|Year : 2016 | Volume
| Issue : 3 | Page : 717-721
Value of transvaginal cervical ultrasonographic assessment and bacterial vaginosis in prediction of preterm birth
Mohamed M Fahmy, Sherief M.S. Abd El Salam, Mohamed A Emarah, Abeer A El Sobky
Department of Obstetrics and Gynecology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
|Date of Submission||08-Aug-2015|
|Date of Acceptance||01-Oct-2015|
|Date of Web Publication||23-Jan-2017|
Abeer A El Sobky
Department of Obstetrics and Gynecology, Faculty of Medicine, Menoufia University, Menoufia, 32511
Source of Support: None, Conflict of Interest: None
The objective of this study was to determine the diagnostic value of cervical length (CL) measurement, in the second trimester of pregnancy, and the impact of bacterial vaginosis (BV) as a preterm labor (PTL) predictor.
Preterm birth is the leading direct cause of neonatal death and morbidity, and it imposes large costs to the healthcare system. Early detection of pregnant women at risk of PTL will help reduce the occurrence of prematurity-related mortality and morbidity. Cervical insufficiency and BV are two items that have been recently known to have an essential role in preterm delivery. They can be diagnosed using safe, simple, and reliable methods.
Patients and methods
This is a prospective cohort study that included 580 pregnant women with uncomplicated singleton pregnancy between 20 and 22 weeks of gestation to assess CL, which was measured by a transvaginal probe immediately after collecting a vaginal swab for the diagnosis of BV by Amsel's criteria. CL) less than 30 mm was considered a short cervix and suggested cervical insufficiency. The vaginal swab fulfilled three out of four Amsel's criteria and was considered positive for BV. Patients were followed up until delivery.
Our final analysis was based on the results of 500 participants. The incidence of PTL was 100 out of 500 (20%). The incidence of PTL in women who had BV was 52 out of 100 (52%), which is statistically significant. The incidence of PTL in cases with short CL less than and equal to 30 mm was 39 out of 100 (39%), whereas the incidence of short cervix cases in full term was three out of 400 (0.8%), which was statistically significant. The incidence of PTL was 16% for cases with BV and short CL, whereas there were no cases for full-term labor, which is statistically significant (P < 0.001).
The assessment of CL by transvaginal ultrasound and detection of BV during pregnancy have significant value in prediction of PTL.
Keywords: bacterial vaginosis, cervical length measurement, preterm birth, second trimester
|How to cite this article:|
Fahmy MM, Abd El Salam SM, Emarah MA, El Sobky AA. Value of transvaginal cervical ultrasonographic assessment and bacterial vaginosis in prediction of preterm birth. Menoufia Med J 2016;29:717-21
|How to cite this URL:|
Fahmy MM, Abd El Salam SM, Emarah MA, El Sobky AA. Value of transvaginal cervical ultrasonographic assessment and bacterial vaginosis in prediction of preterm birth. Menoufia Med J [serial online] 2016 [cited 2020 Mar 29];29:717-21. Available from: http://www.mmj.eg.net/text.asp?2016/29/3/717/198789
| Introduction|| |
Preterm labor (PTL) is defined as the onset of labor at a gestational age between 20 and 37 weeks of pregnancy. The incidence of preterm birth had gradually increased over the past few decades (from 8.9% in 1980 to 12% in 2002). Preterm premature rupture of the membranes is antecedent to ∼one-third of these births  .
Cervical insufficiency and bacterial vaginosis (BV) are two items that have been recently known to play an essential role in preterm delivery. They can be diagnosed using safe, simple, and reliable methods. These problems are also potentially treatable  .
An increasing risk of preterm birth as cervical length (CL) decreases has been consistently observed in all populations. Short CL at 16-28 weeks is the cervical change best related to the risk of preterm birth, with a particularly strong relationship when it occurs before 24 weeks or in women with a prior preterm birth, especially before 32 weeks  . Reproducible measurement of CL becomes possible at about 14 weeks of gestation, when the cervix normally becomes distinct from the lower uterine segment. The protocol for initiating CL measurements is based on the patient's prior obstetrical history. Women with no prior preterm birth are screened between 18 and 23 weeks of gestation; women with a prior preterm birth are screened beginning at 14-16 weeks of gestation  .
BV represents a complex change in the vaginal flora characterized by a reduction in concentration of the normally dominant hydrogen-peroxide-producing lactobacilli and an increase in concentration of other organisms, especially anaerobic Gram-negative rods  . Pregnant women with BV are at a higher risk of preterm delivery  . The increased risk of preterm birth attributable to BV appears to be linked to PTL due to chorioamnionitis. Spontaneous PTL is mostly found in ∼30-50%, and BV is one of the many causes of PTL. Pregnancy with BV is a higher risk for preterm delivery  . There is an inverse relationship between CL by ultrasound and gestational age at delivery; a high Bishop or cervical score on digital examination is also associated with increased odds of preterm birth  .
