Cervical effacement

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The cervix is located in the lower part of the uterus and connects the uterine cavity to the vagina. The cervix consists of two parts; the upper part lies in the pelvic/abdominal cavity and the lower part is intravaginal. Illu cervix.svg
The cervix is located in the lower part of the uterus and connects the uterine cavity to the vagina. The cervix consists of two parts; the upper part lies in the pelvic/abdominal cavity and the lower part is intravaginal.

Cervical effacement or cervical ripening refers to the thinning and shortening of the cervix. This process occurs during labor to prepare the cervix for dilation to allow the fetus to pass through the vagina. While this is a normal, physiological process that occurs at the later end of pregnancy, it can also be induced through medications and procedures. [2]

Contents

During gestation, the cervix maintains pregnancy by increasing synthesis of various proteins. These proteins have defined interactions that allow the formation of matrix proteins to help fortify the uterine cervix. [3] Toward the end of pregnancy, a series of hormone-mediated biochemical process takes place to degrade the collagen and fiber network to cause the cervix to ripen during labor. Failure to ripen the cervix during labor may delay its onset and cause complications. [4] Current efforts to induce labor include pharmacologic, non-pharmacologic, mechanical and surgical methods.

Cervical ripening has primarily been performed in the inpatient setting. Due to a variety of reasons, such as cost and patient preference, the capacity to undergo outpatient cervical ripening is being explored. [5]

Mechanism

Physiological

Prior to effacement, the cervix is like a long bottleneck, usually about four centimeters in length. Throughout pregnancy, the cervix is tightly closed and protected by a plug of mucus. Effacement is accompanied by cervical dilation. When the cervix effaces, the mucus plug is loosened and passes out of the vagina. The mucus may be tinged with blood and the passage of the mucus plug is called bloody show (or simply "show"). As effacement takes place, the cervix then shortens, or effaces, pulling up into the uterus and becoming part of the lower uterine wall.

Diagram showing an outline of the changes occurring during cervical ripening Cells-11-03690-g001-550.jpg
Diagram showing an outline of the changes occurring during cervical ripening

Histological and biochemical

Further Information: Signaling Pathways Regulating Human Cervical Ripening in Preterm and Term Delivery [6]

Histologically, the cervix undergoes significant changes towards the end of gestation, allowing the ripening of cervix for the passage of birth delivery. First, there is an increase in the cervical synthesis of glycosaminoglycan hyaluronan (HA), which increases tissue hydration, thereby catalyzing the degradation of collagen and elastin-fibers. Second, there is an increase in the secretion of matrix metalloproteinases that also act to digest components of the extracellular matrix, including proteoglycans, laminin, and fibronectin, which are found in the cervical stroma (parametrium). [7] Third, due to the nature of the cervical effacement process, enzymes and other mediators that regulate allergic and inflammatory responses are also involved. [6] One of the immunomodulating factors, mast cells, is known to secrete inflammatory mediators that modulate the process of cervical ripening through mast cell degranulation. [8] Histamine, one of the allergenic mediators released by mast cells, has shown to have causative relationship with cervical smooth muscle contractility. However, the research is not complete. [6]

Assessment and measurement

Digital pelvic exam is used to measure the width of the opening of the cervix. Pelvic exam nci-vol-1786-300.jpg
Digital pelvic exam is used to measure the width of the opening of the cervix.

Bishop score

The Bishop score is the most common method of assessing the need for induction of labor. The scoring is based on a digital cervical exam and takes into consideration cervical dilation, position, effacement, consistency of the cervix and fetal station. [10]

Cervical dilation, effacement and station are scored from 0 to 3. Cervical consistency and position are scored from 0 to 2. The total score ranges with a minimum of 0 and maximum of 13. A Bishop score of 6 and below indicates that induction is not favorable and no method of induction will be highly effective. In these cases, cervical ripening agents may be used. A score of 8 and above indicates induction of labor is favorable and the possibility of a vaginal delivery with induction will be similar to spontaneous labor. [10]

Cervical effacement is an important component of the Bishop score and is reported as a percentage. 0% indicates the cervix is at normal length, 50% indicates the cervix is half of the expected length and 100% effaced means the cervix is paper thin. [10]

