
==== Front
Mater Sociomed
Mater Sociomed
Mater Sociomed
Materia Socio-Medica
1512-7680
1986-597X
AVICENA, d.o.o., Sarajevo Bosnia and Herzegovina

MSM-35-118
10.5455/msm.2023.35.118-122
Original Paper
Correlation of Qualitative Alpha1-microglobulin, Values of Interleukin 6, Cervicometry and Cervical Infection in Pregnant Women with Symptoms of Preterm Birth
Banicevic Arnela C. 1
Ceric Amela 2
Popovic Miroslav 1
Micic Zvjezdana Ritan 1
1 Clinic for Gynecology and Obstetrics, Faculty of Medicine. University of Banja Luka, Banja Luka, Bosnia and Herzegovina
2 Clinic for Hematology, Faculty of Medicine. University of Banja Luka, Banja Luka, Bosnia and Herzegovina
Corresponding author: Assistant Professor Arnela Banicevic, MD, PhD. Clinic for Gynecology and Obstetrics. Faculty of Medicine. University of Banja Luka, Banja Luka, Bosnia and Herzegovina. E-mail: banicevici@gmail.com. ORCID ID: http//www.orcid.org/0000-0004-7241-2810.
2023
35 2 118122
14 4 2023
23 5 2023
© 2023 Arnela C. Banicevic, Amela Ceric, Miroslav Popovic, Zvjezdana Ritan Micic
2023
https://creativecommons.org/licenses/by-nc/4.0/ This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background:

One of the problems in modern obstetrics is how to identify and select pregnant women who are most likely to give premature birth. In the last ten years, due to false-positive test results, i.e., tests with low positive predictive values, there is an increase in unnecessary hospitalization days as well as unnecessary therapy. The probability of preterm birth is 25% in a population of pregnant women with symptoms of preterm birth.

Objective:

The aim was to analyze diagnostic accuracy of tests for the purpose of predicting premature births in< 37th and <34th week of pregnancy. Incidence of preterm births in < 37th week of pregnancy was 28%, while the incidence of preterm births up until 34th week of pregnancy, was < 8%.

Methods:

We included two groups of pregnant women in a prospective study; one group with the symptoms of threatening preterm birth between 22nd and 37th week of pregnancy and the other one of the same gestation period with no symptoms.

Results:

Each pregnant woman underwent test for placental alpha microglobulin-1, cervical length screening, cervical sampling for microbiological analysis, blood sampling for IL6 and CRP analysis. There were 16% of preterm births, up until 7 days from hospitalization, and they were all PAMG-1 positive; There is 75% of preterm births if PAMG-1 is positive with cervical length under 25mm. Combining tests, we reached the best predictive accuracy with positive PAMG-1 test, cervical length under 15mm along with the increase of CRP values above 15.96%.

Conclusion:

Total number of hospitalization days was 29% with preterm births up to 71% with full term births regardless the symptomatology, which justifies further studies towards releasing the pressure from the health care system and from doctors as well in the process of reaching a decision on treatment of pregnant women with the signs of preterm birth.

PAMG-1
cervicometry
preterm birth
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pmc1. BACKGROUND

Definition and incidence

Preterm birth and its short-term and long-term consequences are the biggest problems in today’s obstetrics. It is defined as childbirth from 22nd week of pregnancy and before full 37th week of pregnancy, with the incidence in general population of pregnant women in Europe between 5% and 9% (1), and in USA and Canada up to 12% (1,2). Despite the improvements in health care and nursing, the use of new and ‘improved’ medication along with new technologies in the majority of developed countries, the incidences of preterm birth have not been reduced at all in the last few decades, but have rather increased up to 5%, compared to 30 years ago. The consequences of preterm birth are related to 75% of neonatal deaths along with more than 50% of short-term and long-term morbidities; more than two-thirds of complications occur with children born before the 34th week of pregnancy (1-4). Also, its incidences and neonatal morbidities represent important epidemiological indicators of health care system quality of a certain country. Incidences of neonatal morbidity are in proportion with the gestational age when the child was born, and is growing in lower gestation period.

