Predictive values of cervix length measurement based on transvaginal ultrasonography

Abstract

BACKGROUND:

Pregnancy is an important process in women’s life, which is widely concerned by women. In recent years, the incidence of premature delivery (PTD) becomes more and more higher due to the development of auxiliary reproduction and ovulation induction technologies and the changes of pregnant women’s lifestyle and physical quality. PTD not only affects postpartum recovery and causes great physical pains, but it also has adverse effects on the birth state of neonates and even leads to neonatal death

OBJECTIVE:

The predictive values of cervix length (CL) measurement based on transvaginal ultrasonography (TVUS) and pathological examination of placenta for premature delivery (PTD) were investigated and the correlation between PTD and infection was analyzed.

METHODS:

120 pregnant women with PTD or high-risk factors for PTD admitted to The Affiliated Hospital of Southwest Medical University between February 2020 and March 2022 were included as the subjects and underwent pathological examination of placenta and TVUS for CL measurement. The final gestational age was set as the standard for the evaluation on the predictive values of pathological examination of placenta and TVUS. What’s more, 36 subjects in PTD group and 84 in normal delivery group (control group) underwent pathological examination of placenta for the analysis of the correlation between PTD and infection.

RESULTS:

The joint inspection method showed significantly better sensitivity, specificity, PPV, and NPV compared to single CL or pathological examination of the placenta ( $P<$ 0.05). Among pregnant women, those with CL $\leqslant$ 30 mm and positive placental pathology had a higher proportion compared to those with CL $>$ 30 mm and negative placental pathology ( $P<$ 0.05). Furthermore, the incidence of Ureaplasma Urealyticum (UU), Chlamydia Trachomatis (CT), and Chorioamnionitis (CA) in vaginal discharge of the preterm delivery (PTD) group was significantly higher than that of the control group ( $P<$ 0.05).

CONCLUSION:

The combination of CL $\leqslant$ 30 mm and positive placental pathology could effectively predict PTD and placental infection was notably correlated with the occurrence of PTD.

Keywords

Transvaginal ultrasonography cervix length pathological examination of placenta premature delivery infection

1. Introduction

Pregnancy is an important process in women’s life, which is widely concerned by women [1]. In recent years, the incidence of premature delivery (PTD) becomes more and more higher due to the development of auxiliary reproduction and ovulation induction technologies and the changes of pregnant women’s lifestyle and physical quality [2, 3]. PTD not only affects postpartum recovery and causes great physical pains, but it also has adverse effects on the birth state of neonates and even leads to neonatal death [4, 5]. In most cases, premature infants who are born before week 32 can only survive for less than 1 year. Survivors suffer from various complications, such as cerebral palsy, pulmonary diseases, and visual and hearing disorders, bringing about huge economic burdens to neonates and their families [6, 7]. PTD can be predicted through various examination methods and early evaluation of pregnant women’s delivery status can effectively prevent PTD and improve neonatal survival rate [8, 9]. Based on PTD prediction, early detection and intervention and the prolongation of gestational weeks can apparently reduce premature infant mortality and improve prognosis [10]. At present, the common clinical methods for PTD prediction mainly include cervix length (CL) measurement, neonatal fibronectin examination, and human chorionic gonadotropin (HCG) examination. Transvaginal ultrasonography (TVUS) is the main method for CL measurement, which is widely applied in clinical practice. It is characterized by simple operation, low price, and little trauma to pregnant women. Based on TVUS, fetal physical health and pregnant women’s cervix status can be better understood. TVUS is not harmful to pregnant women and fetuses with high sensitivity and specificity [11, 12]. PTD can be reliably predicted and intervention is performed in time through TVUS-based CL measurement, which plays a positive role in preventing and controlling PTD [13]. Progressive stretching and shortening of cervical canal and progressive dilation of internal cervical orifice mark the beginning of labor [14, 15]. Before cervical dilation, cervical images can be generated through TVUS. In addition, intervention can be performed on any abnormality before cervical dilation is detected. Hence, ultrasonography and CL measurement can be carried out to obtain basic data on cervix for PTD prediction and the reduction in PTD incidence [16, 17]. Moreover, pathological examination of placenta can also be applied to PTD prediction for obtaining the general data on parturients and neonates [18]. Intrauterine infection may result in PTD and is related to various complications among premature infants. The investigation into the relationship between PTD and infection is of great significance in clinical practice [19, 20].