The Bishop score has been modified in current medical practice. The modified scoring method takes into consideration only 3 parameters: dilation, effacement, and fetal station. These are scored between the range of 0 to 3 each with a score of 5 or above being favorable for induction of labor. [10]

Other methods

Given that cervical effacement is measured as a percentage, this method requires a consensus on a standard uneffaced cervix length. However, this can vary among physicians. This requirement presents itself as an opportunity for error, miscommunication and inappropriate care in the process of assessing cervical effacement. Other methods used in assessing and measuring cervical effacement may be more accurate than the Bishop score, such as the metric system of measuring the cervix. Integrating the metric system of measurement of the cervix may reduce and eliminate the risk of error and assumptions on cervical length. [11]

Imaging methods are also being considered to measure cervical effacement. Elastography measures the stiffness and ability of soft tissue and can be used to assess how the cervical tissue deforms under pressure. This cannot be assessed manually and can be a useful parameter in predicting a preterm or full term delivery. There are two methods of elastography. Static elastography measures the tissue displacement in response to manual compression or movement. Dynamic elastography measures speed of shear wave propagation. [12] Both methods can provide useful information on the stiffness of the cervix in considering induction of labor.

Contra-indications

Cervical ripening is contraindicated in pregnancies presenting with the following conditions: [13]

Contraindications to cervical ripening also include those of vaginal birth. [15] Absolute contraindications can result in life-threatening events, and relative contraindications should be considered with caution. The absolute and relative contraindications to vaginal birth include, but are not limited to the following:

Absolute contraindications: [15]

Relative contraindications: [15]

Risks and complications

Labor induction poses different risks to the woman and fetus. As such, risks and complications relating to cervical effacement can be classified as being a risk to the woman or the fetus.

Risk to woman

Infection

Cervical ripening via transcervical balloon catheter can increase the risk of infection to the woman. Approximately 11% of pregnancies develop an intrapartum infection, 3% a postpartum infection and 5% a neonatal infection. Only intrapartum infection was deemed a clinically significant risk. [16]

Uterine hyperstimulation

The risk of uterine hyperstimulation as it relates to labor induction is higher with dinoprostone and vaginally administered misoprostol than it is with oxytocin and mechanical methods. [17]

Fetal risks

Autism

Oxytocin dysregulation has been linked to Autism or autism spectrum disorder. As oxytocin is one of the methods used for cervical ripening, the Committee on Obstetric Practice at the American College of Obstetricians and Gynecologists conducted a review of existing research regarding this link, and concluded that there was insufficient evidence of a causal link between cervical effacement via oxytocin and autism/ASD. [18]

Fetal distress or hyperstimulation

Low dose oral misoprostol for the purpose of labor induction, is associated with a lower risk of fetal distress than vaginally administered misoprostol. [19]

Vaginally administered dinoprostone is associated with an increased risk of fetal hyperstimulation with or without fetal heart rate abnormalities. [17]

Cervical ripening in the outpatient setting and the inpatient setting

Inpatient and outpatient cervical ripening done via vaginally administered dinoprostone or balloon catheters in low risk pregnancies do not have different rates of caesarean section. [2] Cervical ripening using dinoprostone vaginal inserts have the same rates of neonatal morbidity, caesarean section, and labor onset when used in the outpatient setting and the inpatient setting. [20]

Methods

Pharmacologic

Oxytocin is one of the most commonly used medications for cervical effacement. It is given as an infusion to either start or increase uterine contractions. Epidurals are often used together for pain. Oxytocin may also be used in the setting of amniotomy as well as balloon catheters to further contractions in conjunction to these procedures.

Misoprostol is a medication that can cause contractions for cervical effacement. When used with balloon catheters, vaginal delivery was more likely to occur within the next 24 hours after initiation. It is known as a type of prostaglandin and available worldwide. It can also be used for early termination of pregnancy.

Also in the class of prostaglandins, dinoprostone increases contractions. It is available in both gel and vaginal insert form and while both are safe and efficacious, one study has found that in those with a bishop score of less than or equal to 4, the vaginal insert seemed to be more effective in spontaneous vaginal delivery by about 20%.

Non-pharmacologic

Red raspberry leaf tea is an herbal option for cervical effacement. In a retrospective observational study conducted in 1999, while there was not significant difference in time for second and third stage of labour, the "mean time in first stage of labour is also substantially lower in the raspberry leaf group". The data, however, was not proven to be statistically significant.

