**2.1. Fetal fibronectin (fFN)**

exposed to high doses of this drug. Recent studies have revealed that even perinatal mortality increases (RR 1.12) in pregnant women using this medication, single cycle, for protection

Also is considered another form of tertiary prevention of preterm birth the use of magnesium sulfate for fetal neuroprotection during labor or previous to delivery, in gestations below 32th

According to the WHO, preterm birth is today the main cause of death in the first 5 years of life in the world. Thus, prevention of prematurity is of extreme importance to minimize the

Primary prevention begins with a good detection index of the problem. The previous preterm birth is undoubtedly a significant predictor of prematurity, and this is also valid for twin pregnancies [6]. The more premature the previous delivery was, the higher the risk of recurrence. In addition, other factors can contribute to increase preterm birth rates in multiple

Some studies showed higher prematurity rates in black, younger, and low-schooling level pregnant women [13]. Smoking and primiparity seem to be related to shorter gestational age

In secondary prevention of preterm birth, cervix evaluation is an important strategy, once uterine overdistension in multiple pregnancy can perhaps contribute to higher rates of short cervix and, therefore, higher rates of prematurity. So, many efforts were made to improve the prediction and prevention of preterm birth in twin pregnancy, in order to enhance the

Transvaginal ultrasound for uterine cervix evaluation is currently the main tracking method for this severe disease [15], and second trimester ultrasound, between 18 and 24 weeks, is

A retrospective cohort study in twin pregnancy concludes that cervical shortening between 18

In twins, the association of preterm birth frequently caused by uterine overdistension is largely aggravated by the presence of short cervix, and this association is more evidenced

It is true that a small performance improvement in this association of problems may completely change the prognostics of the newborn. Therefore, the recommendation of carrying out transvaginal ultrasound of the uterine cervix is of vital importance for diminishing pre-

In twin pregnancy, with the previous spontaneous preterm birth or late miscarriage but with atypical history of cervical insufficiency, strict follow-up of the uterine cervix is necessary

morbidity/mortality perinatal and the high costs involved with this disease.

against complications caused by prematurity [12].

**2. Prevention of preterm birth**

190 Multiple Pregnancy - New Challenges

at birth too in twin pregnancy [8].

term delivery in twin gestation.

week, administered between 12 and 24 hours prior to delivery.

pregnancies, as race, schooling, smoking, and short cervix.

newborn prognosis, and cervix evaluation is one of them [14].

and 25 weeks of gestation was a good predictor of SPB [16].

considered the best period to make the cervical transvaginal ultrasound.

because of high indexes of preterm birth incompatible with extrauterine life.

The fFN test consists of detection of this cervicovaginal glycoprotein, collected between 24 and 34 weeks and 6 days. In normal conditions, fFN should not be present at high concentrations (cutoff is 50 ng/mL) after 20 weeks, and the objective of this test is to predict spontaneous preterm birth within 7:10 days [20]. False-positive results can occur in the sample contaminated with blood and within 24 hours after intercourse or cervical examination (as transvaginal ultrasound or vaginal examination), and it should not be performed in cases of premature rupture of membranes and cervical dilatation ≤3 cm

The American College of Obstetricians and Gynecologists (ACOG) [7] does not recommend its use in asymptomatic women with multiple pregnancy as routine, and some reviews have failed finding enough evidence to support fFN screening [21], once perinatal outcome was not affected by this intervention, although lower incidence of preterm birth before 37 weeks was reached.

However, in symptomatic women, this test can be useful to decide the best moment to administer antenatal corticosteroids in order to promote fetal pulmonary maturation. Published studies in multiple gestation that evaluated fFN test and cervical changes presented high sensitivity and high negative predictive value in predicting preterm birth [22, 23]. Probably, the association of these factors can enhance the approach of twin pregnancies and should be seriously considered in prevention of prematurity.
