The PROLONG Trial (Progesterone for Preterm Birth, Part II)

Last week, we introduced our major progesterone trial series with a discussion of the Meis trial. We finish up this week talking about the follow up trial: the PROLONG study.

The PROLONG Trial 

Methods

• Location

  • 93 total centers across 9 countries  

• Eligibility criteria and exclusion criteria: pretty much the same as the earlier trial 

• Randomization and treatment 

  • Randomized 2:1 to receive 17OHP weekly, to start between 16-20w6d 

  • Placebo was benzyl benzoate, caster oil, benzyl alcohol 

• Outcomes 

  • Measured preterm birth <35 weeks 

  • Composite neonatal morbidity and mortality index 

  • Secondary outcomes: 

    • Neonatal death, PTB <32 weeks, PTB <37 weeks and also medical indicated preterm births 

  • Primary safety outcome: fetal/early infant death 

• Stats 

  • Unlike previous trial, wanted it to have adequate power to identify both the primary efficacy and the primary safety analyses 

  • Therefore, needed 1665 liveborn infants to detect a reduction of 35% in the rate of the composite index 

  • Needed 1707 patients to provide 98% power to detect a reduction of approximately 30% in the rate of PTB <35w0d

Results 

• Timeline: November 12, 2009 - October 8, 2018 

• Total of 1740 women were consented and agreed to study 

  • 1130 allocated to 17OHP, 578 allocated to placebo 

  • 390 were randomized in the US, 1317 randomized in non-US 

• Demographics were similar between groups 

  • 88.8% vs. 87.2% Caucasion in 17OHP vs. placebo groups 

  • Prepregnancy BMI 23 

  • Almost 90% were married, living with partner compared to just about 50% in the other study 

  • Only 7-8% smoked in pregnancy compared 20-22% in other study 

• So… similar for each arm of this study, but very different demographic compared to the Meis trial.

• Primary Outcome 

  • Preterm birth prior to 35 weeks: 11.0% in 17OHP vs. 11.5%

    • Spontaneous was 8.4 vs 8.9%, RR 0.93, 95% CI 0.67-1.30

  • Not a primary outcome, but PTB <37 weeks: 23.1% vs 21.9% RR 1.06, 95% CI 0.88-1.28! 

    • So different from 36 vs. 50% in Meis study 

  • Neonatal outcomes: 

    • Unsurprisingly, given no diff in preterm labor, no diff in composite neonatal morbidity and mortality 

• Secondary Outcome 

  • Preterm birth <32 weeks - also not different 

  • Other things: cerclage, preterm labor eval, tocolysis, corticosteroids, maternal GDM, preeclampsia, chorio, abruption, CS all not different 

  • Neonatal: no difference in anything, including neonatal death, RDS, NEC, IVH, NICU admission, birth weight, TTN, PDA, ROP

Conclusions

• Study was done in consultation with the FDA as part of approval for use of 17OHP 

• Unlike the findings in the MFMU trial, this study had much lower event rate of PTB and did not confirm treatment efficacy 

Discussion points

• While the Meis study was conducted in the USA, the PROLONG study was mostly not, and that was because the findings from the Meis study had changed practice 

• Most places in the US were already prescribed 17OHP and likey didn’t want to change their practice 

• Also, the Meis showed a large predominance of black women (60%), while there were very few in the PROLONG study 

• Finally, there was a huge discrepancy in baseline preterm labor rates between the two studies, with the rates in PROLONG about ½ has much as that of the Meis study 

• Why castor oil? 

