http://informahealthcare.com/jmf ISSN: 1476-7058 (print), 1476-4954 (electronic) J Matern Fetal Neonatal Med, Early Online: 1–5 ! 2014 Informa UK Ltd. DOI: 10.3109/14767058.2014.947474
ORIGINAL ARTICLE
Salivary progesterone and cervical length measurement as predictors of spontaneous preterm birth Ahmed M. Maged1, Mohamed Mohesen2, Ahmed Elhalwagy1, and Ali Abdelhafiz1 J Matern Fetal Neonatal Med Downloaded from informahealthcare.com by University of Guelph on 08/18/14 For personal use only.
1
Obstetrics and Gynecology Department, Kasr AlAini Hospital, Cairo University, Cairo, Egypt and 2Obstetrics and Gynecology Department, Benisuef Hospital, Beni-Suef University, Benisuef, Egypt Abstract
Keywords
Objective: To evaluate the efficacy of salivary progesterone, cervical length measurement in predicting preterm birth (PTB). Methods: Prospective observational study included 240 pregnant women with gestational age (GA) 26–34 weeks classified into two equal groups; group one are high risk for PTB (those with symptoms of uterine contractions or history of one or more spontaneous preterm delivery or second trimester abortion) and group 2 are controls. Results: There was a highly significant difference between the two study groups regarding GA at delivery (31.3 ± 3.75 in high risk versus 38.5 ± 1.3 in control), cervical length measured by transvaginal ultrasound (24.7 ± 8.6 in high risk versus 40.1 ± 4.67 in control) and salivary progesterone level (728.9 ± 222.3 in high risk versus 1099.9 ± 189.4 in control; p50.001). There was a statistically significant difference between levels of salivary progesterone at different GA among the high risk group (p value 0.035) but not in low risk group (p value 0.492). CL measurement showed a sensitivity of 71.5% with 100% specificity, 100% PPV, 69.97% NPV and accuracy of 83%, while salivary progesterone showed a sensitivity of 84% with 90% specificity, 89.8% PPV, 85.9% NPV and accuracy of 92.2%. Conclusion: The measurement of both salivary progesterone and cervical length are good predictors for development of PTB.
Cervical length, preterm birth, salivary progesterone
Introduction According to the WHO, a preterm birth (PTB) is any birth that occurs up to 37 weeks’ gestation [1]. About 40% of PTBs follow idiopathic preterm labor, 35% follow preterm prelabor rupture of membranes and the remainders are iatrogenic because of obstetric or medical indications [2]. PTB affects approximately 12.9 million babies worldwide every year, representing an incidence of PTB of 9.6%, with 85% of all PTBs occurring in Africa and Asia [3]. The early detection of preterm labor or preterm rupture of membranes in traditional antenatal care is often problematic because symptoms or signs may vary only a little from the normal physiologic symptoms and signs of pregnancy [4]. As of early 2005, only two tests have received approval by the FDA as predictor markers for preterm labor: fetal fibronectin (Adeza Biomedical, Sunnyvale, CA) and salivary estriol (Salest, Biex, Dublin, CA) [5]. Progesterone is essential for the maintenance of pregnancy [6].
History Received 12 January 2014 Revised 11 July 2014 Accepted 19 July 2014 Published online 13 August 2014
Concentration of the progesterone in saliva reflects the unbound, unconjugated and therefore the biologically active fraction of the plasma hormone level profile. As saliva specimens are easy to collect and store, measurement of saliva hormone levels can be readily introduced into clinical practice when found to be of value [7]. There is a marked increase in the saliva oestriol (E3) concentration and the saliva E3 to progesterone ratio before term labor and in symptomatic women who deliver preterm [7]. The measurement of saliva progesterone may be of value in the prediction of early preterm labor and in determining which women might benefit from progesterone supplementation [6]. The work of the National Institute of Child Health and Human Development Maternal–fetal Medicine Unit Network has shown a short cervix (525 mm) to be significantly more common in high-risk women [8]. The primary aim of our study is to evaluate the efficacy of salivary progesterone, cervical length measurement and combining both in predicting PTB.
Material and methods Address for correspondence: Ahmed Mohamed Maged, 135 King Faisal Street, Haram, Giza, Egypt. Tel: 01005227404. Fax: 35873103. E-mail: [email protected]
This prospective observational study was conducted at Kasr El Aini and Beni Suef University Hospitals, Egypt, in the
J Matern Fetal Neonatal Med Downloaded from informahealthcare.com by University of Guelph on 08/18/14 For personal use only.
