ABOG Maternal-Fetal Medicine cheat sheet

Chronic hypertension plus new proteinuria or end-organ dysfunction after 20 weeks defines superimposed preeclampsia; delivery is the only cure.

Low-dose aspirin 81 mg daily started before 16 weeks reduces early-onset preeclampsia risk in high-risk patients.

Gestational diabetes screening: 1-hour 50-g glucose challenge; abnormal threshold commonly 130-140 mg/dL, followed by 3-hour 100-g OGTT (Carpenter-Coustan).

Pregestational diabetes: target HbA1c <6.5% preconception; malformation risk rises with periconceptional HbA1c >10%.

Maternal cardiac disease: most deaths from pulmonary hypertension, Marfan aortopathy, and Eisenmenger syndrome; vaginal delivery with epidural preferred when feasible.

Thyroid: untreated maternal hypothyroidism impairs neurodevelopment; levothyroxine requirement typically rises 20-50% in pregnancy.

SLE flares are most common in the second half of pregnancy and postpartum; antiphospholipid antibodies raise preeclampsia, thrombosis, and fetal loss risk.

Epilepsy: lamotrigine and levetiracetam have lower malformation rates; lamotrigine levels fall markedly in pregnancy requiring dose adjustment.

Twin-twin transfusion syndrome: Quintero stage II-IV before 26 weeks is treated with fetoscopic laser photocoagulation of placental anastomoses.

Twin reversed arterial perfusion (TRAP): intrafetal radiofrequency ablation or cord occlusion is preferred over expectant management when cardiac failure develops.

TTTS donor shows oligohydramnios (deepest vertical pocket <2 cm) with a stuck twin; recipient shows polyhydramnios (DVP >8 cm).

Fetoscopic tracheal occlusion (FETO) for severe left congenital diaphragmatic hernia improves survival but increases preterm premature rupture of membranes.

Intrauterine transfusion for fetal anemia: use middle cerebral artery peak systolic velocity >1.5 multiples of the median as the trigger.

RhD alloimmunization prevention: 300 mcg anti-D at 28 weeks and within 72 hours postpartum for RhD-negative unsensitized patients.

Selective fetal reduction in higher-order multiples reduces preterm birth and low birth weight compared with expectant management.

Fetal surgery for myelomeningocele before 26 weeks reduces need for shunting and improves motor function but raises preterm birth risk.

Postpartum hemorrhage: cumulative quantified blood loss >1000 mL or bleeding with hemodynamic instability; uterotonics, tranexamic acid 1 g IV within 3 hours, then escalation.

Shoulder dystocia maneuvers in sequence: McRoberts, suprapubic pressure, internal rotation, posterior arm delivery, then cephalic replacement or cleidotomy.

Preeclampsia with severe features: magnesium sulfate 4-6 g IV load then 1-2 g/h; monitor reflexes, respirations, urine output; calcium gluconate is antidote.

Uterine tachysystole: >5 contractions in 10 minutes averaged over 30 minutes; reduce or stop oxytocin and consider tocolysis.

Category III fetal heart tracing: absent baseline variability with recurrent decelerations or bradycardia; requires prompt evaluation and likely expedited delivery.

Placenta accreta spectrum: planned cesarean hysterectomy at 34-36 weeks by a multidisciplinary team reduces hemorrhage morbidity.

Vaginal birth after cesarean success is roughly 60-80%; induction and prior cesarean for arrest disorder lower success.

Preterm labor before 32 weeks: antenatal corticosteroids (betamethasone 12 mg IM x2) reduce neonatal respiratory distress, intraventricular hemorrhage, and mortality.

Cell-free DNA screening detects trisomy 21 with sensitivity >99% but is a screening test; diagnostic confirmation requires amniocentesis or chorionic villus sampling.

Amniocentesis after 15 weeks carries procedure-related loss of roughly 1 in 500-1000; CVS at 10-13 weeks carries similar or slightly higher risk.

First-trimester combined screening (nuchal translucency, free beta-hCG, PAPP-A) detects about 85-90% of trisomy 21 at 5% false-positive rate.

Cystic fibrosis carrier frequency in non-Hispanic Whites is about 1 in 25; autosomal recessive with delta-F508 the most common mutation.

Fragile X premutation (55-200 CGG repeats) in a mother risks expansion to full mutation (>200) in offspring; full mutation causes intellectual disability.

Karyotype detects balanced rearrangements and aneuploidy; chromosomal microarray detects submicroscopic deletions/duplications and is preferred for anomalies.

Trisomy 18 and 13 are usually lethal; trisomy 21 survival to adulthood is common with variable intellectual disability.

Neural tube defects: folic acid 4 mg daily before conception reduces recurrence risk by about 70% in women with a prior affected pregnancy.

Estimated fetal weight uses Hadlock formulas from biparietal diameter, head circumference, abdominal circumference, and femur length; accuracy is ±10-15%.

Oligohydramnios: deepest vertical pocket <2 cm; polyhydramnios: DVP >8 cm; amniotic fluid index <5 cm or >24 cm respectively.

Ductus venosus absent or reversed a-wave and umbilical artery absent end-diastolic flow indicate severe placental insufficiency.

Cervical length <25 mm at 16-24 weeks in a singleton predicts preterm birth; cerclage or vaginal progesterone may be offered.