  • Not that it has shown to cause preterm labor, but castor oil can cause contractions, usually due to GI distress when ingested 

• Consequences of the Studies 

  • After Meis, everyone started doing 17OHP 

  • After PROLONG, an FDA advisory committee proposed to take Makena (17OHP) off the market in 2019 (9 to 7 vote) 

    • https://www.nytimes.com/2022/03/25/health/fda-drug-approvals-makena.html ← NY times article about all this 

  • Plan: Oct 17-19 the FDA’s advisory committee will meet to discuss the medicine and hear arguments if it should stay on the market 

• Follow up to the study 

  • EPPPIC - Evaluating Progesterone for Preventing Preterm birth International Collaborative - meta-analysis of individual participant data from randomized controlled trials 

    • Published in the Lancet in 2021 

    • Basically: 31 trials were included with individual participant data

      • From these studies, it seems that vaginal progesterone and 17OHP both reduce birth before 34 weeks gestation in high risk singleton pregnancies 

      • Absolute risk reduction is greater for women with short cervices 

      • The data seems a little better for vaginal progesterone in consistently decreasing preterm birth <37 weeks and <34 weeks

      • For 17OHP the data just crosses the line of no effect at <34 weeks 

The Meis Trial (Progesterone for Preterm Birth, Part I)

One of the hottest controversies in OB in the last several years has been about the role of progesterone for treating preterm birth. We covered these trials very briefly in our episode on preterm birth prevention. Today, let’s dive deeper and start with part I - talking through the Meis Trial.

Next week, we’ll talk in depth about the PROLONG trial and some takeaways for your practice.

Background: 

• Titles 

  • The Meis Trial - Prevention of Recurrent Preterm Delivery by 17 Alpha-Hydroxyprogesterone Caproate 

  • The PROLONG Trial - 17-OHPC to Prevent Recurrent Preterm Birth in Singleton Gestations (PROLONG Study): A multicenter, International, Randomized Double-Blind Trial 

• Who wrote the papers and where were they published? 

  • Meis: Dr. Paul Meis!  - Done with the NICHHD as part of the MFMU 

    • Published in the NEJM! Very fancy - published 2003 

  • PROLONG: Done by Dr. Sean Blackwell (was a president of SMFM!) and a bunch of people who are active in SMFM like Dr. Cynthia Gyamfi-Bannerman, Dr. Brenna Hughes, Dr. Judette Louis 

    • Published in American Journal Perinatology in 2020; which is a good journal but… nowhere near the impact factor of NEJM lol 

• Who funded the studies? 

  • Meis: NICHD

  • PROLONG: AMAG Pharmaceuticals (those that make Makena) 

• Why were the studies done? 

  • The initial study (Meis) was done to try and decrease preterm delivery (leading cause of infant mortality and morbidity in the US!). There had been small trials with prophylactic treatment with progestational compounds that had shown promise, but not all of them had positive results 

    • Had been a meta-analysis restricted to 17-OHP that showed a reduction in preterm delivery 

  • The second study was done after the first study was stopped early because it was thought to be unethical to continue recruitment given the robustness of evidence (spoilers, sorry) 

    • The FDA granted conditional approval for 17-OHP for commercial use in 2011 under the provision that another well-conducted randomized controlled trial was done 

    • This was a confirmatory trial for 17-OHP, and the FDA also required a long-term infant follow-up study 

• Question to answer: Does the use of weekly 17-OHP in pregnancy decrease the risk of preterm birth? 

The MEIS Trial

Methods

• Done at 19 participating centers, primary USA based 

• Eligibility criteria

  • History of spontaneous preterm delivery in previous pregnancy between 20w-36w6d 

  • Current pregnancy between 15w0d-20w3d gestation 

  • Ultrasound between 14w0d-20w6d to confirm duration of gestation and to identify any major fetal anomalies 

• Exclusion criteria 

  • Multifetal gestation

  • Known fetal anomaly 

  • Progesterone or heparin treatment during current pregnancy 

  • Current or planned cerclage 

  • Hypertension requiring medication

  • Seizure disorder 

  • Plan to deliver somewhere other than the 19 participating center 

• Intervention 

  • Patients that consented were randomized to either IM study drug (17 OHP) or castor oil (omg - need to talk about this after!)

