Cervical stenosis and pregnancy rate after ultrasound guided cervical dilation in women undergoing saline infusion sonography

Women who received cervical dilation under local or general anaesthesia were included as group A (cases). Cases where cervix was stenosed but dilation was also unsuccessful with Foley’s were not included in the final analysis. Women who did not consent to dilation functioned as group B (controls). They were followed for the study duration but not offered dilation after the initial enrolment, till the completion of study. Those who requested dilation later on during the study period were also excluded to avoid protocol deviation.

Sexual contact was encouraged and the women were asked to report back if they became pregnant. Transvaginal scan was done to confirm fetal heart beat.

All women were followed for a period of twelve months. The follow up was maintained via telephone calls and repeat transvaginal scans at 3, 6, 9 and 12 months. Those who did not comply with the follow up were not included in the final statistical analysis. The primary outcome measure was women who had clinical pregnancy i.e. fetal heartbeat present on transvaginal scan after they were serum beta hCG positive during the follow up period.

All participants provided informed consent. In lieu of formal ethics committee or formal institutional review board approval, Helsinki’s declaration was followed. No subjects were harmed, confidentiality was maintained, and no subject was enrolled in the study without formal informed consent.

The Shapiro-Wilk test was used to assess normality of data distribution. The Quantitative variables, such as age, duration of infertility and duration from treatment to conception were presented by means and standard deviation. The t- test for two independent samples was used to compare means for both groups; those requesting dilation and those who did not. Frequency and percentages were computed for qualitative variables: type of infertility and conception. Chi square test was used to compare the groups.

Survival analysis was performed to evaluate the probability of conceiving in both groups. Curves were compared by means of Mantel-Haenszel log-rank test for categorical variables, which in this case was pregnancy. Analyses were performed using SPSS version 15.0 statistical package (SPSS, Inc.,) with statistical significance denoted by a p-value of less than 0.05.

Our study showed that cervical stenosis existed in 10.7% of women with unexplained subfertility. History of endometriosis, pelvic inflammatory disease, prior surgery and polyps is significantly associated with cervical stenosis.

Cervical dilation in these women leads to better conception rates.

Our study shows the importance of a full assessment of a couple before labelling them as having unexplained subfertility. Around 10.7% women had cervical stenosis and dilation led to conception in 70.54% of them. Another major strength is its case control design and extended follow up.

The major limitation of the study is the fact the single centre design; therefore generalizability of results in other populations needs to be verified with further larger multicentre trials.

Cervical stenosis is typically considered as a factor that may lead to infertility in women who have had surgery for cervical intraepithelial neoplasia (CIN)⁽⁹⁾. However, it can also be a culprit in cases where no such history is present. About 10.7% of women in our study had cervical stenosis, which is almost twice the figure reported in literature⁽²⁾.

Cervical stenosis is defined as a narrowing of the cervical canal, but no standardized diagnostic method is mentioned in literature. A recent study labelled women with stenosis if there was difficulty in passing a 3.5 mm sheath hysteroscope into the internal cervical os. We included women when it was difficult to pass a 7 French Foley’s catheter⁽¹⁰⁾. Foley’s catheter has a smaller softer tip that would theoretically include more women as having stenosis than when using a hysteroscope. We also argue that a hysteroscope is not accessible to all clinicians in outpatient departments and an opportunity would be missed in all such cases if the above criterion is used. A Foley’s catheter is readily available and diagnosis is pretty straightforward with introduction into cervical canal.

A historical study showed that retrograde menstruation occurs when the external os is less than 4.5 mm, which may lead to endometriosis and subfertility⁽¹¹⁾. We would still argue that such a constriction may be notable to the woman and the clinician due to symptoms. If women were assessed for unexplained infertility any such history of retrograde menstruation would be conflicting. Furthermore, a 7 French Foley’s has an outer diameter of 2.33 mm, which is less than both the 3.5 mm hysteroscope and the external os diameter of 4.5 mm. This cut-off needs to be assessed in further studies.

Because cervical stenosis is difficult to suspect and diagnose, many cases may go unnoticed until and unless the cervix is evaluated. This evaluation becomes more pressing in cases with certain risk factors. In their analysis, Moramazi et al. showed a significant correlation with endometriosis, polyps and myomas⁽¹⁰⁾. In our study, prior history of endometriosis, reproductive tract surgery, polyps and pelvic inflammatory disease were significantly associated with cervical stenosis. These findings are in agreement with previous reports^(12,13).

It is important to diagnose and treat cervical stenosis. It hinders sperm deposition in both natural breeding and intrauterine transfers. False passages created during such iatrogenic intervention can be minimized by performing this intervention under ultrasound guidance⁽¹⁴⁾. We performed all dilations under ultrasound guidance. No false passages were created during the study.

Conception can increase after the cervical hindrance to sperm is removed. This has been the essence for adoption of intrauterine insemination in women with cervical factor subfertility⁽¹⁵⁾. Lin et al. demonstrated that cervical resection with hysteroscope in cases of stenosis improved conception at subsequent embryo transfer or intrauterine insemination⁽¹⁶⁾. In our analysis, women conceived spontaneously after dilation, and no intrauterine insemination or IVF was needed. This further cements the observation that cervical stenosis is a clinical entity that can be easily treated and women can conceive without further treatment.

The treatment modalities for unexplained subfertility are currently under scrutiny. Intrauterine insemination, ovulation induction and IVF have all been assessed in trials and currently no consensus exists^(17,18). In our study, a cervical cause was identified and the patients subsequently conceived after receiving dilation. It can be argued that this was not the cause of subfertility in these patients and a stringent protocol may have aided in ascertaining the actual cause. In response we would counter-argue that it may be the case that these women did not have unexplained infertility to begin with. Estimates for natural conception reported from a recent analysis show that women with unexplained subfertility have a 25% chance of conception even without treatment⁽¹⁹⁾. In our study, 70% of women who received dilation conceived compared to only 18% of the controls (who had stenosis defined as per criterion but refused dilation). This observation shows that such dilation is in fact curative and cervical stenosis does lead to subfertility. Natural conception rate of 18% in the control group also shows that in the absence of investigation for cervical factor these women would still have been classified as unexplained group and their conception rate was similar to that reported previously in larger trials⁽¹⁹⁾.