Abstract
Background
Current methods used to assess the progress of labor are often invasive and may cause discomfort to the mother. The purple line offers potential as a non-invasive marker for monitoring the labor process. However, its sensitivity and specificity in assessing critical components of labor, such as cervical dilatation and fetal descent, have not been adequately studied in different populations. This study was conducted to evaluate the effectiveness of the purple line, a method for assessing labor progress.
Methods
Data for this observational study were collected from 304 pregnant women who presented to a maternity hospital for birth on the Anatolian side of Istanbul between May and November 2021. The inclusion criteria for the study were that women were 38–42 weeks of gestation, spontaneous labor had started and were in active labor phase. Participants were selected by random sampling method among women who met the study criteria during labor. Data collection included demographic information, partograph records, and measurements of the purple line. Women’s birth was assessed and documented on a partogram, with the purple line measured hourly via a disposable tape measure until birth. Descriptive analyses including means and standard deviations, medians and interquartile ranges, and cut-off point and sensitivity-specificity (ROC) values were performed for data analysis.
Results
A purple line was seen in 85.9% of pregnant women at any stage of labour, with a specificity of 86% and sensitivity of 65%. During the active phase of labor, the measurements of the purple line length in the sacral region increased proportionally with cervical dilatation. The sensitivity was 56%, and the specificity was 65% when the fetal head descent reached the − 2 level.
Conclusions
In conclusion, the purple line in the sacral region is a non-invasive method to assess the course of labor and can be used as an adjunct to vaginal examinations and may reduce the number of vaginal examinations in clinical settings.
Supplementary Information
The online version contains supplementary material available at 10.1186/s12884-025-07300-0.
Keywords: Purple line, Labor monitoring, Labor progress, Partograph, Midwife
Highlights
This study evaluates the diagnostic accuracy of the purple line, a non-invasive method, for monitoring labor progress, specifically cervical dilatation and fetal head descent.
Data from 304 pregnant women in Istanbul, Türkiye, included demographic details, partograph records, and purple line measurements. Descriptive and ROC analyses were performed.
The purple line was observed in 85.9% of women, with highest sensitivity (0.962) at 5 cm dilatation and specificity (0.651) at 6 cm. It showed moderate diagnostic value for fetal head descent, with sensitivity (0.563) and specificity (0.652) at level -1.
The purple line demonstrates potential as a reliable, non-invasive tool for assessing labor progression, particularly cervical dilatation. Its integration into clinical practice could reduce the need for vaginal examinations and improve childbirth experiences.
Further research should explore the purple line’s usability, impact on maternal satisfaction, and integration into midwifery–led care. Education on purple line monitoring in childbirth should be incorporated into training programs to enhance positive birth experiences.
Supplementary Information
The online version contains supplementary material available at 10.1186/s12884-025-07300-0.
Background
Approximately 140 million births occur worldwide every year, with more than four births occurring every second [1, 2]. A positive childbirth experience is important for every woman worldwide. The World Health Organization (WHO) defines a positive birth as an experience that espouses women’s sociocultural beliefs and meets their expectations [3]. A systematic review and meta-analysis of 20 studies involving 22,800 participants from twelve countries indicated that support during childbirth, preparation for childbirth, and minimal interventions during labor were the most important factors leading to a positive birth experience [4].
Women can perceive their childbirth experiences as positive or negative or have mixed emotions about them. Negative childbirth experiences are attributed to various factors, such as a lack of knowledge, inability to use decision-making mechanisms, media influences, deficiencies in healthcare facilities, behaviors of healthcare personnel, cultural beliefs, and negative childbirth narrations by family elders [2]. However, it is crucial to monitor the progress of labor carefully and offer compassionate care during childbirth for a positive childbirth experience [5, 6].
The progress of labor can be monitored via a series of signs and symptoms, including cervical dilatation, cervical effacement, and fetal descent, along with the observation and measurement of the purple line in the sacral region, respiratory rate, changes in behavior, sounds, and movements [7–11]. Although various methods are available for monitoring the progress of labor, vaginal examination (manual examination) is predominantly preferred for evaluating cervical dilatation, cervical effacement, and fetal descent in clinical settings [7]. Several studies have shown that monitoring cervical dilatation increases concerns about the decisions made and interventions performed during labor [8, 12–15]. Furthermore, vaginal examination is described as an unpleasant, intrusive, embarrassing, and discomforting experience for women [16–19]. The frequency of vaginal examinations and lack of care during the procedure lead to pain, discomfort, anxiety, and negative emotions such as fear, embarrassment, guilt, and weakness among women, thereby reducing childbirth satisfaction [18]. Women with a history of sexual violence and posttraumatic stress disorder experience more stress during vaginal examinations [19]. Additionally, there is a positive relationship between the number of vaginal examinations and the risk of puerperal sepsis and genital tract infections [20].
