Fetal Anomalies

Symptoms

• Fetal anomalies do not typically cause 'symptoms' in the pregnant person. Instead, signs are detected during prenatal screening and diagnostic procedures.
• Abnormal results from maternal serum screening tests (e.g., atypical levels of AFP, hCG, estriol, inhibin A).
• High-risk or positive results from Non-Invasive Prenatal Testing (NIPT) for specific chromosomal conditions.
• Increased nuchal translucency (NT) or absent nasal bone observed during first-trimester ultrasound.
• Identification of structural abnormalities (e.g., heart defects, neural tube defects, limb differences, cleft lip/palate) during a second-trimester anomaly scan.
• Abnormal fetal growth (either too small or too large) detected by ultrasound.
• Abnormal amniotic fluid volume (too much fluid, called polyhydramnios, or too little, called oligohydramnios).
• Presence of 'soft markers' on ultrasound, such as an echogenic intracardiac focus or choroid plexus cysts, which may indicate an increased risk for certain conditions.
• Significantly decreased fetal movement.
• Vaginal bleeding.
• Preterm labor.
• Rapid increase in abdominal size (suggesting severe polyhydramnios).
• Fundal height significantly larger or smaller than expected for gestational age.

Causes & Risk Factors

• Genetic Factors (approximately 25-30% of cases): These include chromosomal abnormalities like Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), Patau syndrome (Trisomy 13), or single gene defects such as cystic fibrosis or sickle cell anemia.
• Environmental Factors / Teratogens (approximately 10% of cases): These involve exposure to certain maternal infections (e.g., Zika, rubella), medications (e.g., valproic acid, isotretinoin), chemicals, or radiation during pregnancy.
• Multifactorial Inheritance (approximately 20-25% of cases): This involves a complex combination of multiple genetic and environmental factors. Examples include many congenital heart defects and cleft lip/palate.
• Unknown Causes (approximately 40-60% of cases): In a significant number of cases, the specific cause of a fetal anomaly cannot be identified.
• Advanced Maternal Age: Increases the risk for chromosomal abnormalities like Down syndrome.
• Advanced Paternal Age: May be linked to certain new genetic mutations, though evidence is less strong than for maternal age.
• Family History/Genetics: A previous pregnancy with a fetal anomaly, parents being carriers for a genetic condition, or a personal/family history of a congenital anomaly.
• Consanguinity (parents being blood relatives): Increases the risk of autosomal recessive genetic disorders.
• Ethnicity: Certain anomalies are more common in specific ethnic groups (e.g., sickle cell disease, Tay-Sachs disease).
• Maternal Health Conditions: Poorly controlled pre-existing diabetes, obesity, or hypothyroidism.
• Maternal Infections during Pregnancy: Infections such as Zika virus, rubella, cytomegalovirus (CMV), syphilis, or toxoplasmosis.
• Nutritional Deficiencies: Insufficient folic acid intake is a known risk factor for neural tube defects (e.g., spina bifida).
• Substance Use: Alcohol consumption (leading to Fetal Alcohol Spectrum Disorders), smoking, or illicit drug use during pregnancy.
• Medication Exposure: Use of certain medications known as teratogens, such as some anticonvulsants, retinoids, or ACE inhibitors.
• Environmental Exposures: High doses of ionizing radiation or exposure to heavy metals (like mercury, lead) and certain industrial chemicals.
• Lack of Folic Acid Supplementation: Not taking folic acid before and during early pregnancy increases the risk of neural tube defects.
• Poor Management of Maternal Conditions: Inadequate control of pre-existing diabetes or maternal phenylketonuria (PKU).
• Lack of Vaccination: Not being vaccinated against preventable infections like rubella, which can cause congenital rubella syndrome.