    • Had to be given first dose between 16w0d-20w6d; if they did not return before 20w6d, could not participate

    •  Weekly injections until 36 weeks 

• Outcomes 

  • Date of delivery, birth weight, neonatal course - to assess for preterm delivery!  

• Statistics 

  • Power calculation: 

    • Estimated 37% of patients in placebo group would have a preterm delivery 

    • Sample size calculation of 500 women, with 334 in progesterone group and 166 in placebo to find a reduction of 33% in rate of preterm delivery 

  • At second interim analysis, when 463 patients had undergone randomization, outcome data was available for 351 patients

    • The boundary (p=0.015) for test of significance had been crossed for preterm delivery, and enrollment was halted 

Results

• Timeline: 

  • Started in April 1998, but ultimately stopped in February 1999 because the FDA ordered the company that supplied to the active drug to shut down and mandated a total recall of the company’s drugs because of poor quality control and documentation 

    • 150 patients had been enrolled 

  • The study was then restarted with a new drug company. The 150 women previously with other med were not included in the study data analyses 

  • New Timeline: 

    • September 1999 - February 2002 

• Patient Demographics 

  • 1039 eligible, 463 eligible women gave their consent  

    • 310 in progesterone group 

    • 153 in placebo group 

  • Patients were similar in mean duration of previous gestational age (that qualified them for the study), mean gestational age at time of randomization, race, marital status, BMI, smoking, education level, etc. 

    • Of note, interestingly, approximately 60% of those in the study identified as non-Hispanic black (compare to PROLONG, which has very different demographics) 

    • Prepregnancy BMI 26 

  • But, women in the placebo group had more previous preterm deliveries (1.6 vs. 1.4, p=0.007) 

  • 91.5% of women were compliant with their injections (meaning they didn’t go more than 10 days without an injection) 

  • 50% reported at least one adverse effect 

    • Most common: 34.2% reported soreness at sight of injection; 14% reported swelling, 11% itching, 6.7% bruising 

    • More women with progesterone had swelling or a lump at injection sight 

• Primary outcome 

  • Preterm delivery

    • Data was available for 459/463 women

    • Delivery before 37 weeks was reduced, 36.3% for 17-OHP group, 54.9% for placebo group (wtf, that’s super high) RR 0.66, 95% CI 0.54-0.81 

      • Spontaneous PTL was 29.4% vs. 45.1% respectively 

    • Findings were similar for black vs nonblack women 

    • Even more interesting, significant for delivery before 35 and 32 weeks gestation

      • Delivery before 35 weeks: 20.6% vs. 30.7%, RR 0.67, 95% CI 0.48-0.93 

      • Delivery before 32 weeks: 11.4% vs 19.6%, RR 0.58, 95% CI 0.37-0.91

  • Other things were not different: hospital visit for PTL, tocolytic therapy, corticosteroid use, CS, chorio 

• Secondary outcome 

  • Fetal and neonatal outcomes 

    • No difference in fetal death, antepartum or intrapartum 

    • There was a significant difference in birthweight

      • <2500g was 27.2% vs. 41.1%, RR 0.66 (95% CI 0.51-0.87)  

    • Also difference in supplemental oxygen use (14.9% in 17OHP vs. 23.8% in placebo) 

    • And lastly, difference in IVH (1.3% vs 5.2%) 

  • No difference in neonatal death, TTN, RDS, bronchopulmonary dysplasia, vent support, NEC, retinopathy, etc. 

Conclusions 

• Authors concluded: treatment with 17OHP weekly from 16-20 weeks to 36 weeks of gestation reduced preterm delivery at 37, 35, and 32 weeks in patients with history of sPTB

  • But … they also did say that there was an overall very high rate of preterm delivery (50% in placebo vs. 36% for 17OHP)

  • Next week, we’ll contrast with PROLONG!

