Triggers of Spontaneous Preterm Delivery – Why Today?

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Sexual activity was more common during the 0-24 hour window than the 48-72 hour window among cases, although the 95% CI included the null.

“Sexual activity was also more common during the 0–24 hour window, although the 95%CI included the null.”

May combine two claims.

Compared with controls, cases were more likely to be Hispanic, had slightly lower family income and fewer years of education, and were less likely to be married.

“Compared with controls, cases were more likely to be Hispanic, had slightly lower family income and fewer years of education, and were less likely to be married.”

May combine two claims.

Disturbed sleep and skipping meals were more common during the 0-24 hour window than during the 48-72 hour window among cases, but a similar pattern was also seen among controls.

“Disturbed sleep and skipping meals were more common during the 0–24 hour window than during the 48–72 hour window among cases; but a similar pattern was also seen among controls.”

May combine two claims.

Cases were less likely to go to work and more likely to skip meals and have sleep interruptions during the 24h preceding onset of spontaneous preterm labor.

“Similarly, cases were less likely to go to work and more likely to skip meals and have sleep interruptions during the 24h preceding onset of spontaneous preterm labor.”

May combine two claims.

Neither exertion nor stressors had a significant association with PTL/PPROM, while going to work was inversely associated.

“Similarly, as shown in Table 3, neither exertion nor stressors had a significant association while going to work was inversely associated with PTL and PPROM.”

May combine two claims.

Cases were more likely than controls to have been diagnosed with depression/anxiety, have a history of preterm labor, have required fertility treatments such as IVF, carry twins, and have had vaginal bleeding during pregnancy.

“Cases were also more likely to have been diagnosed with depression/anxiety, have a history of preterm labor, have required fertility treatments such as IVF, carry twins, and have had vaginal bleeding during pregnancy.”

May combine two claims.

Cases had a higher prevalence of twin pregnancy, prior preterm, IVF/fertility treatment, asthma, and previous therapeutic abortion compared to controls.

“The higher prevalence of twin pregnancy, prior preterm, IVF/fertility treatment, asthma, and previous therapeutic abortion among cases compared to controls (Table 1) highlight that this is a susceptible population.”

May combine two claims.

Physical exertion overall was similar among cases and controls during the 24 hours before the index time, although exercise of more than 5 METs (vigorous exertion) was less frequent among cases.

“Physical exertion overall was similar among cases and controls during the 24 hours before the index time, although exercise of more than 5 METs (vigorous exertion) was less frequent among cases.”

May combine two claims.

The study did not find the previously suggested associations with physical exertion and psychological stress, although stress was associated with PTL in the case-control analysis.

“We did not find the previously suggested associations with physical exertion11,12 and psychological stress,20,21 although stress was associated with PTL in the case-control analysis.”

• cites [11] sourceNot checked yet

  Not checked in the free run.

• cites [12] sourceNot checked yet

  Not checked in the free run.

• cites [20] sourceNot checked yet

  Not checked in the free run.

May combine two claims.

The frequency of sexual intercourse during the 24 hours before the index time was similar for case and control subjects; however, it was lower during the 48-72 hour window among cases.

“Interestingly, the frequency of sexual intercourse during the 24 hours before the index time was similar for case and control subjects; however, it was lower during the 48–72 hour window among cases.”

Classified as probably not a substantial claim.

By conducting this pilot study we demonstrated the feasibility of identifying, approaching, enrolling and interviewing women admitted for PTL or PPROM.

“By conducting this pilot study we demonstrated the feasibility of identifying, approaching, enrolling and interviewing women admitted for PTL or PPROM.”

Probably not a substantial claim: may not pass S3 (load-bearing).

In the course of the study we uncovered certain challenges associated with the application of this design to abrupt adverse pregnancy outcomes.

“However, in the course of the study we also uncovered certain challenges associated with the application of this design to abrupt adverse pregnancy outcomes.”

May combine two claims.

Stressful events, as well as anxiety and depression, were associated with spontaneous preterm delivery in the case-control analysis.

“However, stressful events, as well as anxiety and depression, were associated with spontaneous preterm delivery in the case-control analysis.”

Classified as probably not a substantial claim. May combine two claims.

Previous observational studies suggest that various factors (coitus, prolonged standing, infections, physical exertion, caffeine, smoking, cocaine, marijuana, alcohol, skipping meals, psychological stress) may trigger preterm delivery.

“Previous observational studies suggest that coitus7, prolonged standing8,9, urinary tract and other infections10, physical exertion11,12, caffeine intake13, smoking14–16, cocaine use17, marijuana use18, alcohol use17, skipping meals19, and psychological stress20,21 may trigger preterm delivery.”

