Dr. Renuka Malik is working as a Professor and Consultant in Obstetrics and Gynecology in PGIMER and DR. RML Hospital, a CGHS Hospital, New Delhi, for more than 25 years. She has a keen interest in laparoscopy and high-ri s k obstetrics.
Introduction : Non-progress of labour forms the largest indication caesarean section. The diagnosis of failure of descent using serial digital examination is objective, poor reproducibility, carries the risk of infection and is painful to the labouring patient. There is a need if not an alternative, adjunctive to digital vaginal examination. Measuring angle of descent (AOD) to predict vaginal birth in late labour by transperineal ultrasound provides an alternative without any of the above-mentioned drawbacks.
Materials and Methods : A prospective observational study in 64 patients in the late first stage and second stage of labour with cephalic presentation was carried out, from September 2017 to December 2018, in PGIMER and DR. RML Hospital. Angle of descent was measured by transperineal ultrasound. Angle of descent is the angle between the longitudinal axis of pubic bone and a line joining the lowest edge of the pubis to the lowest convexity of the foetal skull. Time of assessment of AOD1 was noted, and if patient did not deliver within 2 h, another AOD2 was recorded. Eighty-five readings were obtained, and AOD predicting successful vaginal delivery was calculated.
Results and Discussion : AOD of 116° and more resulted in vaginal delivery, spontaneous or instrumental. As the angle of descent increased, there was a decrease in time interval to vaginal delivery with correlation coefficient of − 0.939.
Conclusions : The use of intrapartum transperineal ultrasound and measurement of angle of descent can prove to be a valuable adjunct in management of labour, especially in cases of prolonged first and second stages of labour in predicting successful vaginal delivery. AOD of 116° or more can predict successful vaginal delivery within 2 h. AOD can be used in centres having facilities of intrapartum ultrasound. The authors recommend the use of ultrasound in labour room as it is non-invasive and can provide a lot of information. This method is currently useful for tertiary centres or medical colleges.
Keywords : Transperineal ultrasound · Angle of descent · Progress of labour
Traditionally, the assessment of progress of labour in a woman is based upon dilatation and descent of presenting part by periodic vaginal examination. However, clinical examination of head station and position is inaccurate and subjective, especially when caput succedaneum impairs palpation of sutures and fontanelles. Assessment of descent as well as dilatation on digital vaginal examination has a drawback of being highly subjective, uncertain reproducibility and operator dependent. These methods involve an unrealistic expectation of clinicians to possess an uncanny perception of three-dimensional relationships. Assessment of station of descent of foetal head is dependent upon an imaginary line drawn between the often inaccessible ischial spines. Nevertheless, this is the sole criterion used in clinical practice today.
Ultrasound imaging has already been reported as an adjunctive method for evaluating the level of the foetal presenting part within the maternal pelvis [1, 2]. Intrapartum transperineal ultrasound has the advantage of being objective and highly reproducible as compared to digital examination [3–6].
The recent years have seen a change in many trends—the importance of non-invasive techniques, reliability, reproducibility of documentation, trends in minimising infection, change in criteria for non-progress of labour (NPL) and steps to reduce the alarming rise of caesarean delivery (ACOG 2014). NPL forms the largest indication for primary caesarean section. The diagnosis of failure of descent using serial digital examination is objective, poor reproducibility, carries the risk of infection and is painful to the labouring patient. There is a need if not an alternative, adjunctive to digital vaginal examination.
Measuring angle of descent to predict vaginal birth in late labour by transperineal ultrasound provides an alternative without any of the above-mentioned drawbacks.
Descriptive Characteristics of Study PopulationAmong the total of 64 study subjects, labouring patients were in the age group of 20–40 years. Maximum patients were present in the age group of 20–30 years. 79.69% patients were in the age group of 20–30 years, and 20.31% were in the age group of 30–40 years. 54.69% patients were primigravida and 45.31% patients were multigravida. Among the total of 64 study subjects, 57 (89.2%) females had vaginal delivery and 7 (10.94%) patients had LSCS. Two patients (3.13%) had instrumental (vacuum-assisted) vaginal delivery.
In our study population, it was found that with angle of descent reading of more than 116 all the patients delivered vaginally. None of the patients delivered when angle of descent was < 90°. All patients who had LSCS had angle of descent less than 110°. Between 101° and 110°, seven patients had LSCS and one patient had vaginal delivery. Seven patients had caesarean for non-progress of labour, five were in the first stage and two were in the second stage. There was no foetal distress in any of the seven patients, undergoing LSCS. When angle of descent was between 111° and 120°, five patients had spontaneous vaginal delivery and two patients had vacuum-assisted vaginal delivery (Table 1). The average angle of descent in vaginal deliveries was 150° (SD 22.02) compared to 110° in caesarean sections and 120° in vacuum-assisted vaginal delivery (P < 0.00002) (Table 2, Fig. 3).
