Background: Prevention of the premature birth occurrence remains  is considered one of the most tough challenges for obstetricians worldwide, mainly to avoid neonatal prematurity complications leading to short and long term morbidities additionally prematurity prevention will reduce premature neonatal mortality rates which is considered a major health concern of obstetricians, neonatologists and families.

Objective: To compare and contrast the efficacy of Sildenafil citrate, Nifedipine and Dydrogesrone in prevention of premature labor in gestations with short cervix.

 Setting: Obstetrics & Gynecology Departments, Faculties of medicine, south Valley and Al-Azhar (Asyut) Universities, Egypt.

Duration: from September 2014 to March 2018.

Patients And Methds:  the study was conducted on 300 pregnant women who randomly divided into three groups: Group I included 100 cases received Sildenafil citrate (Respatio tablet 20mg twice daily orally), Group II included     100 cases received Nifedipine (Epilat retard tablets 20mg twice daily orally) and Group III included 100 pregnant women received dydrogesreone 10 mg (Duphaston) twice daily orally.

Results: incidence of preterm labor was (9.37, 8.51 and 14.28) in (Group I, Group II and Group II) respectively. Mean ± SD of cervical length at 32 weeks of gestation was mildly statistically significant among groups (p value <0.05) but no significance in neonatal outcome (p value >0.05) except birth weight which had a highly statistically significant difference (p value < 0.001). There was a highly statistically significant difference among studied groups as regard to drug side effects in (p value <0.001).

Conclusion: Sildenafil citrate was as effective as Nifedipine and better than oral Dydrogesterone on myometrial relaxation and prevention of preterm birth in pregnant women who had short cervix.

Reccommendation: Sildenafil citrate could be one of the most successful agents in prevention of preterm labor in threatened preterm cases.

Preterm labor is defined as delivery of fetus after 20 weeks and less than 37 completed  gestational weeks. Preterm birth is always a major obstetric healthcare issue worldwide [1,2]. It represents a major cause of neonatal, infant and child death and disability up to age of 5 years in the developed world and represents the leading cause of perinatal mortality and morbidity in the whole world [3&4], about fifteen million premature neonates are born every year globally, and a million of them die because of prematurity complications [4,5]. Preterm babies are at greater risks of grave perinatal morbidities [6, 8]. Although many babies delivered prematurely had a normal and completely healthy life, some significant proportion experienced life-long disabilities and health issues [9]. The chief dilemma of premature births is its negative impact on neonates themselves, their families, and society as a whole in which there is significant healthcare costs due to perinatal health issues and long term disabilities [1, 4, 7, 10]. Prevention of preterm labor has the priority in health care system programs since preventive measures are superior than treatment protocols [11].

Prevention of preterm labor to be successful requires multiple approaches including public health efforts with educational health programs, modification of patient lifestyle, optimal obstetric protocols of healthcare, efficient approaches for prediction and diagnosis of threatened and established preterm labor and implementation of effective, tailored case management pathways according to case scienario [12].  Preconception intervention modalities e.g weight reduction in obese female population, nutritional supplementation for underweight women, and cessation of smoking have a favourable impact on premature birth rates and its clinical sequelae  [13,14]. Dydrogesreone is a progesterone stereoisomer acts at biochemical level as a selective progestin with a high receptor affinity, due to its retro-structure that binds to the progesterone receptor. Dydrogesreone is safe and have well acceptable tolerability. It is similar to natural progesterone hormone in molecular structure and pharmacological properties with sufficient oral bioavailability. 2–5 hours is the maximum time required for Dydrogesreone to reach peak plasma concentration levels after oral intake, 20 mg/day of Dydrogesterone is equivalent to 200mg of progesterone administered vaginally [15]. Nifedipine is a calcium channel blocker that could be used as an key tocolytic agent [16, 17]. The most substantial updated Cochrane review [18] concerning  calcium channel blockers displays that it could be used for tocolysis in prevention of acute threatened preterm delivery according to different 12 RCTs (10 of them used Nifedipine)  1029 patients were recruited in these trials. This review had concluded that, as comparison to any other tocolytic agent (as beta-mimetic mainly), calcium channel blockers (Nifedipine mainly) could diminish the hazardous  risk of premature labor within 7 days of administration. Sildenafil citrate in fact enhances smooth muscle relaxation by preventing cGMP degradation (the second messenger) by phosphodiesterase enzyme (PDE5) [19,20]. Moreover, the BKCa channels had been implicated by direct or indirect fashion in the sildenafil mode of action [21, 22].