2
A. M. Maged et al.
period from September 2011 to May 2013. Informed written consent was obtained from 240 pregnant women attending the obstetric outpatient clinic. Eligible participants were pregnant women between 26 and 34 weeks with a singleton living fetus. Gestational age (GA) was calculated based on regular last normal menstrual period then confirmed by ultrasound. Exclusion criteria included maternal medical problems as preeclampsia, those using tocolytic drugs or medications known to affect hormonal levels as antidepressants, steroids and progesterone, women with uterine or cervical abnormalities, rupture of membranes or oral problems interfering with saliva collection as bleeding gums. Pregnancies with evidence of fetal anomalies, intrauterine growth restriction or abruption placenta were also excluded. Participants were classified into two groups: group I included 120 women complaining of symptoms of uterine contractions or history of one or more spontaneous preterm delivery before 37 weeks or second trimester abortion and group II included 120 healthy women as control. During the first antenatal care visit, full history taking was obtained. Special concerns about age, parity and full detailed obstetric history about previous miscarriages and deliveries were obtained. Weight and height were measured, and body mass index (BMI) was calculated as weight in kilograms divided by height in meters squared. Full general, abdominal and vaginal examinations to evaluate cervical conditions were performed. The ultrasound examination was performed using an Accuvix (Medison Co., Ltd., Seoul, Korea) machine equipped with a 4–7 MHz transabdominal (3D4–7EK), a 5–8MHz transvaginal (3D5–8EK) probe. Transabdominal ultrasound was done to ensure absence of any of exclusion criteria. Transvaginal ultrasound was done for measurement of cervical length with the patient lying in dorsal lithotomy position with transvaginal probe placed in the anterior fornix after patients evacuated the bladder, and then a saggital view of the cervix was obtained with echogenic end cervical mucosa being used to measure the distance between the external and internal os. Fundal pressure was applied for 30 s by the sonologist as a provocative maneuver to detect spontaneously occurring cervical shortening. It was considered that patients with cervical length of 30 mm or less are high risk to preterm labor [9]. Women were instructed to collect 2–3 ml saliva between 9 AM and 8 PM (to avoid diurnal variation) without salivary stimulus, patients were instructed to rinse the mouth with water, wait for 10 min and allow saliva to run freely into standard plastic jars, samples were kept cold to avoid bacterial growth, and then samples were refrigerated after collection within 30 min and frozen at or below –20 C within 4 h of collection. Precautions included avoiding the use of salivary stimulus as, Salivettes, the Salimetrics Oral Swab, Sorbettes, cotton or polyester materials [10] and avoiding sample collection within 60 min after eating a major meal. Enzyme immunoassay for the in vitro diagnostic quantitative measurement of active free progesterone in saliva. Progesterone was measured using electrochemiluminescence immune assay on cobas e immunoassay analyzer using kits supplied by Roche (Roche Diagnostics GmbH, Sandhofer Strasse 116, D-68305 Mannheim).
J Matern Fetal Neonatal Med, Early Online: 1–5
Statistical analysis Data were statistically described in terms of mean ± standard deviation (± SD), median and range or frequencies (number of cases) and percentages when appropriate. Comparison of numerical variables between the study groups was done using Student t test for independent samples. For comparing categorical data, Chi square (v2) test was performed. Exact test was used instead when the expected frequency is less than five. Accuracy was represented using the terms sensitivity, specificity, positive predictive value, negative predictive value and overall accuracy. Receiver operator characteristic analysis was used to determine the optimum cut off value for the studied diagnostic markers (Figure 4). p values less than 0.05 was considered statistically significant. All statistical calculations were done using computer programs SPSS (Statistical Package for the Social Science; SPSS Inc., Chicago, IL) version 17 for Microsoft Windows.
Results The 240 participants were classified into two groups: group I (high-risk group) included 120 women complaining of symptoms of uterine contractions or history of one or more spontaneous preterm delivery before 37 weeks or second trimester abortion, 13 of them were lost during follow-up period and 107 were analyzed, and group II (low risk group) included 120 healthy women as control, 16 of them were lost during follow-up period and 104 were analyzed. There was no significant difference between the two study groups regarding maternal age, parity, BMI and GA at screening (Table 1). There was a highly significant difference between the two study groups regarding GA at delivery (p50.001) being earlier in high risk group (Table 1). There was a highly significant difference between the two study groups regarding cervical length measured by transvaginal ultrasound (p50.001) being shorter in high risk group (Table 1). There was a highly significant difference between the two study groups regarding salivary progesterone level (p50.001) being lower in high-risk group (Table 1). Our study showed a statistically significant difference between levels of salivary progesterone at different GA among the high risk group (p value 0.035) but not in low risk group (p value 0.492; Table 2). There was a highly significant correlation between level of salivary progesterone and the GA, and there was no
Table 1. Demographic data, GA at study and delivery and predictors distribution among study population.