The ROC curve for angle of descent for vaginal delivery showed an area under the curve (AUC) of 0.989. The value of the angle of descent that optimises the curve is 116°. There was no caesarean section with angle of descent more than 116°, that is, all patients delivered vaginally.
116° AOD showed sensitivity of 96.49% and specificity of 96.43% for cut-off value of 116° in cases who delivered vaginally, value higher than that found in cases delivered by caesarean section. This difference was of high statistical significance AUC of 0.989 (Fig. 4).
We noticed an inverse and significant relationship between the AOD and the duration of the second stage of labour, so at a greater angle of descent, a shorter duration of the second stage was found (P < 0.0001). Mean time interval to vaginal delivery when measurement of angle of descent was between 90° and 120° was found to be 107 min, for angle of descent between 121° and 150° was 54 min, for angle of descent between 151° and 180° was 20 min and for angle of descent > 180° was 3.6 min (Table 3).
Eighty-five sets of measurements, consisting of transperineal ultrasound angle and time until delivery, were obtained from 64 women during the active stage of labour. Out of 21 patients who required a second measurement of AOD ( AOD2), 15 patients had vaginal delivery (13 normal vaginal delivery and 2 instrumental delivery) with AOD2 more than 116° and 6 patients had LSCS with AOD2 less than 116° (Fig. 5).
In order to determine whether the time to delivery was associated with the magnitude of the transperineal angle, transperineal angles were divided into four groups ≤ 135°, 136°–167°, 168°–200° and > 200°. Table 4 lists the descriptive statistics for the mean time to delivery for each group based on Kaplan–Meier analyses. It is observed that larger transperineal ultrasound angles during the second stage of labour were associated with significantly decreased time to delivery. The group with smallest angles (< 135°) had had markedly greater time of delivery (mean 85 min) than the other groups (136–167°) with mean 39 min, 168–200° with mean time 10 min and > 200 with mean time 1 min. The decrease in time to delivery became relatively smaller as the magnitude of the angle increased (Fig. 6). In our study, it was found that as the angle of descent increases there is a decrease in time interval to vaginal delivery with correlation coefficient of − 0.939. This is of high statistical significance P < 0.0001 (Table 4, Fig. 6).
Along with angle of descent, several other parameters that reflect foetal head descent in mid sagittal section have been proposed, including progression distance (the distance between leading edge of the foetal skull and the line perpendicular to the inferior edge of the pubis), head direction (the angle between the major longitudinal axis of foetal head and the line perpendicular to the inferior edge of pubis), head–symphysis distance and head–perineum distance. Among them, angle of descent was one of the most reliable parameters because of the minimal inter- and intraobserver errors [1, 7]. To summarise, in our study it was found that with angle of descent reading of more than 116° all the patients delivered vaginally (P < 0.00002). There was an inverse and significant relationship between the angle of descent and the duration of the second stage of labour, so at a greater angle of descent, a shorter duration of the second stage was found (P < 0.0001). As the angle of descent increased, there was a decrease in time interval to vaginal delivery with correlation coefficient of − 0.939, which was of statistical significance P < 0.0001. Similar studies in past have also predicted a cut-off value as 120°. In 2009, Barbera et al. studied the similar angle and described intra- and inter-observer variability of less than 3°. Their data in 88 term labouring patients showed that an angle of at least 120° was always associated with subsequent vaginal delivery. A similar study was conducted by Silvia Pina Perez et al. in 2017 who found that the value of angle of descent of 125° had 85% probability of vaginal delivery [8–11].
The strength of our study was that it was non-invasive technique, easy, reliable and gave a reproducible documentation of findings which can help in decision making in terms of leaving the patient for vaginal delivery as opposed to termination by caesarean in cases of prolonged second stage.
The weakness of our study was small size of the study and the absence of occipito-posterior position in our study group. A large number of patients and a computerised measurement of angle of descent are required in future studies.
Measurement of AOD is an easy method and has been successfully used even by midwives with good reproducibility [12]. Measuring AOD has an edge over traditional per vaginal examination which has person-to-person variability [13]. However, at present, due to a limited number of studies it is recommended as an ancillary tool to tradition per vaginal digital examination used to assess progress of labour. AOD can be used in centres having facilities of intrapartum ultrasound. Authors recommend the use of ultrasound in labour room as it is non-invasive and can provide a lot of information. This method is currently useful for tertiary centres or medical colleges. More studies are required to validate the degree of AOD to predict successful vaginal delivery in Indian pregnant women.
