Physiologic Changes of Pregnancy: Part 1

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10/01/2023
As part of our brief break for parental leave, we’re revisiting some of our most popular episodes! Today we’re revisiting Physiologic Changes of Pregnancy - almost five years to the day since we released it! Check out our reprisal of part II next week with the all-encompassing table of changes.

As promised, our first episode on pregnancy! Join us on “Fei and Nick’s Fabulous Adventure Through Pregnancy!”

Today we tackled the changes of the immunologic and hematologic systems seen in pregnancy. There’s quite a bit of information there! If you feel like we’ve missed anything, feel free to reach out via email or social media.

Next week, we’ll release Part 2 and have some more resources ready for your studying!

What Your Charge Nurse Wants You to Know: Feat. Julie Park, RN

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It’s July, and with everyone moving up into new roles, we thought we’d think a bit about our nursing colleagues!

Today, we welcome Julie Park, an assistant nurse manager and labor and delivery charge nurse at the University of Washington Medical Center. She tells us a bit about her career in nursing, what a charge nurse is and what they do, and offers some tips for success for L&D clinicians and nurses of all experience levels.

Operative Vaginal Birth

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So today’s episode won’t be a “how to” on operative birth; that requires some years of residency and even fellowship, but we want to help you recognize what operative births are and when to use them. For more reading, check out the new ACOG PB 219.

Operative vaginal birth is when an obstetrician or other trained birthing provider uses a device such as vacuum extractor or forceps during the second stage of labor to achieve or expedite a vaginal birth for maternal or fetal indications. The two tools generally available are forceps or vacuum extractors.

Forceps 

  • Generally, metal devices with two blades that are placed around the head of the fetus to assist in birth.

  • Consist of the components of blade, shank, lock or articulating portion, and handle 

  • The blades have a toe (front) and a heel (back toward the provider), as well as a pelvic curve and cephalic curve:

OBGynKey

  • Some history on forceps:

    1. First developed by the Chamberlen family of surgeons in France as early as possibly 1634, though they kept them secret for about 150 years.

    2. They largely haven’t changed. Simpson forceps (split shanks), for example, were created in 1848, and Elliot forceps (overlapping shanks) in 1860.

    3. There are multiple types, but the majority of forceps in use today are in the Simpson or Elliot class. Some you may encounter:

      1. Simpson - Luikhart: split shank (Simpson type), pseudofenestrated blade.

      2. Luikhart - McLain: Elliot type with pseudofenestrated blade.

      3. Tucker McLain: Elliot type, no fenestration to blade.

Vacuum Extractor 

  • A suction cup that is placed on the head of the baby approximately 2-3 cm anterior from the posterior fontanelle over the flexion point to guide the head through the birth canal.

  • Some history 

    1. The first vacuum extractor was developed by James Young Simpson in 1849.

    2. Didn’t really catch on until a Swedish doc named Tage Malmstromo developed the “ventouse” or Malmstrom extractor in the 1950s.

A Kiwi vacuum extractor

Indications and Prerequisites for Operative Vaginal Birth

  1. Indications 

    1. Prolonged second stage of labor.

    2. Suspicion of immediate or potential fetal compromise.

    3. Shortening of second stage of labor for maternal benefit (ie. maternal exhaustion or maternal cardiac issues that may make it difficult for them to Valsalva for an extended amount of time).

  2. Prerequisites (“checks” before attempt).

    1. Cervix is fully dilated and membranes are ruptured.

    2. Engagement of the fetal head.

    3. Position of fetal head is known (either by exam or by ultrasound).

    4. EFW has been performed and assessment that the pelvis is adequate for vaginal birth (don’t want to pull into a shoulder!).

    5. Adequate anesthesia.

    6. Maternal bladder has been emptied.

    7. Patient has agreed after being informed of risks and benefits of procedure.

    8. Willingness to abandon the attempt, with back-up place (ie. cesarean) in case of failure to deliver.

    9. We do not recommend doing a prophylactic episiotomy anymore, but if you have to, reasonable to give prophylactic antibiotics, per the ANODE trial, and also give if there is a 3rd or 4th degree laceration.

  3. When should you NOT perform an operative vaginal birth: 

    1. If fetal head is unengaged or fetal head position is unknown.

    2. If fetus is suspected to have osteogensis imperfecta or other both demineralization condition.

    3. If fetus is thought to have bleeding disorder (ie. thrombophilia or von Willebrand disease).

  4. Categorization of forceps deliveries (we don’t do high forceps anymore… YIKES!) 

    1. Midforceps 

      1. Station is above +2 cm, but head is engaged.

    2. Low forceps 

      1. Leading point of the fetal skull is at station +2 cm or more and not on the pelvic floor.

      2. Without rotation: rotation is 45 degrees or less (ROA, ROP, LOA, LOP).

      3. With rotation: Rotation is > 45 degrees, requires rotation with rotational forceps or Scanzoni maneuver.

    3. Outlet forceps

      1. Fetal scalp is visible at the introitus without separating the labia.

      2. Fetal skull has reached the pelvic floor.

      3. Fetal head is at or on perineum.

      4. Sagittal suture is in an AP diameter or ROA, ROP, LOA, LOP.

      5. Rotation does not exceed 45 degrees.

Counseling a Patient on Operative Vaginal Birth

  • Benefits 

    1. Avoidance of cesarean delivery for the indications above.

    2. Operative vaginal delivery is undeniably faster to achieve delivery, and when indicated, helps to avoid major surgery and its recovery and potential complications.

