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Other Surrogate Outcomes (Key Question 2) Prolongation of pregnancy. The strength of evidence
favoring SQ terbutaline pump compared with oral
Studies reported surrogate outcomes of preterm labor
tocolytics or no treatment is insufficient or low for
much more frequently than neonatal or maternal
women with twin gestation and/or RPTL (difference in
clinical endpoints. However, none of the included
means range 5.50–25.30, 95% CI range: 0.79–16.77,
studies examined incidence of delivery < 28 weeks 13,15-18
8.72–33.83) (Table B). This evidence came from
(strength of evidence is insufficient, Table B), need for
five cohort studies of medium to high risk of bias,
oxygen per nasal cannula, or ratio of birth
mostly from the Matria database. Two small RCTs
weight/gestational age at delivery.
(n=52 and n=42), which did not pertain to any of the
Incidence of delivery at various gestational ages. populations of interest, showed nonsignificant
Incidence of delivery < 32 weeks: The strength of differences between SQ terbutaline pump and
evidence favoring SQ terbutaline pump compared with placebo. 10,11
either oral tocolytics or no treatment is low for women In one Matria-based cohort study, more women in the
with RPTL and those additionally with twin gestation SQ terbutaline pump group had pregnancy prolonged
(OR range = 0.04–0.52, 95% CI range: 0.00–0.35, > 7 days compared with women who received oral
0.50–0.76) (Table B). The evidence originated in six, nifedipine (OR = 7.84, 95% CI: 3.59, 17.12). Other
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mostly Matria-based, cohort studies of medium to high Matria-based studies reported statistically significant
risk of bias. 13,15-19 benefits in favor of the pump compared with oral
Incidence of delivery < 34 weeks: The strength of tocolytics for prolongation > 14 days (OR range =
evidence for this outcome is insufficient (Table B). One 1.93–3.47, 95% CI range: 0.87–2.34, 2.65–5.15). 15-19
small RCT (n=52) that did not address any of the
Birth weight. Cohort studies of women with RPTL and
populations of interest, showed a nonsignificant
single or twin gestation demonstrated statistically
difference between SQ terbutaline pump and placebo in
significant differences in mean birth weight in favor of
women with singleton gestation. 10
SQ terbutaline pump compared with oral tocolytics or
Incidence of delivery < 37 weeks: The strength of no treatment (range of mean difference in grams =
evidence favoring SQ terbutaline pump compared with 136–721, 95% CI range: 83–355, 189–1087). 13,16-19
oral tocolytics or no treatment is insufficient or low for Aside from one study, all were from the Matria
women with RPTL (Table B). Four of five cohort database. 16-19 Two small RCTs (n=52 and n=42), which
studies of medium to high risk of bias, mostly from the did not pertain to any of the populations of interest,
Matria database, reported statistically significant reported nonsignificant differences between SQ
differences in favor of SQ terbutaline pump (OR range terbutaline pump and placebo. 10,11
= 0.04–0.75, 95% CI range: 0.01–0.58,
Incidence of low birth weight (< 2500 g) and very low
0.23–1.20). 13,15,17,18,20
birth weight (< 1500 g) were reported in cohort studies.
Mean gestational age at delivery. Larger cohort Most of these studies originated from the Matria
studies of medium to high risk of bias in women with database. All studies that reported low birth weight
RPTL and single or twin gestation demonstrated found statistically significant differences in favor of SQ
consistent benefit of SQ terbutaline pump compared terbutaline pump compared with no treatment or oral
with oral tocolytics or no treatment (RPTL and tocolytics (OR range = 0.24–0.64, 95% CI range:
singleton gestation: difference in means range = 0.06–0.51, 0.62–0.96). 13,15-19 Most studies also found
0.70–3.40 weeks, 95% CI range: 0.28–1.80 weeks, statistically significant differences in favor of the pump
0.98–5.00 weeks; RPTL and twin gestation: difference for incidence of very low birth weight (OR range =
in means = 0.70 weeks, 95% CI range: 0.43–0.48 0.22-0.46, 95% CI range: 0.07–0.29, 0.60–1.06). 16-19
weeks, 0.92–0.97 weeks). 13,15-19 Most participants in the
Pregnancy prolongation index. Pregnancy
cohort studies came from the Matria database. RCT
prolongation index was reported in two cohort
evidence not directly addressing the populations of
studies. 13,20 Both found statistically significant
interest yielded a nonsignificant effect estimate between
differences in favor of the SQ terbutaline pump
the pump and placebo (n=52 and n=42). 10,11

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