Multifetal Gestation

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Multifetal gestations are on the rise: twins now represent 33/1000 birth, and triplets or higher order gestations represent 1.53/1000 births. This is likely due to increased maternal age at conception and increased use of assistive reproductive medications and technologies. Certainly a multiple gestation pregnancy is exciting for patients, but convey a multitude of other risks for both maternal and fetal morbidity in pregnancy. Higher rates of almost anything you can imagine, including PIH/preeclampsia (RR 2.6 twins compared to singletons), placental abruption, HELLP, gestational diabetes, hyperemesis, anemia, hemorrhage, CD, PPD, cholestasis, PUPPS are elevated.

Most commonly preterm birth and its associated neonatal morbidity are encountered with these higher order pregnancies. Women with multifetal gestation are 6x more likely to deliver preterm and 13x more likely to deliver before 32 weeks compared to women with singleton gestation. Twins deliver on average around 35-36w and triplets around 32-33w. Furthermore, compared to gestational age matched premature singleton neonates, those in multifetal gestation have worse outcomes, higher rates of stillbirth, neonatal death, intraventricular hemorrhage, periventricular leukomalacia, and cerebral palsy And unfortunately, there are no strategies that exist to reliably mitigate this risk, including progesterone, cerclage, or pessary. However, many ongoing trials seek to answer this question. Multifetal reduction can help to mitigate these risks in higher-order gestations.

Diagnosing Multiple Gestation

The components of chorionicity and amnioniticity are ideally noted in a first or early second trimester sonogram (best at 10-14 weeks).

  1. Super important as this dictates antepartum management and delivery recommendations! 

    1. Dating in spontaneously conceived twins: if there is a CRL discordance, most radiologists would date pregnancy with larger CRL in order to not underdiagnose FGR (ART use transfer/IUI dating).

  2. Chorionicity (fetal side of uteroplacental interface) and amnionicity (sac with amniotic fluid)

  • Fraternal twins: dizygous 70% different sperm and different egg, same genetic relationship as any other set of siblings born at different ages -> dichorionic gestation (which implies diamnionicity as well).

  • Monozygous 

    1. Split within 3 days: dichorionic (20% of monozygous)

    2. Split 4-8 days: monochorionic / diamniotic (70%)

    3. Split 9-12 days: monochorionic / monoamniotic (1% of all monochorionic twins) 

    4. Split 13(+): conjoined (unlucky 13)

  • Rule of thumb, monochorionic always higher risk than dichorionic.

  1. Diagnosis: going back to episode 68 OB ultrasound

    • Dichorionic gestation can be diagnosed by any of the following: two distinct placentas, different fetal sex, or twin peak/lambda sign vs T-sign.

“Lambda” sign for dichorionic gestation. The OBG Project / Nevit Dilmen Creative Commons Attribution-Share Alike 3.0 license https://creativecommons.org/licenses/by-sa/3.0/deed.en

“Lambda” sign for dichorionic gestation. The OBG Project / Nevit Dilmen Creative Commons Attribution-Share Alike 3.0 license https://creativecommons.org/licenses/by-sa/3.0/deed.en

“T” sign for monochorionic, diamniotic gestation. The OBG Project / Nevit Dilmen Creative Commons Attribution-Share Alike 3.0 license https://creativecommons.org/licenses/by-sa/3.0/deed.en

“T” sign for monochorionic, diamniotic gestation. The OBG Project / Nevit Dilmen Creative Commons Attribution-Share Alike 3.0 license https://creativecommons.org/licenses/by-sa/3.0/deed.en

Common Antepartum Considerations for Multiple Gestations

Recommended weight gain

  1. CO 548 weight gain in pregnancy 

    1. Normal weight: 37-54

    2. Overweight: 31-50

    3. Obese: 25-42

Aneuploidy screening

  1. Inherent increased risk with dizygous gestation - two babies, twice the risk!

  2. Serum screening is not as sensitive because analyte levels are estimated by mathematical modeling. In reading serum levels from a multiple gestation, they are essentially “averaged out,” so a genetically normal twin can mask the abnormal level of the twin affected by aneuploidy.

    1. Can add nuchal translucency for increased sensitivity since you can see which twin may have an anomaly.

  3. NIPT (cell free DNA, Mat21 esp) in small studies have high sensitivity and specificity similar to singleton gestation, but the reported cases are small and we likely need larger studies to better get at the true sensitivity and specificity.