This study was conducted between March 2015 and June 2016 at Obstetrics and Gynaecology Department of Bangalore Baptist Hospital, Karnataka.
The study was powered to detect 0.5% difference in glycaemic control between the groups. The estimated sample size of 50 subjects in each group (total of 100) would give a power of 80% with 95% confidence interval.
This study was a randomized open-labelled trial on 99 pregnant women diagnosed with overt diabetes and gestational diabetes.
The criteria for eligibility were pregnant women with a diagnosis of pregestational diabetes (if diagnosed before pregnancy), overt diabetic (if FBS > 126 mg/dl, HbA1c- > 6.5 and RBS > 200 mg/dl, to be confirmed with FBS or HbA1c), gestational diabetes based on 75 g OGTT (DIPSI)—2 h > 140 mg/ dl, 75 gms OGTT (HAPO)—FBS > 92 mg/dl, 1 h > 180 mg/ dl, 2 h > 153 mg/dl, 100 gm OGTT (ACOG)—FBS > 95 mg/ dl, 1 h > 180 mg/dl, 2 h > 155 mg/dl, 3rd h > 140 mg/dl and gestational glucose intolerance based on 75 g OGTT (DIPSI)—2 h > 120–139 mg/dl.
Pregnant women with multiple pregnancies, hypertension, chronic kidney or liver disease and those not giving consent were excluded from the study.
The summary of the study design is illustrated in Fig. 1. The recruited participants were block randomized by a computergenerated random number sequence into group A and group B by the central randomization team of the research department. Rigour in allocation and concealment was addressed through techniques like central randomization, using sequentially numbered, opaque and sealed envelopes (SNOSE).
Pregnant ladies belonging to group A were screened for vitamin D deficiency as soon as they entered the study.
Women in group B were screened for vitamin D deficiency when they were admitted for delivery as it is not ethical to leave them as a control group if vitamin D deficiency was detected in the antenatal period.
Forty women in group A were found to be vitamin D deficient and were included in the supplemented group (group D).
They were given 60,000 units of vitamin D3 once a month till delivery. Vitamin D supplementation is not teratogenic, and ACOG guidelines recommend vitamin D supplementation in those who are found to be deficient [5, 6]. A number of Indian trials with 60,000 IU/month indicated better patient compliance as compared to 2000 IU/4000 IU per day doses. There is substantial evidence that a higher dose (60,000 IU) per month does not show any clinical side effects in vitamin D-deficient pregnant women [7]. The participants were contacted every month when they came for their antenatal check-ups or by telephone after the initiation of the trial. This was to ensure that the study medication was taken correctly and to register any adverse events. Telephonic reminders were made to the patients to remind them to take vitamin D capsules as per schedule every month. They were also informed to report any interval morbidity including nausea, vomiting, excessive thirst, frequent urination, constipation, abdominal pain, weakness and confusion.
Both arms were given routine antenatal care. Participants were advised to maintain their usual medical care and life style in the study period. Glycaemic control, medication changes, mode of delivery and neonatal outcomes were recorded.
Group B were screened for vitamin D deficiency when they were admitted for delivery, and those who were found to be vitamin D deficient were included in the control group (group C). At the completion of study glycaemic control, mode of delivery and neonatal outcomes were compared between vitamin D-deficient women in the intervention group (group D) and the control group (group C).
This study was approved by the institutional review board of the hospital.
On the basis of previous study “A new method to assess fetal head descent in labor with Transperineal ultrasound” by Barbera et al. in 2009 (− 0.8 to − 0.95) and taking this value as reference, the minimum required sample size with 10% margin of error and 5% level of significance is 60 patients. So total sample size taken is 64. Formula used is:
where Zα is the value of Z at two sided alpha error of 5%, ME
is margin of error and p is prevalence rate.
Categorical variables were presented as number and percentage (%), and continuous variables were presented as mean ± SD and median. Normality of data was tested by the Kolmogorov–Smirnov test. If the normality was rejected, then nonparametric test was used. Quantitative variables were compared using Mann–Whitney test (as the datasets were not normally distributed) between the two groups and Kruskal–Wallis test between more than two groups. Qualitative variables were correlated using Chisquare test. Spearman’s rank correlation coefficient was used to assess the correlation of quantitative parameters with each other. Receiver operating characteristic curve was used to find out cut-off point of angle of descent for predicting vaginal delivery. Kaplan–Meier survival analysis curve was used to find out time of vaginal delivery. The data analysis was performed using Statistical Package for Social Sciences (SPSS), version 21.0.
Conflict of interest The authors declare that they have no conflict of interest.
Ethical Approval Hospital ethical committee clearance for study was taken (file no-1776/17 dated 30.10.17).
Informed consent Written and informed consent was obtained from patients for publication of data.