Warm bath is a common method used by midwives to ease labor pain and also induce labor. In a study conducted in 2019, "cervical dilation increased in all groups (p<.001), as well as the number of uterine contractions increased, mainly in the group that used combined bath and ball and also showed shorter labor time". Safety precautions should be taken to make sure that the water temperature is not too high as it can lead to fetal distress.

Mechanical

Balloon Catheters are catheters that can be inserted into the cervix in the setting of pregnancy to induce labor. Saline is used to inflate the balloon, causing increased pressure to the cervix. This is to imitate the pressure of a fetal head that would be pressing on the cervix during labor, which in turn speeds up the process.

Hygroscopic dilator is a dilator that is inserted into the cervix and expands in size as it absorbs genital tract moisture. They can also be used for early termination of pregnancy.

According to a study conducted in Japan from 2012-2014, the rate of delivery at term seemed to be equivalent between the group that used balloon catheter and that of the hygroscopic dilator. [26]

Surgical

Amniotomy is a procedure where a hook is inserted into the amniotic membranes to puncture, causing the amniotic fluid to drain from the amniotic sac that holds the fetus. The reason for the surgical procedure could either be for cervical effacement or to look at fetal status as a device can be inserted into the amniotic sac for monitoring. The sign of successful procedure is when the amniotic fluid immediately comes out once the membrane is punctured. Certain amniotic fluid colors can indicate fetal distress, which is why it is important for the obstetrician or midwife to check the color.

Membrane stripping, otherwise known as membrane sweeping, is a procedure where the obstetrician inserts a finger into the cervix and moves in a sweeping motion to detach the amniotic membrane from the uterus. It is thought to be different from other procedures in that it is less costly compared to the other. While it may be an inexpensive procedure, it comes with its own risks. Membrane sweeping may rupture the amniotic sac for 1 out of 10 women who get this procedure done, which will then lead for the need to formally induce labor within 24 hours. Membrane sweeping can also be very painful and can cause bleeding and irregular contractions. Membrane sweeping is also not effective for 7 out of the 8 women that get this procedure done.

Related Research Articles

<span class="mw-page-title-main">Childbirth</span> Conclusion of the human pregnancy with the expulsion of a fetus from mothers womb

Childbirth, also known as labour, parturition and delivery, is the completion of pregnancy where one or more babies exits the internal environment of the mother via vaginal delivery or caesarean section. In 2019, there were about 140.11 million human births globally. In the developed countries, most deliveries occur in hospitals, while in the developing countries most are home births.

<span class="mw-page-title-main">Misoprostol</span> Medication to induce abortion and treat ulcers

Misoprostol is a synthetic prostaglandin medication used to prevent and treat stomach and duodenal ulcers, induce labor, cause an abortion, and treat postpartum bleeding due to poor contraction of the uterus. It is taken by mouth when used to prevent gastric ulcers in people taking nonsteroidal anti-inflammatory drugs (NSAID). For abortions it is used by itself or in conjunction with mifepristone or methotrexate. By itself, effectiveness for abortion is between 66% and 90%. For labor induction or abortion, it is taken by mouth, dissolved in the mouth, or placed in the vagina. For postpartum bleeding it may also be used rectally.

Labor induction is the process or treatment that stimulates childbirth and delivery. Inducing (starting) labor can be accomplished with pharmaceutical or non-pharmaceutical methods. In Western countries, it is estimated that one-quarter of pregnant women have their labor medically induced with drug treatment. Inductions are most often performed either with prostaglandin drug treatment alone, or with a combination of prostaglandin and intravenous oxytocin treatment.

Rupture of membranes (ROM) or amniorrhexis is a term used during pregnancy to describe a rupture of the amniotic sac. Normally, it occurs spontaneously at full term either during or at the beginning of labor. Rupture of the membranes is known colloquially as "breaking (one's) water," especially when induced rather than spontaneous, or as one's "water breaking". A premature rupture of membranes (PROM) is a rupture of the amnion that occurs at full term and prior to the onset of labor. In cases of PROM, options include expectant management without intervention, or interventions such as oxytocin or other methods of labor induction, and both are usually accompanied by close monitoring of maternal and fetal health. Preterm premature rupture of membranes (PPROM) is when water breaks both before the onset of labor and before the pregnancy's 37 week gestation. In the United States, more than 120,000 pregnancies per year are affected by a premature rupture of membranes, which is the cause of about one third of preterm deliveries.