  4. As always, diagnostic testing with CVS or amniocentesis most accurate and should be offered. Loss rate about 1-2% for both procedures and slightly higher than in singleton gestation.

    1. Amnio for dichorionic gestation: can sample one sac, inject indigo carmine, then sample second sac to ensure clear fluid and ensure sampling of two separate sacs.

    2. Amnio for monochorionic gestation - if chorionicity has been confidently established, unlikely to have discordance between the two fetuses so might only sample one; although its possible to have genetic discordance due to fetal mosaicism 

Twin growth

  1. Used to have twin growth rates curves, but didn’t pan out in follow up studies. So now we use a singleton growth curve, and note a slow down after 30 weeks.

  2. Should obtain anatomy ultrasound 18-22w, and given increased risk of congenital anomalies reasonable to start with L2 or specialized ultrasound.

    1. Monozygous twins have higher rates of anomalies (especially cardiac), so fetal echoes are recommended.

  3. Growth ultrasounds every 4 weeks measure % discordance. If discordance > 20% may warrant closer evaluation (EFW lg - EFW sm / EFW lg), could be a sign of developing FGR and associated with poor neonatal outcomes.

    1. Monochorionic every 2-3 weeks after 16w.

    2. Dichorionic every 4-6 weeks after anatomy scan in otherwise uncomplicated pregnancies.

  4. Twin gestation with one fetal growth restricted fetus associated with worse perinatal outcomes.

  5. Cord anomalies (basically moot, since they’re already getting monitored for growth):

    1. Velamentous cord insertion 

      • 7-12% twin pregnancies compared to 2% in singleton gestation 

    2. Marginal cord insertion 

    3. Placenta previa

      • Higher incidence likely due to more placental mass 

    4. Vasa previa

      • Systematic review of cohort and case control series found that of 438 cases of vasa previa, 11% in twins.

Specific Monochorionic Considerations 

  1. Diamniotic (US 16-18 weeks)

    • Twin Twin Transfusion Syndrome

      1. 10-15% of mono/di pregnancies due to arteriovenous connections → unequal vascular sharing; by contrast, in 6% of monochorionic pregnancies  

      2. Diagnosis by Quintero staging 

        1. Stage 1: oligo/poly DVP.

        2. Stage 2: absent bladder in donor twin.

        3. Stage 3: abnormal doppler findings 

          1. UA, DV, UV

        4. Stage 4: hydrops

        5. Stage 5: death of one or both twins  

      3. Stage can remain stable, regress, or progress (sometimes rapidly).

      4. Earlier the diagnosis more severe the disease

      5. Treatment is laser ablation of anastomoses or amnioreduction 

      6. Monitoring:

        1. Weekly AFI 

        2. Every 3-4 weeks growth scan.

        3. After 30 week weekly BPP.

    • TAPS twin anemia polycythemia sequence 

      1. Atypical chronic TTTS where the transfusions happens super slowly, through the smallest vessel connections, manifested in >MCA 1.5 MoM of one twin and < 1.0 MoM of the other twin 

        1. 2-13% due to post-TTTS laser (large anastomosis obliterated, smaller ones persist).

    • To distinguish TTTS vs single IUGR - guide is fluid volume.

    • Twin Reverse Arterial Perfusion (TRAP) Sequence

      • Acardiac twin 

        1. One twin absent head/heart but stays living, other pump twin can develop high output heart failure with 50% mortality rate.

      • Requires ultrasonic laser ablation of acardiac twin vasculature.

  2. Monoamniotic

    1. Cord entanglement/accident → IUFD

      • Antenatal management hard to agree upon, some do daily NST beginning in the late second or early third trimester, IP vs OP management, no consensus.

      • Rare, but can have TTTS in mono/mono.

What happens if a twin demises? 

  1. Spontaneous reduction or vanishing twin 36% in the first trimester and even higher for higher order multiples 

  2. Second trimester: up to 5% twins and 17% triplets undergo death of one of the fetuses 

    1. Monochorionic set higher rate of stillbirth and neurologic deficits in surviving twin than dichorionic set, recommendation to continue with pregnancy until at least 34 weeks. 

    2. Thought to be due to hemodynamic changes where intrauterine demise of one twin becomes a low pressure system, and the other twin can effectively exsanguinate or have hypotension/anemia from perfusion being directed towards the demised twin, subsequently causing death or neurologic injury of surviving twin.

Preterm labor 

  1. Asymptomatic

    1. Counseling patients they will be at a higher risk of PTL 

    2. No recommended screening for asymptomatic women, since no interventions have been proven to be helpful for women with multifetal gestation.

