The relationship between prior cervical conization, cervical microbial colonization and preterm premature rupture of the membranes

Association between loop electrosurgical excision procedure and adverse pregnancy outcomes: a meta-analysis

OBJECTIVE

To assess the association between loop electrosurgical excision procedure (LEEP) and adverse pregnancy outcomes.

METHODS

The databases including PubMed, Embase, Cochrane Library and Web of science were searched from inception to December 27th, 2020. Odds ratio (OR) and 95% confidence interval (CI) were utilized to calculate the association between LEEP and adverse pregnancy outcomes. Heterogeneity test was performed for each outcome effect amount. If I² ≥ 50%, the random-effects model was conducted, otherwise, fixed-effects model was performed. Sensitivity analysis was performed on all outcomes. Publication bias was performed by Begg's test.

RESULTS

A total of 30 studies containing 2,475,421 patients were included in this study. The results showed that patients who received the LEEP before pregnancy had a higher risk of preterm delivery (OR: 2.100, 95%CI: 1.762-2.503, p  <  .001), premature rupture of fetal membranes (OR: 1.989, 95%CI: 1.630-2.428, p  <  .001) and low birth weight infants (OR: 1.939, 95%CI: 1.617-2.324, p  <  .001) in comparison with controls. Subgroup analysis further found that prenatal LEEP treatment was associated with the risk of preterm birth subsequently.

CONCLUSION

LEEP treatment before pregnancy may increase the risk of preterm delivery, premature rupture of fetal membranes and low birth weight infants. It is necessary to do a regular prenatal examination and early intervention in a timely manner to reduce the risk of adverse pregnancy outcomes after LEEP.

Cervical excisional treatment increases the risk of intraamniotic infection in subsequent pregnancy complicated by preterm prelabor rupture of membranes

BACKGROUND

Excisional treatment of cervical intraepithelial neoplasia or very early stages of cervical cancer increases the risk of preterm prelabor rupture of membranes in subsequent pregnancies. The risk increases with the length of the excised cone. The subset of cases with preterm prelabor rupture of membranes and a history of cervical excisional treatment could also be at higher risk of intraamniotic infection/inflammation. However, there is a paucity of relevant information on this subject.

OBJECTIVE

This study aimed to assess the differences in the rates of intraamniotic infection/inflammation and early-onset neonatal sepsis between singleton preterm prelabor rupture of membranes pregnancies without and with a history of cervical excisional treatment, and to investigate the association between these complications of preterm prelabor rupture of membranes and the excised cone length.

STUDY DESIGN

This retrospective cohort study included 770 preterm prelabor rupture of membranes pregnancies in which transabdominal amniocentesis was performed as part of standard clinical management to assess the intraamniotic environment. The maternal and perinatal medical records of all included women were reviewed to obtain information on the absence or presence of history of cervical excisional treatment and neonatal outcomes. Women whose records contained any information on history of cervical excisional treatment were contacted by phone and in writing to inform them of the study and request permission to collect relevant information from their medical records. Women were divided into 4 subgroups according to the presence of microorganisms and/or their nucleic acids (through culturing and molecular biology methods) in amniotic fluid and/or intraamniotic inflammation (through amniotic fluid interleukin-6 concentration evaluation): intraamniotic infection (presence of both), sterile intraamniotic inflammation (intraamniotic inflammation alone), microbial invasion of the amniotic cavity without inflammation (presence of microorganisms and/or their nucleic acids in amniotic fluid alone), and negative amniotic fluid for infection/inflammation (absence of both).

RESULTS

A history of cervical excisional treatment was found in 10% (76/765) of the women. Of these, 82% (62/76) had a history of only 1 treatment, and information on cone length was available for 97% (60/62) of them. Women with a history of cervical excisional treatment had higher rates of intraamniotic infection (with, 25% [19/76] vs without, 12% [85/689]; adjusted odds ratio, 2.5; adjusted P=.004), microbial invasion of the amniotic cavity without inflammation (with, 25% [19/76] vs without, 11% [74/689]; adjusted odds ratio, 3.1; adjusted P<.0001), and early-onset neonatal sepsis (with, 8% [11/76] vs without, 3% [23/689]; adjusted odds ratio, 2.9; adjusted P=.02) compared with those without such history. Quartiles of cone length (range: 3-32 mm) were used to categorize the women into 4 quartile subgroups (first: 3-8 mm; second: 9-12 mm; third: 13-17 mm; and fourth: 18-32 mm). Cone length of ≥18 mm was associated with higher rates of intraamniotic infection (with, 29% [5/15] vs without, 12% [85/689]; adjusted odds ratio, 3.0; adjusted P=.05), microbial invasion of the amniotic cavity without inflammation (with, 40% [6/15] vs without, 11% [74/689]; adjusted odds ratio, 6.1; adjusted P=.003), and early-onset neonatal sepsis (with, 20% [3/15] vs without, 3% [23/689]; adjusted odds ratio, 5.7; adjusted P=.02).