This research was conducted to explore the predictive values of CL based on measurement TVUS combined with pathological examination of placenta for PTD and analyze the correlation between PTD and infection. In addition, CL and placental pathology of PTD patients and pregnant women with normal delivery were compared, the prediction effects of different examination methods on PTD were analyzed, and the incidence of postpartum and neonatal complications in different groups were investigated to provide guidance and references for normal delivery and clinical references for the prevention and control of PTD.

2. Materials and methods

2.0.1 Subjects

120 pregnant women with PTD or high-risk factors for PTD admitted to The Affiliated Hospital of Southwest Medical University between February 2020 and March 2022 were included as the subjects and enrolled into two groups based on pregnancy outcomes, including PTD group (36 cases) and control group (84 with normal delivery). The absence of significant statistical differences in age and education between the PTD group and control group does not rule out the possibility of practical differences that should be taken into account. It is crucial to evaluate not only statistical significance but also the meaningfulness of the research findings. All subjects underwent pathological examination of placenta and TVUS for CL measurement. The final gestational age was set as the standard for the evaluation on the predictive values of pathological examination of placenta and TVUS for PTD. What’s more, the predictive values of single examination and joint inspection for pregnancy outcomes were analyzed and postpartum and neonatal outcomes of two groups were compared. Statistical methods are used to analyze the predictive values of single examination and joint inspection for pregnancy outcomes. These values can be calculated using data from a sample of pregnant women and can be used to determine the accuracy of the test or tests in predicting adverse pregnancy outcomes and to compare the predictive values of single examination and joint inspection. Transvaginal ultrasonography is used during pregnancy to evaluate the health of both the mother and the fetus. Comparing postpartum and neonatal outcomes can help assess the effectiveness of interventions used during pregnancy. This technique provides information on fetal growth, any complications, and the mother’s reproductive organs. It helps medical professionals make informed decisions about necessary interventions and treatments. No statistical differences but comparability was detected in age and years of education between two groups. The Affiliated Hospital of Southwest Medical University’s Ethics Committee approved the research’s performance.

The inclusion criteria were listed below.

Patients with complete medical records

Patients over 18 years old

Patients without contraindications to TVUS

Patients without surgical history

Patients who volunteered to participate part in the research and signed informed consent reports.

The exclusion criteria were listed below.

Patients with incomplete medical records

Patients with major organ diseases

Patients with mental disorder or dementia

Patients who were unwilling to cooperate with the research

Patients with other diseases during pregnancy

Patients who had to withdraw due to severe complications and specific physiological changes

2.1 Methods

The pregnant women in the two groups both received TVUS. Color Doppler ultrasound diagnosis instrument (HITACHI Preirus, Japan) was utilized and probe frequency ranged from 4 MHz to 9 MHz. Color Doppler ultrasonography is a non-invasive medical imaging technology which generates images of blood flow in the body using sound waves. It can detect vascular and heart diseases, as well as diagnose obstetrical and gynecological conditions. During the procedure, a handheld wand is moved over the area of interest, emitting and receiving sound waves, which are processed into visual images. Color Doppler ultrasound provides real-time diagnostic information and is safe for patients. After that, TVUS was carried out to measure the subjects’ CL. Transvaginal ultrasonography (TVUS) is used to measure cervical length (CL) during pregnancy. An ultrasound probe is inserted into the vagina to take pictures of the cervix, and calipers are used to measure the distance between the internal and external os. A shorter cervical length is linked to an increased risk of preterm labor, whereas a longer cervical length is linked to a lower risk Pregnant women were instructed to take vesical calculus position after emptying bladder. Consequently, the structures of internal and external cervical orifices were clearly displayed. The internal and external cervical orifices are female reproductive system structures that can be observed during a pelvic exam. A speculum may be used to open the vaginal canal and view the cervix, and then a light and/or magnifying device may be used to examine the cervical orifices for any abnormalities. If necessary, additional diagnostic tests such as cervical biopsies or colposcopies may be performed. Only qualified healthcare professionals should perform these procedures. Next, CL was measured. Finally, all subjects underwent pathological examination of placenta.

2.2 Observation indicators

The general data on the two groups were summarized, mainly including years of education, average age, body mass index (BMI), and number of pregnancies. The calculation method for BMI was displayed as Eq. (1).

$\displaystyle\textit{BMI}=\frac{\textit{Weight}}{\textit{Height}^{2}}$ (1)

CL of two groups was compared and analyzed.