In recent years, research has focused on the incorporation of objective, noninvasive, or less invasive methods into the monitoring of labor progress. Accurate assessment tools for the progress of labor are essential to reduce unnecessary interventions during childbirth. Noninvasive methods have been used to monitor the progress of labor to minimize interventions during childbirth [15]. Intrapartum ultrasound is used to determine the degree of cervical dilatation, fetal head position, and descent. The World Association of Perinatal Medicine published guidelines and recommendations on the use of ultrasound during childbirth in 2022. These guidelines suggest that the use of intrapartum ultrasound is an easy, simple, and noninvasive method that can serve as an adjunct that can correlate with digital vaginal examination findings. A recent systematic review recommended sonographic assessment of various fetopelvic parameters as a new gold standard for predicting the progress of labor, but further research is needed to confirm this finding [15]. Additionally, in recent years, the measurement of the purple line visualized in the sacral region of women, depending on ethnic origin and skin tone, has emerged as a different method for evaluating the progress of labor [14, 17, 21]. The purple line was first described in the literature by Byrne and Edmonds in 1990 [22].
During the progression of labor, the fetal head generates intrapelvic pressure as it moves through the birth canal. This pressure leads to congestion in the sacral region, resulting in the appearance of a purple line. The purple line extends upwards from the anal region along the sacral region during the first and second stages of labor [21]. The direction of this progression is upwards along the intergluteal line between the sacrococcygeal joint, akin to the movement of a mercury column in a thermometer [5, 21–24] and can be observed when the woman takes a side or quadruped position. Research has revealed a relationship between the length of the purple line and both cervical dilatation and fetal descent [5, 24].
It has been reported in the literature that the purple line emerges in 48 − 86.5% of women [21]. In a study conducted in Iran, the sensitivity, specificity, and accuracy rates of the emergence and progression of the purple line during childbirth were reported to be 87.91%, 39.53%, and 85.25%, respectively [23]. In another study, the purple line was observed in 56% of the women, and 81% of the women were not bothered by the purple line [17]. In a study analysing the diagnostic value of the purple line, the purple line was observed in 75.3% of women during active labor, and its appearance predicted the progress of labor with a sensitivity of 90.2%, specificity of 45.3%, and positive predictive value of 88.1% [5]. A systematic review based on data from six studies involving a total of 982 women revealed that the purple line was observed in 77.3% of the women. A moderate positive correlation was found between the length of the purple line and both cervical dilatation (r = + 0.64; 95% CI: 0.41–0.87) and fetal descent (r = + 0.50; 95% CI: 0.32–0.68). For women who underwent spontaneous or induced labor, the average length of the purple line was reported to be greater than 9.4 cm when the degree of cervical dilatation was 9–10 cm and greater than 7.3 cm when the degree of cervical dilatation was 3–4 cm. Consequently, this systematic review indicated that the purple line could be used as a noninvasive method for assessing the progress of labor [21].
In a Cochrane systematic review, uncertainty exists regarding which methods are most effective or acceptable for assessing the progress of labor, and more evidence about the assessment of the sacral purple line is needed [15].
In the current literature, there are several studies on the use of the purple line as a potential tool for monitoring the progress of labour. However, the sensitivity, specificity, and efficacy of the purple line in detecting cervical dilatation and foetal descent have not been adequately investigated. Although studies in different countries have provided some evidence, this biomarker requires validation and further research in different populations [5, 10, 17, 23, 24]. Research suggests that ethnic or geographical factors may influence physiological responses to the birth process [25, 26]. Genetic differences, cultural birth practices, dietary habits and social support systems may influence the occurrence of the purple line during labour.
Therefore, it is important to identify differences in the formation of the purple line in various populations. Factors such as the hormone profiles, skin texture and general health status of women from different ethnic backgrounds may alter the appearance of the purple line. For example, hormonal differences between some women may create differences in muscle tone or skin elasticity during labour. This study will evaluate the purple line as a biomarker in Turkish women and aims to provide a broader perspective on monitoring the progress of labour by comparing findings in different populations. In particular, by investigating the efficacy of the purple line in determining cervical dilatation and fetal descent, we aim to expand the current knowledge and contribute to clinical practice. The study also aimed to achieve the following objectives:
To determine the incidence of the purple line in the first and second stages of labor.
To evaluate the sensitivity and specificity of purple line measurements in determining the degree of cervical dilatation.
To evaluate the sensitivity and specificity of purple line measurements in determining the degree of fetal descent.
Method
Research methodology
This research design is an observational research method.