CONCLUSION

History of cervical excisional treatment increases risks of intraamniotic infection, microbial invasion of the amniotic cavity without inflammation, and development of early-onset neonatal sepsis in a subsequent pregnancy complicated by preterm prelabor rupture of membranes.

First-trimester prediction of preterm prelabour rupture of membranes incorporating cervical length measurement

OBJECTIVES

To examine early pregnancy risk factors for preterm prelabour rupture of membranes (PPROM) and develop a predictive model.

STUDY DESIGN

Retrospective analysis of a cohort of mixed-risk singleton pregnancies screened in the first and second trimesters in three Danish tertiary fetal medicine centres, including a cervical length measurement at 11-14 weeks, at 19-21 weeks and at 23-24 weeks of gestation. Univariable and multivariable logistic regression analyses were employed to identify predictive maternal characteristics, biochemical and sonographic factors. Receiver operating characteristic (ROC) curve analysis was used to determine predictors for the most accurate model.

RESULTS

Of 3477 screened women, 77 (2.2%) had PPROM. Maternal factors predictive of PPROM in univariable analysis were nulliparity (OR 2.0 (95% CI 1.2-3.3)), PAPP-A < 0.5 MoM (OR 2.6 (1.1-6.2)), previous preterm birth (OR 4.2 (1.9-8.9)), previous cervical conization (OR 3.6 (2.0-6.4)) and cervical length ≤ 25 mm on transvaginal imaging (first-trimester OR 15.9 (4.3-59.3)). These factors all remained statistically significant in a multivariable adjusted model with an AUC of 0.72 in the most discriminatory first-trimester model. The detection rate using this model would be approximately 30% at a false-positive rate of 10%. Potential predictors such as bleeding in early pregnancy and pre-existing diabetes mellitus affected very few cases and could not be formally assessed.

CONCLUSIONS

Several maternal characteristics, placental biochemical and sonographic features are predictive of PPROM with moderate discrimination. Larger numbers are required to validate this algorithm and additional biomarkers, not currently used for first-trimester screening, may improve model performance.

Ultrasound Control of Cervical Regeneration after Large Loop Excision of the Transformation Zone: Results of an Innovative Measurement Technique

The objective of this research is to evaluate cervical regeneration after large loop excision of the transformation zone (LLETZ) through the identification of a new sonographic reference point at the level of the uterine margins. In the period March 2021-January 2022, a total of 42 patients affected by CIN 2-3 were treated with LLETZ at the University Hospital of Bari (Italy). Before performing LLETZ, cervical length and volume were measured with trans-vaginal 3D ultrasound. From the multiplanar images, the cervical volume was obtained using the Virtual Organ Computer-aided AnaLysis (VOCAL™) program with manual contour mode. The line that connects the points where the common trunk of the uterine arteries reaches the uterus splitting into the ascending major branch and the cervical branch was considered as the upper limit of the cervical canal. From the acquired 3D volume, the length and the volume of the cervix were measured between this line and the external uterine os. Immediately after LLETZ, the removed cone was measured using Vernier's caliper, and before fixation in formalin, the volume of the excised tissue was evaluated by the fluid displacement technique based on the Archimedes principle. The proportion of excised cervical volume was 25.50 ± 17.43%. The volume and the height of the excised cone were 1.61 ± 0.82 mL and 9.65 ± 2.49 mm corresponding to 14.74 ± 11.91% and 36.26 ± 15.49% of baseline values, respectively. The volume and length of the residual cervix were also assessed using 3D ultrasound up to the sixth month after excision. At 6 weeks, about 50% of cases reported an unchanged or lower cervical volume compared to the baseline pre-LLETZ values. The average percentage of volume regeneration in examined patients was equal to 9.77 ± 55.33%. In the same period, the cervical length regeneration rate was 69.41 ± 14.8%. Three months after LLETZ, a volume regeneration rate of 41.36 ± 28.31% was found. For the length, an average regeneration rate of 82.48 ± 15.25% was calculated. Finally, at 6 months, the percentage of regeneration of the excised volume was 90.99 ± 34.91%. The regrowth percentage of the cervical length was 91.07 ± 8.03%. The cervix measurement technique that we have proposed has the advantage of identifying an unequivocal reference point in 3D cervical measurement. Ultrasound 3D evaluation could be useful in the clinical practice to evaluate the cervical tissue deficit and express the "potential of cervical regeneration" as well as provide the surgeon useful information about the cervical length.

