Different impacts of various tocolytic agents on increased risk of postoperative hemorrhage in preterm labor women undergoing Cesarean delivery: A population-based cohort study

Tocolytic agents, commonly used for inhibiting preterm labor, pose the risk of uterine atony, leading to postpartum hemorrhage. This study elucidated the effects of different tocolytic agents on postoperative hemorrhage among women in preterm labor undergoing Cesarean delivery (CD). Data from Taiwan National Health Insurance Research Database were analyzed. The risk (adjusted hazard ratio [aHR] and 95% confidence intervals [CI]) of postoperative hemorrhage in CD women with preterm labor diagnosis using tocolytic agents (Tocolysis group) comparing to CD women not using tocolytic agents (Control group) were determined. Impacts of different tocolytic agents in this regard were also investigated. Our data revealed that the incidence (11.7% vs 2.6%, P < .001) and risk (aHR: 1.21, 95% CI: 1.12-1.31, P < .001) of postoperative hemorrhage were significantly higher in the Tocolysis group (n = 15,317) than in the Control group (n = 244,096). Ritodrine was the most frequently used tocolytic agent (80.5%), followed by combination therapy (using more than one tocolytic agents) (8.5%), magnesium sulfate (MgSO4, 4.6%), calcium channel blockers (3.8%), betamimetics other than ritodrine (1.9%), prostaglandin synthase inhibitors (0.5%), and nitrates (0.1%). Barring those using calcium channel blockers and combination therapy, the use of MgSO4 (aHR: 1.43, P = .001), betamimetics other than ritodrine (aHR: 1.71, P < .001), prostaglandin synthase inhibitors (aHR: 2.67, P < .001) and nitrates (aHR: 3.30, P = .001) was associated with higher risks of postoperative hemorrhage compared with ritodrine. In conclusion, CD women with preterm labor diagnosis using tocolytic agents exhibit an increased risk of postoperative hemorrhage and that this risk varies with the use of different tocolytic agents.

Effects of Maternal Magnesium Sulfate Treatment on Neonatal Feeding Tolerance

OBJECTIVE

To determine whether antenatal exposure to magnesium sulfate has an effect on neonatal enteral feeding tolerance.

METHODS

In this single-center, retrospective, observational study, charts of pregnant women who received intravenous magnesium sulfate infusions prior to delivery between July 1, 2012, and July 31, 2013, were reviewed. Neonates born at 24 weeks' gestational age or greater admitted to the neonatal intensive care unit (NICU) whose mothers received magnesium sulfate infusions prior to delivery were included. Neonates with independent factors that could lead to feeding intolerance were excluded. The primary outcome was incidence of neonatal enteral feeding intolerance measured by deviations from the NICU feeding protocol. Secondary outcomes included days on parenteral nutrition, incidence of necrotizing enterocolitis, time to first stool, and urine output in the first 72 hours of life.

RESULTS

Cumulative maternal magnesium sulfate dose was significantly higher in the enteral feeding intolerance group than those infants who tolerated enteral feeds (70.4 ± 52.3 vs 47.4 ± 40.1 g; p = 0.04). Infants exposed to more than 80 g of maternal magnesium sulfate therapy were more likely to develop enteral feeding intolerance (44% vs 22%; p = 0.04). Multivariate logistic regression indicated that prematurity and cumulative maternal magnesium sulfate dose were the strongest predictors of neonatal enteral feeding intolerance.

CONCLUSIONS

Infants of mothers who received more than 80 g of intravenous magnesium sulfate prior to delivery were more likely to develop feeding intolerance. Prematurity also was a significant predictor of intolerance.

Success rate in preterm uterine contraction inhibition with tocolytic agents in a tertiary care center

Objective

This study aims to assess the success rate of inhibiting preterm uterine contraction with tocolytic agents to delay delivery for at least 48 hours and risk factors of failure inhibition.

Materials and methods

Between January 2013 and July 2014, medical records of all singleton pregnant women between 24 ^0/7 and 33 ^6/7 weeks of gestation with the diagnosis of preterm labor (with cervical dilatation) or threatened preterm labor (without cervical dilatation) who received tocolytic agents were reviewed. The success rate of preterm uterine contraction inhibition was accounted in patients with 48 hours delayed delivery. The risk factors of the inhibition failure and neonatal outcomes were also investigated in this study.