    3. One study showed prophylactic cerclage in women with twin gestation and short cervix on US actually increased the rate of sPTB with a RR of 2.2 

  2. Managing spontaneous PTL 

    1. Short term of tocolysis for administration of corticosteroids recommended, as those trials included some women with multiple gestation less than 34w.

      • Includes one course of rescue steroids (risk of delivering within the next 7 days, most recent course was at least 7 days ago) and extending to 23w after counseling on expectations and working closely with NICU to go over available resources.

    2. What about ALPS steroids for multiple gestation?

      • They were not included in the original trial, but we extrapolate their benefits and do recommend them at our institution.

      • Currently the ACTWIN trial, a multicenter RCT enrolling based out of Seoul, is attempting to answer this question.

    3. Magnesium sulfate for neuroprotection under 32 weeks regardless of fetal number.

Delivery planning 

  1. Dichorionic 

    1. In uncomplicated pregnancies, delivery no later than 38th week.

    2. Candidate for vaginal delivery if presenting twin vertex and someone with experience with internal podalic version and vaginal breech delivery available, including TOLAC candidates (one previous).

  2. Monochorionic 

    1. 34 to 37’6, with same principles as above for VD vs CS.

  3. mono/mono 

    1. 32-34w scheduled CS.

COVID-19 for the OB/GYN

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Today’s episode is an audio summary of the CDC and SMFM guidelines for COVID-19, focusing on the virus, identification, containment, and considerations for pregnancy and postpartum care. We do not explore treatments or any intricacies in either outpatient or inpatient care.

Rather than posting those guidelines here verbatim, we have gone through and identified a lot of reputable sources with factual, up-to-date information for healthcare providers:

We also mention in the episode a registry being established for pregnant patients with COVID-19. Please listen to learn more about how you can be involved.

Sepsis

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In today’s podcast, we try to provide an update on sepsis for OB/GYN’s. It’s a long one but hopefully full of lots of good information for your practice and knowledge.

Sepsis definitions have changed recently, put forth in 2016 the Third International Consensus Conference for the Definitions of Sepsis and Septic Shock Task Force. These marked a major departure from previous iterations, which were defined by the “SIRS” or “Systemic Inflammatory Response Syndrome” criteria. This also ushered in a new scoring system for sepsis evaluation, known as the Sequential Organ Failure Assessment tool, and a quick bedside version known as qSOFA.

Common obstetric and gynecologic etiologies include urinary tract infections and pyelonephritis; chorioamnionitis/endometritis; wound infections and necrotizing fasciitis; septic abortions; toxic shock syndrome; and ruptured tuboovarian abscess. Non-obstetric or non-gynecologic causes should also be considered. Some of these more common etiologies include gastrointestinal causes, such as appendicitis, diverticulitis, or peritonitis; respiratory causes, such as influenza or pneumonia; and skin infections including cellulitis. 

In our hospital, we remember the primary interventions for sepsis using the acronym “BLAST”: Blood Cultures, Labs/Lactate, Antibiotics, Saline, Time.

B: Blood Cultures; L: Lactate/Laboratories

With the suspicion for sepsis, laboratory evaluation is essential. CBC, BMP, lactic acid, and blood cultures are often part of the initial workup.

Lactic acid production partially results from the shift of aerobic to anaerobic cellular metabolism, so it functions as a proxy marker of poor tissue perfusion. In sepsis, higher lactic acid levels have been associated with worsened outcomes. Surviving Sepsis Campaign guidelines do recommend guiding resuscitation to lactate normalization.  The SMFM consensus statement does recommend lactate measurement for suspected sepsis in pregnancy.

Blood cultures are important to obtain upfront, prior to the initiation of antibiotic therapy. Even with an initial antibiotic exposure, blood cultures can become useless. Two sets of peripheral blood cultures, with each set consisting of aerobic and anaerobic cultures, are recommended (13). If an infection site is suspected and can be easily accessed for culture in a timely manner, cultures are recommended prior to antibiotic initiation.  

In obstetric patients, the most common causes of sepsis include septic abortion, chorioamnionitis and postpartum endometritis, urinary tract infections, pneumonia, and gastrointestial origins such as appendicitis.