Study population and sample
The study population consisted of women who underwent vaginal birth at a maternal hospital located on the Anatolian side of Istanbul in 2021 (N = 1531 births). Convenience sampling was adopted, and the study sample comprised pregnant women presenting to hospital for birth between May and November 2021, were willing to participate in the study, and were 38–42 weeks of gestation. On the basis of the reported frequency of occurrence of the purple line during childbirth in the literature [10], the sample size was calculated via the OpenEpi program at 95% confidence interval, resulting in 275 participants. Considering the risk of data loss, the sample size was increased by 10% to 304 participants to ensure data adequacy.
The inclusion and exclusion criteria for the study were having 38–42 weeks of gestation, being admitted to the birth room with the onset of spontaneous labor, being Turkish, and being in the active phase of labor (having at least 4 cm of cervical dilatation) without any psychological or physical discomfort. These criteria were assessed by the research midwife in the delivery room.
Study results
In this study, independent and dependent variables are referred to as study outcomes. The independent variables of the study were cervical dilatation during labor and fetal head descent relative to the ischial spine, while the dependent variable was the length of the purple line observed and measured in the sacral region of women.
Data collection instruments
Five data collection instruments were employed in the study: an informed consent form, a personal identification form, a partograph form for labor monitoring, and a purple line tracking measurement tool, and a intrapartum assessment form.
Personal identification form
Developed by researchers on the basis of the literature [7, 14, 23], this form consists of 32 questions regarding sociodemographic characteristics such as age, education, income, and obstetric features, including pregnancy, birth, miscarriage, and abortion.
Partograph form for labor monitoring
Developed as a basic tool to monitor and evaluate the progression of labor within the scope of evidence-based medicine practices, the partograph helps early detection of abnormal conditions and diagnosis of prolonged labor by continuous and detailed recording of data related to the progression of labor and fetal health [27].
Sacral purple line measurement record form
Developed by researchers in light of the literature [5, 24, 28], this form was utilized to record the presence of the purple line in the sacral region, measured in cm using a measuring tape at hourly intervals during labor. A paper measuring tape with intervals of cm was used as the measurement tool (Fig. 1).
Fig. 1.
Measurement of the purple line
Intrapartum assessment form
Developed by researchers on the basis of the literature [29, 30], this form consists of 12 questions about the mode of birth, interventions applied during childbirth, and Apgar score.
Data collection procedure
The research team comprised academic and clinical midwives. The pregnant women who met the inclusion criteria and agreed to participate in the study were provided with an informed consent form upon admission to the birth room. Then, a personal identification form was filled out and data were collected using a partograph form and a sacral purple line measurement record form. The purple line was measured with a tape measure at hourly intervals with the woman in a comfortable position (on her side or on all fours). Vaginal examination was performed every 4 h according to clinical need. Vaginal examination was performed by the attending midwife, and the measurement of the purple line was conducted by the researcher. Findings from the vaginal examination and the length of the purple line were recorded by individuals who were blinded to the groups. All the pregnant women were routinely monitored, and the findings were recorded in the partograph. The length of the purple line was measured by a researcher blinded to the vaginal examination findings. The purple line was tracked by the same researcher. Purple line tracking continued hourly until the completion of labor. Labor progress was monitored via the partograph form, with data recorded at a maximum of four-hour intervals to avoid unnecessary interventions. After the completion of labor, the intrapartum assessment form was completed.
Data analysis
The obtained data were analysed via the Statistical Package for the Social Sciences. The normality of the data was assessed via the Kolmogorov‒Smirnov test. Descriptive statistical methods (frequency, percentage, mean, standard deviation) were utilized for data evaluation. Receiver operating characteristic (ROC) curve analysis and sensitivity and specificity tests were performed to analyse the diagnostic accuracy of the purple line as a diagnostic tool in medicine. It was used to determine the cut-off point of Roc analysis. This method provided optimum sensitivity and specificity to obtain clinically meaningful results. Determination of the cut-off point was favoured to reduce the effects of inter individual variation and to increase the clinical significance of the measurement results. p ≤ 0.05 was considered statistically significant.
Ethical considerations
Ethical approval for the research was obtained from the Clinical Research Ethics Committee of Zeynep Kamil Women and Children’s Diseases Training and Research Hospital (approval number: 109; approval date: 05.05.2021). Written informed consent was obtained from the pregnant women in accordance with the Helsinki Declaration.
Results
The results of this study include the following study outcomes: cervical dilatation during labor as independent variable, descent of the fetal head relative to the ischial spines as independent variable, and the length of the purple line observed and measured in the sacral region of women during labor as dependent variables.
