Pocket ObGyn – Congenital Anomalies

Pocket ObGyn – Congenital Anomalies
See Abbreviations

Definitions and Terminology

Terminology: Description related to etiology

Malformation: Due to an intrinsic process in embryonic dev (prior to 8 w).

Deformation: Due to intrauterine process unrelated to fetus (eg, tumor, multi gest).

Disruption: Due to interference w/ nml dev (eg, amniotic band syn).

Dysplasia: Due to abn growth of cells into tissues.

Patterns of anomalies: Multi anomalies can be described by overarching

Syndrome: Assoc anomalies due to single pathologic etiology (eg, Turner syn)

Sequence: Group of anomalies related to a common upstream pathologic cause (eg, Potter’s sequence in which renal agenesis ® oligohydramnios ® bone fractures).

Developmental field defect: Due to disruption of dev in a particular region of the embryo that leads to disruption in related areas (eg, bladder exstrophy) Association: Group of anomalies unrelated pathologically occurring more com-

monly than one would expect by chance (eg,VACTERL association).

Teratogens

Definition: An agent that causes an anomaly in the developing

Mat illness: Due to toxic metabolites or antibodies from mother crossing placenta.

Pregestational diabetes: 6–7% risk (2´ nml pop) of congen anomalies including NTDs, congenital heart disease (CHD) & caudal agenesis (rare but 15–20% causes a/w DM).

Systemic lupus erythematosus: A/w fetal congen complete heart block.

Infxn: Commonly TORCH infxns, varicella, or parvovirus B19. Nonspecific US findings: Microcephaly, calcifications, IUGR, HSM, hydrops, cardiac malformations.

Meds: Thalidomide & its association w/ limb reduction is classic example.

Environmental: Lead, ionizing radiation, fever, hyperthermia, & mercury consump.

Embryologic development by organ system
System	Embryology	Timing
Neural tube	Neural plate ® neural folds ® fuse to form neural tube	Weeks 3–4
Cardiovascular	Primitive heart tube ® looping & division ® formation of primitive structures (BC, outflow tracts, sinus venosus, PA, & PV) ® septum primum/ secundum separate RA & LA ® endocardial cushions divide atria & ventric ® BC becomes RV & PV becomes LV separated by musc ventricular septum ® outflow tract septates & divides & remodeling forms semilunar valves	Weeks 4–8: Week 4 primitive heart tube is formed & begins looping ® weeks 4–5 atria divided by septum primum ® week 6 ventricles divided ® weeks 7 & 8 outflow tract divided
Pulm	Bronchial tree & assoc pulm arteries undergo branching & division	Weeks 3–16 Surfactant production starts at 20 w
Gastrointestinal	Physiologic herniation of abdominal contents into extraembryonic coelom to allow space for growth of abdominal organs	Weeks 9–11. Physiologic herniation resolved by 12 w
Genitourinary	Pronephros ® mesonephros ® ureteric bud ® invades metanephric blastema to make metanephros ® kidney ® migrates caudally. Metanephros fuses w/ cloaca to make bladder	Develops weeks 4–6. Producing urine by week 11 Bladder fusion begins at week 5

Neural Tube Defects (Int J Gynaecol Obstet 2003;83:123)

Epidemiology: 4–2 per 1000 pregnancies; 2nd most common anomaly worldwide.
Etiology: NTDs not a/w syndromes can be genetic or

Genetic: Risk of NTDs higher in pts who have a child w/ prior NTD; only 5% of NTDs have familial association.

Environmental: Assoc factors include diet (low folic acid consump), teratogen exposure (anticonvulsants,Vit A), mat diabetes w/ poor 1st trimester gluc control, high mat core temperature in the 1st trimester.

Pathophysiology: Failure of closure

Cranial defects: Egs, anencephaly, encephalocele, exencephaly, iniencephaly. All cranial defects except small encephaloceles (failure of skull formation w/ extrusion of brain into membranous sac) are lethal. Termination of Preg valid option.

