to the main investigator. He will perform an initial check of
the report, request any additional information, and he will notify it to the Ethics
Committee and CFDA. All SAE information will be recorded. It may be appropriate that
some SAEs do not require immediate reporting but this must be justified. Justification
might be determined, for example, by admission to hospital, or prolongation of
hospitalization, where this is to be expected in the underlying disease or condition.
All adverse events (AE) life-threatening or resulting in death will be notified within 24
hours. All AE that are not life-threatening will be notified within 15 days. The rest of AE
will be recorded and analyzed at the end of the study.

6. Efficacy assessment
6.1. Specification of efficacy parameters: Primary and secondary endpoints.
This study aims to investigate the benefit of a prophylactic cervical pessary treatment
in women at high risk of PTB due to a history of at last one previous preterm delivery
and/or a history of late abortion on the perinatal outcome .
6.2. Methods and timing to assess records and analyze the efficacy parameters.
The pregnant women will be assessed according to usual obstetrical management in
a high-risk pregnancy.
Regular
Preventive Exam
12+0-18+0 WoG
Regular
Preventive Exam
34+0 WoG
Postnatal
evaluation
Study procedure
study inclusion
Informed consent
signature
x
randomisation
x
Pessary
placement
x
(Pessary-Group)
Pessary/cerclage
removal
x
progesterone
x
x
physical exams
Abdominal US
x
x
Vaginal US
BV/trichomonad/
mycete
Neonatal
examination
x
Ages & Stages
test
(corrected age)
7. Statistics
7.1. Description of statistical methods.
A descriptive analysis by preterm birth will be carried out calculating means and
medians
for
quantitative
variables
and
proportions
for
categorical
variables.

Two-sided Z-tests will be used for comparing among exposure and outcomes groups
per pregnancy. A multivariate logistic regression will be fitted to control for possible
confounders. Relative risks and 95% confidence interval will be calculated for the
outcomes.
All analysis will be carried out with SPSS® 19.0 statistical package (IBM Company
SPSS Inc. Headquarters, Chicago, Illinois. USA). Statistical significance will be
accepted in all cases with a p<0.05.
Outcome
Statistical Test
Birth before 34 Weeks of Gestation
Two-sided Z-Test (RR, 95% CI)
Time to Birth
Log-rank test (HR, 95% CI)
Birthweight
Multilevel model (mean +SD
Fetal / Neonatal Death
Two-sided Z-Test (RR, 95% CI)
Neonatal Morbidity
Two-sided Z-Test (RR, 95% CI)
Need for Hospitalization
Two-sided Z-Test (RR, 95% CI)
Days of Hospitalzation
Two-sided Z-Test (RR, 95% CI)
Maternal Adverse Events
Two-sided Z-Test (RR, 95% CI)
Pessary Intolerance
Two-sided Z-Test (RR, 95% CI)
Vaginal Infections
Two-sided Z-Test (RR, 95% CI)
the complete data set for the secondary endpoints will be available after the last
women enrolled in this study has given birth, so the analysis of these outcome
parameter will be done right after this event.
7.2. Expected number of subjects to be included.
Group sample size of 121 in Group 1 and 121 in Group 2 achieve 80% power to
detect a difference between the group proportions of 0,1240. The proportion in Group
1 (the treatment group) is assumed to be 0,8 under the null hypothesis and 0,9240
under the alternative hypothesis. The proportion in Group 2 (the control group) is
0,8000. The test statistic used is the two-sided Z test with pooled variance. The
significance level alpha of the test was 5 %. To account for a drop out rate around
20%, sample size of 121 in each group, overall n=242 women will be recruited.
7.3. Criteria for the completion of the trial.
A non-justified case of maternal death (temporary stop until complete evaluation of
the case by an external committee).
7.4. Selection of subjects to be included in each analysis.
The analysis will include all the subjects that have been randomised.

8. Quality and Control Assurance
Main investigator and collaborators: In order to ensure the Quality of the data they will
provide instructions and training to the sites involved in the trial; review the CRF data;
and detail of any other steps taken to ensure quality of research.
The main investigator will sign the study protocol and the “investigator’s commitment;
he will apply for the Ethics Committee and the Director’s approval; and he will review
the final report of the study.
The collaborators will assess patient’s eligibility, they will inform the patients and ask for
the informed consent; and they will be responsible of the CRF and obtaining and
registering all data.
Monitor: he will perform regular monitoring according to ICH GCP. Data will be
evaluated for compliance with the protocol and accuracy in relation to source
documents. Monitors will verify that the clinical trial is conducted and data are
generated, documented and reported in compliance with the protocol, GCP and the
applicable and local regulatory requirements.
Serious Breaches: A serious breach is defined as “A breach of GCP or the trial protocol
which is likely to effect to a significant degree: (a) the safety or physical or mental
integrity of the subjects of the trial; or (b) the scientific value of the trial”. All serious
breaches will be notified to the competent Regulatory Authority according to applicable
legislation.
9. Ethical issues
The Sponsor, participating Centres and Investigator will ensure that this study is
conducted in accordance with the Protocol, the principles of the Declaration of
Helsinki (see annex III), ICH Guidelines for Good Clinical Practice and in full
conformity with relevant regulations as well as applicable national laws, the German
Law and in accordance with regulations and guidelines applicable to clinical trials
relating to medical devices.
The protocol, informed consent form, participant information sheet and any applicable
documents will be submitted to an appropriate Ethics Committee (EC) and Regulatory
Authority for written approval. All substantial amendments to the original approved
documents will be also sent to an appropriate Ethics Committee (EC) and Regulatory
Authority for written approval. The study will not begin until the approval of the EC and
Director’s consent.
10. Data Management and Registry File