Placental pathology of two groups was compared and analyzed.

The incidence of ureaplasma urealyticum (UU), chlamydia trachomatis (CT), and chorioamnionitis (CA) of two groups was compared and analyzed.

The predictive effects of various examination procedures on pregnancy outcomes, including sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV), were compared and investigated. Specificity measures the true negatives out of all negative cases, whereas sensitivity measures the real positives out of all positive situations. Accuracy is the fraction of right predictions overall, and PPV and NPV are the proportions of true positives and true negatives among positive and negative predictions, respectively. By calculating these measures for each examination method, such as ultrasound, amniocentesis, and non-invasive prenatal testing (NIPT), their comparative predictive abilities for specific pregnancy outcomes, such as fetal chromosomal abnormalities, can be determined. It is important to consider the specific context and outcome when interpreting these measures. The gold standard for the diagnosis was final gestational age. The calculation methods for sensitivity, specificity, accuracy, PPV, and NPV were shown as Eqs (2), (3), (4), (5), and (6), respectively. PB, PM, YDB, YDM, DB, and DM represented the number of patients with negative outcomes, positive outcomes, negative PTD, positive PTD, negative outcomes, and positive outcomes in cervical examination or pathological examination of placenta, respectively.

$\displaystyle\textit{Sensitivity}=\frac{\textit{DM}}{\textit{PM}}\times 100\%$ (2) $\displaystyle\textit{Specificity}=\frac{\textit{DB}}{\textit{PB}}\times 100\%$ (3) $\displaystyle\textit{Accuracy}=\frac{\textit{DM}+\textit{DB}}{\textit{PB}+% \textit{PM}}\times 100\%$ (4) $\displaystyle\textit{Positive predictive value}=\frac{\textit{DM}}{\textit{YDM% }}\times 100\%$ (5) $\displaystyle\textit{Negative predictive value}=\frac{\textit{DB}}{\textit{YDB% }}\times 100\%$ (6)

Neonatal outcomes of two groups were compared and analyzed, mainly including neonatal asphyxia, neonatal pneumonia, and pathologic jaundice. The calculation method for the incidence of neonatal complications (Complication_N) was presented as Eq. (7). Number of complications_N and Total_N referred to the number of neonates with complications and total number of neonates, respectively.

$\displaystyle\textit{ComplicationN}=\frac{\textit{Number of complicationsN}}{% \textit{TotalN}}$ (7)

Postpartum outcomes of two groups were compared and analyzed, mainly including postpartum infection, postpartum hemorrhage, and difficult wound healing. The calculation method for the incidence of postpartum complications among pregnant women (Complication_P) was displayed as Eq. (8). Number of complications_P and Total_P represented the number of pregnant women with postpartum complications and total number of pregnant women, respectively.

$\displaystyle\textit{ComplicationP}=\frac{\textit{Number of complicationsP}}{% \textit{TotalP}}$ (8)

2.3 Statistical processing

SPSS 20.0 was used for data statistics and analysis, while Excel 2016 was used to collect and summarize data. The t test was used to examine measurement data, which was represented by mean standard deviation. The X2 test was used to examine enumeration data, which was represented by percentages (%). P0.05 indicated statistical significance.

3. Results

3.1 Comparison of the general data on two groups

As illustrated in Table 1, years of education, average age, BMI, and number of pregnancies of control and PTD groups amounted to 12.14 $\pm$ 3.62 vs 12.23 $\pm$ 3.81, 30.66 $\pm$ 5.21 vs 30.19 $\pm$ 5.58, 25.38 $\pm$ 3.15 kg/m² vs 25.46 $\pm$ 3.58 kg/m², and 2.19 $\pm$ 1.28 vs 2.23 $\pm$ 1.45, respectively. No statistical differences but comparability was detected in the above general data between two groups ( $P>$ 0.05).

Table 1
The general data on two groups

Group	Years of education (years)	Age (years)	BMI (kg/m²)	Number of pregnancies
Control group	12.14 $\pm$ 3.62	30.66 $\pm$ 5.21	25.38 $\pm$ 3.15	2.19 $\pm$ 1.28
PTD group	12.23 $\pm$ 3.81	30.19 $\pm$ 5.58	25.46 $\pm$ 3.58	2.23 $\pm$ 1.45

3.2 Comparison and analysis of CL in two groups

Figure 1A and B showed the number and proportion of cases with different CL, respectively. The number of pregnant women with CL greater than 30 mm, between 20 and 30 mm, and less than 20 mm in control and PTD groups amounted to 69 (82.14%) vs 7 (19.44%), 11 (13.1%) vs 19 (52.78%), and 4 (4.76%) vs 10 (27.78%), respectively ( $P<$ 0.05).