Age (years) Parity BMI (kg/m2) GA at screening (weeks) GA at delivery (weeks) Cervical length (mm) Salivary P level (pg/ml)
High-risk group
Low-risk group
p value
27.6 ± 4.7 1.7 ± 1.2 27.9 ± 2.5 28.1 ± 0.98 31.3 ± 3.75 24.7 ± 8.6 728.9 ± 222.3
26.7 ± 4.3 1.8 ± 0.9 27.8 ± 2.6 27.3 ± 0.98 38.5 ± 1.3 40.1 ± 4.76 1099.9 ± 189.4
40.05 40.05 40.05 40.05 50.001 50.001 50.001
Data presented as mean ± SD. BMI: body mass index; GA: gestational age; and P: progesterone.
Preterm labor prediction
DOI: 10.3109/14767058.2014.947474
Table 2. Salivary progesterone levels among study population. Progesterone
Low-risk group
ANOVA
Range
Mean ± SD
f
p value
30 31 32 33 34 31 32 33 34
270.5–867.0 557.0–868.9 629.4–1010.0 541.0–1152.0 657.0–1100.0 947.0–979.8 881.6–1170.0 754.0–1216.0 618.1–1572.0
601.60 ± 310.40 751.97 ± 169.96 798.44 ± 141.20 859.84 ± 173.47 889.68 ± 140.05 963.40 ± 23.19 1049.49 ± 101.38 1061.22 ± 129.65 1124.06 ± 233.10
2.920
0.035*
0.820
2.5 2.0
.5 0.0 -.5 200
400
600
800
1000
1200
Prog.
P-value=0.721
Figure 2. Shows correlation coefficient between progesterone and parity accuracy of progesterone between cases and control as regard Prog. *Values distribution.
30 Age
J Matern Fetal Neonatal Med Downloaded from informahealthcare.com by University of Guelph on 08/18/14 For personal use only.
r =0.058
1.5 1.0
0.492
*Statistically significant difference.
40
P-value=0.873
3.0
GA
Parity
High-risk group
r=−0.026
3.5
3
Table 3. Correlation coefficient between progesterone level, age, GA and parity.
20
Prog.
10 200
400
600
800
1000
1200
Prog.
Cases
R
p value
Significance
Age GA Parity
0.058 0.271 0.026
0.721 0.095 0.873
N/S H/S N/S
Figure 1. Shows correlation coefficient between progesterone and age. *Values distribution. Table 4. Showing sensitivity, specificity and accuracy and predictive value of predictors.
Cervical length Salivary progesterone Combined (any is positive)
Cut off
Sensitivity
Specificity
PPV
NPV
Accuracy
30 mm 933.6 (pg/ml)
71.5 84 100
100.00 90.00 100
100.00 89.8 100
69.97 85.9 100
83.00 92.2 100
significant correlation between level of salivary progesterone with age (Figure 1) and parity (Figure 2; Table 3). Salivary progesterone had higher sensitivity and accuracy than ultrasonographic measured cervical length (Table 4). Combining measurement of salivary progesterone and cervical length measurement gives perfect sensitivity, specificity and accuracy in predicting PTB (Table 4; Figure 3).
Discussion Measurement of both salivary progesterone at a cutoff value of 933.6 (pg/ml) and cervical length at a cutoff value of 30 mm are good predictors for development of preterm labor and help identifying women at risk for development of PTB. In our study, there was a highly significant difference between the high risk and low risk study groups regarding salivary progesterone level (729.2 ± 223.3 versus 1097.9 ± 180.283, respectively).
That finding appears logic as progesterone is essential for maintenance of pregnancy. It promotes uterine relaxation by suppressing the formation of gap junction, reducing prostaglandin synthesis and the concentration of oxytocin receptors in the myometrium. Progesterone also increases cellular calcium-binding capacity and it also has anti inflammatory properties, lower than normal progesterone status, preterm labor could contribute to an exaggerated response to bacterial invasion [6]. Our study showed a highly significant difference between the high-risk and low-risk study groups regarding cervical length measured by transvaginal ultrasound (24.45 ± 8.43 versus 42.94 ± 4.76, respectively). Priya et al. in their prospective study evaluated salivary progesterone as a predictor of early PTB and compared it with transvaginal sonographic (TVS) cervical length in asymptomatic high-risk women. They found that the mean value of salivary progesterone was significantly lower in all women