Bishop score, also Bishop's score or cervix score, is a pre-labor scoring system to assist in predicting whether induction of labor will be required. It has also been used to assess the likelihood of spontaneous preterm delivery. The Bishop score was developed by Professor Emeritus of Obstetrics and Gynecology, Edward Bishop, and was first published in August 1964.

Cervical dilation is the opening of the cervix, the entrance to the uterus, during childbirth, miscarriage, induced abortion, or gynecological surgery. Cervical dilation may occur naturally, or may be induced surgically or medically.

Bloody show or show is the passage of a small amount of blood or blood-tinged mucus through the vagina near the end of pregnancy. It is caused by thinning and dilation of the cervix, leading to detachment of the cervical mucus plug that seals the cervix during pregnancy and tearing of small cervical blood vessels, and is one of the signs that labor may be imminent. The bloody show may be expelled from the vagina in pieces or altogether and often appears as a jelly-like piece of mucus stained with blood. Although the bloody show may be alarming at first, it is not a concern of patient health after 37 weeks gestation.

Dilation and evacuation (D&E) or dilatation and evacuation is the dilation of the cervix and surgical evacuation of the uterus after the first trimester of pregnancy. It is a method of abortion as well as a common procedure used after miscarriage to remove all pregnancy tissue.

Fetal fibronectin (fFN) is a fibronectin protein produced by fetal cells. It is found at the interface of the chorion and the decidua. Fetal fibronectin is found normally in vaginal fluid in early pregnancy prior to 22 weeks due to normal growth and development of tissues at the junction of the uterus and amniotic sac. It may also be found in vaginal fluid after 36 weeks as labor approaches. However, fFN should not be detected between 22 and 36 weeks.

<span class="mw-page-title-main">Prelabor rupture of membranes</span> Breakage of the amniotic sac before the onset of labour

Prelabor rupture of membranes (PROM), previously known as premature rupture of membranes, is breakage of the amniotic sac before the onset of labour. Women usually experience a painless gush or a steady leakage of fluid from the vagina. Complications in the baby may include premature birth, cord compression, and infection. Complications in the mother may include placental abruption and postpartum endometritis.

Cervical weakness, also called cervical incompetence or cervical insufficiency, is a medical condition of pregnancy in which the cervix begins to dilate (widen) and efface (thin) before the pregnancy has reached term. Definitions of cervical weakness vary, but one that is frequently used is the inability of the uterine cervix to retain a pregnancy in the absence of the signs and symptoms of clinical contractions, or labor, or both in the second trimester. Cervical weakness may cause miscarriage or preterm birth during the second and third trimesters. It has been estimated that cervical insufficiency complicates about 1% of pregnancies, and that it is a cause in about 8% of women with second trimester recurrent miscarriages.

Prostaglandin E<sub>2</sub> Chemical compound

Prostaglandin E2 (PGE2), also known as dinoprostone, is a naturally occurring prostaglandin with oxytocic properties that is used as a medication. Dinoprostone is used in labor induction, bleeding after delivery, termination of pregnancy, and in newborn babies to keep the ductus arteriosus open. In babies it is used in those with congenital heart defects until surgery can be carried out. It is also used to manage gestational trophoblastic disease. It may be used within the vagina or by injection into a vein.

Postterm pregnancy is when a woman has not yet delivered her baby after 42 weeks of gestation, two weeks beyond the typical 40-week duration of pregnancy. Postmature births carry risks for both the mother and the baby, including fetal malnutrition, meconium aspiration syndrome, and stillbirths. After the 42nd week of gestation, the placenta, which supplies the baby with nutrients and oxygen from the mother, starts aging and will eventually fail. Postterm pregnancy is a reason to induce labor.