3.3 Comparison and analysis of placental pathology of two groups

As presented in Fig. 2, Fig. 2A and B showed the number of proportion of pregnant women with positive and negative outcomes in two groups, respectively. The number of positive and negative cases in control and PTD groups amounted to 18 (21.43%) vs 29 (80.56%) and 66 (78.57%) vs 7 (19.44%), respectively ( $P<$ 0.05).

3.4 Comparison and analysis of the incidence of CT, UU, and CA in two groups

As displayed in Fig. 3, Fig. 3A and B showed the incidence of CT, UU, and CA, respectively. The incidence of CT, UU, and CA in control and PTD groups amounted to (3.57%, 26.19%, 19.05%) vs (13.89%, 52.78%, 58.33%), respectively ( $P<$ 0.05).

3.5 Comparison and analysis of the predictive effects of different examination methods on pregnancy outcomes

As illustrated in Table 2, the sensitivity of pathological examination of placenta, CL examination, and joint inspection among pregnant women undergoing delivery for less than 3 d, 7 d, and 37 weeks amounted to (100%, 100%, 100%), (83.33%, 77.78%, 88.89%), and (66.67%, 66.67%, 77.78%), respectively. The sensitivity of joint inspection was notably superior to that of single examination ( $P<$ 0.05). Moreover, the predictive sensitivity was the highest among those undergoing delivery for less than 3 d, which was followed by that among those receiving delivery for less than 7 d.

Table 2
Sensitivity of the prediction pregnancy outcomes by different examination methods

Delivery time	Sensitivity (%)
	Pathological examination of placenta	CL	Joint inspection
$<$ 3 days	100	100	100
$<$ 7 days	83.33	77.78	88.89
$<$ 37 weeks	66.67	66.67	77.78

Table 3

Specificity of the prediction pregnancy outcomes by different examination methods

Delivery time	Specificity (%)
	Pathological examination of placenta	CL	Joint inspection
$<$ 3 days	72.22	77.78	83.33
$<$ 7 days	88.57	85.71	91.43
$<$ 37 weeks	90.32	87.10	93.55

As presented in Table 3, the specificity of pathological examination of placenta, CL examination, and joint inspection among pregnant women undergoing delivery for less than 3 d, 7 d, and 37 weeks amounted to (72.22%, 77.78%, 83.33%), (88.57%, 85.71%, 91.43%), and (90.32%, 87.1%, 93.55%), respectively. The specificity of joint inspection was remarkably superior to that of single examination ( $P<$ 0.05). The predictive specificity was the highest among those undergoing delivery for less than 37 weeks, which was followed by that among those receiving delivery for less than 7 d.

As displayed in Table 4, the accuracy of pathological examination of placenta, CL examination, and joint inspection among pregnant women undergoing delivery for less than 3 d, 7 d, and 37 weeks amounted to (81.48%, 85.19%, 88.89%), (86.79%, 83.02%, 90.57%), and (85%, 82.5%, 90%), respectively. The accuracy of joint inspection was notably superior to that of single examination ( $P<$ 0.05).

Table 4

Accuracy of the prediction pregnancy outcomes by different examination methods

Delivery time	Accuracy (%)
	Pathological examination of placenta	CL	Joint inspection
$<$ 3 days	81.48	85.19	88.89
$<$ 7 days	86.79	83.02	90.57
$<$ 37 weeks	85	82.50	90

As illustrated in Table 5, PPV of pathological examination of placenta, CL examination, and joint inspection among pregnant women undergoing delivery for less than 3 d, 7 d, and 37 weeks amounted to (64.29%, 69.23%, 75%), (78.95%, 73.68%, 84.21%), and (66.67%, 60%, 77.78%), respectively. PPV of joint inspection were dramatically superior to those of single examination ( $P<$ 0.05). PPV was the highest among those undergoing delivery for less than 7 d.