The mean age of the women in the study was 27.74 ± 4.81 years, and the mean duration of marriage was 4.74 (4.12) years. Among all the women, 49% were high school graduates, and 69.4% were employed. The mean age at first pregnancy was 24.51 ± 4.30 years, the mean number of pregnancies was 1.92 ± 1.12, the mean number of living children was 1.23 ± 1.08, and the mean gestational age at birth was 39.05 ± 1.59 weeks (Table 1).
Table 1.
The distribution of the women by their sociodemographic and obstetric characteristics (n = 304)
| Variables | n | % | |
|---|---|---|---|
| Education Status | Illiterate | 9 | 3.0 |
| Primary School | 25 | 8.2 | |
| Middle School | 64 | 21.1 | |
| High School | 150 | 49.3 | |
| Undergraduate and above | 56 | 18.4 | |
| Not working | 4 | 1.3 | |
| Social Security Status | Insured | 287 | 93,1 |
| Uninsured | 21 | 6.9 | |
| Income Status | Good | 106 | 34.9 |
| Centre | 194 | 63.8 | |
| Bad | 4 | 1.3 | |
| Body Mass Index | Weak (< 18.5) | 22 | 7.2 |
| Normal (18.5–24.9) | 165 | 54.3 | |
| Overweight (25-29.9) | 79 | 26.0 | |
| Obese (> 30) | 38 | 12.5 | |
| Smoking status during pregnancy | Yes | 274 | 90.1 |
| No | 30 | 9.9 | |
| Alcohol Drinking During Pregnancy | Yes | 2 | 0.7 |
| No | 302 | 99.3 | |
| Exercise Status in Pregnancy | Yes | 189 | 62.2 |
| No | 115 | 37.8 | |
| Number of Pregnancy | Nulliparous | 146 | 48.0 |
| Multiiparous | 158 | 52.0 | |
| Total | 304 | 100.0 | |
| Variables | Mean (M) ± Standard Deviation (SD) | ||
| Number of Pregnancy | 1.92 ± 1.12 | ||
| Age | 27.74 ± 4.81 | ||
| Age at First Pregnancy | 24.51 ± 4.30 | ||
| Number of Living Children | 1.23 ± 1.08 | ||
| Pregnancy Week | 39.05 ± 1.59 | ||
Evaluation of the purple line according to cervical dilatation
The incidence of the first occurrence of the purple line was 57.9% in the first stage of labor and 66.4% in the second stage of labor. Among the 304 women who participated in the study, the follow-up of the presence of purple line in any stage of labour was 85.9% (Table 2).
Table 2.
Presence of a Purple line according to the stages of Labor
| Variable | Phase One | Phase Two | Purple Line at Any Stage of Labour | ||||
|---|---|---|---|---|---|---|---|
| (n) | % | (n) | % | (n) | % | ||
| Purple Line Presence | Available | 176 | 57.9 | 85 | 66.4 | 261 | 85.9 |
| None | 128 | 42.1 | 43 | 33.6 | 43 | 14.1 | |
| Total | 304 | 100.0 | 128 | 100.0 | 304 | 100.0 | |
Analyses of the sensitivity and specificity of the purple line when cervical dilatation was between 4 and 10 cm revealed that the highest sensitivity was 0.962 at 5 cm dilatation, and the highest specificity was 0.651 at 6 cm dilatation (Table 3; Fig. 2).
Table 3.
Diagnostic values of the measurement values of the length of the purple line in the progression of labor according to the degree of cervical dilatation
| Cervical Dilatation | ROC Area | Standard Error | p | Occurrence of purple line | Sensitivity | Specificity | Purple line Cut-off Value (cm) | |
|---|---|---|---|---|---|---|---|---|
| n | % | |||||||
|
3 cm Dilatation |
0.558 | 0.051 | 0.222 | 5 | 1.6 | - | - | 1.5 |
|
4 cm Dilatation |
0.713 | 0.049 | 0.0001 | 166 | 54.6 | 0.916 | 0.488 | 3.5 |
|
5 cm Dilatation |
0.969 | 0.010 | 0.0001 | 192 | 63.1 | 0.962 | 0.419 | 8.5 |
|
6 cm Dilatation |
0.775 | 0.045 | 0.0001 | 261 | 85.9 | 0.858 | 0.651 | 9.5 |
|
7 cm Dilatation |
0.733 | 0.048 | 0.0001 | 252 | 82.8 | 0.904 | 0.512 | 10.5 |
|
8 cm Dilatation |
0.737 | 0.048 | 0.0001 | 248 | 81.5 | 0.889 | 0.558 | 10.5 |
|
9 cm Dilatation |
0.642 | 0.052 | 0.003 | 233 | 76.6 | 0.927 | 0.326 | 11.5 |
|
10 cm Dilatation |
0.756 | 0.046 | 0.0001 | 197 | 64.8 | 0.881 | 0.605 | 13.5 |
*p < 0.05, **p < 0.001
Fig. 2.