Updates in Preterm Birth Prevention

Check out reading for this episode: PB 234

Our last podcast on preterm birth prevention was 2 years ago in November 2019, right after the PROLONG trial was published… and there have been some major guideline changes! We’ll do prevention of preterm birth redux today, going over everything once again to provide the most up-to-date summarization of ACOG’s recommendations..

Also important: we still have podcasts on assessing/managing preterm labor where nothing has really changed! Be sure to check that out as an important CREOG topic!

Why care about preterm birth?

• Exceedingly common: 10.2% of newborns in the USA are born prematurely.

  • PTB accounts for 75% of perinatal mortality and >50% of long-term neonatal morbidity (and associated costs)

• Preterm birth rates are actually increasing in the USA:

  • Had decreased from 2007-2014, but as of 2019 had increased back to 10.2%

    • Driven primarily by increase in late preterm birth (34-36 wks)

    • Rates of early preterm birth  (less than 34wk)  largely unchanged since 2014 (2.8%)

• Preterm birth rates are disparate amongst racial/ethnic groups:

  • White women: 9.3% rate of PTB, vs Hispanic 10%, non-Hispanic Black 14.4%, AI/AN 11.5%, Hawaiian/PI 11.8%. 

    • Non-Hispanic Black women also have a disproportionately higher rate of < 34wk PTB (4.9% vs 2.7% overall rate)

• Preterm birth is not just spontaneous preterm birth:

  • 50% follow preterm labor

  • 25% follow PPROM

  • 25% are intentional, medically-indicated PTB for maternal or fetal indications

Risk factors for PTB

• Clinical

  • Prior history: prior spontaneous preterm birth <34 weeks has about a 35% recurrence risk!

    • Number of prior PTBs (more) and degree of prematurity (earlier) significantly affect this risk

    • Preterm birth followed by term birth → risk lowers

    • Twin preterm birth → still higher risk for preterm birth in subsequent singleton gestation, and as high as 40% if twins born before 30 weeks!

  • Bacterial vaginosis: 2x increased risk of spontaneous PTB, more strongly associated in early pregnancy. 

    • Treatment has not been demonstrated consistently to reduce PTB risk though.

  • UTIs in pregnancy: conflicting results based on Cochrane reviews examining risk with asymptomatic bacteriuria or symptomatic UTIs and preterm birth risk

    • However still prudent to treat - risk of pyelonephritis → sepsis, which definitely increases risk.

  • Periodontal disease: conflicting results of risk and association

  • History of prior D&C: slightly increased risk in 21-study meta-analysis of 2 million women (OR 1.29), though mechanism is uncertain. Risk slightly increased with history of multiple D&C (OR 1.74).

  • Multiple gestation: Preterm birth rate in twins of 60.3%, with 19.5% born before 34 weeks.

    • Triplets born preterm 98.3% of time, with 82.6% born before 34 weeks.

  • Short cervical length: a transvaginal short cervical length under 25mm between 16-24 weeks is associated with higher risk of PTB in a variety of screened populations.

  • History of cervical conization: inconsistent data regarding risk, though likely pronounced risk if short interval from conization-to-conception or excision greater than 15mm deep. 

• Other modifiable risks:

  • Tobacco use: likely due to vasoconstriction, hypoxic-ischemic pathways

  • Low maternal pre-pregnancy weight: BMI < 18.5

  • Interpregnancy interval < 18 months: some association in observational studies

  • Unintended pregnancy

    • Importantly for these last two, some observational data points to increased access to LARC and family planning services is associated with lower rate of preterm birth.

• What about race?

  • As we’ve discussed on the show before: race as a risk factor needs to be studied further -- a social, not a biological construct

  • Chronic stress related to exposure to racism is a potential explanation

  • Social and economic disadvantage are persistently associated with increased risk of preterm birth, with some factors including:

    • Lower educational attainment

    • Residence in ZIP code/region/states with economic disadvantage

    • Lack of access to prenatal care

  • More work is needed in evaluating and exploring these mechanisms, and more work is desperately needed in evaluating ways to correct inequity 

Screening Strategies: Identifying Patients who may Benefit from Interventions:

• Lots of things that have been tried:

  • Fetal fibronectin assay: in asymptomatic patient, has not been shown to be helpful given low PPV.