Table 5

PPV of the prediction pregnancy outcomes by different examination methods

Delivery time	Positive predictive value (%)
	Pathological examination of placenta	CL	Joint inspection
$<$ 3 days	64.29	69.23	75
$<$ 7 days	78.95	73.68	84.21
$<$ 37 weeks	66.67	60	77.78

As displayed in Table 6 and Figure 4, NPV of pathological examination of placenta, CL examination, and joint inspection among pregnant women undergoing delivery for less than 3 d, 7 d, and 37 weeks amounted to (100%, 100%, 100%), (91.18%, 88.24%, 91.43%), and (90.32%, 90%, 93.55%), respectively. NPV of joint inspection were much superior to those of single examination ( $P<$ 0.05) and NPV was the highest among those undergoing delivery for less than 3 d.

Table 6

NPV of the prediction pregnancy outcomes by different examination methods

Delivery time	Negative predictive value (%)
	Pathological examination of placenta	CL	Joint inspection
$<$ 3 days	100	100	100
$<$ 7 days	91.18	88.24	91.43
$<$ 37 weeks	90.32	90	93.55

3.6 Comparison and analysis of neonatal outcomes in two groups

As presented in Fig. 5, the number of neonates with asphyxia, pneumonia, and pathologic jaundice in control and PTD groups amounted to 2 (2.38%) vs 2 (5.55%), 1 (1.19%) vs 7 (19.44%), and 8 (9.52%) vs 4 (11.11%), respectively ( $P<$ 0.05).

3.7 Comparison and analysis of postpartum outcomes in two groups

As illustrated in Fig. 6, the number of pregnant women with postpartum infection, hemorrhage, and difficult wound healing in control and PTD groups amounted to 8 (9.52%) vs 9 (25%), 10 (11.9%) vs 11 (30.56%), and 5 (5.95%) vs 6 (16.67%), respectively ( $P<$ 0.05).

4. Discussion

Premature infants are light in weight and weak in constitution and most of their organs are not fully mature. Even worse, some neonates die during perinatal stage. Furthermore, various short- and long-term complications seriously affect normal neonatal development [21, 22]. TVUS-based CL measurement plays a positive role in PTD prediction. During TVUS, cervical compression should be avoided to prevent the deformity of anatomical morphology. In addition, cervical sagittal plane is scanned to show the length of endocervical mucosa, observe internal and external cervical orifices, and measure the distance between them [23, 24]. TVUS can not only be adopted for CL measurement, but it is also applied in the observation on cervical morphology and internal and external orifices [25, 26]. With the advent of expected date of delivery, uterus continuously dilate so that cervical canal is compressed and cervix is gradually shortened. CL is an important predictor for PTD through which labor and fetal status can be understood and delivery time can be estimated [27, 28]. In addition, PTD can be predicted based on placental pathology. The joint inspection is more specific and sensitive in PTD prediction, so it is widely recognized by patients and shows remarkable clinical application values.

Thain et al. (2020) [29] analyzed the relationship between PTD and CL and found that CL of PTD group was much shorter than that of term group during pregnant metaphase (weeks 18 to 22) and late pregnancy (weeks 28 to 32). The CL of the PTD group was found to be shorter during the early stages of pregnancy (weeks 11 to 14) and was notably reduced during the 2nd and 3rd trimesters (weeks 18 to 22 and weeks 28 to 32), based on the analysis of receiver operating characteristic (ROC) curves. With a strong negative predictive value (NPV) and appropriately outstanding specificity, the CL is a relatively effective predictor of PTD. During weeks 18 to 22, ultrasound CL screening for Asian pregnant women (cut-off length 2.48 cm) was beneficial in predicting PTD risk. The identification of PTD was a clinical challenge. The shortening of CL during the whole trimester of pregnancy might be the predictor for spontaneous PTD. However, it remained unclear that whether the shortening of CL from asymptomatic to symptomatic state could predict spontaneous PTD when patients suffered from PTD symptoms. Romero et al. (2021) [30] analyzed the practicability of CL (the predictor for spontaneous PTD) from asymptomatic time point (anatomical ultrasound) to the occurrence of PTD. They found that the total incidence of spontaneous PTD amounted to 8.3% and the length of 19% cervixes was shortened by more than 10 mm. The incidence of spontaneous PTD was notably higher among patients with CL shortening greater than 10 mm than among those with CL shortening equal to or less than 10 mm. The sensitivity, specificity, PPV, and NPV of CL shortening greater than 10 mm amounted to 47.8%, 83.9%, 21.2%, and 94.7%, respectively. The above outcomes demonstrated that CL (more than 10 mm shorter than anatomical ultrasound) was related to the increasing risk of spontaneous PTD among PTD women. Khamees et al. (2022) [31] analyzed the predictive effects of uterine cervix angle and CL on PTD and found that uterine cervix angle greater than 105^∘ and CL less than 30 mm were the high-risk factors for PTD, which showed good performance in the diagnosis of high-risk patients. Muniz et al. (2022) [32] evaluated the correlation between CL measurement parameters and PTD and found that postpartum total CL and upper cervix length were both associated with gestational age and PTD risk during delivery. Spearman’s correlation coefficient is a statistical technique used to determine the strength and direction of a relationship between two variables. It is useful for non-linear or non-normally distributed data, as well as ordinal data. Data for each variable are ranked as part of the process. However, correlation does not always imply causation, and further investigation is required to determine causation. After cervical cerclage during ultrasonography, total CL or upper cervix length could predict gestational age and PTD risk during delivery, which suggested that TVUS-based CL measurement played a positive role in PTD prediction, so it could be applied for pregnant women and parturients.