Receiver operating characteristic (ROC) curve for the use of the Purple Line as a diagnostic tool for labor progress
As the degree of cervical dilatation increased, the cut-off value of the purple line also increased proportionally. The cut-off values were 3.5 cm at 4 cm, 8.5 cm at 5 cm, 9.5 cm at 6 cm, 10.5 cm at 7 cm, 8 cm, 11.5 cm at 9 cm, and 13.5 cm at 10 cm (Table 3).
Evaluation of the purple line according to fetal head descent
In the first stage of labor, the relationship between the sacral purple line length and the descent level of the fetal head was examined. When the fetal head descent was at level + 2, the average purple line length was greater than that at levels − 3, -2, and − 1. There was no significant correlation between fetal head descent at levels − 3 and + 2 and purple line length. However, a significant correlation was found between purple line length and fetal head descent at levels − 2, -1, 0, and + 1 (Table 4; Fig. 3).
Table 4.
Mean Purple Line Lengths and their correlations with fetal head descent levels in Labor Progression
| Fetal head descent | Purple Line Length | Pearson correlation coefficient | |||
|---|---|---|---|---|---|
| n |
|
SS | Min- Max | ||
| -3 | 43-(32 − 11) | 9.96 | 1.53 | 7.00–13.00 |
r = 1 - |
| -2 | 147 (116 − 31) | 8.90 | 1.36 | 5.00–12.00 |
r = 0.488 p < 0.001 |
| -1 | 157 (141 − 16) | 8.89 | 1.31 | 6.00–12.00 |
r = 0.643 p < 0.001 |
| 0 | 157 | 8.40 | 0.93 | 5.00–10.00 |
r = 0.791 p < 0.001 |
| 1 | 44 | 8.0 | 0.00 | 8.00–8.00 |
r = 0.846 p < 0.001 |
| 2 | 18 | 12.5 | 1.00 | 12.00–14.00 |
r:1 - |
*Min: minimum, Max: maximum
Fig. 3.
Collinearity value of the purple line length in the progression of labor according to fetal head descent levels
To determine the sensitivity and specificity of the purple line presence according to fetal head descent level, a value deemed significant (p < 0.05) was observed at the head level of -1, with a sensitivity of 0.563 and a specificity of 0.652 (Tables 4 and 5).
Table 5.
Diagnostic values of the measurement values of the length of the purple line in the progression of labor according to the level of head descent
| Fetal Head Descent | Fetal Head Descent | Fetal Head Descent | p | Occurrence of purple line | Sensitivity | Specificity | Purple line Cut-off Value (cm) | |
|---|---|---|---|---|---|---|---|---|
| n | % | |||||||
| -3 | 0.436 | 0.093 | 0.531 | 32 | 10.5 | 1.000 | 0.875 | 3.6 |
| -2 | 0.493 | 0.058 | 0.924 | 141 | 46.4 | 1.000 | 0.730 | 4.7 |
| -1 | 0.335 | 0.073 | 0.030 | 141 | 46.4 | 0.563 | 0.652 | 5.6 |
| 0 | 0.313 | 0.073 | 0.221 | 40 | 13.2 | 1.000 | 0.750 | 5.5 |
| 1 | 0.111 | 0.080 | 0.009 | 12 | 4.0 | 1.000 | 1.000 | 3 |
| 2 | - | - | - | - | - | - | - | - |
Discussion
The aim of this study was to evaluate the diagnostic accuracy of the length of the purple line in the sacral region as an additional method of determining cervical dilatation and fetal head descent as a method of monitoring the progression of labor. The purple line was found to have diagnostic accuracy in determining dilatation, and at 4–10 cm dilatation, its lowest sensitivity and specificity were 0.858 and 0.326, respectively. It was also shown to have diagnostic accuracy in determining fetal head descent, and at a fetal head descent of -1, its sensitivity and specificity were 0.563 and 0.652, respectively. These findings suggest that the presence of a purple line can be considered as an additional method to vaginal examination to assess cervical dilatation and descent of the head.
Studies in the literature have reported that 56–87.9% of women develop purple lines in the sacral regions during the active phase of labor [5, 10, 17, 23, 24, 31]. In a systematic review, purple line length for monitoring labor progression was reported to have an accuracy of 81–85%, meaning that more than 80% of women with normal labor progression could potentially be detected [32]. These findings support the results of the study and suggest that the purple line may often appear during the active phase of labor.
