Organized by what you're treating, not what class the drug belongs to — safety tier at a glance, then the dosing and use-specifics that differ (or don't) from the non-pregnant patient.
From 1979 to 2015, the FDA assigned every prescription drug a letter — A, B, C, D, or X — summarizing fetal risk based on available human and animal data:
The system was officially retired on June 30, 2015, replaced by the Pregnancy and Lactation Labeling Rule (PLLR), which requires a narrative risk summary instead of a single letter — the FDA's own stated reason was that clinicians and patients were treating the letters as a linear safety grade (A better than B better than C…) when that was never how the categories were actually built; a "C" can reflect total absence of data just as easily as a worrying animal signal, and isn't necessarily riskier than a "B" that merely got lucky in animal testing. Drugs approved before June 2001 were allowed to keep their old letters on the label until June 2018, when the letters were required to be removed entirely. No new drug has received an FDA pregnancy letter since 2015 — but because most of the agents in emergency and obstetric medicine are older, generic drugs, their legacy letters are still what you'll find in Micromedex, Epocrates, Lexicomp, and Briggs' Drugs in Pregnancy and Lactation, and are reproduced below for exactly that reason.
A handful of agents below were never assigned a letter at all — naturally occurring hormones used for their approved obstetric indication (oxytocin), non-absorbed adsorbents (activated charcoal), and IV electrolytes (calcium gluconate) don't fit the letter framework and are labeled "not classified" rather than guessed at.
Tier assignments from Figure 2 of Tamirisa et al., JACC Clin Electrophysiol 2022 (checked drug by drug, 2026-10-13), cross-referenced and expanded with acute dosing.
6 mg rapid IV push, then 12 mg if needed — identical to non-pregnant dosing. First-line for SVT; extremely short half-life means negligible fetal exposure per dose.
Standard loading/maintenance dosing, but levels can run falsely elevated late in pregnancy due to a circulating digoxin-like immunoreactive substance — treat the rhythm and clinical picture, not the number alone.
Not a rate-control agent here: no arrhythmia dosing regimen is established for it. For IV beta-blocker rate control in pregnancy, use metoprolol or propranolol, the beta-blockers named for tachyarrhythmias in pregnancy. Labetalol's 20–40–80 mg escalation is the hypertensive-emergency regimen (below). With any beta-blocker near delivery, watch for neonatal bradycardia.
Avoid except for maternal life-threatening arrhythmia refractory to everything else — associated with fetal hypothyroidism, growth restriction, and prematurity. If truly life-saving, use it; don't let the avoidance tier become a reason to withhold it from a dying mother.
Maternal hemodynamic stability is fetal stability — don't undertreat a genuine maternal arrhythmia out of fetal-risk hesitancy. Every "avoid" tier here still has a "unless life-threatening" escape clause.
Magnesium sulfate is a distinct pharmacologic category from every other anticonvulsant here — it isn't a benzodiazepine, isn't a GABA agent, and its dosing and toxicity monitoring don't map onto standard seizure protocols.
Loading 4–6 g IV over 15–20 min, then maintenance 1–2 g/hr continuous infusion. Superior to both phenytoin and benzodiazepines for preventing recurrent eclamptic seizures — this is a pregnancy-specific first-line agent with no equivalent role in non-obstetric seizure management.
Monitor deep tendon reflexes, respiratory rate, and urine output for toxicity (loss of reflexes precedes respiratory depression) — calcium gluconate 1 g IV is the antidote for magnesium toxicity.
Lorazepam 4 mg IV over 3–5 min, or diazepam 5–10 mg IV slowly — standard non-pregnant seizure dosing, used here as second-line if magnesium fails or is contraindicated (e.g., myasthenia gravis).
60 mg/kg IV, max 4,500 mg for persistent seizure after magnesium and a benzodiazepine — an emerging next step in eclampsia algorithms, and already established as safe in pregnant women with epilepsy.
20 mg PE/kg IV at 150 mg PE/min for seizures persisting after magnesium and benzodiazepine — reserve for refractory cases; not a substitute for magnesium as first-line.
Reach for magnesium first even if your seizure instincts say benzodiazepine — this is the one scenario in emergency medicine where the "obvious" anticonvulsant is not the right first move.
Severe hypertension in pregnancy/postpartum (SBP ≥160 or DBP ≥110) should be treated within 30–60 minutes. ACOG states any of the three first-line agents below is appropriate — the choice is about access and comorbidity, not superiority.
20 mg IV; if BP still elevated at 10 min, give 40 mg; if still elevated at 10 more min, give 80 mg (max single dose); repeat at 10 min if needed to a cumulative 300 mg. Avoid in asthma/heart failure/bradycardia.