The aim of this research study is to compare the effectiveness of different tocolytic agents (Sildenafil citrate, Nifedipine and Dydrogesreone) in prevention of premature labor in gestations with short cervix.

The study was performed on 300 gestations from those visitingto Obs fetal medicine units of Obstetrics & Gynecology departments at South valley and Al-Azhar (Asyut) University Hospitals in the period from September 2014 to March 2018. Inclusive research criteria; 19 – 40 years old, BMI < 30> included 100 pregnant women received oral Dydrogesterone 10 mg (Duphaston) twice daily orally. To fulfill the target number of cases for this study (300 cases), we actually examined about 5000 pregnant women at mid-gestation.

 (1) Full clinical history taking including meticulous menstrual history for precise estimation of expected date of delivery (2) Full clinical physical examination and assesment, involving general, obstetric and local examinations (3) laboratory investigations e.g CBC, RBS, kidney and liver function tests (4) Sonographic examination and assesment: (a) Trans-abdominal sonography for fetal biometry (including BPD, HC, FL and AC), placental site and grading, amniotic fluid volume, fetal anomalies (b) Trans-vaginal sonography for cervical length (CL) measurement (at 24, 28 and 32 weeks of gestation).

Recruited subjects were allocated randomly into 3 research groups by using a computer-generated randomization system (Microsoft office excels, 2010). The randomization list was hidden, expressed by sequential numbers and sealed in opaque envelopes just before start of allocation. Each number was linked to a ready prepared pack which contained sildenafil citrate (Respatio 20mg), calcium channel blocker (Epilat retard 20mg) or Dydrogesterone (Duphaston 10mg). The process of packing, numbering and sealing were performed by 2 different persons other than the investigator. Both investigator and observer were not aware about which drug cases had received (double-blinding).

Follow up: (a) All patients were followed up every two weeks until time of delivery and for one week later (b) Any episodes of premature labor contractions were clinically assessed carefully and recorded (c) If manifestations of threatened preterm labor progressed and not controlled with the regimen in this study, the patients were admitted to the hospital and magnesium sulphate in intravenous drip was commenced in a dose of 6 g in 500 ml glucose 5% and repeated every 6 hours till premature uterine contractions have resolved (d) Any complications developed were recorded. During follow up 12 cases dropped from the study (4 cases in group I, 6 cases in group II and 2 cases in group III) due to difficult communications or departure outside the area of study so the final number of cases continued in the study was 288 cases that delivered at South Valley and Al Azhar universities hospitals. Data of all patients finally was collected, tabulated and statistically analyzed.

Statistical analysis:

Data management and analysis were performed using Sigma Stat program; version 3.5 The Figures were done using Microsoft Excel. Data were statistically described in terms, mean±standard deviation (±SD) or number and percentage. Comparisons between categorical variables were done by the chi-square test. P-values was considered significant if <0>

Incidence of preterm labor was (9.37, 8.51 and 14.28) in (Group I, Group II and Group II) respectively (table 3). Mean ± SD of cervical length at 32 weeks of gestation was statistically significant among studied groups with p value > 0.05 (table 2). There was a highly statistically significant difference among the 3 groups in birth weight with p value <0.001 (figure 1) but there was no statistically significant differences as regards TTN, RD, NICU or neonatal death (figure 2) with p value > 0.05. There was a highly statistically significant difference among studied groups in drugs side effects as headache, hot flushes and palpitations with p value< 0.001 (figure 3).

P value>0.05

Table (1): Demographics data of the 3 studied groups

Table (2): Comparison between the 3 research study groups  concerning cervical length measurement at 24, 28 and 32  gestational weeks

Table (3): Incidence of preterm labor in the 3 studied groups

* statistically significant

Figure (1): comparison between 3 research groups as regards neonatal birth weight in grams

Figure (2): comparison between 3 research groups as regards, transient tachypnea of new born, respiratory distress, neonatal intensive care unit admission and neonatal mortalities

Figure (3): Drugs side effects in the 3 studied research groups