<span class="mw-page-title-main">Uterine atony</span> Loss of tone in the uterine musculature

Uterine atony is the failure of the uterus to contract adequately following delivery. Contraction of the uterine muscles during labor compresses the blood vessels and slows flow, which helps prevent hemorrhage and facilitates coagulation. Therefore, a lack of uterine muscle contraction can lead to an acute hemorrhage, as the vasculature is not being sufficiently compressed. Uterine atony is the most common cause of postpartum hemorrhage, which is an emergency and potential cause of fatality. Across the globe, postpartum hemorrhage is among the top five causes of maternal death. Recognition of the warning signs of uterine atony in the setting of extensive postpartum bleeding should initiate interventions aimed at regaining stable uterine contraction.

<span class="mw-page-title-main">Vaginal delivery</span> Delivery through the vagina

A vaginal delivery is the birth of offspring in mammals through the vagina. It is the most common method of childbirth worldwide. It is considered the preferred method of delivery, as it is correlated with lower morbidity and mortality than caesarean sections (C-sections), though it is not clear whether this is causal.

<span class="mw-page-title-main">Osmotic dilator</span> Medical device to dilate the uterine cervix

Osmotic dilators are medical implements used to dilate the uterine cervix by swelling as they absorb fluid from surrounding tissue. They may be composed of natural or synthetic materials. A laminaria stick or tent is a thin rod made of the stems of dried Laminaria, a genus of kelp. Laminaria sticks can be generated from Laminaria japonica and Laminaria digitata. Synthetic osmotic dilators are commonly referred to by their brand names, such as Dilapan. Dilapan-S are composed of polyacrylonitrile, a plastic polymer. The hygroscopic nature of the polymer causes the dilator to absorb fluid and expand.

A uterotonic, also known as an oxytocic or ecbolic, is a type of medication used to induce contraction or greater tonicity of the uterus. Uterotonics are used both to induce labor and to reduce postpartum hemorrhage.

Artificial rupture of membranes (AROM), also known as an amniotomy, is performed by a midwife or obstetrician and was once thought to be an effective means to induce or accelerate labor. The membranes can be ruptured using a specialized tool, such as an amnihook or amnicot, or they may be ruptured by the proceduralist's finger. The different techniques for artificial rupture of membranes have not been extensively compared in the literature. In one study comparing amnihook versus amnicot for artificial rupture of membranes, use of an amnicot was associated with fewer neonatal scalp lacerations.

Uterine Tachysystole is a condition of excessively frequent uterine contractions during pregnancy. It is most often seen in induced or augmented labor, though it can also occur during spontaneous labor, and this may result in fetal hypoxia and acidosis. This may have serious effects on both the mother and the fetus including hemorrhaging and death. There are still major gaps in understanding treatment as well as clinical outcomes of this condition. Uterine tachysystole is defined as more than 5 contractions in 10 minutes, averaged over a 30-minute period.

<span class="mw-page-title-main">Prolonged labor</span> Medical condition

Prolonged labor is the inability of a woman to proceed with childbirth upon going into labor. Prolonged labor typically lasts over 20 hours for first time mothers, and over 14 hours for women that have already had children. Failure to progress can take place during two different phases; the latent phase and active phase of labor. The latent phase of labor can be emotionally tiring and cause fatigue, but it typically does not result in further problems. The active phase of labor, on the other hand, if prolonged, can result in long term complications.