4
A. M. Maged et al.
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who delivered at 537 weeks of gestation (n ¼ 38), compared with the term group (n ¼ 52; p50.001) [11]. Salivary progesterone decreased significantly from the first to the second visit, with the maximum decrease observed in women who delivered at 534 weeks of gestation (29.6%, 95% CI: 17.8–41.4%, p50.002). The single predictive critical cut-off value for salivary progesterone was 2575 pg/ml, below which more than 80% of women delivered prematurely before 34 weeks of gestation, with sensitivity, specificity and positive and negative predictive values of 83% (95% CI: 58.6–96.4%), 86% (95% CI: 75.9–93.1%), 60% (95% CI: 38.6–78.8%) and 95% (95% CI: 87.1–99.0%), respectively. The TVS cervical
Figure 3. Accuracy (area under ROC curve) of prog. Acceptable discriminative and predictive ability of prog. between cases and control by the area under the ROC curve (the distance between the curve and diagonal) or accuracy of 0.9.
Figure 4. Cut off value of prog. by sensitivity and specificity of cases and control.
J Matern Fetal Neonatal Med, Early Online: 1–5
length decreased significantly (p50.001) in the women who delivered prematurely [11]. They concluded that low salivary progesterone concentration can be used for predicting early PTB in asymptomatic high-risk women [11]. Our study showed a highly significant difference between the high-risk and low-risk study groups regarding cervical length measured by transvaginal ultrasound (24.45 ± 8.43 versus 42.94 ± 4.76, respectively). Sotiriadi et al. in 2010 reviewed 28 studies fulfilled the selection criteria. For birth within one week from presentation, the pooled sensitivity, specificity, LR+ and LR of cervical length 515 mm were 59.9% (95% CI: 52.7–66.8%), 90.5% (95% CI: 89.0–91.9%), 5.71 (95% CI: 3.77–8.65) and 0.51 (95% CI: 0.33–0.80), respectively. The same estimates for studies with presentation at or before 34 + weeks were 71.0% (95% CI: 60.6–79.9%), 89.8% (95% CI: 87.4–91.9%), 5.19 (95% CI: 2.29–11.74 and 0.38 (95% CI: 0.11–1.34), respectively [12]. For prediction of birth before 34 weeks, the pooled sensitivity, specificity, LR+ and LR of cervical length 515 mm were 46.2% (95% CI: 34.8–57.8%), 93.7% (95% CI: 90.7–96.0%), 4.31 (95% CI: 2.73–6.82) and 0.63 (95% CI: 0.38–1.04), respectively. They concluded that measurement of cervical length in symptomatic women can detect a significant proportion of those who will deliver within one week and help to rationalize their management [12]. Our study showed a statistically significant difference between levels of salivary progesterone at different GA among the high-risk group but not in low-risk group. We found a highly significant correlation between level of salivary progesterone and the GA but no significant correlation between level of salivary progesterone with age and parity. Our study found that salivary progesterone had higher sensitivity and accuracy than ultrasonographic measured cervical length in predicting PTB. Combining measurement of salivary progesterone and cervical length measurement
Preterm labor prediction
DOI: 10.3109/14767058.2014.947474
gives ideal sensitivity, specificity and accuracy in predicting PTB. Our study is unique among previous studies as it used easy, non invasive and non painful measurement with proper sample size and reached the gold standard of prediction of PTB when combining salivary P and CL measurement. We concluded that measurement of both salivary progesterone and cervical length are good predictors and combining them together could be the gold standard for development of preterm labor.
5. 6. 7.
8.
Declaration of interest The authors declare no conflicts of interest.
9.