• cites [7] sourceNot checked yet

  Not checked in the free run.

• cites [8] sourceNot checked yet

  Not checked in the free run.

• cites [9] sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

Spontaneous preterm delivery following PTL or PPROM accounts for approximately 50% of all preterm deliveries.

“Spontaneous preterm delivery following premature labor (PTL) or preterm premature rupture of membranes (PPROM) accounts for approximately 50% of all preterm deliveries4.”

• cites [4] sourceNot checked yet

  Not checked in the free run.

May combine two claims.

Sexual activity and spicy food may trigger PTL/PPROM in susceptible women.

“sexual activity and spicy food may trigger PTL/ PPROM in susceptible women.”

May combine two claims.

Skipping meals and disturbed sleep may be associated with imminent PTL/PPROM.

“Skipping meals and disturbed sleep may be associated with imminent PTL/ PPROM”

Classified as probably not a substantial claim.

Controls were frequency matched to cases on gestational age and calendar month to account for gestational and seasonal trends in the factors under study.

“Controls were frequency matched to cases so that they had a similar distribution of gestational ages (in completed weeks) and calendar month of visit as cases, to account for gestational and seasonal trends in the factors under study (e.g. avoidance of physical exertion as women advance in pregnancy or during the winter months).”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

Inclusion of false positives would tend to dilute any potential association.

“Inclusion of false positives would tend to dilute any potential association.”

Probably not a substantial claim: may not pass S2 (checkable).

The dearth of information about acute causes and modifiable risk factors prevents clinicians from adequately advising women about behaviors that might be altered to reduce preterm delivery risk.

“The dearth of information about acute causes and modifiable risk factors prevents clinicians from adequately advising women about behaviors that might be altered to reduce the risk of preterm delivery.”

• AssumptionRests on an assumption: Immediate triggers of spontaneous preterm delivery are largely unknown.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Data were collected through in-person interviews with direct entry of responses and instantaneous coding, following a standardized protocol and script.

“Data were collected through in-person interviews with direct entry of responses and instantaneous coding. The interviewer followed a standardized protocol and script for each question.”

May combine two claims.

If the associations found are the result of reverse causation, they would not identify possible interventions to prevent preterm delivery, but they would still be informative as predictors of imminent premature labour.

“If the associations we found are the result of reverse causation, they would not identify possible interventions to prevent preterm delivery, i.e., avoiding skipping meals or improving sleep quality would not prevent onset of labour. However, associations would still be informative---suggesting that these behaviours may predict an imminent premature labour.”

May combine two claims.

These findings are consistent with the theory that sexual intercourse is an acute risk factor for PTL and PPROM, but only in a selective group of susceptible individuals.

“These findings are consistent with the theory that sexual intercourse is an acute risk factor for PTL and PPROM, but only in a selective group of susceptible individuals (e.g., women with shortening cervical length).”

Classified as probably not a substantial claim.

For cases, interviews were conducted within 48 hours of admission to minimize potential recall bias.

“For cases, interviews were conducted within 48 hours of admission to the hospital to minimize the potential for recall bias.”

Probably not a substantial claim: may not pass S2 (checkable), S4 (based).

Case-only designs are restricted, by definition, to subjects with a predisposition to develop the outcome.

“In general, it is worth noting that case-only designs are restricted, by definition, to subjects with a predisposition to develop the outcome.”

May combine two claims.

In the setting of relatively few discordant pairs, all confidence intervals were wide, including that for sexual activity.

“In the setting of relatively few discordant pairs, all confidence intervals were wide, including that for sexual activity.”

May combine two claims.

The existing literature suggests that sex does not increase the risk of preterm delivery in low-risk pregnancies; evidence is inconsistent for high-risk gestations.

“The existing literature suggests that sex does not increase the risk of preterm delivery in low-risk pregnancies; evidence is inconsistent for high-risk gestations.33”

• cites [33]Not checked yet

  Not checked in the free run.

May combine two claims.

PTL and PPROM are probably related conditions and share common risk factors.

“Since PTL and PPROM are probably related conditions and share common risk factors,30 we combined them in our primary analyses.”

• cites [30] sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Other potential triggers could not be evaluated because of lack of discordance (e.g., smoking, caffeine) or too few exposed cases overall (e.g., illicit drugs, alcohol, heat exposure).

“Other potential triggers could not be evaluated because of lack of discordance (e.g. smoking, caffeine) or just too few exposed cases overall (e.g. illicit drugs, alcohol, heat exposure).”

Probably not a substantial claim: may not pass S3 (load-bearing).

Numbers were too small to evaluate triggers among twin pregnancies.