A: Antibiotics

Empiric antimicrobial therapy should be broad in coverage, but also directed towards the most likely source, if one is known. The SMFM consensus statement, the Surviving Sepsis Campaign, and the SEP-1 core measure promote administration of appropriate antibiotic therapy within three hours of presentation. Mortality risk in septic shock appears time-dependent with respect to antibiotic therapy based on observational data.

Combination or “double coverage” therapy for critically ill or neutropenic patients (using two antibiotics to cover the same spectrum of pathogen) is not recommended. However, one notable exception is a source of sepsis more commonly encountered by gynecologists: toxic shock syndrome (TSS).

TSS results from the production of noxious exotoxins by Streptococcus and is described with retained objects, such as tampons, in the vagina. The antibiotic therapy of choice in this case is a combination of penicillin and clindamycin, as clindamycin acts as a transcription inhibitor to the production of bacterial exotoxins.

S: Saline

Crystalloid fluid is the choice for initial resuscitation in severe sepsis or septic shock. The landmark trial on early-goal directed therapy (EGDT), published by Rivers in 2001, randomized patients to standard therapy versus targeted fluid therapy with placement of both central venous and arterial lines, with strict goals for mean arterial pressure (MAP), central venous pressure (CVP,) venous oxygen saturation, hematocrit, and urine output. Fluid administered prior to randomization in both arms was 20-30 cc/kg over 30 minutes. This has ultimately become the standard of care for initial fluid resuscitation.

In pregnancy, this may be overly aggressive, and predispose patients to pulmonary edema; thus, the SMFM consensus statement on sepsis in pregnancy recommends an initial bolus of 1-2 L. Frequent reevaluation of volume status should be performed.

T: Time

The SEP-1 core measure from CMS is predicated on two major time points, with time starting at the time of patient presentation with severe sepsis or septic shock. The SEP-1 bundle requirements at three hours and six hours are shown in Figure 2. The entirety of the “BLAST” protocol covers the initial, “three hour” time point.

The next marker is six hours, which states there should be a redrawn lactate if there was a diagnosis of severe sepsis or septic shock. There also should be a full physical examination, The reexamination can include central venous pressure measurement, central venous oxygen measurement, a bedside cardiovascular ultrasound, or a passive leg raise test as well. For obstetricians and gynecologists, likely the physical examination and passive leg raise are the most easily performed. This may not work in pregnancy due to aortocaval compression; thus, SMFM recommends continued bolus with small fluid volumes (250 - 500 cc) and close monitoring of vital signs to determine if patients are fluid responsive.

If patients in septic shock do not respond to fluid and are persistently hypotensive despite adequate fluid resuscitation, the SEP-1 core measure requires administration of vasopressors by the six hour mark. Norepinephrine is the primary choice in sepsis both in and out of pregnancy. Norepinephrine is associated with lower rates of arrhythmia and overall mortality compared with other vasopressors.

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We go into a lot more detail in the podcast on some additional points, but be sure to check out the SMFM Sepsis guideline for all the deep reading on this topic!

Preventing the Primary Cesarean, Part II

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We’re re-visiting an old episode of ours on preventing the primary cesarean, with some more and differently focused information. We heard some great feedback from our last episode so we’re incorporating some of that here! This time around, we want to focus some more on how to promote normal labor and physiological birth! 

Let’s start off with talking about shared decision-making. This is a framework for taking situations with various individuals with different sets of knowledge, belief systems, and priorities and coming together to form a mutually satisfying plan to get everyone where they want to go. ACOG CO 587 reviews this in part, stating SDM can increase patient engagement and reduce risk with resultant improved outcomes, satisfaction, and treatment adherence.

Shared decision making can take the form of a variety of tools in prenatal care and on the labor floor:

  1. Partograms - allowing patients to see where they are in their labor course compared to others.

  2. Birth plans - providers and patients can come together early in their course of the pregnancy to identify patient goals and desires for their labor. Also allows recognition of some goals/desires may not be feasible due to the patient’s individual risk factors, pregnancy complications, etc. 

  3. Patient education resources - we love www.birthtools.org, but there’s a number that exist (and some probably specific to your institution) that can help set expectations for the birthing process.

In identifying a patient’s desires in labor, one of the most common questions has to do with analgesia. Prental care is an excellent time to discuss both pharmacologic and non-pharmacologic options for coping. While epidurals are common in the USA, continuous labor support is another option for coping and also has been shown to reduce cesarean rates in trials. It can take on many forms, and be administered by anyone a laboring person trusts:

  1. Physical support - positioning, use of touch, application of cold and heat and control of environment.

  2. Emotional support - being present with the laboring woman, use of distraction.

  3. Instructional/informational support - assistance with relaxation and breathing, using effective communication techniques.