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References 1. World Health Organization. The incidence of low birth weight: a critical review of available information. World Health Stat Q 1980; 33:197–224. 2. Iams JD. Preterm birth. In: Gabbe SG, Niebyl JR, Simpson JL, eds. Obstetrics: normal and problem pregnancies. 4th ed. Philadelphia: Churchill Livingstone; 2002:755–826. 3. Beck S, Wojdyla D, Say L, et al. The worldwide incidence of preterm birth: a systematic review of maternal mortality and morbidity. Bull World Health Organ 2010;88:31–8. 4. James DK, Steer PJ, Weiner CP, Gonik B. Screening for spontaneous preterm labor and delivery. In high risk pregnancy
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5
management options. 3rd ed. Philadelphia (PA): Elsevier Saunders; 2006. Chapter 61:1881–95. Ascarelli MH, Morrison JC. Use of fetal fibronectin in clinical practice. Obstet Gynecol Surv 1997;53:S1–12. Lachelin GC, McGarrigle HH, Seed PT, et al. Low saliva progesterone concentrations are associated with spontaneous early preterm labour. BJOG 2009;116:1515–19. Darne J, McGarrigle HH, Lachelin GC. Increased saliva oestriol to progesterone ratio before preterm delivery: a possible predictor for preterm labor? Br Med J (Clin Res Ed) 1987;294:270–2. Goldenberg RL, Iams JD, Das A, et al. The preterm prediction study: sequential cervical length and fetal fibronectin testing for the prediction of spontaneous preterm birth. Am J Obstet Gynecol 2000;182:636–43. Anderson HF. Ultrasound evaluation of the cervix and value of cervical cerclage. In: Elder MG, Romeo R, Lamont RF, eds. Preterm labor. Edinburgh: Churchill Livingstone; 1997: 165–84. Shirtcliff EA, Granger DA, Schwartz E, Curran MJ. Use of salivary biomarkers in biobehavioral research: cotton-based sample collection methods can interfere with salivary immunoassay results. Psychoneuroendocrinology 2001;26:165–73. Priya B, Mustafa MD, Guleria K, et al. Salivary progesterone as a biochemical marker to predict early preterm birth in asymptomatic high-risk women. BJOG 2013;120:1003–11. Sotiriadis A, Papatheodorou S, Kavadias A, Makrydimas G. Transvaginal cervical length measurement for prediction of preterm birth in women with threatened preterm labor: a meta-analysis. Ultrasound Obstet Gynecol 2010;35:54–64.
ORIGINAL ARTICLE
Salivary progesterone and cervical length measurement as predictors of spontaneous preterm birth Ahmed M. Maged1, Mohamed Mohesen2, Ahmed Elhalwagy1, and Ali Abdelhafiz1 J Matern Fetal Neonatal Med Downloaded from informahealthcare.com by University of Guelph on 08/18/14 For personal use only.
1
Obstetrics and Gynecology Department, Kasr AlAini Hospital, Cairo University, Cairo, Egypt and 2Obstetrics and Gynecology Department, Benisuef Hospital, Beni-Suef University, Benisuef, Egypt Abstract
Keywords
Objective: To evaluate the efficacy of salivary progesterone, cervical length measurement in predicting preterm birth (PTB). Methods: Prospective observational study included 240 pregnant women with gestational age (GA) 26–34 weeks classified into two equal groups; group one are high risk for PTB (those with symptoms of uterine contractions or history of one or more spontaneous preterm delivery or second trimester abortion) and group 2 are controls. Results: There was a highly significant difference between the two study groups regarding GA at delivery (31.3 ± 3.75 in high risk versus 38.5 ± 1.3 in control), cervical length measured by transvaginal ultrasound (24.7 ± 8.6 in high risk versus 40.1 ± 4.67 in control) and salivary progesterone level (728.9 ± 222.3 in high risk versus 1099.9 ± 189.4 in control; p50.001). There was a statistically significant difference between levels of salivary progesterone at different GA among the high risk group (p value 0.035) but not in low risk group (p value 0.492). CL measurement showed a sensitivity of 71.5% with 100% specificity, 100% PPV, 69.97% NPV and accuracy of 83%, while salivary progesterone showed a sensitivity of 84% with 90% specificity, 89.8% PPV, 85.9% NPV and accuracy of 92.2%. Conclusion: The measurement of both salivary progesterone and cervical length are good predictors for development of PTB.
Cervical length, preterm birth, salivary progesterone
Introduction According to the WHO, a preterm birth (PTB) is any birth that occurs up to 37 weeks’ gestation [1]. About 40% of PTBs follow idiopathic preterm labor, 35% follow preterm prelabor rupture of membranes and the remainders are iatrogenic because of obstetric or medical indications [2]. PTB affects approximately 12.9 million babies worldwide every year, representing an incidence of PTB of 9.6%, with 85% of all PTBs occurring in Africa and Asia [3]. The early detection of preterm labor or preterm rupture of membranes in traditional antenatal care is often problematic because symptoms or signs may vary only a little from the normal physiologic symptoms and signs of pregnancy [4]. As of early 2005, only two tests have received approval by the FDA as predictor markers for preterm labor: fetal fibronectin (Adeza Biomedical, Sunnyvale, CA) and salivary estriol (Salest, Biex, Dublin, CA) [5]. Progesterone is essential for the maintenance of pregnancy [6].