Adenocarcinoma in situ or early-stage cervical cancer is a risk factor for preterm delivery after cervical conization: a multicenter observational study

OBJECTIVE

Pregnancy after conization is associated with a high risk of preterm delivery. However, because risk factors for preterm delivery after conization remain unknown, we conducted a multicenter observational study to investigate risk factors associated with preterm delivery.

METHODS

We selected patients who had previously undergone conization and reviewed medical records from 18 hospitals in cooperation with Keio University School of Medicine between January 2013 and December 2019. Women were classified as nulliparous and primiparous, and a multiple logistic regression analysis was performed to evaluate the relative contributions of the various maternal risk factors for preterm delivery (i.e. delivery before 37 gestational weeks).

RESULTS

Among 409 pregnant women after conization, 68 women delivered preterm (17%). The incidence of nulliparity (p = .014) was higher and a history of preterm delivery (p = .0010) was more common in the preterm delivery group than in the term delivery group. Furthermore, the proportion of women diagnosed with adenocarcinoma in situ (AIS) and cervical cancer in the preterm delivery group was higher than that in the term delivery group (p = .0099 and .0004, respectively). In multiple regression models in nulliparous women, cervical cancer or AIS (Odds ratio [OR]: 4.16, 95% CI: 1.26-13.68, p = .019) and a short cervix in the second trimester (OR: 13.41, 95% CI: 3.88-46.42, p < .0001) increased the risk of preterm delivery. Furthermore, a history of preterm delivery (OR: 7.35, 95% CI: 1.55-34.86, p = .012), cervical cancer or AIS (OR: 5.07, 95% CI: 1.24-20.73, p = .024), and a short cervix in the second trimester (OR: 4.29, 95% CI: 1.11-16.62, p = .035) increased the risk of preterm delivery in the multiple regression models in primiparous women.

CONCLUSION

Pregnant women who previously underwent conization are at risk for preterm delivery. The histological type of AIS and cervical cancer was evaluated as a risk factor for preterm delivery. KEY MESSAGESPrior preterm delivery, presence of a short cervix, and cervical cancer or AIS were predictors of preterm delivery after conization.The depth of conization in cervical cancer or AIS group was significantly larger than that in the CIN group.

The impact of cervical conization size with subsequent cervical length changes on preterm birth rates in asymptomatic singleton pregnancies

The study aimed to explore the impact of cervical conization size (CCS) with subsequent cervical length (USCL) changes on preterm birth (PTB) rates in asymptomatic singleton pregnancies as compared to pregnancy outcomes in healthy women with an intact cervix (ICG), and to estimate PTB prevention efficiency in patients with a short cervix. Pregnancy outcomes in populations of similar age, ethnicity, residency, education and harmful habits having undergone cervical conization (CCG) were retrospectively analyzed and compared to ICG and cervical conization sub-populations adjusted by USCL during pregnancy (adequate cervical length vs. a short cervix) and a progesterone-only group (POG) vs. a progesterone-pessary group (PPG). Cervical conization was not associated with an increased PTB risk (CCG vs. ICG) when parameters of CCS and USCL were not adjusted (p = NS). A significantly higher proportion of parous women was observed in the CCG population than in the ICG (p = 0.0019). CCS turned out to be a key PTB risk during pregnancy, the larger CCS being associated with a short cervix (p = 0.0001) and higher PTB risks (p = 0.0001) with a notably increased PTB rate (p = 0.0001) in nulliparous women (p = 0.0022), whereas smaller CCS with adequate cervical length and a lower PTB rate was predominantly observed in women with prior parity. An initial equal USCL size was to be considerably elongated in women with adequate cervical length (p < 0.0001), and shortened in those with a short cervix (p < 0.0001). USCL assessment during pregnancy proved to be the PTB risk-predicting tool, with CCS supplementation apt to increase its diagnostic value. No substantial impact on pregnancy outcomes could be linked to any particular PTB prevention mode (POG or PPV). However, during pregnancy, the USCL changes relating to CCS proved to be more critical in pregnancy outcomes.