  4. Advocacy labor support - building trust, providing security and giving laboring women control.

Nutrition and hydration during labor is another common sticking point. It is very common for nutritional deprivation at NPO or clear liquid diets to occur in labor. This is for ostensibly, a good reason: fear of aspiration of stomach contents in the event for need for general anesthesia, or for vomiting due to decreased GI motility. However, a Cochrane review demonstrated no statistical difference in maternal or newborn outcomes related to type of birth or Apgar scores at five minutes. Nutritional deprivation provided no benefit or harm, and so evidence does not support nutritional deprivation. This review further stated that nutritional deprivation can cause maternal distress, unbalanced nutritional status, and increased pain in labor.

What about our original fear of aspiration? Current studies don’t show that nutritional deprivation ensure low stomach residue or acidity. When combined with decreased use of general anesthesia in modern obstetrics, concern for aspiration risk does not provide sound basis for implementation of withholding food or fluid from women in labor.

Next, let’s review the benefits of collaborative care models:

Labor is a team sport that contains the woman, her support person/people, her nurse, and provider (midwife/obstetrician/family practitioner). It shares the workload for this 24 hour in house care, providing a variety of perspectives on the case, in a mutually respectful environment. Now certainly, there are challenges to what sounds so harmonious: interdisciplinary mistrust, inconsistent communication, variable skill sets, scheduling logistics, hospital structure, to name a few. However, we know that this is evidence based! Studies where there have been 24 hour laborists and strip review and collaboration have led to significant decrease in NTSV rate. Why does it work? Well, it likely promotes consideration of alternative options, with experts of multiple perspectives and skill level.

Lastly, systems-based and structural design challenges may also contribute to cesarean. This work is nascent, but check out the awesome work by the folks at Ariadne Labs’ Delivery Decisions Initiative to learn more.

Group B Strep

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Today’s episode covers the ACOG Committee Opinion on Group B Streptococcus, also known as GBS or Streptococcus agalactiae.

The OBG Project has a phenomenal summary of these new guidelines; we encourage you to check out their outline which was hugely helpful in preparing the podcast for today! And be sure to check out how you can get their premium product, OBG First, absolutely FREE if you’re a chief resident. Check out the sidebar to learn more!

Get to know Group B Strep

Streptococcus agalactiae or GBS is a common flora of the vagina and rectum of women, with a prevalence of colonization between 10-30%.  In newborns, two types of GBS-related disease exist:

  • Late Onset Disease occurs between 7 days and 2-3 months after birth, and is characterized by sepsis, more commonly meningitis, and organ/soft tissue infection.

  • Early Onset Disease is present within 7 days of birth.

    • Occurs secondary to vertical transmission; fetal/neonatal aspiration during labor process; or both. 

    • Manifestations of disease occur most likely within 12-48 hours after birth. 

    • Characterized by sepsis, pneumonia, and less commonly meningitis.

    • The most common cause of early-onset neonatal sepsis.

      • 72% of cases of Early Onset Disease occur in term newborns; however, mortality is markedly higher in premature infants (19.2% in premies vs 2.1% at term), and premature infants are more likely to require higher levels of intensive care intervention. 

    • When treating GBS in labor, this is what we are primarily aiming to prevent! 

    • Risk factors for GBS Early Onset Disease:

      • Gestational age < 37 weeks

      • Very low birth weight

      • Prolonged rupture of membranes > 18 hours

      • Intraamniotic infection

      • Young maternal age

      • Black race

      • Heavy vaginal-rectal colonization or GBS bacteriuria (proxy for heavy colonization)

      • Previous newborn affected by GBS early onset disease

The Screening Recommendations

  • Screening in the USA is universal, meaning this should be a standard part of prenatal care. 

    • ACOG recommends universal screening for vaginal-rectal colonization between 36’0 - 37’6.

      • These results are considered “valid” for 5 weeks — thus the majority of women will be captured with screening at 36’0 (assuming inductions for most women at 41’0). 

      • This is also recommended for women planning to deliver by cesarean.

  • What about GBS bacteriuria?

    • If GBS bacteriuria is present in any amount at any time during pregnancy, this is considered a positive result (proxy for heavy colonization), and thus repeat screening is not necessary.

    • If asymptomatic GBS bacteriuria is present at >10^5 CFU/mL, treatment should be considered as you would for any other form of ASB. 