Results

Among 424 pregnant women diagnosed of preterm labor or threatened preterm labor, 103 singleton pregnant women met the study criteria. Overall success rate of preterm uterine contraction inhibition to prolong pregnancy for at least 48 hours was 86.4% (95% confidence interval [CI]: 78.3, 92.3). However, the success rate among the threatened preterm labor group was 93.8% (95% CI: 88.3, 99.1) while the preterm labor group was 60.9% (95% CI: 39.3, 82.4). The significant factor associated with inhibition failure was preterm labor (adjusted odds ratio 7.22; 95% CI: 1.99, 26.20).

Conclusion

The success rate of preterm uterine contraction inhibition with tocolytic agents to delay delivery for at least 48 hours was high in threatened preterm labor and low in preterm labor. A significant risk factor for inhibition failure was the preterm uterine contraction with cervical change.

Factors affecting maternal serum magnesium levels during long-term magnesium sulfate tocolysis in singleton and twin pregnancy

AIM

Our aim was to determine factors that affect maternal serum magnesium (Mg) levels, to help ensure the safety and efficacy of long-term magnesium sulfate (MgSO4 ) therapy for threatened preterm labor in singleton and twin pregnancies.

MATERIAL AND METHODS

We retrospectively and arbitrarily studied 100 patients (singleton pregnancy, n = 65; twin pregnancy, n = 35) who received i.v. MgSO4 for >48 h for tocolysis of threatened preterm labor. We used multiple regression analysis to investigate the functional relations between the candidate factors and maternal serum Mg levels.

RESULTS

MgSO4 was administered as a loading dose of 3 g for 1 h followed by a maintenance dose of 1.0-2.0 g/h. There were no maternal severe adverse events related to the elevated Mg levels in any of the subjects. The results of multiple regression analysis revealed that total dose of MgSO4 for 24 h before blood collection (g/day), total serum protein level (g/dL), serum total calcium level (mg/dL), serum creatinine level (mg/dL) and maternal bodyweight (kg) significantly affected maternal serum Mg levels in both singleton and twin pregnancies (all P-values were < 0.001). Gestational age (weeks) and period of MgSO4 administration (days) at blood collection had no significant effect in singleton or twin pregnancies.

CONCLUSION

Our study statistically shows that dose of MgSO4 , total serum protein level, serum total calcium level, serum creatinine level and maternal bodyweight are key factors to achieving safe and effective long-term tocolysis with MgSO4 in not only singleton but also twin pregnancies.

Oxytocin receptor antagonists for inhibiting preterm labour

BACKGROUND

Preterm birth, defined as birth between 20 and 36 completed weeks, is a major contributor to perinatal morbidity and mortality globally. Oxytocin receptor antagonists (ORA), such as atosiban, have been specially developed for the treatment of preterm labour. ORA have been proposed as effective tocolytic agents for women in preterm labour to prolong pregnancy with fewer side effects than other tocolytic agents.

OBJECTIVES

To assess the effects on maternal, fetal and neonatal outcomes of tocolysis with ORA for women with preterm labour compared with placebo or any other tocolytic agent.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (1 December 2013).

SELECTION CRITERIA

We included all randomised controlled trials (published and unpublished) of ORA for tocolysis of labour between 20 and 36 completed weeks' gestation.

DATA COLLECTION AND ANALYSIS

Two review authors independently evaluated methodological quality and extracted trial data. When required, we sought additional data from trial authors. Results are presented as risk ratio (RR) for categorical and mean difference (MD) for continuous data with the 95% confidence intervals (CI). Where appropriate, the number needed to treat for benefit (NNTB) and the number needed to treat for harm (NNTH) were calculated.

