Trial of Labor after Cesarean (TOLAC)

In 2016, the US cesarean delivery rate was 31.9%. With ever increasing volumes of cesarean delivery, TOLAC has become a popular option for patients desiring vaginal delivery. On today’s episode, we examine TOLAC and share some counseling pointers in thinking about your patient. ACOG PB 205 is the requisite reading for the topic.

While there are no RCTs comparing TOLAC to planned cesarean, the relative benefits are easy to see: there is less recovery time, the patient avoids major surgery, and the potential sequelae of complications from major surgery — worsened bleeding, more opportunity for infection, more risk of complications requiring additional procedures. However, TOLAC is not without risk. We primarily counsel with respect to uterine rupture. Evaluations of “rupture” though have varied in the literature; it’s important to keep a discerning eye, as what is classified as rupture in some series is very different than what is in others. ACOG suggests the rate of uterine rupture in a patient with one low transverse cesarean delivery is around 0.5 - 0.9 %. Otherwise, maternal risks are fairly equal. Neonatal risks are also considered fairly equal, though with some increased risk associated with TOLAC.



We can think about patients who should be counseled against TOLAC:

  • Those at high risk of uterine rupture: ie. those with classic uterine incision, T-incision, prior uterine rupture, or extensive prior uterine fundal surgery like a myomectomy.

  • Women who are not otherwise candidates to have vaginal deliveries: ie. previa.

  • Women who desire homebirth: While ACOG does not definitely say that you cannot TOLAC in this instance, if you don’t access to emergency cesarean delivery, it is recommended that these patients have a discussion regarding the hospitals resources and possibly referral to a hospital that does have access to emergency cesarean delivery.

We can also consider patients for whom there may be a question of whether TOLAC is appropriate:

  • Low vertical incision? 

    1. Few studies, but those that have looked at them have shown similar rates of vaginal deliveries as low transverse. Can consider TOLAC!

  • Twins? 

    1. Studies show similar rates of successful VBAC in twins as in singleton gestations 

  • Obesity 

    1. Unfortunately, higher BMI seems to have an inverse relationship with success of VBAC. 85% of normal weight women achieve VBAC while only 65% of morbidly obese women do. However, morbidly obese women also can have more complications with an elective repeat cesarean, so counseling should be individualized

  • Induction and augmentation of labor 

    1. Mechanical dilation can be used - ie. cervical foley 

    2. Misoprostol has been shown to have increased risk of uterine rupture, so should not be used in term patients who have had c/s or other major uterine surgery for induction 

    3. However, in women undergoing second trimester labor inductions (ie. for missed abortion, induction of labor for stillbirths), use of prostaglandins have shown similar results in women who have had scars on their uterus and those without; so these women can still have prostaglandins, especially because no fetal considerations 

  • What if they’ve had a uterine rupture? 

    • If the site of rupture or dehiscence is in the lower part of the uterus, their risk of uterine rupture in labor is 6%. If it is in the upper segment of the uterus, the rate of dehiscence in labor is up to 32%. While there is no high quality data to guide this, recommendations are generally for subsequent pregnancies to be delivered by cesarean between 36-37 weeks.

Counseling should be individualized, and the MFMU has excellent calculators to help guide you and your patients to a decision about TOLAC:

(not in labor)

(at admission)

Considerations for Planned Singleton Breech Vaginal Delivery

Today’s episode dives more into the realm of expert opinion rather than hard science, and we hope some of our listeners will share their own experiences and criteria for offering planned breech labor!

ACOG CO 745, in addition to PB 161 on external cephalic version, deal with this topic, but there is much variation in the literature available. In particular, international guidelines on this topic are rather variable. The ObG Project has a great summary and links to these varying resources that is worth checking out.

There are particular risks to breech labor, and experienced provider hands are necessary, which is why almost 90% of planned term breech birth in the USA is performed by cesarean section. The 2000 Term Breech Trial, a multicenter randomized trial, noted perinatal morbidity and mortality was overall reduced with planned cesarean delivery than with planned vaginal delivery of term breech (1.6% vs 5.0%), with no differences in reported maternal morbidity or mortality. Follow up studies to the Term Breech Trial, however, have noted no differences in maternal or neonatal outcomes at 2 years.

Additional studies performed since this time have been mixed. While some prospective studies demonstrated excellent maternal and neonatal outcomes, both short- and long-term, they utilized very strict criteria and protocols for the selection of candidates offered a trial of breech labor. Cohort studies of breech birth in general populations demonstrates at least short-term risk of neonatal morbidity, including birth injury, nerve injury, and need for assisted ventilation. This risk is present with any trial of breech labor, including if intrapartum cesarean is performed, versus planned cesarean delivery.

Below is a sample protocol based on some of these studies with stricter inclusion criteria. We recognize there is likely some significant debate to be had on these criteria, and in particular clinical scenarios, so be sure to discuss with experienced obstetricians in your area as well as check your hospital’s own breech birth protocol.

(c) CREOGs over Coffee, 2019. Adapted from Hofmeyr/UpToDate, 2019.