  • Home uterine contraction monitors

  • Ongoing research into biomarkers, microbiome research, cervical texture, genetic associations…

• Best and most important screening strategy we have: transvaginal cervical length screening in the 2nd trimester (16-24 weeks)

  • TVCL beyond 24 weeks is less predictive overall.

• Recommendation for universal assessment of cervix at the time of anatomy ultrasound, with TVUS then performed if suspicious:

  • TAUS under 36mm identifies 96% of patients with TVCL under 25mm, and 100% of patients with TVCL of 20mm or less.

    • This universal assessment of length outright with TVCL is debated, though the cervix should at least be visualized to assess for previa, and a TACL is a reasonable 1st screen.

• What cervical lengths are important to remember?

  • Compared to old guidelines, ACOG simplifies things in this document. There are two primary lengths to remember (both transvaginally assessed):

    • 25mm 

    • 10mm

  • Then, there are a few major interventions that can be considered:

    • Progesterone, either vaginal or intramuscular (17-OHP)

    • Cerclage

    • Pessary

  • The recommendations and intervention options vary by the history/clinical scenario of the patient (summarized in the table from the PB), so let’s review from there!

View fullsize

ACOG PB 234

Singleton Pregnancy with No Prior History of Preterm Birth:

• Shortened cervix under 25 mm:

  • Vaginal progesterone

    • Dosing: 200mg micronized, from time of dx until 34-37 weeks gestation (Varies by trial)

    • Effects:

      • Multiple trials demonstrating lowered risk of early preterm birth (less than 34 weeks) by approximately 50%.

      • OPPTIMUM meta-analysis of progesterone demonstrated vagP reduced risk of spontaneous preterm birth prior to 34 weeks by about 40%, with an NNT of 14 patients to prevent one sPTB before 34 weeks.

  • Intramuscular progesterone

    • Dosing: 500mg weekly IM

    • Effects:

      • Very few trials on this in this population (singleton, no PTB history)

      • The few direct trials of this that exist generally have not found benefit

      • Not recommended in this population.

  • Exam-indicated cerclage

    • Identified painless cervical dilation prior to 24 weeks

    • Effects:

      • Associated with pregnancy prolongation by approximately 34 days and increased neonatal survival in a meta-analysis of multiple study types → thus recommended practice if truly painless cervical dilation.

    • Technique notes:

      • Amniocentesis to assess for infection pre-procedure: 

        • limited data, no RCT described in bulletin. Retrospective data colored by amnio-performance was tied to more severe cases. 

      • Antibiotic and tocolytic use:

        • RCT of periop abx + indomethacin demonstrated improved pregnancy lengths in rescue cerclages receiving medications, but no difference in neonatal outcomes overall (good or bad) → reasonable to consider

    • Contraindications:

      • PPROM

      • Suspected infection

      • Preterm labor or active bleeding

      • Fetal demise or anomaly incompatible with life

  • Ultrasound-indicated cerclage

    • Cervical shortening without dilation prior to 24 weeks.

    • Prior ACOG recommendation: cerclage not indicated in this population (only rescue cerclage was indicated without history of PTB)

    • NEW ACOG recommendation: possibly of benefit with extreme cervical shortening < 10mm

      • Based on a subgroup analysis of 126 patients in a meta-analysis of 5 RCTs. 

        • CL < 25mm - cerclage did not reduce risk of PTB <34wk

        • CL < 10mm - cerclage reduced risk of PTB <35 weeks (39.5% vs 58%). 

      • Importantly -- none of these patients were on vaginal progesterone, nor are there trials comparing vagP to cerclage in this population, or their combined effect.