  • Maternal Complications 

    1. Higher risk of anal sphincter injury (10-20%), though it may be difficult to separate this out from other risks that are associated with operative vaginal birth like prolonged second stage, fetal size, episiotomy, etc. 

      1. One study that controlled for all these other clinical factors: forceps still associated with 6x increase in 3rd and 4th degree tears, and vacuum associated 2x increase.

      2. However, other studies do not clearly show that there is a significant difference in fecal or flatal incontinence through 1 year postpartum.

  • Fetal/Newborn Complications 

    1. Very low in general! Intracranial hemorrhage occurs 1/650-850 operative vaginal births and neurologic complication 1/220-385.

    2. Vacuum: usually due to traction on fetal scalp, ie. laceration, cephalohematoma, subgaleal or ICH.

    3. Forceps: facial lacerations, facial nerve palsy, corneal abrasion, and external ocular trauma, skull fracture, ICH.

      1. Rates of ICH are similar for forceps, vacuum, and cesarean deliveries performed during labor.

    4. Compared to those delivered by cesarean, those delivered by:

      1. Forceps: higher rates of fracture, facial nerve palsy, and brachial plexus injury, but lower rates of neurologic complications (ie. seizures, IVH, subdural hemorrhage),

      2. Vacuum: higher rates of cephalohematoma, fracture, and brachial plexus injury, but not central neurologic complications.

    5. Few data assess long-term consequences of operative vaginal birth on the infant, but of the studies we have, there does not appear to be significant differences in cognitive development from those born from forceps or vacuum compared to spontaneous vaginal birth.

When should you abandon operative vaginal birth? 

  1. Traditionally, it’s 3 pop-offs for the vacuum extractor, but this may depend on the type of vacuum and institutional policy.

  2. With deterioration of the fetal heart tracing without progress, or just no progress in general.

  3. Maternal request.

A Pros and Cons Comparison of Methods of Operative Vaginal Birth

Obstetrical Ultrasound

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Sonographic nomenclature breaks down into three main types of ultrasound:

  1. Limited US: for a specific, singular purpose (i.e., viability, placental location, presentation, cervical length).

  2. Standard US: A more thorough examination, which requires a number of elements including:

    • Fetal presentation and number 

    • Amniotic fluid volume

      1. AFI (normal 5-25) or DVP (normal 2-8)

      2. SMFM recommends using DVP over AFI to diagnose oligo in the third trimester as using AFI leads to more interventions without improving perinatal outcomes 

    • Fetal Heart Rate / Rhythm

    • Placental location 

      1. Previa covers cervical os, either partially or wholly.

      2. Low lying placental edge is within 2cm of os.

        1. Partial or marginal previa is unfavored terminology.

      3. Suspicion for abnormal placentation for previa in setting of history of cesarean. With previa, history of 

        1. 1 prior cesarean = 3% risk of PAS

        2. 2 prior cesarean = 11% risk of PAS

        3. 3 prior cesarean = 40% risk of PAS

        4. 4 prior cesarean = 61% risk of PAS

    • Fetal biometry/anatomic survey.

    • Cervix and adnexa when clinically appropriate and when technically feasible. 

  3. Specialized US: A highly technical ultrasound that focuses on particular organ systems or uses dynamic measures.

    1. Examples include level 2 ultrasounds which provide further anatomic detail than a standard US, or fetal doppler ultrasonography, biophysical profiles, or fetal echocardiograms.

Important Facts for Ultrasound, by Trimester:

First Trimester: Know the absolute and relative criteria for early pregnancy failure, from SRU’s publication in NEJM:

(c) NEJM, 2013

2nd / 3rd Trimester: Know components of a basic growth scan by the Hadlock formula. Some representative photos are here! Images courtesy of www.fetalultrasound.com. Be sure to check out The OBG Project 2nd Trimester Ultrasound Atlas if you’re a chief resident with access to OBG First!

Appropriate plane for BPD and HC measurements

Appropriate plane for fetal abdominal circumference.

Appropriate plane for fetal abdominal circumference.

Appropriate plane and landmarks for fetal femoral length measurement.

Preventing the Primary Cesarean Section

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This mega-episode was inspired by a two-part Grand Rounds series written by our PGY-4 Brown OBGYN class. We’ll dive into some of the history of cesarean, the challenges and data with respect to deciding on cesarean delivery, and current evidence-based strategies to reduce the risk of primary cesarean in low-risk women.