References

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  3. ↑ Winkler M, Rath W (1999). "Changes in the cervical extracellular matrix during pregnancy and parturition". Journal of Perinatal Medicine. 27 (1): 45–60. doi:10.1515/JPM.1999.006. PMID   10343934. S2CID   25915432.
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  7. ↑ Nagase, Hideaki; Woessner, J. Frederick (1999). "Matrix Metalloproteinases". Journal of Biological Chemistry. 274 (31): 21491–21494. doi: 10.1074/jbc.274.31.21491 . PMID   10419448.
  8. ↑ Elieh Ali Komi, Daniel; Wöhrl, Stefan; Bielory, Leonard (2020). "Mast Cell Biology at Molecular Level: a Comprehensive Review". Clinical Reviews in Allergy & Immunology. 58 (3): 342–365. doi:10.1007/s12016-019-08769-2. ISSN   1080-0549. PMID   31828527. S2CID   209312232.
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  14. ↑ American College of Obstetricians and Gynecologists (2019). "Avoidance of Nonmedically Indicated Early-Term Deliveries and Associated Neonatal Morbidities Committee Opinion No. 765". Obstet Gynecol. 133 (2): e156–e163. doi: 10.1097/AOG.0000000000003076 . PMID   30681546. S2CID   59251667 . Retrieved 2023-07-27.
  15. 1 2 3 Desai NM, Tsukerman A (2023). "Vaginal Delivery". StatPearls. Treasure Island (FL): StatPearls Publishing. PMID   32644623 . Retrieved 2023-07-27.
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  17. 1 2 Mozurkewich, Ellen L; Chilimigras, Julie L; Berman, Deborah R; Perni, Uma C; Romero, Vivian C; King, Valerie J; Keeton, Kristie L (2011). "Methods of induction of labour: a systematic review". BMC Pregnancy and Childbirth. 11 (1): 84. doi: 10.1186/1471-2393-11-84 . ISSN   1471-2393. PMC   3224350 . PMID   22032440.
  18. ↑ "Labor Induction or Augmentation and Autism". www.acog.org. 2014. Retrieved 2023-07-31.
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  20. ↑ Mazzoli I, O'Malley D (2022). "Outpatient versus inpatient cervical ripening with a slow-release dinoprostone vaginal insert in term pregnancies on maternal, neonatal, and birth outcomes: A systematic review". Birth. 50 (3): 473–485. doi: 10.1111/birt.12687 . PMID   36332128. S2CID   253350933.
  21. ↑ "Oxytocin Drug Information". UpToDate. Retrieved 2023-07-27.
  22. ↑ McDonagh, Marian; Skelly, Andrea C.; Hermesch, Amy; Tilden, Ellen; Brodt, Erika D.; Dana, Tracy; Ramirez, Shaun; Fu, Rochelle; Kantner, Shelby N. (2021-03-22). Cervical Ripening in the Outpatient Setting (Report). Agency for Healthcare Research and Quality (AHRQ). doi:10.23970/ahrqepccer238.
  23. ↑ Triglia MT, Palamara F, Lojacono A, Prefumo F, Frusca T (2010). "A randomized controlled trial of 24-hour vaginal dinoprostone pessary compared to gel for induction of labor in term pregnancies with a Bishop score < or = 4". Acta Obstetricia et Gynecologica Scandinavica. 89 (5): 651–657. doi:10.3109/00016340903575998. PMID   20199360. S2CID   28283910.
  24. ↑ Parsons M, Simpson M, Ponton T (1999). "Raspberry leaf and its effect on labour: safety and efficacy". Australian College of Midwives Incorporated Journal. 12 (3): 20–25. doi:10.1016/s1031-170x(99)80008-7. PMID   10754818.
  25. ↑ Cavalcanti AC, Henrique AJ, Brasil CM, Gabrielloni MC, Barbieri M (2019). "Complementary therapies in labor: randomized clinical trial". Revista Gaucha de Enfermagem. 40: e20190026. doi: 10.1590/1983-1447.2019.20190026 . PMID   31553374. S2CID   202815594.
  26. 1 2 Shindo R, Aoki S, Yonemoto N, Yamamoto Y, Kasai J, Kasai M, Miyagi E (2017). Hawkins SM (ed.). "Hygroscopic dilators vs balloon catheter ripening of the cervix for induction of labor in nulliparous women at term: Retrospective study". PLOS ONE. 12 (12): e0189665. Bibcode:2017PLoSO..1289665S. doi: 10.1371/journal.pone.0189665 . PMC   5741218 . PMID   29272277.
  27. ↑ "Dilapan-S® | Next Day Cervical Ripening". www.dilapans.com. Retrieved 2023-07-27.
  28. ↑ Mahdy, Heba; Glowacki, Christopher; Eruo, Frederick U. (2023), "Amniotomy", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID   29261890 , retrieved 2023-08-04
  29. ↑ Finucane, Elaine M; Murphy, Deirdre J; Biesty, Linda M; Gyte, Gillian ML; Cotter, Amanda M; Ryan, Ethel M; Boulvain, Michel; Devane, Declan (2020-02-27). Cochrane Pregnancy and Childbirth Group (ed.). "Membrane sweeping for induction of labour". Cochrane Database of Systematic Reviews. 2020 (2): CD000451. doi:10.1002/14651858.CD000451.pub3. PMC   7044809 . PMID   32103497.
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