In this research, the predictive effects of pathological examination of placenta-based CL measurement on PTD were compared and CL and placental pathology of PTD patients and pregnant women undergoing normal delivery were analyzed. What’s more, the effects of different examination methods on PTD prediction were compared and the incidence of postpartum and neonatal complications in different groups was summarized. It was demonstrated that the proportion of cases with CL $>$ 30 mm was relatively lower in PTD group, while the proportion of cases with CL $<$ 30 mm was apparently higher ( $P<$ 0.05). In addition, the proportion of positive cases was much higher while that of negative cases was relatively lower in PTD group ( $P<$ 0.05). Moreover, the incidence of CT, UU, and CA in control and PTD groups amounted to 3.57% vs 13.89%, 26.19% vs 52.78%, and 19.05% vs 58.33%, respectively. Joint inspection was more sensitive, specific, and accurate than single examination ( $P<$ 0.05) and the sensitivity was the highest among pregnant women undergoing delivery for less than 3 d. What’s more, the specificity was the highest among those undergoing delivery for less than 37 weeks. The incidence of asphyxia, pneumonia, and pathologic jaundice was higher in PTD group ( $P<$ 0.05), so was the incidence of postpartum infection, hemorrhage, and difficult wound healing ( $P<$ 0.05). It was verified that CL measurement with pathological examination of placenta possessed more remarkable advantages in PTD prediction with high specificity, sensitivity, and accuracy. Therefore, it was worthy of clinical application.

5. Conclusion

This research was conducted to compare the predictive effects of different examination methods on PTD. It was found that TVUS-based CL measurement combined with pathological examination of placenta was more effective with high specificity, sensitivity, and accuracy. Hence, it was an excellent prediction method and worthy of clinical application. The limitation of this research lies in the investigation into the predictive effects of CL and placental pathology on PTD without comparative study on other prediction methods. In subsequent research, other prediction methods should be included for the comparison of predictive effects to provide references for successful pregnancy.

Funding

No funds, grants were received by any of the authors.

Data availability

All data generated or analyzed during this study are included in the manuscript.

Code availability

Not applicable.

Author contributions

All author is contributed to the design and methodology of this study, the assessment of the outcomes and the writing of the manuscript.

Footnotes

Conflict of interest

There is no conflict of interest among the authors.

References

Li J, Gao JS, Wang CC, Ng Ernest hy, Wu XK. Evidence-based interventions of threatened miscarriage. World Journal of Traditional Chinese Medicine. 2017; 3(1): 50-59.

Aboulghar

, Aboulghar

,Singleton birth weight and premature birth after in vitro fertilization: Do we have evidence? Fertil Steril, 2021; 116(1): 64-65.

Pruski P, Correia GDS, Lewis HV, Capuccini K, Inglese P, Chan D, Brown RG, Kindinger L, Lee YS, Smith A, Marchesi J, McDonald JAK, Cameron S, Alexander-Hardiman K, David AL, Stock SJ, Norman JE, Terzidou V, Teoh TG, Sykes L, Bennett PR, Takats Z, MacIntyre DA. Direct on-swab metabolic profiling of vaginal microbiome host interactions during pregnancy and preterm birth. Nat Commun. 2021; 12(1): 5967.