Nuchal translucency >3.5 mm warrants anatomic survey, echocardiography, and genetic evaluation even with normal karyotype.

Doppler of the middle cerebral artery: peak systolic velocity >1.5 MoM suggests fetal anemia; cerebroplacental ratio <1 suggests redistribution.

Choroid plexus cysts and echogenic intracardiac foci are soft markers; isolated findings in low-risk patients rarely warrant invasive testing.

Three-dimensional and multiplanar imaging improve characterization of facial clefts, skeletal dysplasias, and CNS anomalies.

Group B Streptococcus: universal rectovaginal screening at 36 0/7-37 6/7 weeks; intrapartum penicillin G is first-line prophylaxis.

Cytomegalovirus is the most common congenital viral infection; primary maternal infection carries highest transmission and sequelae risk.

Toxoplasmosis: avoid undercooked meat and cat litter; primary infection treated with pyrimethamine plus sulfadiazine after the first trimester.

HIV: combination antiretroviral therapy with viral load suppression reduces perinatal transmission below 1%; avoid breastfeeding where safe replacement feeding is feasible.

Syphilis: penicillin G is the only proven regimen; desensitize penicillin-allergic pregnant patients rather than substitute alternatives.

Listeria: associated with soft cheese, deli meats; presents with fever and flu-like illness; treat with ampicillin plus gentamicin.

Hepatitis B: administer hepatitis B vaccine and immunoglobulin to the neonate within 12 hours of birth.

Influenza and Tdap vaccines are recommended in pregnancy; Tdap ideally at 27-36 weeks each pregnancy.

Amniotic fluid embolism: sudden hypoxia, hypotension, and coagulopathy; treatment is supportive with aggressive transfusion and cardiopulmonary support.

Maternal cardiac arrest: left uterine displacement, continuous chest compressions, and perimortem cesarean within 4-5 minutes if no return of circulation.

Sepsis in pregnancy: give broad-spectrum antibiotics and fluids within 1 hour; lactate and cultures guide resuscitation.

Massive transfusion protocol: balanced ratios of plasma to red cells (1:1 to 1:2) with platelets and cryoprecipitate for fibrinogen <150 mg/dL.

Diabetic ketoacidosis occurs at lower glucose levels in pregnancy; treat with insulin infusion, fluids, and potassium replacement.

Acute fatty liver of pregnancy: third-trimester nausea, jaundice, hypoglycemia, coagulopathy; delivery is definitive and urgent.

Magnesium toxicity: loss of deep tendon reflexes, respiratory depression, then cardiac arrest; give calcium gluconate 1 g IV.

Venous thromboembolism: low-molecular-weight heparin is preferred; compression ultrasound is first-line imaging for suspected deep vein thrombosis.

Neuraxial labor analgesia: epidural or combined spinal-epidural reduces pain without increasing cesarean rate; hypotension is managed with fluids and vasopressors.

Preeclampsia with thrombocytopenia (<100,000) or coagulopathy contraindicates neuraxial anesthesia until platelet count and coagulation status are clarified.

General anesthesia for cesarean: rapid sequence induction with cricoid pressure and preoxygenation; difficult airway risk is higher in pregnancy.

Postdural puncture headache: conservative therapy, caffeine, then epidural blood patch for persistent symptoms.

Local anesthetic systemic toxicity: stop injection, airway support, and give 20% lipid emulsion 1.5 mL/kg bolus.

Nitrous oxide for labor analgesia has rapid onset and offset but variable efficacy and requires scavenging.

Remifentanil patient-controlled analgesia is an alternative when neuraxial analgesia is contraindicated; monitor for respiratory depression.

Anticoagulation and neuraxial timing: hold low-molecular-weight heparin at least 12 hours (prophylactic) or 24 hours (therapeutic) before neuraxial placement.

Relative risk and odds ratio: RR is preferred in cohort studies; OR approximates RR only when outcome is rare.

Number needed to treat = 1/absolute risk reduction; number needed to harm = 1/absolute risk increase.

Sensitivity = true positives/(true positives + false negatives); specificity = true negatives/(true negatives + false positives).

Positive predictive value depends on prevalence; a highly sensitive test is best for ruling out disease.

Randomized controlled trials with intention-to-treat analysis reduce selection and attrition bias.

Confidence intervals excluding 1 for ratios or 0 for differences indicate statistical significance at the stated alpha.

Systematic reviews with meta-analysis pool effect estimates; heterogeneity is quantified by I-squared.

Case-control studies are efficient for rare outcomes but susceptible to recall and selection bias.

Informed consent requires capacity, disclosure of risks/benefits/alternatives, and voluntariness; documented discussion supports the process.

Maternal autonomy generally prevails over fetal interests when the pregnant patient has decision-making capacity.

Emergency exceptions permit treatment without consent when imminent harm exists and no surrogate is available.

Root cause analysis targets system failures rather than individual blame and generates corrective actions.

TeamSTEPPS tools: SBAR communication, briefs, huddles, and debriefs improve perinatal safety.

Sentinel events require immediate containment, disclosure to the patient, and reporting per institutional policy.

Conflicts of interest must be disclosed; research participation requires IRB approval and separate consent.

Mandated reporting of suspected child abuse or intimate partner violence follows state law and institutional protocol.