Spinal defects: Often a/w ventriculomegaly (often require shunt placement) Spina bifida: Failure of fusion of caudal portion of neural tube Meningocele: Failure of fusion, meninges exposed

Meningomyelocele: Failure of fusion, meninges & neural tissue exposed

Clinical manifestations: Higher lesions generally indicate worse prog

Bladder/bowel: Dysfxn common, even w/ lower spinal lesions. Bladder dysfxn ®

UTIs, stones, & significant morbidity. Sexual dysfxn common.

Neuro: Sensory & motor handicap correlated w/ level of lesion; ventriculomegaly a/w ¯ intelligence quotient.

Dx: amniotic fluid & mat serum AFP

Screening: 89–100% of pregnancies w/ NTD have MSAFP

Other causes of MSFAP: (1) incorrect GA, (2) multi gestations, (3) abdominal wall defects, (4) abnormalities of placentation such as accreta ( MSAFP risk factor for placental abruption), (5) IUFD, (6) Finnish nephrosis, (7) sev skin anomalies such as lethal ichthyosis.

US able to identify many causes – done after MSAFP collection at a GA that will allow for detailed analysis of fetal anatomy.

US: 97% sens & 100% spec for NTD in experienced centers.

Dx: 2% of women w/ positive MSAFP have fetus w/ NTD. Confirmatory test can be an amniocentesis for AFP.

If amniotic AFP ® confirmatory testing (AF acetylcholinesterase – 2.2/1000 false positive rate)

Prevention: Avoidance of teratogens & suppl w/ folic acid (see Nutrition) This behavior should start prior to Preg & continue throughout
Rx: Deliv at hospital w/ NICU support; consideration of fetal Surg

Breech presentation common in fetus w/ NTD necessitating Cesarean deliv; vaginal deliv should be considered if fetus in cephalic presentation.

Other Neurologic Anomalies

Ventriculomegaly: vol of cerebral ventricles on

Isolated: Often found to be a/w NTD or other malformations after birth.

Associations: Can be related to infxn (toxoplasmosis, CMV, lymphocytic choriomeningitis virus), genetic syndromes, or aneuploidy.

W/u: Amniocentesis should be offered for aneuploidy/infxn w/u. F/u 3rd trimester scan should look for progression or other identifiable causes.

Hydrocephalus: Pathologic ventriculomegaly from pres
CPCs: Cystic sonolucent lesions w/i choroid plexus

Not a true anomaly, but identified as marker of aneuploidy (esp Trisomy 18). Isolated CPCs usually benign & typically resolve by 3rd trimester.

Cardiovascular Anomalies

Nonimmune hydrops fetalis NIHF: Cardiac anomalies cause up to 40% of

Manifestations: Pts can present w/ size > dates & ¯ FM. US: Ascites (visualized as rim of fluid around abdominal organs), pleural effusions, pericardial effusions, skin edema (late finding), polyhydramnios, & placentomegaly.

Associations: Structural heart dx, tachyarrhythmias (treated by giving ratecontrolling agents to mother or directly to fetus), or bradyarrhythmias.

• Hypoplastic left heart syndrome HLHS:

Anatomy: Underdeveloped LV w/ hypoplasia, stenosis, or atresia of aortic valve, MV, &/or aorta. Survival dependent on PDA & ASD to allow for flow from RV to aorta.

Dx: Identified on US w/ findings of small or nonfunctioning LV, small aortic root, small aortic arch, or absent Doppler velocities through the aortic valve, abn MV, & restricted or reversed flow through the foramen ovale (usually right to left flow in utero).

Associations: Trisomy 18, trisomy 13, Turner syn, or sporadic

Mgmt: Identification can allow for birth planning (administration of prostaglandins to ensure persistent PDA) & poss fetal intervention. Dilation of AS can reverse HLHS physiology. In utero atrial septostomy can allow for ASD creation.

AVSDs: Atrial & ventricular septal defects w/ singular, multileaflet atrioventricular Diagnosed on US, confirmed w/ echo. AVSDs a/w aneuploidy.
Conotruncal anomalies: Tetralogy of Fallot, persistent truncus Should prompt testing for DiGeorge syn (microdeletion of chromo 22q11, detectable by FISH).

Thoracic Anomalies

CCAM:

Sporadic lesion due to abnormalities in branching of pulm tree ® cystic or solid lung lesions. Classified based on size cystic or solid components. Different types confer varying risks of regression, progression, or malig transformation.

