Chapter 11: Fetal Medicine

Diagnosis, therapy & management of the fetus | Prenatal screening, anomalies, hydrops, fetal therapy, teratogens, congenital infections, twin–twin transfusion, non‑immune hydrops, amniocentesis, chorionic villus sampling, fetal surgery
📌 Core concepts: Fetal medicine integrates prenatal diagnosis (USS, CVS, amniocentesis), management of structural anomalies, medical fetal therapy (arrhythmias, hydrops), twin–twin transfusion syndrome (TTTS), intrauterine growth restriction (IUGR), and prevention of congenital infections. Multidisciplinary approach essential.

📖 Core Summary: Fetal Medicine

🔬 Prenatal screening & diagnosis
1st trimester: nuchal translucency, serum β‑hCG, PAPP‑A. 2nd trimester quadruple screen. Invasive: CVS (11–14 wk), amniocentesis (≥15 wk). Fetal MRI, detailed USS for anomalies.
🧬 Common fetal anomalies
Neural tube defects (NTD), congenital heart disease (CHD), diaphragmatic hernia, abdominal wall defects (gastroschisis, omphalocele), renal anomalies, skeletal dysplasias.
🔄 Twin–twin transfusion syndrome (TTTS)
Monochorionic twins with oligohydramnios/polyhydramnios sequence. Stages I–V. Treatment: laser photocoagulation, amnioreduction, septostomy.
💧 Hydrops fetalis (immune & non‑immune)
Immune: Rh alloimmunization (preventable with anti‑D). Non‑immune: CVS anomalies, arrhythmias, infection (parvovirus B19), α‑thalassemia, TTTS. Prenatal therapy: transfusion, antiarrhythmics.
⚠️ Teratogens & congenital infections
TORCH: Toxoplasma, rubella, CMV, HSV, syphilis, Zika, parvovirus. Prevention: vaccination (rubella), hygiene, antiviral therapy (CMV hyperimmune globulin in trials).
📊 Key fetal interventions: Intrauterine transfusion (IUT) for anemia, fetal atrial flutter (digoxin, flecainide), fetal tracheal occlusion for CDH, radiofrequency ablation for TRAP sequence, EXIT procedure.

🔍 Approach to common fetal medicine scenarios

1
Increased nuchal translucency (NT) – 1st trimester marker. Assess for chromosomal anomalies (T21, T18, T13), structural defects (CHD), genetic syndromes. Offer CVS and fetal echocardiography.
2
Fetal hydrops (skin edema, effusions, ascites) – Immune workup (direct Coombs, maternal antibodies). Non‑immune: detailed anatomy scan, Doppler MCA for anemia, infection screen (TORCH, parvovirus, syphilis), fetal echocardiography, alpha‑thalassemia screening.
3
Monochorionic diamniotic twins with polyhydramnios & oligohydramnios – Suspect twin–twin transfusion syndrome (TTTS). Stage according to Quintero; refer to fetal center for laser therapy or amnioreduction.
4
Fetal arrhythmia (supraventricular tachycardia) – M‑mode echocardiography. Initial maternal digoxin or flecainide/sotalol. Monitor for hydrops. Cordocentesis for refractory cases.
5
Maternal serum AFP elevation (2nd trimester) – Suspect neural tube defect (open spina bifida, anencephaly), ventral wall defect (gastroschisis), multiple gestations. Detailed fetal anatomy USS.

📋 Stepwise management of fetal conditions

1
Preconception & early prenatal care – Folic acid (400–800 mcg) to prevent NTD. Rubella immunity, diabetes optimization, avoid teratogens (valproate, warfarin, ACEi, isotretinoin).
2
First‑trimester screening (NT + biochemistry) – Risk calculation for trisomies. Offer NIPT (cell‑free DNA) for high‑risk patients. CVS for definitive diagnosis.
3
Detailed anomaly scan (18–22 weeks) – Systematic evaluation of CNS, heart, chest, abdomen, skeleton, placenta. Refer to fetal medicine for abnormalities.
4
Fetal therapy options – Laser coagulation for TTTS, intrauterine transfusion for anemia (parvovirus, alloimmunization), thoracoamniotic shunting for pleural effusion, EXIT procedure for airway obstruction.
5
Prevention of congenital infections – Rubella vaccination (preconception), CMV hygiene education, treatment of maternal syphilis (penicillin), Toxoplasma (spiramycin), HSV (acyclovir near term).
6
Delivery planning – Plan site (tertiary center) and timing for anomalies (e.g., CDH, gastroschisis, sacrococcygeal teratoma). Ex utero intrapartum therapy (EXIT) for giant neck masses.
⚡ Key reminder: Rh(D) alloimmunization is largely preventable with antenatal anti‑D at 28 weeks and after sensitizing events. Non‑immune hydrops has broad differential; treat underlying cause.

🧠 Reflex prompts – Fetal medicine high‑yield

🤰 33yo G2P0, 12 weeks: NT 4.5 mm (>99th centile). Next step?
Offer CVS for karyotype and microarray. Detailed anatomy scan at 18–20 weeks, fetal echocardiography.
🩺 Monochorionic twins, 20 weeks: polyhydramnios (donor) & oligohydramnios (recipient). Diagnosis?
Twin–twin transfusion syndrome (TTTS). Stage I: observation; stage II–IV: laser photocoagulation.
⚠️ MCA peak systolic velocity >1.5 MoM at 28 weeks. What is the concern?
Fetal anemia (immune or non‑immune). Causes: parvovirus B19, Rh alloimmunization, fetomaternal hemorrhage. Cordocentesis + intrauterine transfusion.
📉 Maternal serum AFP very high at 18 weeks, fetus with anterior abdominal wall defect, bowel loops outside.
Gastroschisis (not covered by membrane). Associated rarely with other anomalies. Plan delivery at tertiary center, silo or primary closure.
💊 Fetal SVT with hydrops. First‑line maternal antiarrhythmic?
Digoxin. Consider flecainide or sotalol. Monitor fetal umbilical artery Doppler and right atrial pressure.
🧬 Non‑immune hydrops in Southeast Asian fetus. Most likely genetic cause?
α‑Thalassemia major (homozygous α‑thalassemia – deletion of all four α‑globin genes). Hydrops fetalis, severe anemia.