MAIN RESULTS

This review update includes eight additional studies (790 women), giving a total of 14 studies involving 2485 women.Four studies (854 women) compared ORA (three used atosiban and one barusiban) with placebo. Three studies were considered at low risk of bias in general (blinded allocation to treatment and intervention), the fourth study did not adequately blind the intervention. No difference was shown in birth less than 48 hours after trial entry (average RR 1.05, 95% CI 0.15 to 7.43; random-effects, (two studies, 152 women), perinatal mortality (RR 2.25, 95% CI 0.79 to 6.38; two studies, 729 infants), or major neonatal morbidity. ORA (atosiban) resulted in a small reduction in birthweight (MD -138.86 g, 95% CI -250.53 to -27.18; two studies with 676 infants). In one study, atosiban resulted in an increase in extremely preterm birth (before 28 weeks' gestation) (RR 3.11, 95% CI 1.02 to 9.51; NNTH 31, 95% CI 8 to 3188) and infant deaths (up to 12 months) (RR 6.13, 95% CI 1.38 to 27.13; NNTH 28, 95% CI 6 to 377). However, this finding may be confounded due to randomisation of more women with pregnancy less than 26 weeks' gestation to atosiban. ORA also resulted in an increase in maternal adverse drug reactions requiring cessation of treatment in comparison with placebo (RR 4.02, 95% CI 2.05 to 7.85; NNTH 12, 95% CI 5 to 33). No differences were shown in preterm birth less than 37 weeks' gestation or any other adverse neonatal outcomes. No differences were evident by type of ORA, although data were limited.Eight studies (1402 women) compared ORA (atosiban only) with betamimetics; four were considered of low risk of bias (blinded allocation to treatment and to intervention). No statistically significant difference was shown in birth less than 48 hours after trial entry (RR 0.89, 95% CI 0.66 to 1.22; eight studies with 1389 women), very preterm birth (RR 1.70, 95% CI 0.89 to 3.23; one study with 145 women), extremely preterm birth (RR 0.84, 95% CI 0.37 to 1.92; one study with 244 women) or perinatal mortality (RR 0.55, 95% CI 0.21 to 1.48; three studies with 816 infants). One study (80 women), of unclear methodological quality, showed an increase in the interval between trial entry and birth (MD 22.90 days, 95% CI 18.03 to 27.77). No difference was shown in any reported measures of major neonatal morbidity (although numbers were small). ORA (atosiban) resulted in less maternal adverse effects requiring cessation of treatment (RR 0.05, 95% CI 0.02 to 0.11; NNTB 6, 95% CI 6 to 6; five studies with 1161 women).Two studies including (225 women) compared ORA (atosiban) with calcium channel blockers (CCB) (nifedipine only). The studies were considered as having high risk of bias as neither study blinded the intervention and in one study it was not known if allocation was blinded. No difference was shown in birth less than 48 hours after trial entry (average RR 1.09, 95% CI 0.44 to 2.73, random-effects; two studies, 225 women) and extremely preterm birth (RR 2.14, 95% CI 0.20 to 23.11; one study, 145 women). No data were available for the outcome of perinatal mortality. One small trial (145 women), which did not employ blinding of the intervention, showed an increase in the number of preterm births (before 37 weeks' gestation) (RR 1.56, 95% CI 1.13 to 2.14; NNTH 5, 95% CI 3 to 19), a lower gestational age at birth (MD -1.20 weeks, 95% CI -2.15 to -0.25) and an increase in admission to neonatal intensive care unit (RR 1.70, 95% CI 1.17 to 2.47; NNTH 5, 95% CI 3 to 20). ORA (atosiban) resulted in less maternal adverse effects (RR 0.38, 95% CI 0.21 to 0.68; NNTB 6, 95% CI 5 to 12; two studies, 225 women) but not maternal adverse effects requiring cessation of treatment (RR 0.36, 95% CI 0.01 to 8.62; one study, 145 women). No longer-term outcome data were included.