  • Pessary

    • Cervical pessaries can compress, elevate, and posteriorly rotate the cervix.

    • Trials overall have not demonstrated effectiveness of pessary in those with short cervix without prior history of PTB, alone or in combination with vaginal progesterone.

Singleton Pregnancy in Patient with Prior Spontaneous Preterm Birth

• Cervical Length Screening

  • In addition to the usual screen, in patients with prior PTB history, serial cervical length assessment has been studied:

    • A TVCL under 25mm before 24 weeks had a sensitivity of 65% for PTB under 35 weeks; PPV 33%, NPV 92%. However, sensitivity and PPV is similar for just risk factor of prior PTB.

    • Many studies have assessed utility of cervical length screening, without definitive data to guide frequency/schedule of assessment.

    • Most protocols will perform screening starting at 16 weeks and repeat q1-4 weeks through 24 weeks.

      • Because treatment is available for short cervix (US-indicated cerclage, we’ll get to that in a minute!), even with absence of superb data, serial screening is reasonable to perform.

• IM Progesterone

  • We talked about this controversy on our previous podcast with the Meis trial and the PROLONG trial. 

    • Meis trial: RCT 463 patients, IM progesterone vs placebo. Reduced risk of PTB before 35 weeks by about 33% (20.6% vs 30.7%). Overall considered to be a higher risk population than the PROLONG trial, which came later.

    • PROLONG trial: RCT 1740 patients, no difference in PTB before 35 wks (11% vs 11.5%) or neonatal outcomes.

  • SQ progesterone is also available, but there is no direct evidence to support its efficacy vs IM or other formulations. 

  • In the interim, ACOG and SMFM have released statements supporting shared decision-making and patient preference in using progesterone supplementation (IM or vaginal), given the mixed evidence.

• Vaginal Progesterone

  • Vs placebo:

    • 3 blinded RCTs demonstrate no benefit in reducing recurrent PTB.

    • 5 trial meta-analysis lookig at vagP for use in short cervix with sPTB history demonstrated a reduction of preterm birth by about 40%. 

  • Vs 17-P:

    • Meta-analysis of 3 trials comparing 17-P to vag P demonstrated patients receiving vagP had lower risk of PTB before 34 weeks, though the trials were not blinded and excluded patients with short cervix. 

    • Meta-analysis of multiple progesterone supplementation strategies suggested more robust evidence for BagP in preventing PTB prior to 34 weeks

      • Including largely heterogenous trials with a variety of risk factors present, somewhat limiting outright applicability.

• History-Indicated Cerclage

  • Indicated in those with prior spontaneous preterm birth due to painless cervical dilation in the 2nd trimester without identified etiology (i.e., abruption), or in those who have had cerclages in prior pregnancy

  • Can be placed in early 2nd trimester with good effect.

• Ultrasound-Indicated cerclage

  • Five-trial meta-analysis demonstrates that in those with prior sPTB and TVCL <25mm prior to 24 weeks, cerclage reduces the rate of PTB by about 35% (28% vs 41%). 

    • Unknown if progesterone supplementation may augment this effect at all, and there are no trials comparing cerclage to vaginal progesterone vs cerclage in this population.

    • There are ways to do indirect comparisons between trials, and when this is performed the effect size observed seemed to be similar between vagP and cerclage. 

      • Thus, ACOG states that cerclage or vagP are acceptable options in those with prior sPTB and short cervix, and states that cerclage may be offered in addition to continuation of progesterone.

• Pessary

  • Evidence has not demonstrated any efficacy of pessary alone.

Multifetal Gestations

• Cervical Length Screening

  • Multifetal pregnancies will generally have a shorter cervical length in the 2nd trimester, but the short cervix remains an effective predictor of early preterm birth:

    • TVUS < 25 mm at 20-24wks had PPV of 75.5% for delivery prior to 37 weeks, and 25.8% for delivery before 28 weeks. 

