Where is the presenting part of the fetus when station is -1
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Fetal head descent can be expressed as fetal station and engagement. Station is traditionally based on clinical vaginal examination of the distal part of the fetal skull and related to the level of the ischial spines. Engagement is based on a transabdominal examination of the proximal part of the fetal head above the pelvic inlet. Clinical examinations are subjective, and objective measurements of descent are warranted. Ultrasound is a feasible diagnostic tool in labor, and fetal lie, station, position, presentation, and attitude can be examined. This review presents an overview of fetal descent examined with ultrasound. Ultrasound was first introduced for examining fetal descent in 1977. The distance from the sacral tip to the fetal skull was measured with A-mode ultrasound, but more convenient transperineal methods have since been published. Of those, progression distance, angle of progression, and head-symphysis distance are examined in the sagittal plane, using the inferior part of the symphysis pubis as reference point. Head-perineum distance is measured in the frontal plane (transverse transperineal scan) as the shortest distance from perineum to the fetal skull, representing the remaining part of the birth canal for the fetus to pass. At high stations, the fetal head is directed downward, followed with a horizontal and then an upward direction when the fetus descends in the birth canal and deflexes the head. Head descent may be assessed transabdominally with ultrasound and measured as the suprapubic descent angle. Many observational studies have shown that fetal descent assessed with ultrasound can predict labor outcome before induction of labor, as an admission test, and during the first and second stage of labor. Labor progress can also be examined longitudinally. The International Society of Ultrasound in Obstetrics and Gynecology recommends using ultrasound in women with prolonged or arrested first or second stage of labor, when malpositions or malpresentations are suspected, and before an operative vaginal delivery. One single ultrasound parameter cannot tell for sure whether an instrumental delivery is going to be successful. Information about station and position is a prerequisite, but head direction, presentation, and attitude also should be considered. Show High station at specific points in the first stage of labor, such as a floating head on admission, or at 4-cm dilation or when arrest of dilation occurs, is associated with higher rates of failure to deliver vaginally. Therefore it could be useful to know if station is within an expected range at a given dilation during first stage. Arrest of descent disorders have been defined thus far on criteria applicable in the second stage. Statistical modeling is an attractive methodology to characterize the relationship between station and dilation because the resulting mathematical expressions could be used as a reference for comparison in the future. In addition, they can be used to produce a finely graded assessment of descent using numerical terms such as percentile rankings. A 2-step approach to potentially improving the assessment of station could be to develop a statistical model that describes the general relationship between station and dilation in the first stage of uncomplicated births and then determine if such a model would have identified births with complications related to poor labor progress. Given the complex nature of labor data, especially the imprecision of dilation and station measurement, it is not immediately evident that such a model is identifiable or what its precision would be. ObjectiveWe sought to characterize in mathematical terms the relationship of station to dilation during the first stage of labor for nulliparous and multiparous women with spontaneous vaginal births. Study DesignThis retrospective cohort study included 28,121 exams from 5555 women with singleton cephalic presentations at ≥37 weeks’ gestation with electronic fetal monitoring tracings, who delivered vaginally without instrumentation and had 5-minute Apgar scores >6 at 2 academic community referral hospitals in 2012 through 2013. Women with a previous cesarean birth were excluded. We used longitudinal statistical techniques suitable to biological data that were irregularly sampled with repeated measures over time. ResultsA linear relationship was observed between station and dilation. For both nulliparous and multiparous women the final model was a linear regression with random effects for intercept and slope and a first-order autoregressive correlation structure. The 5th-95th range of station at any given dilation spanned about 3-4 cm. ConclusionOur results demonstrate a general trend of increasing descent of the presenting part as dilation advances during the first stage of labor in women who delivered vaginally without instrumentation. We propose that the mathematical expressions describing this relationship may be valuable in the assessment of first-stage labor progression.
Key wordsfetal descent fetal station first stage of labor Recommended articles
This study was supported by PeriGen, Cranbury, NJ. Drs Hamilton, Warrick, and Garite are employed by PeriGen. Ms Simoneau, Ms Collins, and Drs Ciampi and Smith have no conflict of interest to declare. Cite this article as: Hamilton EF, Simoneau G, Ciampi A, et al. Descent of the fetal head (station) during the first stage of labor. Am J Obstet Gynecol 2016;214:360.e1-6. When the fetal presenting part is at the level of the ischial spine the station is?0 station. This is when the baby's head is even with the ischial spines.
Where is the presenting part of the fetus one station is?Fetal station chart
The “presenting” or most palpable (able to feel) part of the baby is above the woman's ischial spines. Sometimes a doctor can't feel the presenting part. This station is known as the “floating.” The baby's head is known to be “engaged,” or aligned with the ischial spines.
What does minus 3 station mean in pregnancy?Fetal station is stated in negative and positive numbers. -5 station is a floating baby. -3 station is when the head is above the pelvis. 0 station is when the head is at the bottom of the pelvis, also known as being fully engaged. +3 station is within the birth canal.
What does it mean when baby is at Station?What is Fetal Station?? Fetal station is the measurement of how high or low baby is in the pelvis. Fetal station is measured by assessing where baby's presenting portion (usually the head) is in relation to the ischial spines, two bony protrusions on the back of the pelvis.
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