In a study by Farrag and Eltohamy, the appearance of the purple line during labor monitoring had a sensitivity of 87.91%, specificity of 39.53%, and accuracy of 85.25% [23]. In the study by Kordi et al., the sensitivity and specificity of the purple line in women during the active phase of labor ranged from 68.57 to 87.91% and from 42.66 to 39.53%, respectively, with the purple line being more prominent in women with lighter skin tones than in those with darker skin tones [31]. The sensitivity and specificity values above 0.60 in this study indicate the potential diagnostic utility of the purple line in labor progression. The high sensitivity identified in this study can be explained by the fact that all the participating women were Caucasian. As a result of the review, no other study was found that evaluated the sensitivity and specificity of purple line appearance according to the length of cervical dilatation in centimeters. Existing studies in the literature seem to focus on the presence of a purple line [5, 10, 17, 23, 24, 31].
Irani et al. also evaluated fetal head and purple line length and found that total purple line length was correlated with fetal head position and the mean values were 86.52 ± 23.61 at -3, 93.97 ± 20.7 at -2, 99.21 ± 24.21 at -1, 108.25 ± 19.27 at 0 and 110.82 ± 16.84 at + 1 [7]. These results may indicate a moderate diagnostic value of purple line length in determining fetal head descent. However this study, the diagnostic value of the purple line at the − 3 and + 2 levels could not be interpreted. Positive correlations between fetal head descent at all levels and purple line length have been reported in the literature [7, 23]. The correlation of purple line length with fetal head descent of -2, -1, 0, and + 1 and the lack of correlation of purple line length with fetal head descent of -3 and + 2 can be explained by increased pressure on the sacrum when the fetal head is at levels 2, -1, 0, and + 1, enhancing the visibility of the purple line.
Limitations of the study
This study has several limitations. Firstly, the measurements and assessments of cervical dilatation, fetal head descent and purple line may vary depending on the person performing the measurements. In this study, all measurements were performed by the same investigator to minimise bias due to the measurement process. However, the absence of a second researcher or a second midwife measuring the length of the purple line or cervical dilatation may have caused inter observer variability. Another limitation is that women in induced labor or women of different ethnicity/skin colour were not included in the study.
The Turkish women who participated in the study represent a heterogeneous group with different skin tones (fair, wheat, brunette). However, another limitation of the study is that the skin tones of the participants were not collected and included in the evaluation.
The strength of the study is that it is one of the few studies to assess the length of the purple line during labor, investigating the utility of this phenomenon as a potential diagnostic tool in the follow-up of the labor process. The assessment of the purple line on the basis of each degree of cervical dilatation and fetal head descent is also a strength. Because there are very limited studies on this subject.
The data on the presence and length of the purple line in this study may have been influenced by maternal pelvic bone measurements and fetal head size. This emphasizes the need for studies evaluating the variation of the purple line according to pelvic bone and fetal head measurements.
Conclusion and recommendations
This study showed that the probability of observing the purple line was high, with moderate to high diagnostic value for detecting cervical dilatation and moderate diagnostic value for detecting fetal head descent. Purple line measurement will be useful in reducing the number of vaginal examinations in clinical practice. Different cut-off points corresponding to cervical dilatation were determined in the study. When cervical dilatation was exactly 10 cm (full dilatation), there was an 88% probability that the purple line length was 13.5 cm. However, the variability in the presence of the purple line, which is influenced by physiological and anatomical differences, underlines the need for further investigation, especially in populations with different skin tones and phenotypes. The findings highlight the potential to reduce vaginal examinations but should be interpreted with caution within these parameters.
Based on these results, the purple line may serve as a useful, noninvasive alternative method for monitoring cervical dilatation during labor. However, further studies are necessary to confirm its reliability and generalizability across diverse populations before it can be broadly recommended for clinical practice. It can also be taught in undergraduate and in-service training programs for monitoring labor progression, thereby contributing to the improvement of positive birth experiences. Moreover, policies could be developed to integrate the use of the purple line for labor monitoring under midwifery leadership in maternity units. Additionally, further studies should focus on evaluating the satisfaction of women, maternal and neonatal outcomes, usability, and effectiveness of purple line-guided births.
Electronic supplementary material
Below is the link to the electronic supplementary material.
Acknowledgements
We would like to express our deep gratitude to Prof. Dr. Zekiye KARAÇAM, Midwife Betül Engin, Midwife Sena Nur Karadeniz, Midwife Döne Abbasoğlu, Midwife İpek Yıldız and Midwife Mervenur Kasap for her valuable contributions to the preparation of this article. Prof. Dr. Zekiye KARAÇAM, Midwife Betül Engin, Midwife Sena Nur Karadeniz, Midwife Döne Abbasoğlu, Midwife İpek Yıldız, and Midwife Mervenur Kasap made significant contributions throughout the process with her valuable technical assistance, guidance, and support, greatly enhancing the quality of our study.