Conde-Agudelo

, Romero

,Does vaginal progesterone prevent recurrent preterm birth in women with a singleton gestation and a history of spontaneous preterm birth? Evidence from a systematic review and meta-analysis, Am J Obstet Gynecol. 2022; 227(3): 440-461.e2.

Tong-Hua

, Jian-Xin

, Deng-Lu

, Min

, Li-Guo

, Da-Xiang

, Xiao-Hua

, Xue-Song

, Guang

,Tocolysis Effects of Traditional Chinese Medicine and Their Effective Components,World Journal of Traditional Chinese Medicine.,2022;8(2):188–198.

Vieira VS, Feiten TDS, Ferrari RS, Dalcin PTR, Ziegler B. Predictive factors for premature birth and respiratory exacerbation in pregnancies of women with cystic fibrosis. J Pediatr (Rio J). 2022; 98(1): 33-38.

Kadivnik

, Kralik

, Muller-Vranješ

, Vučemilović-Jurić

, Šijanović

, Wagner

,Progesterone receptor genetic variants in pregnant women and fetuses as possible predictors of spontaneous premature birth: A preliminary case-control study,J Obstet Gynaecol Res.,2022;48(5):1099–1109.

Ronzoni

, Cobo

, D’Souza

, Asztalos

, O’Rinn

SE.

, Cao

, Herranz

, Melamed

, Ferrero

, Barrett

, Aldecoa

, Palacio

,Individualized treatment of preterm premature rupture of membranes to prolong the latency period, reduce the rate of preterm birth, and improve neonatal outcomes. Am J Obstet Gynecol. 2022; 227(2): 296.e1-296.e18.

Jones

AJ.

, Eke

UA.

, Eke

AC.

,Prediction and prevention of preterm birth in pregnant women living with HIV on antiretroviral therapy,Expert Rev Anti Infect Ther.,2022;20(6):837–848.

10.

Serra

, Peñailillo

, Monteiro

LJ.

, Monckeberg

, Peña

, Moyano

, Brunner

, Vega

, Choolani

, Illanes

SE.

,Supplementation of Omega 3 during Pregnancy and the Risk of Preterm Birth: A Systematic Review and Meta-Analysis, Nutrients. 2021; 13(5): 1704.

11.

Hester

AE.

, Ankumah

NE.

, Chauhan

SP.

, Blackwell

SC.

, Sibai

BM.

,Twin transvaginal cervical length at 16-20 weeks and prediction of preterm birth,J Matern Fetal Neonatal Med.,2019;32(4):550–554.

12.

Battarbee

AN.

, Ellis

JS.

, Manuck

TA.

,Beyond Cervical Length: Association between Postcerclage Transvaginal Ultrasound Parameters and Preterm Birth,Am J Perinatol.,2019;36(13):1317–1324.

13.

Masters

HR.

, Warshak

, Sinclair

, Rountree

, DeFranco

,Time required to complete transvaginal cervical length in women receiving universal cervical length screening for preterm birth prevention,J Matern Fetal Neonatal Med.,2022;35(16):3114–3118.

14.

Moloney

ME.

, Hansen

, Cockerham-Morris

CT.

, Li

, Chavan

NR.

,Appalachian Women’s perspectives on preterm birth and transvaginal ultrasound cervical length screening: Implications for addressing disparities in preterm birth, Healthc (Amst). 2021; 9(3): 100558.

15.

Zuo

XF.

, Du

YF.

, Yang

, Cheng

ZY.

, Gong

LJ.

, Zhang

AQ.

, Han

, Wei

, Zhao

YY.

,[Predictive value of cervical length measured by transvaginal ultrasound during the second and the third trimester of pregnancy for preterm birth in twin pregnancies],Zhonghua Fu Chan Ke Za Zhi.,2019;54(5):318–323.

16.

Maia

MC.

, Nomura

, Mendonça

, Rios

, Moron

,Is cervical length evaluated by transvaginal ultrasonography helpful in detecting true preterm labor? J Matern Fetal Neonatal Med, 2020; 33(17): 2902-2908.

17.

Kuusela

, Jacobsson

, Hagberg

, Fadl

, Lindgren

, Wesström

, Wennerholm

UB.

, Valentin

,Second-trimester transvaginal ultrasound measurement of cervical length for prediction of preterm birth: a blinded prospective multicentre diagnostic accuracy study,BJOG.,2021;128(2):195–206.