    • TVUS < 20 mm had PPV of 61.9% before 34 weeks in a separate analysis. 

  • There are not a lot of data regarding screening, and as you’ll see, less consensus regarding effectiveness of intervention in twin pregnancies; thus, serial screening is not necessarily recommended. 

  • A single screen at the anatomy scan should still be performed at minimum, as it is with singleton gestations without prior history.

• IM Progesterone

  • Trial of 661 twin pregnancies of placebo vs 17-P demonstrated no benefit; a Cochrane review of randomized trials actually found slight increase in risk of PTB before 34 weeks with 17-P (though no difference in perinatal outcomes)

  • In those with prior sPTB and subsequent twin pregnancy, 66 patient trial showed less delivery prior to 34 weeks (20.6% vs 46.9%), but mean gestational length didn’t differ, and no significant difference in neonatal outcomes.

    • Bottom line: can consider in those with prior history of sPTB, not for use in those without sPTB history (same as singletons)

• Vaginal Progesterone

  • Outright use - not recommended:

    • Cochrane review: no difference in rates of PTB before 34 weeks, perinatal death, NICU admission, or respiratory distress vs placebo.

    • Two other meta-analyses with similar conclusions, and an RCT subsequent to these meta-analyses demonstrated no difference.

  • Short cervix - could be considered, but insufficient data to make recommendation:

    • Six RCTs with different doses/compounds, but when analyzed together, demonstrates likely reduction in PTB risk prior to 33 weeks with vaginal progesterone.

    • Diffferent meta-analyses have not found a significant difference.

• Cerclage

  • Prophylactic (i.e., place in a cerclage without other risk factors than multiple gestations) -- no evidence to suggest benefit.

  • Ultrasound-indicated

    • Insufficient data to recommend at this time, though trials that exist overall are small and have not found significant benefit, though at least one meta-analysis has shown potential benefit if cervical length is <15mm. 

  • Exam-indicated/”Rescue” cerclage

    • New RCT (2020) of twin gestations with asymptomatic cervical dilation between 16’0 and 23’6 demonstrated reduced risk of PTB before a variety of cut points (24/28/32/34) in patients receiving rescue cerclage vs no cerclage

    • Small trial, but based on limited data, there may be some benefit -- so could consider! Major practice change!

• Pessary

  • Two RCTs looked at prophylactic pessary, and a third looking at pessary for short cervix, did not find benefit. 

  • Many other trials are limited by power and methodology in this space, but generally also have not found benefit.

  • Overall, pessary is not recommended in higher order gestation.

Does activity restriction reduce PTB risk?

• Super common question, and one that this update in the PB directly addresses:

  • RCT of 165 pregnant persons found no relationship between coitus and risk for recurrent PTB

  • Secondary analysis of 17-P RCT for short cervix demonstrated PTB at less than 37 weeks was more common among pts who were placed on an activity restriction, and after controlling for confounders PTB remained more common in those placed on restrictions.

    • Thus, based on available data, activity restriction is not recommended.

Summary:

• Singleton pregnancies without history of PTB:

  • CL screening: visualize at anatomy scan, TVUS if suspected to be short

  • 17-P: not indicated

  • Vag P: indicated if TVCL is <25mm

  • Cerclage: possibly indicated, more strong evidence if TVCL < 10mm; OR can be used for “rescue” with dilated cervix (painless)

• Singleton pregnancies with history of sPTB:

  • CL screening: consider serial length screening from 16-24 weeks

  • 17-P: can be considered

  • Vag P: can be considered, may be of stronger benefit if short cervix identified

  • Cerclage:

    • History-indicated: if prior cerclage, or history of painless cervical dilation leading to loss in prior pregnancy 

    • US-indicated: if TVCL < 25mm, can consider this versus vaginal P

    • Rescue: still available

• Multiples:

  • CL screening: same as singleton: at least visualize at anatomy scan

  • 17-P: Not indicated, unless prior history of sPTB

  • Vag P: not indicated, unless short cervix identified

  • Cerclage:

    • US-indicated: limited inconclusive evidence

    • Rescue: can consider → major practice change!