Finally, intrapartum management should proceed according to usual obstetric practice. However with breech presentations, providers should closely consider a number of factors outlined below. Notably, these factors are largely based on expert opinion and guidelines from international societies.

  • Avoidance of early amniotomy, and preference for spontaneous rupture of membranes.

  • The progress of labor in the active phase, and progress of descent during active pushing. 

    • Cesarean delivery should be recommended with a protracted labor course, particularly in the active phase, as this may be indicative of fetopelvic disproportion. 

    • Use of oxytocin in the active phase of labor is discouraged.

    • With the achievement of full cervical dilation, the breech should reach the pelvic floor.

    • Passive descent should not be permitted for more than 90 minutes after achieving full cervical dilation.

    • With onset of active pushing, delivery by cesarean should be considered if the infant has not delivered within 30-60 minutes.

Cardiac Arrest in Pregnancy

Today we discuss a topic that we hope you never encounter, but want every OB, EM, and really any other person or medical professional to be prepared for cardiac arrest in pregnancy. The American Heart Association (AHA) Scientific Statement on Cardiac Arrest in Pregnancy can be found here and is essential companion reading.

(c) AHA

In preparation for a maternal cardiac event, a cesarean delivery kit should be available as part of the adult code cart. This at minimum should have a scalpel (#10 blade), betadine splash prep, clamps for cutting the umbilical cord, sponges, absorbable suture, and additional clamps and/or retractors if feasible. A neonatal resuscitation cart should accompany the adult cart if a maternal code is ongoing.

BLS is not different from standard for any other adult resuscitation, except for one key component: leftward displacement of the uterus. This allows for improved venous return to the right heart via the inferior vena cava, which may be compressed to some degree as early as 12 weeks gestation. Otherwise hand positioning, compression technique, and ventilation considerations in the BLS portion do not have any differences.

The ACLS algorithm also proceeds as usual, with the notable exception being performance of resuscitative hysterotomy (aka, peri-mortem cesarean section) at 4 minutes of pulseless arrest. This should be performed at any gestation above 20 weeks (i.e., fundal height at or above the umbilicus). It serves the dual purpose of improving maternal venous return, as well as protecting the fetus from consequences of prolonged anoxia.

Otherwise, ACLS algorithms use the same medications and doses, the same indications for shocks, and actually many times the same etiologies for arrest. However there are some pregnancy-specific considerations all physicians should recall, in a simple mnemonic:

(c) Society of Obstetric Anesthesia and Perinatology

Diagnostic Imaging During Pregnancy and Lactation

Today we’re going to review a source of constant consultation and confusion: diagnostic imaging during pregnancy and breastfeeding. ACOG CO 723 is the definitive reading on this subject, and we use it to structure this episode. Critical take home: ACOG states that critical imaging studies should not be withheld from a pregnant patient if needed to make a diagnosis. 


  • Sonography utilizes sound waves to produce a visible image, and is not a form of ionizing radiation.

    • Thus, it is considered the safest mode of imaging in pregnancy.

    • However, ACOG still recommends sticking to the ALARA principle of exposure in pregnancy (“As Low As Reasonably Achievable”) to minimize any potential untoward effects. 

    • One of these theoretical effects involves color or spectral flow Doppler. Due to its intensity, the theoretical temperature increase surrounding the area being study can be as high as 2deg C, or 3.6deg F. It’s unlikely than any temperature increase would be sustained at any fetal anatomic site to cause harm. However, for this reason, even ultrasound exposure should be used judiciously. 


  • Allows for visualization of soft-tissue structures like ultrasound

    • However, as MRI is operator-independent, pick up rates for certain pathologies like appendicitis tend to be higher.

    • There are no special contraindications or considerations in pregnancy for non-contrast MRI, other than the usual screening surrounding metal or magnet-sensitive implants, such as pacemakers. 

  • Non-contrast MRI is sufficient for diagnosis; however, some diagnoses or studies may be improved by the use of gadolinium-based contrast, for which there is uncertainty regarding fetal effects.

    • Gadolinium is water-soluble, and thus crosses the placenta into fetal circulation.

    • Free gadolinium is toxic, so it is bound, or chelated, when administered for studies.

      • There is concern that since this bound gadolinium can enter fetal circulation, it can recycle in the fetal circulation. This potentially could sit for long enough that the gadolinium could dissociate and become free; thus become toxic. 

      • Given at least the concern for potential poor outcomes, gadolinium-based contrast should be limited in use to cases where there is an absolute clear benefit to its administration.

    • Gadolinium’s water-solubility makes it an OK contrast agent to use during lactation.

      • Less than 0.04% of a dose of gadolinium will be excreted in breastmilk in the first 24 hours, and less than 1% of this will be absorbed in the infant GI tract. Thus, breastfeeding should not be interrupted after gadolinium contrast studies.

CT, XRAY, and other ionizing radiation studies
Before talking about ionizing radiation studies, it’s important to know some vocabulary and measurements of radiation:

  • Exposure is the number of ions produced by radiation in the form of X-rays or gamma rays per kilogram of air. This is measured in Roentgen units.

