Table 2 Characteristics of the articles included in the meta-analysis
First author/ Publication year | Country | Study type | Randomization Method | Sample size | Sample characteristics | Intervention | Comparison | outcome | Quality assessment |
|---|---|---|---|---|---|---|---|---|---|
Hassan A. (2023) [22] | Pakistan | RCT | computer-generated random number table (balloting method) | 160 (80 + 80) | "singleton gestation presenting at gestational age 30 weeks to 34 weeks with PTL and cervical dilatation of ≤ 3 cm" | "nifedipine 20 mg orally, followed by 10 mg orally every eight hours for 48 h and vaginal administration of sildenafil citrate, 25 mg at eight-hour intervals, for 48 h" | "nifedipine 20 mg orally, followed by 10 mg orally every 8 h for 48 h." | sildenafil citrate plus nifedipine showed a significant effect in the management of PTL and prolongation in mean gestational age at delivery | high |
Nasrolahei Sh. (2023) [23] | Iran | RCT | block randomization method | 126 (63 + 63) | "PTL at the age of 15–45 yr, cases of threatened PTL (uterine contractions > 4 in 20 min with cervical dilatation and effacement), between 24–34 weeks gestation, intact fetal membranes, cervical dilatation less than 4 cm, does not have any significant chronic medical conditions, has no medical restrictions for Nif and SC therapy, and has not experienced PTL in the past" | Nif 20 mg orally (single dose), then 10 mg every 6-h, and at the same time vaginal SC 25 mg every 8 h (Nif + SC) | Nif 20 mg orally (single dose), then 10 mg every 6-h | Nif with SC is superior to Nif alone in women at risk of PTL due to increasing gestational age and better neonatal outcomes | high |
Mohammadi E. (2021) [16] | Iran | RCT | block randomization method | 132 (66 + 66) | pregnant women with a gestational age of 26–34 weeks with singleton pregnancy and diagnosis of preterm delivery | nifedipine (10 mg every 6 to 8 h, orally) plus sildenafil (25 mg every 8 h, vaginally) | nifedipine (10 mg every 6 to 8 h, orally) | In PTL instances, using SC in addition to nifedipine results in a longer delivery time, a decreased risk of respiratory distress syndrome (RDS), fewer admissions to the NICU, and preservation of neonatal birth weight | high |
Qurat-ul-Ain (2021) [25] | Pakistan | RCT | random number table | 292(146 + 146) | threatened PTL with a singleton pregnancy between 24 and 36 + 6 weeks of gestation | nifedipine 20 mg orally (stat dose), followed by 10 mg orally every 8 h and at the same time oral administration of SC (25 mg at 8‐hourly intervals) | nifedipine 20 mg orally (stat dose), followed by 10 mg orally every 8 h | Oral SC combined with nifedipine is an effective option for tocolytic therapy for threatened PTL | high |
El-Sayed Y. (2023) [17] | Egypt | RCT | computerized random number table | 96 (48 + 48) | Pregnancy with a single fetus between 28 and 34 weeks, with no rupture of the membranes | “Oral nifedipine 20 mg (stat dosage), then 10 mg every 6 h concurrently with oral SC 20 mg given at 8 h” | nifedipine 20 mg orally (stat dose), followed by 10 mg orally every 6 h | A statistically significant difference was observed between the two groups under study in delivery 24,48 and 72 h after admission, with fewer early deliveries among the nifedipine with sildenafil group. Vaginal SC plus with nifedipine is most effective tocolytic medication in threatened PTL | high |
Maher M. (2019) [26] | Egypt | RCT | computerized random number table generator | 239 (121 + 118) | Pregnancies with singleton fetuses between 24 and 34 weeks' gestation are threatened by PTL | " The nifedipine and SC groups received the same dosage as the nifedipine-only group, with the additional dose given by 25 mg of SC every 8 h vaginally." | "nifedipine only group (20 mg nifedipine orally followed by 10 mg orally every 6 to 8 h)" | The combination of SC administration and nifedipine is a highly successful choice for tocolytic therapy in cases of PTL | high |
Singh Sh. (2023) [24] | India | Quasi-experimental | no (convenient sampling) | 60 (30 + 30) | Singleton pregnancy with 28–37 gestational age and without vaginal discharge | "Nifedipine 20 mg orally stat dose followed by 10 mg orally every 6–8 h at the same time as vaginal administration of sildenafil citrate 25 mg at 8th hourly interval every 6-8 h." | "Administer a single oral dose of Nifedipine at 20 mg and a maintenance dose of 10 mg orally every 6–8 h." | SC plus nifedipine is more effective than nifedipine alone in avoiding PTL | high |