Early and late morbidity of preterm born children

In the last thirty years, the incidence of preterm births was increased by 30% which implies two-thirds of preterm births in >34th week of pregnancy. Children born within that gestational period have significantly higher rate of respiratory distress syndrome (RDS), apneic episodes, hypoglycemia, jaundice, kernicterus, feeding difficulties, periventricular leukomalacia along with more frequent hospital admissions, compared to full term born children (6-8). Mortality and early morbidity of newborns, in the group of extremely pre term births and very preterm births, are significantly higher due to insufficient lung maturity along with occurrence of severe forms of respiratory distress syndrome (RDS), necrotizing enterocolitis and sepsis. The overall survival rate of that group is significantly higher in the last twenty years through the application of antenatal corticosteroid prophylaxis, postnatal use of surfactants along with the assisted ventilation and improvement in neonatal intensive care.

Biological marker of preterm birth

Placental alpha microglobulin-1 (PAMG-1) is a human protein that was first isolated in 1975 from amniotic fluid. Placental alpha microglobulin-1 is glycoprotein produced by decidual cells (8,9). According to the latest research, the presence of protein is explained by transudation through chorion spores during uterine contraction or by degradation of extracellular matrix of fetal membranes during inflammatory process. Concentration in the amniotic fluid is from 2000,0 to 25000,0 mg/L, while the concentration in the mother’s blood is between 0,5 and 2,0 mg/L. Commercial test known as PartoSure contains monoclonal antibodies which reveal very small quantities of protein present in the vaginal fluids. PartoSure test sensitivity limit is 5,0 mg/L.

Selection of the pregnant women group with the risk of preterm birth

Shortening of cervical length and examination of internal os only be conducted by transvaginal ultrasound. The earliest changes internal os its opening, takes place in asymptomatic stage, but later comes the gradual shortening of cervical length, opening and patency of external os of cervix, which can be palpated during bimanual examination (15). Cervicometry is well described and standardized method, and one of the most important advantages compared to other methods is small inter-observation and intra-observation variation between 5% and 7%.

2. OBJECTIVE

The aim was to analyze diagnostic accuracy of tests for the purpose of predicting premature births in< 37th and <34th week of pregnancy. Incidence of preterm births in < 37th week of pregnancy was 28%, while the incidence of preterm births up until 34th week of pregnancy, was < 8%.

3. RESPONDENTS AND METHODS

The study was conducted as prospective study in pregnant women with symptoms of preterm birth, from 22nd to 36.6th week of gestation, hospitalized in “KGA” RS Banja Luka. Diagnosis of preterm birth was given with at least one present criteria, as follows: 1. ≥ 5 contractions per hour for longer than 2 hours, 2. Patency of cervical canal from 1 to 3 cm.

The factors of inclusion in treatment group of pregnant women (n=25):singleton pregnancy, symptoms of preterm birth present, gestation from 22nd to 36.6th. The factors for non-inclusion with both of the groups of pregnant women were as follows: pregnancy shorter than 22nd or longer than 36.6th week of pregnancy, pregnant women with premature rupture of membranes, pregnant women with proven fetal abnormality incompatible with life or intrauterine fetal demise, multiple pregnancy, pregnant women with intervention on cervix (conization or cerclage), pregnant women with inborn Müllerian anomalies (uterus duplex,uterus dydelphus, uterus bicornis, cervix duplex), pregnant women with other risk factors for preterm birth (heart condition, kidney disease, diabetes, autoimmune diseases etc.)

Agenda

Potential respondents, in the study, were approached during their stay in the ward of Reproductive Gynecology, Perinatology within the Clinic for Gynecology and Obstetrics at University Clinical Centre of Republic of Srpska, as well as in Polyclinic if it referred to the respondents of other group.

The first examination for both groups of respondents in gestation period higher than 22nd week, included: collecting anamnesis data and using it to assign women to groups, clinical examination, fetal biometry, with the help of ultrasound for the evaluation of gestational age, conducting quality test for PAMG-1, ultrasound cervicometry, cervical sampling for microbiological analysis, IL6 values analysis from serum of pregnant woman, analysis of current laboratory test results, complete blood count test (CBC, C-reactive protein (CRP).