  • Dose is the amount of energy deposited per kilogram of tissue. This is the usual consideration when we talk about radiation in pregnancy. This is measured in rads or in Gray units; 100 rad is equivalent to 1 Gray.

  • Relative effective dose is the amount of energy deposited per kilogram of tissue, and normalized for biological effectiveness on the tissue. This is measured in Roentgen equivalent men (rem) or Sievert units.

Again, the dose is what we usually consider and track with respect to radiation in pregnancy.

  • The background dose of radiation a fetus is exposed to during pregnancy is around 1 mGy.

  • From CO 723 — a reference for doses associated with different imaging studies.



The risk of radiation exposure on a developing fetus depends on both the dose of radiation, as well as the gestational age at which the exposure occurs.

  • For instance, if an exposure of 50-100 mGy occurs prior to implantation (0-2 weeks post fertilization), there is generally an all or none effect; that is to say, this usually results in miscarriage, or no consequence at all.

  • During organogenesis, or 2-8 weeks post-fertilization, congenital anomalies or growth restriction can be seen with cumulative doses of 200-250 mGy.

  • The risk of severe intellectual deficit or microcephaly is most prominent around 8-15 weeks, with doses between 60 - 300 mGy.

    • There is an estimated 25 point IQ loss per 1000 mGy exposure during this time period. 

    • A lower risk of severe intellectual disability may persist through 25 weeks gestation, though again with exposures of 250mGy or more.

  • Other risks include childhood cancer. With respect to leukemia, it is estimated the risk of childhood leukemia increases 1.5-2 fold with a 10-20mGy dose, over a background leukemia risk of 1 in 3000.

  • Radiologists and radiation physicists can help to calculate doses for patients exposed to multiple studies or with occupational hazards. 

With respect to contrast:

  • Oral contrast poses no real or theoretical harm to pregnant or lactating mothers and their infants.

  • IV contrast tends to be iodinated, but is also water-soluble.

    • So similarly to gadolinium, in pregnant patients this crosses the placenta.

    • Animal studies have demonstrated no teratogenic effects from its use, but it is recommended to limit use of iodinated contrast unless necessary.

    • Also similarly to gadolinium, because of this water solubility, iodinated contrast is excreted minimally in breastmilk, and breastfeeding should be continued without interruption.

Nuclear medicine studies

Radioisotopes for nuclear medicine studies, such as VQ scans, thyroid scans, and bone scans, are variable in their potential effects on the fetus.

  • Technetium-99 is one of the most common radioisotopes used for these studies, and given its short half life of 6 hours as well as its pure gamma ray emission, is generally accepted as safe to use when indicated in pregnancy.

  • Radioactive iodine (I-131), by contrast (punny!), readily crosses the placenta and has a half-life of 8 days, and has known adverse effects on the fetal thyroid. Thus, it is contraindicated for use in pregnancy, and is also recommended against use in breastfeeding mothers until breast milk has been cleared of the radioisotope. 

Preterm Labor and PPROM

Today we talk about the routine management of PPROM and PTL. We’ve prepared a little chart that we hope is handy for both teaching and learning! Be sure to also check out ACOB PB 171 and PB 188. For some primary literature, check out the BEAM trial on magnesium sulfate, the most recent Cochrane review on steroid administration, the ALPS trial for Antenatal Late Preterm Steroid administration, and the RCT demonstrating benefit to latency antibiotics in PPROM.

(c) CREOGS over Coffee, 2019

We also use the podcast to highlight a number of controversies, differing practice patterns, or areas of new and active research in these clinical topics (with help from our friends at the ObG Project!)

  • Delivery timing: A 2017 Cochrane review suggested better neonatal outcomes with expectant management of PPROM to 37 weeks, convincing enough to have the Royal College of Obstetrics and Gynecology to change their clinical practice guideline to allow expectant management to 37’0.

  • Administration of Corticosteroids: The ObG Project gives a great summary on when to administer betamethasone. In summary:

    • Between 24-34 weeks in all cases of PPROM and in PTL if delivery is expected within 7 days.

    • A single rescue course should be administered if it has been > 14 days since the last course, and delivery is again expected within the subsequent 7 days.

    • Between 34-36’6 weeks if PPROM or PTL occurs, no prior steroids have been administered, and delivery is expected within the subsequent 7 days.

  • Periviability: The management of periviable PPROM is managed very differently by institution, as resources and optimal management strategies remain to be identified. Protocols and policies should be arranged in accordance with the individual obstetrics and neonatology departments. Ideally, counseling for patients experiencing periviable PTL and PPROM should be performed in an interdisciplinary fashion.

  • Outpatient Management of PPROM: There have a few retrospective studies, the most recent of which came from a large series out of France and received some press attention, suggesting that outpatient management may be appropriate in select candidates. That said, this is definitely NOT the standard of care at this time; inpatient management of PPROM is still the standard set forth by ACOG in the absence of larger, prospective studies.