Cesarean sections have been around for a long time, the very first of which was documented around 1750 BC. However, surgery was originally performed only on a dead or dying mom with the hope of saving the child, or so the infant could be buried separately from mom per religious edicts. And then for the first 3000 years of cesarean, the mortality rate for women was… 100%. And it stayed this way until the mid-18th century! Anesthesia was introduced in 1846 with the discovery of ether, and as the 19th century progressed sutures and antibiotics became live-saving measures that allowed women to survive cesarean.

With the urbanization of the western world through this time period, more women began to deliver in hospitals as cesarean became a viable alternative, rather than delivering at home. In the USA, by 1955, 99% of births occurred in hospital. The rate of cesarean in the US stayed low until the 1970s, which coincided with the introduction of electronic fetal monitoring. A cesarean rate of <10% prior to EFM increased to 17% by 1980, 25% by 1988, and 31.9% in 2016.

Now with the increased use of cesarean, we should expect some benefit to it. And there certainly are! There are life-saving implications for both mother and baby, and when needed, the surgery is absolutely a necessary tool for an obstetrician. That said, cesarean does not come without its own risks. For mothers, cesarean is associated with more risk of bleeding, infection, thrombosis, increased pain, worse satisfaction with the birth experience, and risks to future pregnancy such as increased risk of repeat cesarean and risk of placenta accreta spectrum (PAS) disorders. For infants, cesarean carries slightly higher risks of respiratory difficulty during the transition, breastfeeding difficulty, and intracranial hemorrhage (if laboring prior to cesarean; rates of IVH between SVD and non-laboring cesarean are about equal).

One of the criticisms of cesarean delivery are that its use does not seem standardized. There is a high level of variation between countries, and in the US, there is high variation between states, cities, and even hospitals in the same city! As an example, here are the nulliparous term singleton vertex (NTSV) cesarean rates between US states for 2016:

While no rate of cesarean has proven to be the “optimal” or “ideal” amount, some observational data may provide some clues. The WHO has compared countries’ rates of cesarean with respect to both maternal and neonatal mortality, and also attempted to normalize these countries’ resources by demonstrating their relative wealth. For both maternal and neonatal mortality benefit, the rate seems to sit around 20% — you can see these graphs from the WHO below.

In order to safely choose our use of cesarean delivery, there are evidence-based guidelines to recall. The ACOG/SMFM Obstetric Care Consensus #1 on safe prevention of the primary cesarean delivery is one such tool. In this document, there are three important thresholds to remember. This is nicely outlined in checklist format by the folks at the California Maternal Health Quality Collaborative (CMQCC):

The use of partographs also has some limited data to support their use to help monitor labor progress. While one version over another hasn’t been shown to be superior, in a before-and-after study, the presence of their use helped to reduce cesarean rates, likely because of the closer attention to normal labor progress that was effected by them.

We additionally came across some other exciting ways to try to help reduce cesarean rates or examine cesarean utilization. Some of these things include:

  • Open Access to Cesarean Data 

    • Beth Israel Deaconess’ NTSV rate was a target of a large, stepwise quality project, with a decrease from 35% to 21% over 8 years. However, their single best year of improvement was from 2014-2015, when cesarean data was fully unmasked and shared amongst all physicians who practiced there. Similar findings have been demonstrated in the CMQCC hospitals. Simply put, no one likes to be an outlier amongst their peers!

  • Cesarean Audit Committees

    • These committees meet to review all unplanned cesarean delivery, prepare and interpret data, and look for opportunities for improvement in terms of physician/midwife, nurse, or patient education.

      • These committees offer the advantage of individualized feedback for improvement of practice based on more nuanced classifications that adjust for risk in population than just “NTSV.” 

      • Meta-analyses have demonstrated reduced cesarean rates stemming from a cesarean audit in concert with multifaceted programs to reduce cesarean delivery.

  • Utilizing Labor Dystocia Checklists

    • Several quality collaborative groups use checklists, such as the one from CMQCC above; these are evidence-based, objective, and don’t call into question a provider’s interpretation of labor progress. 

      • Overall decrease PCS by preventing premature C/S for indications of labor dystocia. 

      • Some institutions have gone as far as to institute “double doctor” reviews for cesarean for labor arrest, allowing for a second opinion, particularly regarding the feasibility of operative vaginal delivery.

  • Improved, transparent team communication 

    • Improved communication between physician or midwife, bedside nurse, patient, and support persons allows for appropriate expectations for labor or induction, and allows all members of the team to “be on the same page.”

    • At our institution, we are trialing using a whiteboard to document the partograph in the labor room; this allows the patient to compare patient to where they are on partograph compared to “standard labor progress.”

Have a technique you’re using at your hospital to help reduce primary cesarean delivery? Share it with us! We’d love to hear from you via email or the comments section of the website.