4. RESULTS

In the period from January 10, 2017 to February 1, 2020 we included 50 pregnant women into the study. All the pregnant women met the requested inclusion and exclusion criteria. We analyzed the incidences of preterm births in both groups as well as incidences of preterm births up until 7 days from the day of hospitalization, cervical length in both groups, PAMG-1 test results, IL6 values and endocervical culture. There were no preterm births in the control group, compared to the treatment group with 9 cases of preterm births, i.e., 36%. Based on χ2 test results (χ2=12,080; p=0,002), we came to the conclusion that there was statistically significant (p<0,05)difference among number of respondents within the group with symptoms who gave birth until 34th week of pregnancy and until 37th week of pregnancy, where preterm birth did not occur. Most respondents who had the symptoms did not give preterm birth. It was established that 44,4% of preterm births took place in the period up until 7 days after hospitalization. There was 40% of positive PartuSure test results in treatment group whereas control group had no positive PartuSure test results. Based upon Pearson’s Chi-Squared test results (χ2=12,500; p=0,000), we came to the conclusion that there was statistically important connection (p<0,05) between PartuSure test outcome and the group to which pregnant woman belongs. There was 77,8% of pregnant women with positive PartuSure test results, in the group of those who gave preterm birth,but 22,2% of pregnant women, had negative results with this test. There was 81,3% of pregnant women with negative PartuSure test results, in the group with no preterm births, and 18,8% of pregnant women with positive test results. Based on Fisher’s exact test results (p=0,009) we came to the conclusion that there was statistically significant (p<0,05) dependency between PartuSure and preterm birth. Pregnant women with negative PartuSure test result had fewer preterm births compared to the number of preterm births in pregnant women with positive PartuSure test results. Based on Fisher’s exact test results (p=0,017) we came to the conclusion that there was significantly important (p<0,05) correlation between births in the period up to 7 days from the day of hospitalization and positive PAMG-1 test results. Based on Fisher’s exact test results we came to the conclusion that there was statistically significant (p<0,05) difference between treatment and control group in the cervical length. The average cervical length in treatment group was 20,22±7,25.

The cervical smear was negative in 68% of cases in both, control and treatment group. Positive cervical smear was equally present with both groups, and it was also present in 32% of pregnant women; in each group Fisher’s exact test results (χ2=0,000; p=1,000) showed that there was no statistically significant (p<0,05) difference between pregnant women of treatment and control group in pregnant women distribution compared to the endocervical culture. Fisher’s exact test results(χ2=8,772; p=0,010) showed that there was statistically (p<0,05) significant connection between cervical length and preterm birth. Pregnant women whose cervical length was shorter than 15 mm,had higher incidence of preterm births, while pregnant women with cervical length longer than 25 mm did not give preterm births. Fisher’s exact test results (p=0,011) showed that there was statistically significant (p<0,05) dependency between cervical length and PartuSure test outcome. Pregnant women with cervical length shorter than 15mm, more often had positive PartuSure test results, than negative ones. In pregnant women with cervical length longer than 25 cm, there was higher incidence of those with negative PartuSure test results. Based on Fisher’s exact test results(p= 0,821) we came to the conclusion that there was no statistically significant (p<0,05) correlation between cervical length and cervical smear. Based on Fisher’s exact test results (p=0,001) it was proved that there was significantly important (p<0,05) correlation between births in the period of up to 7 days from the day of hospitalization and PartuSure test results. Pregnant women who gave birth in the period of up until 7 days from the day of hospitalization had positive PartuSure test results. The Mann Whitney U test results showed that there was statistically significant (p<0,05) difference between treatment and control group in CRP values, i.e., pregnant women in treatment group had higher CRP values compared to the pregnant women in control group. There was almost equal incidence in number of women with interleukin levels lower than 1.5 in both groups of pregnant women, i.e., values in both groups were not significantly higher. Fisher’s exact test results showed that there was no statistically significant correlation (p>0,05) between interleukin-6 values in treatment and control group. Probability of preterm birth is increased with shortening of cervical length. Therefore, if the cervical length falls under 25 mm but is higher than 15 mm, the increase of probability of preterm birth is 50%, whereas if cervical length falls under 15 mm, then the probability of preterm birth is increased by 16,7%.The Mann Whitney U test results showed that there was no statistically significant difference in the number of hospitalization days, between pregnant women who gave preterm birth and pregnant women who did not experience preterm birth. Pregnant women who did not give birth earlier, impose pressure upon health care system the same way as pregnant women who gave birth earlier, if we perceive hospital bed as resource. The group of pregnant women who gave birth in the period of up until 7 days from the day of hospitalization, had the ratio of pregnant women who had PAMG-1 test results and cervical length under 25 mm along with those who did not have PAMG-1 test results or cervical length under 25 mm are in inverse proportion with the ratio of the pregnant women group who did not give birth in the period of up until 7 days from the day of hospitalization. Based on Fisher’s exact test results (p=0,007) we came to the conclusion that there was statistically significant (p<0,05) correlation between positive PAMG-1 test result and cervical length shorter than 25 mm on the one hand and childbirth in the period of up until 7 days from the day of hospitalization on the other hand; 75% of pregnant women with positive PAMG-1 test results and cervical length under 25 mm gave birth in the period of up until 7 days from the day of hospitalization.