History Received 12 January 2014 Revised 11 July 2014 Accepted 19 July 2014 Published online 13 August 2014
Concentration of the progesterone in saliva reflects the unbound, unconjugated and therefore the biologically active fraction of the plasma hormone level profile. As saliva specimens are easy to collect and store, measurement of saliva hormone levels can be readily introduced into clinical practice when found to be of value [7]. There is a marked increase in the saliva oestriol (E3) concentration and the saliva E3 to progesterone ratio before term labor and in symptomatic women who deliver preterm [7]. The measurement of saliva progesterone may be of value in the prediction of early preterm labor and in determining which women might benefit from progesterone supplementation [6]. The work of the National Institute of Child Health and Human Development Maternal–fetal Medicine Unit Network has shown a short cervix (525 mm) to be significantly more common in high-risk women [8]. The primary aim of our study is to evaluate the efficacy of salivary progesterone, cervical length measurement and combining both in predicting PTB.
Material and methods Address for correspondence: Ahmed Mohamed Maged, 135 King Faisal Street, Haram, Giza, Egypt. Tel: 01005227404. Fax: 35873103. E-mail: [email protected]
This prospective observational study was conducted at Kasr El Aini and Beni Suef University Hospitals, Egypt, in the
J Matern Fetal Neonatal Med Downloaded from informahealthcare.com by University of Guelph on 08/18/14 For personal use only.
2
A. M. Maged et al.
period from September 2011 to May 2013. Informed written consent was obtained from 240 pregnant women attending the obstetric outpatient clinic. Eligible participants were pregnant women between 26 and 34 weeks with a singleton living fetus. Gestational age (GA) was calculated based on regular last normal menstrual period then confirmed by ultrasound. Exclusion criteria included maternal medical problems as preeclampsia, those using tocolytic drugs or medications known to affect hormonal levels as antidepressants, steroids and progesterone, women with uterine or cervical abnormalities, rupture of membranes or oral problems interfering with saliva collection as bleeding gums. Pregnancies with evidence of fetal anomalies, intrauterine growth restriction or abruption placenta were also excluded. Participants were classified into two groups: group I included 120 women complaining of symptoms of uterine contractions or history of one or more spontaneous preterm delivery before 37 weeks or second trimester abortion and group II included 120 healthy women as control. During the first antenatal care visit, full history taking was obtained. Special concerns about age, parity and full detailed obstetric history about previous miscarriages and deliveries were obtained. Weight and height were measured, and body mass index (BMI) was calculated as weight in kilograms divided by height in meters squared. Full general, abdominal and vaginal examinations to evaluate cervical conditions were performed. The ultrasound examination was performed using an Accuvix (Medison Co., Ltd., Seoul, Korea) machine equipped with a 4–7 MHz transabdominal (3D4–7EK), a 5–8MHz transvaginal (3D5–8EK) probe. Transabdominal ultrasound was done to ensure absence of any of exclusion criteria. Transvaginal ultrasound was done for measurement of cervical length with the patient lying in dorsal lithotomy position with transvaginal probe placed in the anterior fornix after patients evacuated the bladder, and then a saggital view of the cervix was obtained with echogenic end cervical mucosa being used to measure the distance between the external and internal os. Fundal pressure was applied for 30 s by the sonologist as a provocative maneuver to detect spontaneously occurring cervical shortening. It was considered that patients with cervical length of 30 mm or less are high risk to preterm labor [9]. Women were instructed to collect 2–3 ml saliva between 9 AM and 8 PM (to avoid diurnal variation) without salivary stimulus, patients were instructed to rinse the mouth with water, wait for 10 min and allow saliva to run freely into standard plastic jars, samples were kept cold to avoid bacterial growth, and then samples were refrigerated after collection within 30 min and frozen at or below –20 C within 4 h of collection. Precautions included avoiding the use of salivary stimulus as, Salivettes, the Salimetrics Oral Swab, Sorbettes, cotton or polyester materials [10] and avoiding sample collection within 60 min after eating a major meal. Enzyme immunoassay for the in vitro diagnostic quantitative measurement of active free progesterone in saliva. Progesterone was measured using electrochemiluminescence immune assay on cobas e immunoassay analyzer using kits supplied by Roche (Roche Diagnostics GmbH, Sandhofer Strasse 116, D-68305 Mannheim).
J Matern Fetal Neonatal Med, Early Online: 1–5
Statistical analysis Data were statistically described in terms of mean ± standard deviation (± SD), median and range or frequencies (number of cases) and percentages when appropriate. Comparison of numerical variables between the study groups was done using Student t test for independent samples. For comparing categorical data, Chi square (v2) test was performed. Exact test was used instead when the expected frequency is less than five. Accuracy was represented using the terms sensitivity, specificity, positive predictive value, negative predictive value and overall accuracy. Receiver operator characteristic analysis was used to determine the optimum cut off value for the studied diagnostic markers (Figure 4). p values less than 0.05 was considered statistically significant. All statistical calculations were done using computer programs SPSS (Statistical Package for the Social Science; SPSS Inc., Chicago, IL) version 17 for Microsoft Windows.