Management of pregnancy after radical trachelectomy

Radical trachelectomy (RT) is a surgery for early-stage cervical cancer treatment that preserves the childbearing ability, and its use has become increasingly common worldwide. Thus, the rate of conception in women who have undergone RT is increasing. However, pregnancy after RT is associated with a higher risk of several obstetric complications such as preterm delivery, preterm premature membrane rupture, and abnormal bleeding from varices at the site of uterovaginal anastomosis. Furthermore, since RT have a residual prophylactic cerclage, it is difficult to manage first- and second-trimester miscarriages. There is little previous data on the management of pregnancy after RT. In this review article, we summarize various management methods and experiences to provide a guide to clinicians for perinatal management after RT.

Maternal History of Cervical Surgery and Preterm Delivery: A Retrospective Cohort Study

Introduction: Our aim was to investigate whether cervical conization and/or loop electrosurgical excision procedure (LEEP) increases the risk of preterm delivery. Materials and Methods: We conducted a retrospective cohort study of singleton deliveries at our institution from 2010 to 2015. Women aged 16-49 years were included in our study. Univariate and logistic regression were used for statistical analyses. An interaction test was used to assess whether maternal human papillomavirus (HPV) positivity within the 3 years before delivery (referred to as maternal HPV status in this study) is an effect modifier. Results: Of 3933 women who delivered at our institution, 19.8% (n = 792) delivered prematurely. Of these women, 9.1% (n = 362) had a history of cervical surgery, including cervical conization and/or LEEP. Notably, a history of cervical surgery was not associated with current HPV status based on the most recent Pap smear results (p > 0.05). In univariate analysis, a history of cervical surgery was associated with preterm delivery (odds ratio [OR] = 1.54, 95% confidence interval [CI]: 1.26-1.88). This effect was the same among mothers positive (OR = 1.95, 95% CI: 1.16-3.28) and negative (OR = 1.91, 95% CI: 1.10-3.30) for HPV. Pregnancy-induced hypertension, preterm premature rupture of membranes, bacterial vaginosis infection, HPV infection, placenta previa, placental abruption, ethnicity, maternal body mass index, nulliparity, and smoking or drug use were also associated with preterm delivery (p < 0.05). In multivariable analysis, history of cervical surgery remained associated with preterm delivery (OR = 1.75, 95% CI: 1.31-2.33). There was no interaction (p = 0.91) between maternal HPV status and history of cervical conization or LEEP. Discussion and Conclusions: Maternal history of cervical conization and/or LEEP increases the risk of preterm delivery irrespective of concurrent maternal HPV positivity within the 3 years preceding delivery. Maternal HPV status does not modify the effect of history of cervical conization and/or LEEP on preterm delivery.

Pregnancy outcome after electrosurgical cervical cone biopsy using Fischer cone biopsy excisor

OBJECTIVE

To evaluate the pregnancy outcomes of all patients who underwent electrosurgical cone biopsy of the cervix between January 2000 and December 2011 and subsequently became pregnant.

STUDY DESIGN

Retrospective cohort study.

SETTINGS

District General Hospital in the North East of England.

METHODS

Patients were identified from the local colposcopy electronic data, Hospital Episode Statistics and Maternity electronic data. Data were collected on a pro forma with two sections: (1) treatment section and (2) pregnancy section. In the treatment section, year and indication for treatment, volume of cervix removed, histological results and marginal status of specimen were documented. In the pregnancy section, time interval between treatment and pregnancy, pre-treatment obstetric history, cervical length measurements, cervical suture, gestation and mode of delivery and neonatal outcome were documented. Data were analysed using SPSS.