Author contributions
A.D.Y. and T.Y. wrote the main manuscript text and B.A. prepared Figs. 1, 2 and 3. All authors reviewed the manuscript.
Funding
This research received no specific grants from any funding agency in the public, commercial or non-profit sectors.
Data availability
Data is provided within the manuscript or supplementary information files.
Declarations
Ethics approval and consent to participate
Ethical permissions for the research were obtained from the Zeynep Kamil Women and Children Diseases Training and Research Hospital Clinical Research Ethics Committee (Decision:109, Date: 05.05.2021). In accordance with the Helsinki Declaration, informed consent forms were obtained from the pregnant women participating in the research. All participants were fully informed of the purpose and methods of the trial and signed informed consents.
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interests.
Footnotes
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
References
- 1.The World Counts. Impact through awareness. 2024. https://www.theworldcounts.com/populations/world/births. Accessed; 03 Jan 2024.
- 2.Altun E, Kaplan S. Doğum travmasının anne ve bebek bağlanması üzerine etkisi. Türkiye Sağlık Bilimleri Ve Araştırmaları. Dergisi. 2021;4(1):54–66. 10.51536/tusbad.817966. [Google Scholar]
- 3.World Health Organization. Intrapartum care for a positive birth experience Report. 2018. https://www.who.int/publications/i/item/9789241550215.Accessed; 03 Jan 2024.
- 4.Taheri M, Takian A, Taghizadeh Z, Jafari N, Sarafraz N. Creating a positive perception of childbirth experience: systematic review and meta-analysis of prenatal and intrapartum interventions. Reprod Health. 2018;15(1):73. 10.1186/s12978-018-0511-x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Kordi M, Irani M, Tara F, Esmaily H. The diagnostic accuracy of purple line in prediction of labor progress in omolbanin hospital, Iran. Iran Red Crescent Med J. 2014;16(11). 10.5812/ircmj.16183. [DOI] [PMC free article] [PubMed]
- 6.Wonde TE, Mihretie A. Maternofetal outcomes of obstructed labor among women who gave birth at general hospital in Ethiopia. BMC Res Notes. 2019;12:128. 10.1186/s13104-019-4165-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Irani M, Kordi M, Esmaily H. Relationship between length and width of the purple line and foetal head descent in active phase of labor. J Obstet Gynaecol. 2018;38(1):10–5. 10.1080/01443615.2017.1322044. [DOI] [PubMed] [Google Scholar]
- 8.Buchmann EJ, Libhaber E. Accuracy of cervical assessment in the active phase of labor. BJOG: Int J Obstet Gynecol. 2007;114(7):833–7. 10.1111/J.1471-0528.2007.01386.X. [DOI] [PubMed] [Google Scholar]
- 9.Nash K. Is it time for a more holistic assessment of labor progress? Br J Midwifery. 2020;28(8):457–9. 10.12968/bjom.2020.28.8.457. [Google Scholar]
- 10.Irani M, Kordi M, Lotfalizadeh M. Methods of assessing the Labor Progress: a review study. Iran J Obstet Gynecol Infertility. 2019;21(11):80–90. 10.22038/ijogi.2019.12330. [Google Scholar]
- 11.Fumagalli S, Antolini L, Cosmai G, Gramegna T, Nespoli A, Pedranzini A, Colciago E, Valsecchi MG, Vergani P, Locatelli A. Development and validation of a predictive model to identify the active phase of labor. BMC Pregnancy Childbirth. 2022;22(1):641. 10.1186/s12884-022-04946-y. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12.Phelps JY, Higby K, Smyth MH, Ward JA, Arredondo F, Mayer AR. Accuracy and intraobserver variability of simulated cervical dilatation measurements. Am J Obstet Gynecol. 1995;173(3 Pt 1):942–5. 10.1016/0002-9378(95)90371-2. [DOI] [PubMed] [Google Scholar]
- 13.Letić M. Inaccuracy in cervical dilatation assessment and the progress of labor monitoring. Med Hypotheses. 2003;60(2):199–201. 10.1016/s0306-9877(02)00358-4. [DOI] [PubMed] [Google Scholar]
- 14.Shepherd A, Cheyne H, Kennedy S, McIntosh C, Styles M, Niven C. The purple line as a measure of laborprogress: a longitudinal study. BMC Pregnancy Childbirth. 2010;10(54). 10.1186/1471-2393-10-54. [DOI] [PMC free article] [PubMed]