5. DISCUSSION

According to the examination of current literature available, this has been the first study so far, which compared four independent tests (ultrasound measurement of cervical length, placental alpha microglobulin-1, IL6 as well as endocervical culture) in the population of pregnant women with symptoms of threatening preterm birth, cervical length <15 mm, positive PAMG-1 test result, are statistically in significant connection with preterm birth risk in<37th week of pregnancy; where those two positive tests represent additional screening markers of this population and as such could improve current clinical practice in preterm birth risk evaluation.

The breaking point of the length of pregnancy, in this study, is childbirth before <37th week. The total probability of preterm birth was 36% up until 37th week and 22,2% up until 34th week, which is in agreement with the current literature. Childbirth prior to the 35th week of pregnancy covers around 30% of total preterm births, therefore, bears the highest risk of negative preterm birth consequences in the context of the highest rate of newborn mortality as well as early and late morbidity, therefore, that population of pregnant women is the most interesting one in terms of risk assessment. Childbirth between 35th and 37th week, i.e., late preterm birth represents the largest preterm birth group at around 70%. However, negative consequences of preterm births are the mildest, and there is improved neonatal care in developed countries which significantly reduced the incidences of morbidity and mortality in the population of such children.

Monitoring of cervical length through different studies in the last ten years confirmed transvaginal ultrasound as a gold standard method for identifying pregnant women who are symptomatic as well as asymptomatic, which is the biggest problem in preterm birth prediction. Cervical length measurement meets all the criteria of quality screening test: Preterm birth evaluated by cervicometry for the timely treatment, where the cervicometry itself is safe, which is well accepted by pregnant women, harmless, cheap and easily available method.

In our study the median length of cervix was 20,22±7,24 mm with total range from 7 to 47 mm. We monitored the probability of preterm birth with lengths ≤15, 15 do 25, te ≥25 mm. Fisher’s exact test results defined cervical length ≤15 mm in 24% of pregnant women; cervical length from 15 mm to 25 mm in 40% of pregnant women, and the length of ≥25 mm in 36% of pregnant women. The incidence of preterm birth was growing with the shortening of cervical length, therefore, if we measure cervical length under 25 mm but above 15 mm, the increase of probability of preterm birth is 50%, whereas if cervical length is under 15 mm, then the probability of preterm birth is increased by 16,7%.

Clinical borderline for defining short cervical length was in the range from 15 mm to 30 mm in the current literature, depending on population being researched and gestational age being evaluated.

Different PAMG-1 studies, elaborated above, give reasons for further use of PartoSure® test. In spite of the above being said, there is a need for other detailed studies to confirm its use in everyday practise and our study could be contribution in that issue. Although the sensitivity of cervix ultrasound enables identifying group of women in risk, 80% percent of them will not give birth within 7 days, which is in agreement with our data; there was 16% of preterm births up until 7 days.

6. CONCLUSION

The incidence of preterm birth in the treatment group, in pregnant women with preterm birth symptoms, was 36%, whereas with pregnant women in control group, with no symptoms, we did not have preterm birth. There was preterm birth in 16% of the whole group,up until 7 days from the day of hospitalization. There was 44,4% of preterm births up until 7 days from the day of hospitalization, from the total number of preterm births. There was 77,8% of births up until 37th week of pregnancy, and 22% up until 34th week. In the treatment group, we had 40% of pregnant women with positive PAMG-1 test result. Cervical length above 25 mm in the treatment group was in 36% of pregnant women, whereas in control group, we had 84% of them. Probability of preterm birth according to the cervical length is growing, from the length of 15 mm to 25 mm,to 50%, but with the length under 15 mm, the probability is higher by 16,7%. Regarding the correlation of cervical length and positive PAMG-1 test result, pregnant women with cervical length under 15 mm, 40% of them had positive test, and only 5% of them with such cervical length had negative test. Our study used static models, for the first time, and using correlation of monitoring parameters we tried to get the best model and use it to recognize pregnant women who will give preterm birth.

Author’s contribution:

All authors was included in all steps of preparation of this article. Final proofreading was made by the first author.

Conflict of interest:

None declared.

Financial support and sponsorship:

None.
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