Definitions, useful information


Prematurity

Prematurity

Prematurity is defined as birth before 37 weeks of pregnancy. It represents between 6 and 12% of births. Classically, premature birth is divided according to the type (spontaneous or for medical reasons) and the age of the fetus.

For example, spontaneous prematurity occurs as a result of painful contractions or due to the rupture of the membranes (water sac).

In addition, prematurity for medical reasons consists in giving birth to the child before term to improve its health and / or that of his mother. This may occur, for example, as a result of an arterial hypertension problem during pregnancy (pre-eclampsia) or intrauterine growth retardation of the fetus.

 

Prematurity is also defined in respect to the age of birth which can be divided into three categories:

  • extreme prematurity (less than 28 weeks);
  • the great prematurity (between the 28th and the 32nd week);
  • average prematurity, even late (between the 32nd and 36th week).

Measurement of the cervix by endovaginal route

Échographie endovaginale

A short cervix is defined by a cervical length smaller than 25 mm, measured by endovaginal route. This threshold measurement corresponds to a cervical length under the 10th percentile of women pregnant between 18-24 weeks.

The identification of women with a short cervix is performed by an abdominal ultrasound of the cervix. Our study proposes a threshold value of less than or equal to 30 mm, in abdominal, to then continue the examination of the cervix endovaginally.

All studies concerning short cervical lengths have shown an increased risk of prematurity.

However, universal screening of short cervixes by endovaginal ultrasound (as in to say, an endovaginal ultrasound scanning during an ultrasound screening) in the 2nd trimester is not recommended in Canada.

 

The measurement of the cervix by the combination of the abdominal and endovaginal routes

Measurement of the cervix may also be performed by abdominal ultrasound during the second trimester obstetric screening test. It is more comfortable for patients and faster. However, its reproducibility is still uncertain and depends on factors such as bladder filling or presence of excess weight.

Measurement of the cervix by abdominal ultrasound would be overestimated by 8 mm compared to endovaginal measurement.

Some centers propose to perform an initial abdominal examination and, if the cervix is less than 30 mm, to propose an endovaginal measurement.

It is this strategy that we want to use in this project.

 

What does a short cervix of the uterus mean?

The biggest study on the subject1 showed that women with a short cervix have a risk of prematurity of 6 compared to women without a short cervix. There is a continuum between the length of the cervix and the risk of premature birth: the shorter the cervix, the greater the risk of prematurity.

The discovery of a short cervix during the second trimester of pregnancy, allows to propose early a preventive strategy for the patients.

 

pessary

The pessary

This device, usually made of silicone, is generally used to treat the prolapse of pelvic organs (or organ descent) in non-pregnant women.

When placed around the cervix in the vaginal bottom, it could reduce the risk of premature delivery.

The active mechanism of the pessary is not formally established. The modification of the angle is the mechanism most often cited, the pessary to "bend" the neck of the uterus.

Two clinical studies investigated pregnant patients with a short cervix (less than 25 mm) and without the use of progesterone:

PECEP STUDY (View the scientific article of the study)

In 2012, Dr. Goya and her team conducted a study on 385 women who had a short cervix. These women, between 18 and 22 weeks of pregnancy, were divided into two groups: : the group with pessary and the group without pessary.

Several results can be underlined:

1. A reduction in prematurity, before 34 weeks of pregnancy, was found in the group with pessary.

  • In the group without pessary, 28% of children were born before 34 weeks of pregnancy
  • In the group with pessary, 7% of children were born before 34 weeks of pregnancy

2. A reduction of complications in the first weeks of life in the group with pessary.

  • In the group without pessary, 16% of children presented complications in the first months of life.
  • In the group with pessary, 3% of children presented complications in the first months of life.

3. No significant complications occurred in the group with pessary;

4. 95% of patients were satisfied with the pessary.

STUDY conducted by Dr. Nicolaides

A research team from several countries followed 932 women with a short cervix. These women, between 20 and 24 weeks of pregnancy, were divided into two groups: the group with pessary and the group without pessary.

Several results can be underlined:

1. No significant reduction in premature spontaneous delivery, before 34 weeks of pregnancy, between the two groups

  • In the group without pessary, 12% of children were born before 34 weeks of pregnancy
  • In the group with pessary, 11% of children were born before 34 weeks of pregnancy

2. No difference in the complications between the two groups in the first weeks of life, we observe:

  • In the group without pessary, 7% of children had serious complications in the first weeks of life
  • In the group with pessary, 6% of the children presented serious complications in the first weeks of life

3. No major complications occurred in the pessary group;

The following video summarizes the study:
Article and video
Video only

STUDY conducted by Dr. Saccone (View the scientific article of the study)

In 2017, Dr. Saccone and his team published a study on 300 women with a short cervix. These women, between 18 and 23 weeks of pregnancy, were divided into two groups: the group with pessary and the group without pessary.

Several results can be underlined:
1. A reduction in prematurity, before 34 weeks of pregnancy, was found in the pessary group.

  • In the group without pessary, 15% of children were born before 34 weeks of pregnancy
  • In the group with pessary, 7% of children were born before 34 weeks of pregnancy

2. A reduction of complications in the first weeks of life.

  • In the group without pessary, 32% of children had serious complications in the first weeks of life
  • In the group with pessary, 15% of the children presented serious complications in the first weeks of life

3. No major complications occurred in the pessary group;

progesterone

Progesterone

Progesterone is a hormone with different effects including that of supporting pregnancy. Studies2,3 have demonstrated that its use in women with a history of prematurity and / or a short cervix may prolong pregnancy.

In the CAPP study, we propose the use of natural progesterone, vaginally administered daily up to 36th weeks of pregnancy (PROMETRIUM, 200 mg/day progesterone USP, Merck Canada)

References

1. Iams JD, Goldenberg RL, Meis PJ, et al. The length of the cervix and the risk of spontaneous premature delivery. NEJM 1996; 334:567-571.

2. Romero R, Nicolaides K, Conde-Agudelo A et al. Vaginal progesterone in women with an asymtomatic sonographic short cervix in the mid trimester decreases preterm delivery and neonatal morbidity : a systematic review and metaanalysis of individual patient data. AJOG 2012; 206:e1-19.

3. Fonseca EB, Celik E, Parra M et al. Progesterone and the Risk of Preterm Birth among Women with a Short Cervix. NEJM 2007; 357:462-469.