Type 1: Large (>2 cm) multiloculated cysts

Type 2: Smaller uniform cysts

Type 3: Not grossly cystic ® “adenomatoid” type

Can lead to hydrops if large enough to cause mediastinal shift. Rx usually resxn at birth w/ peds at deliv.

Congenital diaphragmatic hernia CDH: Defect in diaphragm ® herniation Diagnosed as solid (on right due to liver) or cystic (on left due to bowel) mass on

US.

Occurs as isolated finding, as part of a sequence, or w/ aneuploidy (10–20%).

Left-sided lesions more common. Right-sided lesions confer worse prog (liver herniation). fetal lung vol improves prog. Can lead to NIHF & dextroposition.

Further w/u includes fetal echo, fetal karyotype, & poss MRI.

Gastrointestinal Anomalies

Omphalocele: Defect in abdominal wall holding herniated abdominal wall

Dx: Diagnosed on US after week 12 GA (before week 12 herniation of contents physiologic). Hernia covered by amnion & peritoneum; herniation at site of cord insertion. Classified by whether or not defect contains liver (liver-containing defect never nml regardless of GA). Causes elevated MSAFP.

Associations: 50% association w/ cardiac lesion (fetal echo recommended); Beckwith–Wiedemann syn, OEIS syn, & amniotic band syn. Association w/ aneuploidy in nonliver containing lesions (chromo analysis recommended).

Gastroschisis: Evisceration of abdominal contents through abdominal wall

Dx: Seen as full thickness abdominal wall defect, generally to right of cord insertion (nml cord insertion is seen on US). Bowel may become thickened & matted w/ increasing GA. No overlying peritoneum.

Associations: No risk of chromosomal aneuploidy but a/w other GI problems.

risk of recurrence w/i families.

Echogenic bowel: echogenicity (brightness) of bowel noted on

Etiology: A/w bleeding events, aneuploidy, CF, growth restriction, infxn, & idiopathic. Idiopathic = most common etiology.

Aneuploidy: 3–25% association w/ aneuploidy, primarily trisomy 21. Offer amniocentesis for chromosomes, CF, & CMV testing.

Genitourinary Anomalies

Renal agenesis: Ureteric bud fails to develop & induce differentiation of

Etiology: Can be bilateral or unilateral. Bilateral usually due to embryonic issue; unilateral difficult to distinguish agenesis from dysplasia & hypoplasia.

Dx: Bilateral renal agenesis diagnosed w/ nonvisualization of kidneys & bladder w/ oligohydramnios. Unilateral diagnosed by absent or abn kidney location (amniotic fluid nml). Full fetal bladder is good indicator of renal fxn.

Prog: Bilateral renal agenesis incompatible w/ life due to pulm hypoplasia. High rate of IUFD due to cord accidents from oligohydramnios.

Associations: 50% association w/ other anomalies; high rate of single umbilical artery

VACTERL: Vertebral anomalies, Anal atresia, Cardiac defects, TE fistula, Renal defects, Limb defects
Müllerian anomalies: Defects in female reproductive tract including separate or absent reproductive See Chap. 8.
OEIS complex: Omphalocele, Exstrophy of the bladder, Imperf anus, Spinal defects

Etiology: Due to abnormalities of cloaca – blind pouch from which rectum & urogenital sinus develop.Typically sporadic & not a/w aneuploidy.

Bladder exstrophy: Diagnosed w/ absent bladder filling, low-set umbilicus, lower abdominal mass increasing in size throughout Independent of OEIS complex, can be other assoc abdominal wall, musculoskeletal, & genital deficits.

Musculoskeletal and Anomalies

Skeletal dysplasias: Qualitatively or quantitatively abn bones on prenatal

Dx: FL or HL <5%ile based on GA.

Etiology: Constitutionally short fetus (isolated abn FL), IUGR (a/w small AC), or skeletal dysplasia. Can be marker of aneuploidy.

W/u: Interval growth in 3–4 w can show normalization of FL or nml interval growth. Comparison to other parameters (AC, BPD, HC) can reveal IUGR. If continued short FL compare to qualitative description of other bones.