5–10 mg IV, repeat in 20 min if needed. Higher risk of maternal hypotension than labetalol or nifedipine — have fluids and fetal monitoring ready.
10 mg orally; repeat with 20 mg at 20 min if still elevated. Preferred when IV access isn't available — some data suggest faster BP control and better urine output than IV agents. Extended-release only for maintenance, never for acute treatment.
Concern about neuromuscular blockade/severe hypotension when combined with magnesium sulfate was not borne out in large reviews, but both are calcium antagonists — monitor.
Long safety track record for chronic/maintenance BP control in pregnancy; not an acute agent — onset too slow for emergency use.
Don't over-lower BP aggressively — placental blood flow autoregulation in severe preeclampsia isn't well established, and dropping pressure too fast can cause fetal distress even while "fixing" the maternal number.
Management is essentially identical to the non-pregnant patient — the one meaningful addition is positioning, and the one meaningful pitfall is hesitating on epinephrine out of fetal-risk concern that the evidence doesn't support.
0.3–0.5 mg IM (1 mg/mL) in the mid-outer thigh, repeatable every 5–15 min — identical dosing to the non-pregnant patient. Do not withhold or under-dose out of concern for uterine/placental vasoconstriction; untreated anaphylactic hypoxia and hypotension are a far greater fetal threat than the drug.
Position the patient with manual left uterine displacement (or full left lateral tilt) once ≥20 weeks gestation to relieve aortocaval compression and improve venous return during resuscitation.
Standard adjunctive dosing as in non-pregnant anaphylaxis — these treat the histamine/inflammatory tail of the reaction and are not a substitute for epinephrine.
The only pregnancy-specific move in anaphylaxis is uterine displacement/left lateral tilt — everything else, including epinephrine dosing, is unchanged from your standard protocol.
An escalating uterotonic ladder plus tranexamic acid — the two contraindications (asthma, hypertension) are the two things you must ask about before reaching for the second-line agents.
Continuous IV infusion, first-line uterotonic. Half-life <10 minutes — requires continuous infusion, not a single bolus, to sustain effect; watch for water intoxication/hyponatremia with high-dose prolonged infusions given its antidiuretic activity.
1 g IV when blood loss exceeds 500 mL (vaginal) or 1000 mL (cesarean) and bleeding persists despite oxytocin. Reduces total blood loss and PPH-related mortality.
0.2 mg IM (standard route — avoid routine IV administration due to hypertensive/stroke risk; if IV is truly necessary, give over ≥60 seconds with continuous BP monitoring). Contraindicated in hypertension/preeclampsia.
0.25 mg IM, repeatable. Contraindicated in asthma — causes significant bronchospasm/bronchoconstriction; also causes vomiting more often than oxytocin alone.
Ask "asthma or hypertension?" before you reach for the second-line uterotonic, not after — the two agents you'd reach for are contraindicated in exactly the two conditions you haven't asked about yet.
Pregnancy's physiologic changes (increased plasma volume, decreased plasma cholinesterase, aortocaval compression) shift drug behavior even when the dose on the syringe looks identical to non-pregnant RSI.
Standard 1–1.5 mg/kg IV dosing — still the most-used agent for obstetric RSI (used in ~86-90% of cases per recent audits) given its fast onset/offset, though decreased plasma cholinesterase in pregnancy can prolong its effect somewhat.
Standard 0.6–1.2 mg/kg IV RSI dosing — 2015 guidelines favor rocuronium over succinylcholine for RSI generally, with sugammadex available for rapid reversal if the airway is lost. Comparable neonatal outcomes to succinylcholine in recent meta-analysis.
Standard induction dosing (~1–2 mg/kg) — pharmacokinetics in pregnancy aren't fully characterized, but it remains the standard induction agent; titrate to effect given altered volume of distribution.
Can increase uterine tone/contractility at higher doses — reasonable in hemodynamically unstable patients (hemorrhage, sepsis) where its sympathomimetic profile is an advantage, but discuss timing with obstetrics if delivery isn't imminent.
Standard analgesic dosing; opioid clearance increases 60-70% in pregnancy versus postpartum, so effect may be shorter-lived than expected at a "normal" dose.
Position matters as much as drug choice here — left uterine displacement during and after induction prevents the aortocaval-compression hypotension that gets blamed on the drug.
First-line is oral and low-tech; the IV escalation ladder is where ED visits actually happen.
First-line for standard nausea/vomiting of pregnancy — oral only, so not useful once vomiting prevents absorption (i.e., not an ED-tier rescue agent on its own).