“Numbers were too small to evaluate triggers among twin pregnancies.”

Probably not a substantial claim: may not pass S2 (checkable).

Defining the exact onset of preterm labour, and therefore timing case and control windows, is challenging.

“Not surprisingly, defining the exact onset of preterm labour, and therefore timing case and control windows, is challenging.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The case-crossover study design was developed in the 1990s to study triggers of acute myocardial infarction and has subsequently been applied to several other acute conditions.

“The case-crossover study design was developed in the 1990s to study triggers of acute myocardial infarction and has subsequently been applied to several other acute conditions24,25.”

• cites [24] sourceNot checked yet

  Not checked in the free run.

• cites [25] sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

Given the small sample size, only crude estimates are presented.

“Given the small sample size, only crude estimates are presented.”

Classified as probably not a substantial claim.

The assumption that the underlying subject-specific probability of exposure to each potential trigger was constant within the 72 hours interval was tested by comparing 0-24 and 48-72 hours windows within control subjects of similar gestational age.

“We implicitly assumed that the underlying subject-specific probability of being exposed to each potential trigger was constant within the 72 hours interval between the control and the case period. We tested this assumption comparing 0–24 and 48–72 hours windows within control subjects of similar gestational age.”

• AssumptionThe authors state this as an assumption: The underlying subject-specific probability of exposure to each potential trigger was constant within the 72 hours interval between control and case periods.

May combine two claims.

This argues that stress may be a non-transient risk factor whose effect may last longer than 72 hours.

“This argues that stress may be a non-transient risk factor; its effect may last longer than 72 hours.”

May combine two claims.

Stressful experiences or their impact likely last more than 24 hours and would extend over both 0-24 and 48-72 hours windows; as a result, they were not identified as triggers in this study.

“Stressful experiences (e.g. unemployment) or their impact (e.g. separation) likely last more than 24 hours and would extend over both 0–24 and 48–72 hours windows. As a result, they were not identified in our study as triggers.”

Classified as probably not a substantial claim. May combine two claims.

If the RR for sexual activity were really 6, around 150 cases would be needed to reach statistical significance; if the RR were close to 2, the sample size would need to be one order of magnitude larger.

“If the RR for sexual activity were really 6, we would need around 150 cases to reach statistical significance. However, if the RR for sexual activity were actually close to 2, the sample size would need to be one order of magnitude larger.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Both normal labour onset and term premature rupture of membranes are more common at night; some authors have suggested an altered diurnal circadian pattern for PTL or very preterm spontaneous onset of labour, but not for PPROM.

“Both normal labour onset and term premature rupture of membranes are more common at night; some authors have suggested an altered diurnal circadian pattern for PTL34, or very preterm spontaneous onset of labour,36 but not for PPROM.37”

• cites [34] sourceNot checked yet

  Not checked in the free run.

• cites [36]Not checked yet

  Not checked in the free run.

• cites [37]Not checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Trends among controls might be due to gestational trends in exposure or, more likely, to the ascertainment methods.

“Trends among controls might be due to gestational trends in exposure or, more likely, to the ascertainment methods.”

Classified as probably not a substantial claim. May combine two claims.

We tried to reduce differential misclassification of exposure by narrowing the gap between case and control windows and not informing subjects of the hypotheses of interest and the corresponding windows.

“We tried to reduce differential misclassification of exposure by narrowing the gap between case and control windows and not informing subjects of the hypotheses of interest and the corresponding windows.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Some of the associations might be partially explained by differential recall within person across study periods.

“It is also possible that some of the associations might be partially explained by differential recall within person across study periods.”

Probably not a substantial claim: may not pass S4 (based).

Women may be more likely to remember factors in the 24 hours before compared to 48 to 72 hours before labour onset.

“Women may be more likely to remember factors in the 24 hours before compared to 48 to 72 hours before labour onset.”

Classified as probably not a substantial claim.

The case-crossover design is best suited to evaluate transient exposures with immediate and transient effects in relation to abrupt outcomes.

“The case-crossover design is best suited to evaluate transient exposures with immediate and transient effects in relation to abrupt outcomes.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Our study identified controls at one of their prenatal visits, which could have affected their work, sleep or eating patterns.

“For example, our study identified controls at one of their prenatal visits, which could have affected their work, sleep or eating patterns.”

May combine two claims.

Findings suggest that sexual intercourse may trigger preterm delivery in susceptible pregnancies; and that impaired appetite or sleep may be predictors of imminent onset of labor.

“In conclusion, findings suggest that sexual intercourse may trigger preterm delivery in susceptible pregnancies; and that impaired appetite or sleep may be predictors of imminent onset of labor.”