18.

Suresh

, Freedman

, Ernst

,Response to: placental pathology and recurrent preterm birth,Am J Obstet Gynecol.,2022;227(6):933–934.

19.

Wie

JH.

, Lee

JS.

, Hwang

HS.

, Kwon

JY.

, Ko

HS.

, Park

IY.

,The risk of preterm birth in women with history of short cervix delivering at term in the previous pregnancy: a retrospective cohort study,Arch Gynecol Obstet.,2022;305(5):1151–1158.

20.

Adekola

, Addo

, Unal

ER.

, James

, Prakash

, Abrams

,Outcomes following Placement and Removal of Transvaginal Cerclage in at Risk Pregnancies: A Single Center Experience, J Pregnancy. 2022; 2022: 4277451.

21.

Wastnedge

, Waters

, Murray

SR.

, McGowan

, Chipeta

, Nyondo-Mipando

AL.

, Gadama

, Masamba

, Malata

, Taulo

, Dube

, Kawaza

, Khomani

PM.

, Whyte

, Crampin

, Freyne

, Norman

JE.

,Reynolds RM; DIPLOMATIC Collaboration, Interventions to reduce preterm birth and stillbirth, and improve outcomes for babies born preterm in low- and middle-income countries: A systematic review. J Glob Health. 2021; 11: 04050.

22.

Wen

, Yang

,Clinical Comparison of Preterm Birth and Spontaneous Preterm Birth in Severe Preeclampsia, Contrast Media Mol Imaging. 2022; 2022: 1995803.

23.

Pedretti

MK.

, Dickinson

JE.

, Doherty

DA.

,The perceptions of pregnant women about cervical length screening for preterm birth prevention,Aust N Z J Obstet Gynaecol.,2021;61(5):735–741.

24.

Almeida JPRFP, Bartosch CMM, Macedo AMPCC. The Impact of Routine Transvaginal Ultrasound Measurement of the Cervical Length on the Prediction of Preterm Birth: A Retrospective Study in a Tertiary Hospital. Rev Bras Ginecol Obstet. 2021; 43(4): 264-274.

25.

Wongkanha

, Sudjai

, Puttanavijarn

,Correlation of transabdominal and transvaginal sonography for the assessment of uterocervical angle at 16-24 weeks’ gestation,J Obstet Gynaecol.,2020;40(5):654–658.

26.

Rennert KN, Breuking SH, Schuit E, Bekker MN, Woiski M, de Boer MA, Sueters M, Scheepers HCJ, Franssen MTM, Pajkrt E, Mol BWJ, Kok M, Hermans FJR. Change in cervical length after arrested preterm labor and risk of preterm birth. Ultrasound Obstet Gynecol. 2021; 58(5): 750-756.

27.

Ramji

, Abdulghani

SH.

, Zhang

, Moretti

FM.

, Fung-Kee-Fung

KM.

,Does late second-trimester cervical length predict unscheduled preterm birth in asymptomatic triplet pregnancies? Matern Fetal Neonatal Med, 2022; 35(23): 4597-4606.

28.

Nazzaro

, Saccone

, Miranda

, Crocetto

, Zullo

, Locci

,Cervical elastography using E-cervix for prediction of preterm birth in singleton pregnancies with threatened preterm labor,J Matern Fetal Neonatal Med.,2022;35(2):330–335.

29.

Thain S, Yeo GSH, Kwek K, Chern B, Tan KH. Spontaneous preterm birth and cervical length in a pregnant Asian population. PLoS One. 2020; 15(4): e0230125.

30.

Romero JA, Downes K, Pappas H, Elovitz MA, Levine LD. Cervical length change as a predictor of preterm birth in symptomatic patients. Am J Obstet Gynecol MFM. 2021; 3(1): 100175

31.

Khamees

RE.

, Khattab

BM.

, Elshahat

AM.

, Taha

OT.

, Aboelroose

AA.

,Uterocervical angle versus cervical length in the prediction of spontaneous preterm birth in singleton pregnancy,Int J Gynaecol Obstet.,2022;156(2):304–308.

32.

Muniz Rodriguez

, Naert

, Colatosti Catanho

, Labovitis

, Rebarber

, Fox

NS.

,The association between sonographic cervical length components and preterm birth in women with ultrasound- or exam-indicated cerclage,J Matern Fetal Neonatal Med.,2022;35(25):5703–5708.