Early detection of pregnant women at risk of PTL will help reduce the occurrence of prematurity-related mortality and morbidity  .
This study aims to determine the value of transvaginal cervical ultrasonography examination and the impact of BV in prediction of the risk of preterm birth.
| Patients and methods|| |
This prospective cohort study started with 580 pregnant women who came to the outpatient clinic at Menoufia University Hospital after acceptance of the ethics committee, but 80 cases were discontinued; this study was conducted from March 2011 to December 2013.
The inclusion criteria were as follows:
- Singleton pregnancy
- Gestational age between 20 and 22 weeks.
The exclusion criteria were as follows:
- Multiple pregnancies
- Obstetrical or medical complications in the current pregnancy by medical history, laboratory investigation, and clinical diagnosis:
- Congenital malformation of the fetus
- Current or planned cervical cerclage
- Uterine malformation
- Ante partum hemorrhage
- Sever anemia or diabetes mellitus or hypertension associated with the current pregnancy.
- Symptomatic cases of vaginal discharge or infection.
An oral informed consent was taken from all the patients before examination. All patients were submitted to the following:
- Full history taking
- General examination
- Obstetric examination.
Assessment for both the vaginal swab for BV and transvaginal ultrasound (TVU) for CL was performed at the time of visit at 22-24 weeks of gestation for all included patients, which was performed as follows.
Diagnosis of bacterial vaginosis
We adopted the most accepted clinical criteria for the diagnosis of BV - 'Amsel's criteria' - as reported by Neelam and Sohail  . A high posterior vaginal swab was collected using nonlubricated sterile vaginal speculum to be examined for 'Amsel's criteria'. BV was diagnosed when three out of four criteria were fulfilled:
- Homogeneous thin milk-like vaginal discharge
- Positive whiff test
- Presence of clue cells under a microscope
- pH greater than 4.5 (normal vaginal pH 3.8-4.2).
All diagnosed cases that were positive for BV as recommended by ethics committee were treated with metronidazole 250 mg three times daily for 7 days.
Examination of cervical length
Empty bladder sonographic examination was performed by endovaginal probe with patients in lithotomy position (5 MHz with Sonata Plus; Mindray, Shenzhen, China); we followed the guidelines for the performance of TVU of the cervix by Berghella et al.  . A CL of 30 mm (the threshold for the fifth percentile) or less was considered short and suggestive of cervical insufficiency. In all cases, the measurement was the mean of three different measurements taken in quick succession.
All patients were followed up at the outpatient clinic through regular routine antenatal visits monthly; at each visit, maternal vital signs were reviewed and abdominal ultrasound was performed for assessment of fetal well-being.
Patients at gestational age from 28 up to 36 weeks were advised to regular antenatal visits every 2 weeks and were instructed to return back in the presence of symptoms of PTL such as regular painful uterine contractions or in case of passage of liquor or vaginal bleeding.
All patients were followed up until delivery, and hospital records were reviewed to obtain the obstetric information.
The clinical and laboratory results obtained are statistically analyzed using statistical package for the social sciences (SPSS, version 19; SPSS Inc., Chicago, Illinois, USA). χ2 -Test and t-test were used for comparing results. P value less than 0.05 was considered statistically significant, and a P value less than 0.001 was considered highly statistically significant.
| Results|| |
This prospective cohort study was conducted at Al Menoufia Hospital; our final analysis was based on results for 500 pregnant women in the second trimester at a gestational age from 20 to 22 weeks of pregnancy.
Our final results showed that the incidence of PTL was 100 out of 500 (20%) women. The incidence of PTL in women with BV was 52 out of 100 (52%), whereas the full-term cases who had BV were 49 out 400 (12.3%), which is statistically significant (P < 0.001), as shown in [Table 1]. The incidence of PTL in cases with short CL less than and equal to 30 mm was 39 out of 100 (39%), whereas the incidence of full-term labor in cases with short cervix was three out of 400 (0.8%); the CL is significantly lower in PTL cases than in full-term cases (P < 0.001), as shown in [Table 2]. The incidence of PTL and the presence of both short CL plus positive BV were 16 out 100 (16%) of the PTL, whereas no cases were found among the full-term cases, which is highly statistically significant (P < 0.001), as shown in [Table 3].
|Table 3 Relation between cervical length plus bacterial vaginosis and time of delivery/week |
Click here to view
| Discussion|| |
Preterm birth is the leading direct cause of neonatal death (death in the first 28 days of life). It is responsible for 27% of neonatal deaths worldwide, comprising over one million deaths annually. The risk of neonatal mortality decreases as gestational age at birth increases, but the relationship is nonlinear  . PTL is still the major cause of perinatal morbidity and mortality. Around 30% of threatened PTL cases were PTLs  .