RESULTS

25 women achieved 47 pregnancies after electrosurgical cone biopsy treatment. Most common indication for cone biopsy was glandular neoplasia accounting for nearly half of the procedures; 21.2% of pregnancies ended in first-trimester miscarriages. The preterm delivery rate (<37 weeks) was 19.4%. Volume of cervix excised was significantly greater in women who delivered preterm compared to women who delivered at term (p = 0.028). The rate of preterm delivery was significantly higher in post treatment pregnancies when compared to pregnancies before treatment in the same women (p = 0.02). The preterm delivery in post-treatment pregnancies was not related to the time interval between treatment and pregnancy (p = 0.54). There was no significant difference in miscarriage rates in pre- and post-treatment pregnancies (p = 0.98).

CONCLUSION

Electrosurgical cone biopsy of cervix is associated with increased risk of preterm labour that is related to the volume of cervix excised.

Reproductive outcomes after laparoscopic radical trachelectomy for early-stage cervical cancer

Objective

The objective of this study was to estimate the reproductive outcome of young women with early-stage cervical cancer who underwent fertility-sparing laparoscopic radical trachelectomy (LRT).

Methods

We performed a retrospective review of the medical records of patients with early-stage cervical cancer who underwent LRT. Clinicopathological data were obtained from patient medical records, and reproductive outcome data were obtained from patient medical records and telephone interviews.

Results

Fifty-five patients who underwent successful LRT were included in this study. The median age of patients was 32 years (range, 22 to 40 years), and the median follow-up time after LRT was 37 months (range, 3 to 105 months). Menstruation resumed in all patients after LRT, with fifty patients (90.9%) and five patients (9.1%) reporting regular and irregular menstruation, respectively. Six patients (10.9%) presented with cervical stenosis, which was manifested by regular but decreased menstrual flow and newly-developed dysmenorrhea. These patients underwent cervical cannulation and dilatation. Eighteen patients (32.7%) attempted to conceive, with six out of 18 patients receiving fertility treatments. Fourteen pregnancies (i.e., four missed abortions, six preterm births and four full-term births) occurred in 10 patients after LRT. Nine out of 10 patients gave birth to 10 healthy babies. The pregnancy rate after LRT was 55.6% (10/18). The spontaneous abortion rate and live birth rate were 28.6% (4/14) and 71.4% (10/14), respectively. The preterm birth rate was 60% (6/10).

Conclusion

Pregnancy and live birth rates after LRT were promising; however, the preterm birth rate was relatively high. Cervical stenosis also occurred in a small percentage of patients.

Cervical surgery and preterm birth

Treatment of cervical intraepithelial neoplasia (CIN) greatly reduces the risk of cervical cancer. Treatment involves ablation or excision of the transformation zone of the cervix, most commonly using an electrosurgical excision technique known as LLETZ. However, the peak incidence of CIN occurs in young women, so if excision of a portion of the cervix has an adverse effect on pregnancy outcome, this might have a significant impact. This review discusses the methodology and findings of the published literature on the association between cervical treatment and preterm birth, and the clinical implications of these findings.

Delivery outcome after cold-knife conization of the uterine cervix

OBJECTIVE

To estimate the risk for preterm delivery and obstetric complications in women with prior cold-knife conization.

METHODS

In a retrospective study, we compared 76 deliveries of 65 women with prior cold-knife conization with the remaining 29,711 singleton deliveries at our institution between 1992 and 2002.

RESULTS

We found significant shorter duration of pregnancies in the conization group. Delivery prior to 37 weeks was found in 22.4% (n = 17) of the conization group and in 6.6% (n = 1961) of the controls (OR = 4.07 [2.22-7.10], P < 0.001). Preterm premature rupture of the membranes was found in 17.1% (n = 13) of the conization group and in 2.6% (n = 775) of the controls (OR = 7.70 [3.87-14.21], P < 0.001). Birth weight less than 2500 g was found in 18.4% (n = 14) of the conization group and in 7.7% (n = 2280) of the controls (OR = 2.72 [1.40-4.92], P = 0.002). Overall, birth weight in the conization group was not significantly lower (median 3147 g vs. 3287 g, P = 0.115). Cervical tears were found more frequently in the conization group (8.8% [n = 6] vs. 1.3% [n = 236], OR = 7.53 [2.63-17.57], P < 0.001). There was no difference in mode of delivery, duration of labor, head circumference, chorioamnionitis and use of oxytocin.

CONCLUSION

Cold-knife conization is a risk factor for preterm birth and preterm premature rupture of the membranes and seems to be a risk factor for cervical tears.