Results The 240 participants were classified into two groups: group I (high-risk group) included 120 women complaining of symptoms of uterine contractions or history of one or more spontaneous preterm delivery before 37 weeks or second trimester abortion, 13 of them were lost during follow-up period and 107 were analyzed, and group II (low risk group) included 120 healthy women as control, 16 of them were lost during follow-up period and 104 were analyzed. There was no significant difference between the two study groups regarding maternal age, parity, BMI and GA at screening (Table 1). There was a highly significant difference between the two study groups regarding GA at delivery (p50.001) being earlier in high risk group (Table 1). There was a highly significant difference between the two study groups regarding cervical length measured by transvaginal ultrasound (p50.001) being shorter in high risk group (Table 1). There was a highly significant difference between the two study groups regarding salivary progesterone level (p50.001) being lower in high-risk group (Table 1). Our study showed a statistically significant difference between levels of salivary progesterone at different GA among the high risk group (p value 0.035) but not in low risk group (p value 0.492; Table 2). There was a highly significant correlation between level of salivary progesterone and the GA, and there was no
Table 1. Demographic data, GA at study and delivery and predictors distribution among study population.
Age (years) Parity BMI (kg/m2) GA at screening (weeks) GA at delivery (weeks) Cervical length (mm) Salivary P level (pg/ml)
High-risk group
Low-risk group
p value
27.6 ± 4.7 1.7 ± 1.2 27.9 ± 2.5 28.1 ± 0.98 31.3 ± 3.75 24.7 ± 8.6 728.9 ± 222.3
26.7 ± 4.3 1.8 ± 0.9 27.8 ± 2.6 27.3 ± 0.98 38.5 ± 1.3 40.1 ± 4.76 1099.9 ± 189.4
40.05 40.05 40.05 40.05 50.001 50.001 50.001
Data presented as mean ± SD. BMI: body mass index; GA: gestational age; and P: progesterone.
Preterm labor prediction
DOI: 10.3109/14767058.2014.947474
Table 2. Salivary progesterone levels among study population. Progesterone
Low-risk group
ANOVA
Range
Mean ± SD
f
p value
30 31 32 33 34 31 32 33 34
270.5–867.0 557.0–868.9 629.4–1010.0 541.0–1152.0 657.0–1100.0 947.0–979.8 881.6–1170.0 754.0–1216.0 618.1–1572.0
601.60 ± 310.40 751.97 ± 169.96 798.44 ± 141.20 859.84 ± 173.47 889.68 ± 140.05 963.40 ± 23.19 1049.49 ± 101.38 1061.22 ± 129.65 1124.06 ± 233.10
2.920
0.035*
0.820
2.5 2.0
.5 0.0 -.5 200
400
600
800
1000
1200
Prog.
P-value=0.721
Figure 2. Shows correlation coefficient between progesterone and parity accuracy of progesterone between cases and control as regard Prog. *Values distribution.
30 Age
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r =0.058
1.5 1.0
0.492
*Statistically significant difference.
40
P-value=0.873
3.0
GA
Parity
High-risk group
r=−0.026
3.5
3
Table 3. Correlation coefficient between progesterone level, age, GA and parity.
20
Prog.
10 200
400
600
800
1000
1200
Prog.
Cases
R
p value
Significance
Age GA Parity
0.058 0.271 0.026
0.721 0.095 0.873
N/S H/S N/S
Figure 1. Shows correlation coefficient between progesterone and age. *Values distribution. Table 4. Showing sensitivity, specificity and accuracy and predictive value of predictors.
Cervical length Salivary progesterone Combined (any is positive)
Cut off
Sensitivity
Specificity
PPV
NPV
Accuracy
30 mm 933.6 (pg/ml)
71.5 84 100
100.00 90.00 100
100.00 89.8 100
69.97 85.9 100
83.00 92.2 100
significant correlation between level of salivary progesterone with age (Figure 1) and parity (Figure 2; Table 3). Salivary progesterone had higher sensitivity and accuracy than ultrasonographic measured cervical length (Table 4). Combining measurement of salivary progesterone and cervical length measurement gives perfect sensitivity, specificity and accuracy in predicting PTB (Table 4; Figure 3).