Diagnosis

• All pregnant individuals should be offered prenatal screening for chromosomal abnormalities, regardless of age or other risk factors.
• A detailed fetal anatomical survey, often called an anomaly scan, is recommended between 18 and 22 weeks of pregnancy.
• First Trimester Screening: Combines maternal blood tests (hCG, PAPP-A) with an ultrasound measurement of nuchal translucency (NT) between 11 and 14 weeks.
• Second Trimester Screening (Quad Screen): A maternal blood test measuring four substances (AFP, hCG, Estriol, Inhibin A) typically between 15 and 22 weeks.
• Integrated/Sequential Screening: Combines results from both first and second-trimester tests.
• Non-Invasive Prenatal Testing (NIPT/NIPS): Analyzes cell-free fetal DNA from the mother's blood to screen for common chromosomal conditions (Trisomy 21, 18, 13) and sex chromosome abnormalities, usually from 10 weeks. This is a screening test, not a definitive diagnosis.
• Chorionic Villus Sampling (CVS): A diagnostic test where a small sample of placental tissue is taken for genetic analysis, typically between 10 and 13 weeks. It carries a small risk of miscarriage.
• Amniocentesis: A diagnostic test where a sample of amniotic fluid is taken for genetic analysis, typically after 15 weeks. It carries a small risk of miscarriage.
• Genetic Analysis of Samples: Karyotyping, chromosomal microarray (CMA), or specific gene testing performed on cells obtained from CVS or amniocentesis to confirm a diagnosis.
• Detailed Anomaly Ultrasound: A comprehensive ultrasound performed by a specialist, usually between 18 and 22 weeks, to thoroughly assess fetal anatomy.
• Fetal Echocardiography: A specialized ultrasound focused on the fetal heart, recommended if a heart anomaly is suspected or if there's an increased risk.
• Fetal MRI: Used as an additional imaging tool to ultrasound, providing more detailed images of certain organs, especially the fetal brain, when an anomaly is suspected.

Treatment Options

• Watchful Waiting / Expectant Management: Monitoring the pregnancy with regular ultrasounds for anomalies that may resolve on their own (e.g., some choroid plexus cysts) or where prenatal intervention is not possible or beneficial.
• Pharmacologic Therapy (In Utero): Administering medications to the mother that cross the placenta to treat the fetus. Examples include digoxin for fetal heart rhythm problems or corticosteroids to help mature fetal lungs if early delivery is expected.
• Open Fetal Surgery: The uterus is opened to operate directly on the fetus, used for conditions like severe spina bifida (myelomeningocele).
• Fetoscopic Surgery: A minimally invasive surgery using small incisions and an endoscope. Used for conditions like twin-to-twin transfusion syndrome or congenital diaphragmatic hernia.
• Ex Utero Intrapartum Treatment (EXIT): A procedure where the baby is partially delivered via C-section, maintaining placental circulation while an airway is secured, for conditions like large neck masses that could block breathing at birth.
• Termination of Pregnancy: An option that should be discussed and offered following the diagnosis of a significant anomaly, in accordance with local laws and regulations, with non-directive counseling.
• Delivery Planning: Determining the optimal timing, method (vaginal or C-section), and location (a specialized hospital with a Neonatal Intensive Care Unit and pediatric specialists) for delivery.
• Postnatal Treatment: Immediate resuscitation and stabilization in the Neonatal Intensive Care Unit (NICU) after birth.
• Surgical Correction After Birth: Surgeries performed after birth for conditions like congenital heart defects, cleft palate, or gastroschisis.
• Long-Term Medical Management and Therapies: Ongoing medical care, physical therapy, occupational therapy, or speech therapy as needed.
• Referral to a Maternal-Fetal Medicine (MFM) specialist upon suspicion or diagnosis of a fetal anomaly.
• Multidisciplinary Consultation: Involving pediatric specialists (e.g., neonatologist, pediatric surgeon, cardiologist, geneticist, neurologist) to plan comprehensive perinatal care.
• Genetic Counseling: To understand the anomaly, its causes, and recurrence risks.
• Perinatal Palliative Care Consultation: For lethal or life-limiting anomalies, to provide support and comfort care planning.

Frequently Asked Questions