- 15.Moncrieff G, Gyte GM, Dahlen HG, Thomson G, Singata-Madliki M, Clegg A, Downe S. Routine vaginal examinations compared to other methods for assessing progress of labor to improve outcomes for women and babies at term. Cochrane Database Syst Rev. 2022;3(3):CD010088. 10.1002/14651858.CD010088.pub3. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Lewin D, Fearon B, Hemmings V, Johnson G. Women’s experiences of vaginal examinations in labor. Midwifery. 2005;21(3):267–77. 10.1016/J.MIDW.2004.10.003. [DOI] [PubMed] [Google Scholar]
- 17.Narchi NZ, Camargo Jda, Salim CS, Menezes NR, de Bertolino M. The use of the purple line as an auxiliary clinical method for evaluating the active phase of birth. Revista Brasileira De Saúde Materno Infantil. 2011;11(3):313–22. http://www.scielo.br/scielo.php?pid=1519-3829%26;script=sci_serial. [Google Scholar]
- 18.Yılar Erkek Z, Özer S. Mothers’ opinions regarding vaginal examination during birth. Anatol J Nurs Health Sci. 2020;23(1):9–16. 10.17049/ataunihem.457236. [Google Scholar]
- 19.Weitlauf JC, Finney JW, Ruzek JI, Lee TT, Thrailkill A, Jones S, Frayne SM. Distress and pain during pelvic examinations: effect of sexual violence. Obstet Gynecol. 2008;112(6):1343–50. 10.1097/AOG.0b013e31818e4678. [DOI] [PubMed] [Google Scholar]
- 20.Shepherd A, Cheyne H. The frequency and reasons for vaginal examinations in labor. Women Birth. 2013;26(1):49–54. 10.1016/J.WOMBI.2012.02.001. [DOI] [PubMed] [Google Scholar]
- 21.Papoutsis D, Antonakou A, Gornall A, Tzavara C. The purple line and its association with cervical dilatation in labor: a systematic review and meta-analysis. Eur J Obstet Gynecol Reprod Biol. 2023;289:91–9. 10.1016/j.ejogrb.2023.08.383. [DOI] [PubMed] [Google Scholar]
- 22.Byrne DL, Edmonds DK. Clinical method for evaluating progress in first stage of labor. Lancet. 1990;335(8681):122. 10.1016/0140-6736(90)90600-a. [DOI] [PubMed] [Google Scholar]
- 23.Eid Farrag R, Abd ElHamed Eltohamy N. Accuracy of purple line to monitor labor progress: longitudinal study. Egypt J Health Care. 2021;12(1):30–44. 10.21608/ejhc.2021.135120. [Google Scholar]
- 24.Nunes RD, Locatelli P, Traebert J. Use of the purple line to diagnose cervical dilatation and fetal head station during labor. Int J Gynecol Obstet. 2018;141(2):250–1. 10.1002/ijgo.12459. [DOI] [PubMed] [Google Scholar]
- 25.Leimert KB, Olson DM. Racial disparities in pregnancy outcomes: genetics, epigenetics, and allostatic load. Curr Opin Physiol. 2020;13:155–65. 10.1016/j.cophys.2019.12.003. [Google Scholar]
- 26.Alhusen JL, Bower KM, Epstein E, Sharps P. Racial discrimination and adverse birth outcomes: an integrative review CEU. J Midwifery Women’s Health. 2016;61:707–20. 10.1111/jmwh.12490. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 27.Ministry of Health Partograph Circular. 2015. https://shgmkalitedb.saglik.gov.tr/TR-94678/partograf-ornegi.html. Accessed; 03 Jan 2024.
- 28.Hobbs L. Assessing cervical dilatation without VEs. Watching the purple line. Pract Midwife. 1998;1(11):34–5. https://pubmed.ncbi.nlm.nih.gov/10214276. [PubMed] [Google Scholar]
- 29.The Royal College of Midwives (The RCM). The RCM standards for midwifery services in the UK Format of report Sect. 1. 2016. Accessed; 05 Jan 2024. https://www.rcm.org.uk
- 30.Rayment J, Rocca-Ihenacho L, Newburn M, Thaels E, Batinelli L, Mcourt C. The development of midwifery unit standards for Europe. Midwifery. 2020;86:102661. 10.1016/j.midw.2020.102661. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 31.Kordi M, Irani M, Tara F, Esmaeily H. Comparing diagnostic accuracy of purple line with Transvers Diagonal of Michaelis Sacral to Predict labor progress. J Midwifery Reproductive Health. 2013;1(1):7–12. 10.22038/jmrh.2013.754. [Google Scholar]
- 32.Pan WL, Chen LL, Gau ML. Accuracy of non-invasive methods for assessing the progress of labor in the first stage: a systematic review and meta-analysis. BMC Pregnancy Childbirth. 2022;22:608. 10.1186/s12884-022-04938-y. [DOI] [PMC free article] [PubMed] [Google Scholar]
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Data Availability Statement
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