Discussion Measurement of both salivary progesterone at a cutoff value of 933.6 (pg/ml) and cervical length at a cutoff value of 30 mm are good predictors for development of preterm labor and help identifying women at risk for development of PTB. In our study, there was a highly significant difference between the high risk and low risk study groups regarding salivary progesterone level (729.2 ± 223.3 versus 1097.9 ± 180.283, respectively).
That finding appears logic as progesterone is essential for maintenance of pregnancy. It promotes uterine relaxation by suppressing the formation of gap junction, reducing prostaglandin synthesis and the concentration of oxytocin receptors in the myometrium. Progesterone also increases cellular calcium-binding capacity and it also has anti inflammatory properties, lower than normal progesterone status, preterm labor could contribute to an exaggerated response to bacterial invasion [6]. Our study showed a highly significant difference between the high-risk and low-risk study groups regarding cervical length measured by transvaginal ultrasound (24.45 ± 8.43 versus 42.94 ± 4.76, respectively). Priya et al. in their prospective study evaluated salivary progesterone as a predictor of early PTB and compared it with transvaginal sonographic (TVS) cervical length in asymptomatic high-risk women. They found that the mean value of salivary progesterone was significantly lower in all women
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who delivered at 537 weeks of gestation (n ¼ 38), compared with the term group (n ¼ 52; p50.001) [11]. Salivary progesterone decreased significantly from the first to the second visit, with the maximum decrease observed in women who delivered at 534 weeks of gestation (29.6%, 95% CI: 17.8–41.4%, p50.002). The single predictive critical cut-off value for salivary progesterone was 2575 pg/ml, below which more than 80% of women delivered prematurely before 34 weeks of gestation, with sensitivity, specificity and positive and negative predictive values of 83% (95% CI: 58.6–96.4%), 86% (95% CI: 75.9–93.1%), 60% (95% CI: 38.6–78.8%) and 95% (95% CI: 87.1–99.0%), respectively. The TVS cervical
Figure 3. Accuracy (area under ROC curve) of prog. Acceptable discriminative and predictive ability of prog. between cases and control by the area under the ROC curve (the distance between the curve and diagonal) or accuracy of 0.9.
Figure 4. Cut off value of prog. by sensitivity and specificity of cases and control.
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length decreased significantly (p50.001) in the women who delivered prematurely [11]. They concluded that low salivary progesterone concentration can be used for predicting early PTB in asymptomatic high-risk women [11]. Our study showed a highly significant difference between the high-risk and low-risk study groups regarding cervical length measured by transvaginal ultrasound (24.45 ± 8.43 versus 42.94 ± 4.76, respectively). Sotiriadi et al. in 2010 reviewed 28 studies fulfilled the selection criteria. For birth within one week from presentation, the pooled sensitivity, specificity, LR+ and LR of cervical length 515 mm were 59.9% (95% CI: 52.7–66.8%), 90.5% (95% CI: 89.0–91.9%), 5.71 (95% CI: 3.77–8.65) and 0.51 (95% CI: 0.33–0.80), respectively. The same estimates for studies with presentation at or before 34 + weeks were 71.0% (95% CI: 60.6–79.9%), 89.8% (95% CI: 87.4–91.9%), 5.19 (95% CI: 2.29–11.74 and 0.38 (95% CI: 0.11–1.34), respectively [12]. For prediction of birth before 34 weeks, the pooled sensitivity, specificity, LR+ and LR of cervical length 515 mm were 46.2% (95% CI: 34.8–57.8%), 93.7% (95% CI: 90.7–96.0%), 4.31 (95% CI: 2.73–6.82) and 0.63 (95% CI: 0.38–1.04), respectively. They concluded that measurement of cervical length in symptomatic women can detect a significant proportion of those who will deliver within one week and help to rationalize their management [12]. Our study showed a statistically significant difference between levels of salivary progesterone at different GA among the high-risk group but not in low-risk group. We found a highly significant correlation between level of salivary progesterone and the GA but no significant correlation between level of salivary progesterone with age and parity. Our study found that salivary progesterone had higher sensitivity and accuracy than ultrasonographic measured cervical length in predicting PTB. Combining measurement of salivary progesterone and cervical length measurement
Preterm labor prediction
DOI: 10.3109/14767058.2014.947474
gives ideal sensitivity, specificity and accuracy in predicting PTB. Our study is unique among previous studies as it used easy, non invasive and non painful measurement with proper sample size and reached the gold standard of prediction of PTB when combining salivary P and CL measurement. We concluded that measurement of both salivary progesterone and cervical length are good predictors and combining them together could be the gold standard for development of preterm labor.
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Declaration of interest The authors declare no conflicts of interest.
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