      • If at less than 10^5 CFU, no correlation has been found between treatment of this lower-level bacteriuria and improved maternal or neonatal outcomes; however, it should still be noted that this patient would be considered GBS positive.

  • Screening may also occur at the time of admission for preterm labor and prelabor premature rupture of membranes (PPROM). 

    • In the case of prematurity, treatment should begin while awaiting screen results.

      • If the screen is positive and preterm labor resolves, the colonization should be considered positive for the remainder of the pregnancy.

      • If the screen is negative, re-screening should be performed after 5 weeks. 

  • The gold standard for screening is obtaining a vaginal-rectal culture. 

    • Recently, nucleic acid amplification tests (NAAT) have also demonstrated promise in obtaining accurate, quick results.

      • Most accurate tests that perform similar to culture do require some culture time prior to the NAAT test performance; results generally aren’t available before 18-24 hours after screening occurs. 

        • NAAT tests that offer results in a shorter time period often have lower accuracy.

      • NAAT tests also do not have the ability to test antibiotic resistance, which is important in the case of a patient with known penicillin allergy.

        • If your patient has known penicillin allergy, the laboratory should be alerted so sensitivity testing can be performed.

    • Given this delay and with someone moving quickly in labor or preterm labor with no known GBS status, risk factor-based screening may also be employed to decide if treatment should be pursued in the absence of a screening result. 

      • If any of the risk factors are present, treatment should be pursued:

        • Prematurity or PPROM (< 36 weeks 6 days)

        • History of a prior newborn affected by GBS disease

        • Amniotic membrane rupture > 18 hours duration

        • Presence of intrapartum fever > 100.4F (38 C)

        • If known GBS positive result in a previous pregnancy (may engage in shared decision making in this clinical scenario).

Intrapartum Antibiotic Treatment 

  • The gold standard for the treatment of GBS colonization intrapartum to reduce risk to neonates for early-onset disease is penicillin G. 

    • Dosed at a loading dose of 5 million units loading, then 2.5-3 million units IV every 4 hours until delivery.

    • Ampicillin is an acceptable alternative, with a loading dose of 2g IV followed by 1g IV every 4 hours. 

      • PCN is preferred as it has a narrower, more targeted spectrum of activity and lower likelihood of inducing resistance in other organisms.

    • For this reason, identification and history of penicillin allergy is super important to flush out in prenatal care! 

      • 80-90% of persons with reported PCN allergy are not truly allergic. 

        • Pruritic rash, urticaria (hives), immediate flushing, angioedema, respiratory distress, or anaphylaxis after PCN or cephalosporin administration is considered a high risk for true allergy.

        • Even with high risk persons, if PCN allergy testing has not been performed, it is recommended to do this — even in pregnancy!

    • When PCN allergy testing has not been performed, the allergy should be classified as “low” versus “high risk,” based on the symptoms just described.

      • If “low risk,” first generation cephalosporins such as cefazolin are recommended. 

        • Cefazolin has very low cross reactivity with penicillin for a 1st gen cephalosporin, and GBS remains highly susceptible to it. 

        • Dosed at 2g IV load, followed by 1g IV q8h until delivery.

      • If “high risk,” or an unknown risk with no allergy testing, susceptibility testing should be performed by the laboratory with screening.

        • Options for therapy will include clindamycin or vancomycin.

          • Clindamycin should only be utilized if culture results have shown susceptibilit.

            • Resistance to clindamycin in GBS is approximately 20%. 

            • Dosing: 900mg q8h until delivery 

          • Vancomycin has good activity against GBS.

            • High risk in creating resistant organisms (i.e., VRE) with widespread use, and thus every effort should be made to rule out penicillin allergy before its use.

            • Dosing: 20mg/kg IV q8h, with maximum of 2g per single dose.

  • How long does it take the antibiotics to work?

    • All antibiotics used for GBS prophylaxis are time-dependent with respect to their ability to lower microbial load.

      • Studies done with PCN or ampicillin prophylaxis demonstrate that 4 or more hours pf prophylaxis is preferable, though 2 hours has been shown to reduce GBS count and decrease neonatal sepsis. 

      • That said, obstetric intervention should not be delayed solely to provide 4 hours of antibiotic administration., when it is indicated.

        • Examples of such interventions that should not otherwise be delayed include oxytocin administration, AROM, or cesarean.

That said, if interventions are not immediately indicated, the benefits of increased antibiotic exposure to reduce GBS exposure should be considered.