Transvaginal Ultrasonography in the Prediction of Preterm Birth After Treatment for Cervical Intraepithelial Neoplasia

OBJECTIVE

To estimate whether cervical length measured by transvaginal ultrasonography in women having had loop electrosurgical excision procedure (LEEP), cold knife conization, or cryotherapy predicts spontaneous preterm birth.

METHODS

Women with a history of LEEP, cold knife conization, or cryotherapy and who were subsequently pregnant with singleton gestations were prospectively compared with both a low-risk control group and women with previous spontaneous preterm birth. A transvaginal ultrasonogram measuring cervical length was performed at 24 to 30 weeks of gestation. Primary outcomes included cervical length and spontaneous preterm birth less than 37 weeks. Secondary outcomes were spontaneous preterm birth less than 34 weeks, low birth weight, and maternal and neonatal outcomes.

RESULTS

Women with previous LEEP (N = 75), cold knife conization (N = 21), and cryotherapy (N = 36) had shorter cervical lengths (3.54, 3.69, and 3.75 cm respectively) than the low-risk control group (N = 81, 4.21 cm) (P < .001, P = .03, P = .02 respectively) and similar lengths to women with a previous spontaneous preterm birth (N = 63, 3.78 cm). Loop electrosurgical excision procedure and cold knife conization, but not cryotherapy, were associated with spontaneous preterm birth less than 37 weeks (odds ratio 3.45, 95% confidence interval 1.28-10.00, P = .02; and odds ratio 2.63, 95% confidence interval 1.28-5.56, P = .009, respectively). Using a cutoff of 3.0 cm, transvaginal ultrasonography had a positive predictive value of 53.8% and negative predictive value of 95.2% for spontaneous preterm birth less than 37 weeks in women with LEEP.

CONCLUSION

Women with a history of LEEP, cold knife conization, and cryotherapy all independently have shorter cervical lengths than low-risk controls and similar lengths to women with previous spontaneous preterm birth. Loop electrosurgical excision procedure and cold knife conization are associated with spontaneous preterm birth less than 37 weeks, and transvaginal ultrasonography predicts preterm birth in women who have had LEEP.

LEVEL OF EVIDENCE

II-2.

The epidemiology of preterm labor

There are many factors that are associated with preterm labor and delivery. These include maternal conditions such as medical illness, anemia and uterine malformation. They may be related to past events such as prior obstetric complication, previous preterm labor, cervical surgery or induced abortion. They may be intrinsic to the current pregnancy, such as reproductive tract infection, multifetal gestation, maternal age, short interpregnancy interval or prolonged menstrual conception interval. Maternal behaviors such as smoking and substance abuse can be risk factors for a short gestation. Demographic variables such as race, employment and socioeconomic status can also be associated with preterm labor. This article briefly reviews these subjects.

The pathobiology of premature rupture of membranes

Premature rupture of membranes arises from what are likely multifaceted and multistep pathogenic pathways. Pathophysiological processes may involve both endogenous and exogenous fetal and maternal factors. This article reviews and analyzes information regarding, first, the form and function of fetal membranes; second, how membranes physically fail (rupture) at term and preterm gestations; and third, evaluates if we can reduce risks of rupture using physiological understanding and evidence-based clinical studies.

Obstetrical prognosis for carbon dioxide laser conisation of the uterine cervix

Carbon dioxide laser conisation is a very reliable surgical technique for cervical intraepithelial dysplasia. As cervical morphology and function are better preserved than with other techniques, obstetrical morbidity should be lower in the often young and pauciparous women who undergo this procedure. In our study comparing the course of 71 pregnancies (55 children) in 54 operated women with that of 82 pregnancies (59 children) in these same women before conisation, the rates for complications at the beginning of pregnancy were similar (respectively, 14.1% and 13.4%, early spontaneous abortions; 2.8% and 2.4%, extrauterine pregnancies; and no late spontaneous abortions). The increased risks of premature delivery (13.2% vs. 8.5%), chorioamnionitis (1.9% vs. 0%), premature rupture of membranes (1.9% vs. 0%) and prematurity (11.3% vs. 1.7%) were not statistically significant. Only the percentage of natural term births was significantly reduced (73.6% vs. 90%; P = 0.025), but this difference was no longer apparent after correction for the prevalence of associated obstetrical pathologies and prematurity and/or cesarean factors which was significantly greater for the 53 pregnancies that developed after carbon dioxide laser conisation.