Combined Hormonal Contraceptives

Today we welcome Dr. Aparna Sridhar, an associate clinical professor of obstetrics and gynecology at UCLA Health. Dr. Sridhar walks us so nicely through the combined hormonal contraceptives, and picking the right one for our patients.

Preventing Preterm Birth

Today’s episode returns back to the world of preterm labor and birth. For the management of active preterm labor or premature prelabor rupture of membranes (PPROM), see our previous episode on the subject. For today, ACOG PB 130 and PB 142 are essential reading, though we’ll also get into the recent controversy on this subject with the PROLONG trial (excellent summary by our friends at the OBG Project here).

Screening: Risk Factors and Sonographic Cervical Length

Spontaneous preterm birth is responsible for significant neonatal morbidity and mortality, and thus its prevention is paramount. Unfortunately, we don’t have a lot of great tools for prediction or prevention right now, but history is the starting point to identify those at risk. Prior history of spontaneous preterm birth carries a 1.5-2.0-fold risk of recurrence. Other associative risk factors include chronic illness or inflammatory states; acute illness such as UTI/pyelonephritis; periodontal disease; history of cervical excisions biopsy (LEEP or CKC); low prepregnancy weight (BMI < 20); smoking or substance use; and short interpregnancy interval. There are likely a number of other environmental factors we just don’t have good data about.

An additional risk factor that often leads to confusion amongst trainees is the shortened cervical length, as measured transvaginally. The indication for intervention depends on the history.

• For women with no prior history of spontaneous PTB: a single measurement of the cervical length transvaginally may be considered if abnormal on abdominal ultrasound.

  • If the cervical length is <20mm, vaginal progesterone supplementation (200 mg PV) can be offered.

• For women with prior history of spontaneous preterm birth: q2week measurements of cervical length vaginally can be a screening tool between 14 or 16-24 weeks.

  • These patients should already be considered for IM progesterone starting at 16 weeks gestation (more on that soon!).

  • Ultrasound-indicated cerclage should be considered if the cervical length is <25mm and the prior PTB occurred at <34 weeks.

• No screening intervention has been shown to be of benefit in multifetal gestations.

Intervention: Using Progesterone

As we’ve briefly mentioned above, progesterone for PTB prevention is in two flavors: vaginal and intramuscular. As shown above, the only ACOG-approved recommendation for vaginal progesterone is for an incidentally-identified short cervix < 20mm prior to 24 weeks, and no prior history of spontaneous PTB.

Intramuscular progesterone (17-hydroxyprogesterone, or 17-OHP for short) is recommended for all women who have a prior history of spontaneous PTB prior to 36 weeks. It is administered as a weekly injection starting at 16 weeks through delivery or 36 weeks.

17-OHP has come under some attention recently due to the publication of the PROLONG trial. Prior to this, the MFM U study authored by Meis demonstrated 17-OHP as an effective option for prevention of recurrent spontaneous PTB. As we note in the podcast, there are some important differences between the trials, which should help you counsel your patients. At this time, ACOG and SMFM still endorse its use as originally marketed, though an FDA advisory panel has issued a non-binding recommendation to remove 17-OHP from the market. We should have an update sometime this summer, so stay tuned!

Intervention: Cerclage Placement

Cerclage placement is another tool for prevention of preterm birth. There are three primary indications:

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ACOG PB 142

It’s important to commit these to memory! The challenge clinically for both history and examination-indicated cerclage are teasing out “painless cervical dilation,” versus true preterm labor. Some physicians may even recommend amniocentesis prior to a procedure to determine if an infection is present before placing a cerclage. It’s also not clear in the history- or sonographic-indicated cerclage classifications if the addition of 17-OHP helps to prevent PTB.