Standard 4–8 mg IV dosing. Large Danish registry data (n=608,385) found no increased risk of major birth defect, stillbirth, or preterm labor; a smaller case-control study flagged a possible cleft-palate signal the authors themselves attributed to chance. Bottom line: reasonable first IV agent, with an honest, shared-decision conversation about the mixed data.
Standard 10 mg IV dosing; effective and has less teratogenicity concern than ondansetron in some reviews, but the 2013 EMA warning limits duration of use to 5 days due to extrapyramidal/tardive risk — watch for acute dystonia.
Effective but higher extrapyramidal/oculogyric-crisis risk than metoclopramide or ondansetron — reasonable second-line if first agents fail, stop immediately if dystonic reaction occurs.
Don't forget the adjuncts — thiamine repletion and fluid resuscitation matter as much as the antiemetic choice in true hyperemesis, and thiamine should be given before/with dextrose-containing fluids to avoid precipitating Wernicke's in a malnourished hyperemesis patient.
The safest anticoagulants in pregnancy don't cross the placenta at all — that single fact drives almost every choice in this category.
Weight-based therapeutic dosing as in non-pregnant patients; does not cross the placenta, making it first-line for VTE/PE treatment and prophylaxis throughout pregnancy.
Preferred over LMWH when rapid reversibility matters (peripartum, planned delivery, or urgent procedure) given its short half-life; requires frequent aPTT monitoring to maintain therapeutic range.
Crosses the placenta; associated with embryopathy, especially with first-trimester exposure — generally avoided for routine VTE/PE. Remains the preferred agent specifically for mechanical heart valves despite the fetal risk, since it carries the lowest maternal valve-thrombosis risk; some patients switch to LMWH for the first trimester and back to warfarin thereafter — an individualized risk/benefit decision, not a protocol.
Limited human pregnancy safety data; generally not recommended in pregnancy or lactation given placental transfer concerns and insufficient safety/efficacy data.
If a patient on a DOAC turns out to be pregnant, that's a bridge-to-LMWH conversation, not a "continue and monitor" one — the data gap here is real, not just theoretical caution.
The governing principle across nearly every antidote: treat the mother as you would any patient. Maternal stabilization is fetal stabilization, and withholding a maternal antidote out of fetal-risk caution is very rarely the right call.
Standard 0.04–0.4 mg IV/IM/IN dosing, titrated to respiration — do not withhold for a pregnant patient with opioid-induced respiratory depression. It can precipitate maternal (and, if near term, neonatal) withdrawal, but untreated maternal hypoxia is the greater fetal threat by far.
Standard weight-based protocol via the Rumack-Matthew nomogram — NAC is protective for the fetus as well as the mother in acetaminophen overdose, since fetal hepatotoxicity mirrors maternal. Never withhold or delay for pregnancy.
Standard loading/maintenance dosing for methanol/ethylene glycol poisoning — preferred over ethanol as the competitive-inhibitor bridge given ethanol's own CNS-depressant and hypoglycemic burden on top of pregnancy.
Same contraindication logic as in the non-pregnant patient (avoid with sodium-channel-blocking co-ingestants/wide QRS) — pregnancy itself is not an additional contraindication, but the usual caution applies regardless.
Pregnancy is very rarely a reason to withhold or underdose a maternal antidote — treat the poisoning aggressively and correctly, and the fetus benefits from the same decision.
Beta-lactams remain the reliable backbone; the "avoid" list is short but consequential, and several agents flip categories specifically near term.
Standard non-pregnant dosing throughout pregnancy — the preferred first-line class for nearly any bacterial infection where they're appropriate coverage. Ceftriaxone caution at term only, given a theoretical kernicterus risk in the neonate from bilirubin displacement.
Safe in the second and third trimesters for uncomplicated UTI; avoid in the first trimester (cleft lip signal) and at term (neonatal hemolysis risk).
A folate antagonist — avoid in the first trimester; considered safe after.
Avoid throughout pregnancy — stains developing fetal bone/teeth and carries rare maternal hepatotoxicity risk with IV use.
Avoid — associated with fetal cartilage/bone concern in animal data (disputed in degree, not existence) plus suggested renal/cardiac/CNS toxicity signals; use only if no alternative exists for a serious infection.
Nitrofurantoin and trimethoprim aren't simply "safe" or "unsafe" — they flip category by trimester. Check gestational age before reflexively prescribing the standard UTI first-line.
Standalone from the Antidotes & Reversal Agents guide and the Intoxicating Substances reference — this document answers "what do I reach for and how do I dose it" for the pregnant patient specifically, organized by clinical scenario rather than drug class.