Patient’s participation in the study will be annotated into the medical history.
The main investigator will perform a list with the participant’s names, ID numbers and
codes. He also will have a file with all the information referring to the study.
All the data will be collected in a database that will be accessed worldwide.
The randomisation will be done on a computer basis. Once entering in the website, if
the patient fulfils the inclusion criteria, the computer generated list will randomise the
patient to “pessary” or “control” group.
The excluded patients will be also collected in the database.
Every participating centre will have its own randomisation list, and it will be accessible
with a username and password.
The trial staff will ensure that the participants’ anonymity is maintained. Only a
participant ID number on the CRF and in the electronic database will identify the
participants. All documents will be stored securely and only accessible by trial staff
and authorized personnel. The study will comply with the Data Protection Legislation
that requires data to be anonymized as soon as it is mandatory to do so.
10.1. Data ownership
Sponsor and participating Center have expressly agreed that any and all data collected
and prepared in the context of the study shall be the property of the Sponsor, provided
that participating Center shall remain the owner of its source data and may utilize such
data as it deems appropriate without the approval, but with the reliable communication
of Sponsor. Furthermore, Sponsor will always have access to the Study data, in terms
of good faith and cooperation, in order to improve their own knowledge and information.
11．Funds and Insurance
According to German legislation and Ethical Committee decisions, it is not necessary
to enter into an insurance contract in order to cover patients while using this medical
device in a clinical trial. Insofar as it has been issued with the appropriate certificate of
the State Medicines Agency to the concrete use of the medical device.
Nevertheless, it will be mandatory to enter into a hedging insurance by any other
participating centre of this clinical trial, in the case that it is mandatory according to the
laws of their country.
No funding is provided for the study.
12．Publication policy
The Sponsor takes the commitment of publishing the results of the study; despite they
are good or bad.

Promoter and participating Centre agree that publications or presentations of any of the
results from the study shall be in accordance with accepted scientific practice,
academic standards and customs.
Authorship and other related publications questions shall be addressed in accordance
with the principles of the ‘Uniform Requirements for Manuscripts Submitted to
Biomedical Journals’ and in accordance with the requirements of the respective
medical journal.
Sponsor agrees to ensure co-authorship for clinical co-investigators on any proposed
multicentre publication.
Sponsor and participating Centres agree that at first they will strive to make a joint
publication. After such joint publication or one year after termination of the study the
following shall be agreed:
As a general principle, the parties agree that prior to submission of a publication or any
other dissemination of the results, including oral presentation, the Sponsor shall have
the right to prior review and comment on the content of the material to be published or
presented within sixty (60) days following the receipt of the publication or any other
dissemination of the results, and Participating Centre ensures that it will take
Promoter’s comments into due consideration.
References
1. Blencowe H, Cousens S, Chou D, Oestergaard M, Say L, Moller AB, et al.
Born too soon: the global epidemiology of 15 million preterm births. Reprod
Health 2013;10(Suppl. 1): S2.
2. Ananth CV, Vintzileos AM. Epidemiology of preterm birth and its clinical
subtypes. J Matern Fetal Neonatal Med 2006; 19:773e82.
3. Goldenberg RL, Culhane JF, Iams JD, Romero R. Epidemiology and causes
of preterm birth. Lancet 2008;371(9606):75e84.
4. Hoffman JD, Ward K. Genetic factors in preterm delivery. Obstet Gynecol Surv
1999: 54: 203-10
5. Book: Oxford Desk Reference: Obstetrics and Gynecology. Ed. S.
Arulkumaran, 2011

6. Kyvernitakis I, Khatib R, Stricker N, Arabin B. Is Early Treatment with a
Cervical Pessary an Option in Patients with a History of Surgical Conisation
and a Short Cervix? Geburtsh Frauenheilk 2014;74:1003-1008.
7. Goya M, Pratcorona L, Merced C, et al. Cervical pessary in pregnant women
with a short cervix (PECEP): an open-label randomized controlled trial. Lancet
2012;379:1800-6.
8. Alfirevic Z, Owen J, Carreras Moratonas E, Sharp AN, Szychowski JM, Goya
M. Vaginal progesterone, cerclage or cervical pessary for preventing preterm
birth in asymptomatic singleton pregnant women with a history of preterm birth
and a sonographic short cervix. Ultrasound in Obstetrics & Gynecology:
2013;41(2):146-51.
9. Abdel-Aleem H, Shaaban OM, Abdel-Aleem MA. Cervical pessary for
preventing preterm birth. The Cochrane database of systematic reviews.
2013(5):CD007873.