Cervical assessment by ultrasound has been correlated with the prediction of spontaneous preterm birth  . There are three methods of ultrasound cervical assessment: transvaginal, transabdominal, and transperineal (also called translabial). The most objective and effective ultrasound method is TVU  .
BV is the most common lower genital tract disorder among women of reproductive age  . Pregnant women with BV are at a higher risk of preterm delivery  .
In our study, it was found that 52% of PTL patients were positive for BV, whereas 12.3% of patients who had a full-term labor were positive for BV, which is statistically significant; these results are in agreement with the study of Hassan et al.  , which was conducted in Basrah Maternity and Children Hospital to assess the association between BV and PTL and to compare it with those who delivered at term. It was a prospective case-control study that was carried out over a 9-month period. This study has confirmed that Gardnerella vaginalis was the most common bacterial pathogen isolated from women with PTL; it was detected in 17 out of 72 (23.6%) women with PTL in comparison with two of 107 (1.9%) women who delivered at term (P < 0.01). Therefore, it can be concluded that BV was detected in a significant number of women with preterm delivery.
This is in agreement with several other authors such as Leitich et al.  , who conducted a case-control study that reported the percentage of BV in PTL to be significantly higher than in term labor.
Finally, Kalemaj et al.  in his prospective study showed that the diagnosis of BV was made according to Amsel's criteria. The prevalence of BV was 32%, whereas in the control group the figure was 14.6% (P = 0.01), which showed a significant correlation between BV and PTL.
On the other hand, the results of our study disagree with the study of Figueroa et al.  , conducted in the University of Alabama at Birmingham, in which it was estimated whether BV, as defined by either Nugent score or vaginal pH, predicts gestational age at delivery in women at risk for recurrent preterm birth. The number of studied cases was 768 women between 16 and 22 weeks of gestation. The prevalence of BV by Nugent score was 11% and by pH it was 33%, and it was not associated with earlier birth. Therefore, the study concluded that the presence of BV at 16-22 weeks of gestation does not predict preterm birth in the study group. This disagreement may be because of the lack of knowledge regarding symptomatic BV treatment, the study design, the selected group of patients in the gestational age group, and laboratory method of diagnosis.
As regards the CL in prediction of PTL, our study showed the following results: the CL is significantly lower in cases of PTL than in cases of full-term labor. The CL measurements of threatened PTL cases were significantly short. The study showed the validity of CL in prediction of preterm birth among the studied group, and showed a new cutoff point of CL, which was 32.2 mm. Our results were in agreement with the study of Kagan et al.  , which was conducted in King's College Hospital, London, UK, who estimated the value of sonographic measurement of CL by TVU at ∼20 weeks of gestation in women attending for routine antenatal care and showed that it is useful for predicting the likelihood of spontaneous early preterm birth. In addition, the study concluded that the TVU scanning of CL is highly reproducible and is acceptable to women. Routine measurement of CL at 20-24 weeks of gestation provides a sensitive prediction of preterm birth. The risk of such preterm birth increases exponentially with decreasing CL.
In addition, our results were in agreement with the studies published by Visintine et al.  and Crane and Hutchens  , who concluded that the measurement of CL provides prediction of risk for early preterm delivery.
Our study showed the relation between occurrence of PTL and the presence of both short CL plus positive BV, and found that 16% of the PTL cases had a combination of the two factors, whereas no cases were found between full-term cases, which is highly statistically significant (P < 0.001).
In agreement with the current results, the study conducted by Mancuso et al.  and Matijevic et al.  reported that a high vaginal pH value and a shortened CL measurement on ultrasound were both significantly correlated with PTL in that low-risk population.
There are other studies that are in agreement with our study on some points, such as the study conducted by Surbek et al.  in University of Basel, Switzerland. It was an observational study in 112 pregnant patients between 24 and 34 weeks of gestation admitted with symptoms of PTL in which measurement of CL was performed by TVU and diagnosis of BV was conducted by Gram stain and treated with systemic metronidazole. The final conclusion of the study was that cervical change in patients with PTL is more pronounced in BV, but without a concomitant increase in the risk for preterm delivery. Despite this association, the CL measured by TVU alone is a useful predictor of preterm delivery, independent of the presence or absence of BV. This difference between the two studies may be because of the difference in the study design, the selected group of patients, and the gestational age group.
| Conclusion|| |
From our study, we can conclude that assessment of CL by TVU and BV during pregnancy can help in prediction of PTL.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]