AUTHORS' CONCLUSIONS

This review did not demonstrate superiority of ORA (largely atosiban) as a tocolytic agent compared with placebo, betamimetics or CCB (largely nifedipine) in terms of pregnancy prolongation or neonatal outcomes, although ORA was associated with less maternal adverse effects than treatment with the CCB or betamimetics. The finding of an increase in infant deaths and more births before completion of 28 weeks of gestation in one placebo-controlled study warrants caution. However, the number of women enrolled at very low gestations was small. Due to limitations of small numbers studied and methodological quality, further well-designed randomised controlled trials are needed. Further comparisons of ORA versus CCB (which has a better side-effect profile than betamimetics) are needed. Consideration of further placebo-controlled studies seems warranted. Future studies of tocolytic agents should measure all important short- and long-term outcomes for women and infants, and costs.

Progestational agents for treating threatened or established preterm labour

BACKGROUND

Prematurity is not only the leading cause of perinatal morbidity and mortality but is associated with long-term impairment. Studies of various tocolytic agents have shown mixed results with little effect in improving pregnancy duration and insufficient data to confirm a definite beneficial effect on neonatal morbidity or mortality. Progesterone is known to have an inhibitory effect on uterine contractility and is thought to play a key role in the maintenance of pregnancy until term.

OBJECTIVES

To determine if the use of progestational agents is effective as a form of treatment or co-treatment for women with threatened or established preterm labour with intact membranes.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 August 2013), CENTRAL (The Cochrane Library 2013, Issue 10), MEDLINE (1966 to August 31 2013) and Embase (1974 to 31 August 2013). We checked the reference lists of all included studies to identify any additional studies and communicated with authors and the pharmaceutical industry.

SELECTION CRITERIA

Randomised controlled trials that compared progestational agents, given either alone or in combination with other tocolytics, with a control group receiving another tocolytic, placebo or no treatment, for the treatment of preterm labour.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality.

MAIN RESULTS

Eight studies were included in this review, involving 563 women, but only seven studies, involving 538 women, contributed data for analyses. There are some data suggesting that the use of progestational agents results in a reduction of preterm deliveries at less than 37 weeks of gestation and an increase in birthweight. The use of a progestational agent may also reduce the frequency of uterine contractions, prolong pregnancy and attenuate the shortening of cervical length. However, the analysis was limited by the relatively small number of available studies. The power of the meta-analysis was also limited by the varying types, dosages and routes of administration of progesterone.

AUTHORS' CONCLUSIONS

There is insufficient evidence to advocate progestational agents as a tocolytic for women presenting with preterm labour.

Oral betamimetics for maintenance therapy after threatened preterm labour

BACKGROUND

Some women who have threatened to give birth prematurely, subsequently settle. They may then take oral tocolytic maintenance therapy to prevent preterm birth and to prolong gestation.

OBJECTIVES

To assess the effects of oral betamimetic maintenance therapy after threatened preterm labour for preventing preterm birth.

SEARCH METHODS

We updated the search of the Cochrane Pregnancy and Childbirth Group's Trials Register on 9 November 2012.

SELECTION CRITERIA

Randomised controlled trials comparing oral betamimetic with alternative tocolytic therapy, placebo or no therapy, for maintenance following treatment of threatened preterm labour.

DATA COLLECTION AND ANALYSIS

Two review authors independently applied the selection criteria and carried out data extraction and quality assessment of studies.

MAIN RESULTS

We did not identify any new trials from the updated search so the results remain unchanged as follows.We included 13 randomised controlled trials (RCTs) with a total of 1551 women. We found no differences for admission to the neonatal intensive care unit when betamimetics were compared with placebo (risk ratio (RR) 1.28, 95% confidence interval (CI) 0.68 to 2.41; two RCTs of terbutaline with 2600 women) or with magnesium (RR 0.80, 95% CI 0.43 to 1.46; one RCT of 137 women). The rate of preterm birth (less than 37 weeks) showed no significant difference in six RCTs, four comparing ritodrine with placebo/no treatment and two comparing terbutaline with placebo/no treatment (RR 1.11, 95% CI 0.91 to 1.35; 644 women). We observed no differences between betamimetics and placebo, no treatment or other tocolytics for perinatal mortality and morbidity outcomes. Some adverse effects such as tachycardia were more frequent in the betamimetics groups than the groups allocated to placebo, no treatment or another type of tocolytic.

AUTHORS' CONCLUSIONS

Available evidence does not support the use of oral betamimetics for maintenance therapy after threatened preterm labour.