MID TRIMESTER ASSESSMENT VIRAL INFECTIONS NORMAN BLUMENTHAL FRANZCOG BLACKTOWN HOSPITAL Question 1 What percentage of pregnancies are complicated by serious (major) birth defects? Serious Birth Defects complicate & threaten the lives of 35% of newborn infants account for 20% of neonatal deaths account for 30% of serious morbidity in infancy and childhood Ultimate aims of prenatal diagnosis provide accurate diagnoses and informative prognoses to the mother and her family with a low or no risk of miscarriage as early as possible in the pregnancy to allow informed decisions about the pregnancy Aims of prenatal diagnosis To provide the options of pregnancy termination in-utero treatment arrangements for the best method of delivery and optimal peri-natal care Question 2 What is the best available serum screening test for neural tube defects and when it is done? Spina Bifida Increased AFP (> 2.5 MoM) correlates with open skin defects Increased risk of a fetus with a NTD Family history of NTD in mother’s or father’s close relatives Pregnant women with IDDM Pregnant women on anti-convulsant medication Current recommendations for Folate (folic acid) Daily folate intake of 5mg for all women who may become pregnant( 1 mth before) Tablets available over the counter – $2.50-$5.20 for 90 tablets Dietary folate – 2 servings of orange, banana, strawberries – 5 servings of asparagus, beans, beetroot, brussel sprouts, broccoli, cabbage, cauliflower, leeks, parsnips, peas, potato, spinach – 7 servings of wheat germ, wheat bran, wholegrain bread, pasta, cereals The Triple Screen Analytes: estriol, AFP, beta-HCG Serum collected at 15-17 weeks gestation Assayed in centralised laboratories Risk of Down syndrome assessed by collating serum results with patient’s age and previous history If risk >1:250 at term - recommend amniocentesis The Triple Screen Advantages: Little skill required to collect blood Assayed in centralised laboratories - good QA performed at 15-17 weeks gestation – subsequent karyotyping by amniocentesis The Triple Screen Disdvantages: Requires pre-test and post-test counselling Results highly dependent on gestational age – thus need a dating ultrasound beforehand Not reliable in twin pregnancies Opportunities for karyotyping only at 16 wk – thus if TOP required - cervagem IOL Not as enjoyable for the patient as NTS The Triple Screen Disdvantages: detection rate approximately 65% Does screening do more harm than good? – Screening raises parents expectations of medicine, and their expectations of a perfect baby – False positives cause anxiety and occasional miscarriages of normal fetuses – False negatives leave parents with an unwanted Down syndrome child to bring up. They often feel misled, betrayed by their “statistics-quoting doctor”, and quite litigious – Some patients become unreassurable, and have an unnecessary procedure Congenital defects: types and frequency Type % of births % all birth defects Structural Malformations 3.0% 60% Monogenic defects 1.4% 28% Chromosomal disorders Total 0.6% 5.0% 12% 100% Ref: Prenat Neonat Med 1999;4:157-164 Normal 4 chamber view Fetal Leg Fracture in Osteogenesis Imperfecta TRV Fetal Abdomen Duodenal Atresia (DoubleBubble sign) TRV Fetal Hand Polydactyly Fetal Feet: Bilateral Club Foot Placenta praevia Question 3 The 18-week morphology scan is good and accurate in the assessment of Downs Syndrome (T/F)? Ultrasonic features of Trisomy 21 at the 18 week anomaly scan thickened nuchal fold >6mm short femurs: actual:expected FL <0.91 short humeri renal pelvic dilatation ventriculomegaly sandal gap toe single umbilical artery widened pelvic angle echogenic bowel hypoplasia/clinodactyly of middle phalanx of 5th finger presence of a simian crease echogenic focus LV Comparison of screening parameters at 18 week anomaly scan Ultrasound screening for aneuploidy is not a useful primary tool in the diagnosis of Down syndrome in the second trimester Because – the findings are subtle – they require much expertise and time for detection Ref: D’Alton ME, Craigo S, Bianchi D. Prenatal diagnosis. Curr Probl Obstet Gynecol Fertil 1994;17(2):41-80 Accuracy of Midtrimester US screening for detectable major fetal malformations Routine scans <24 wk Abn. fetuses detected Anomalies detected CNS GU Craniofacial Cardiac GI Skeletal Tertiary Non-tertiary 2679 (36%) 4648 (64%) 19/54 (35%) 8/64 (13%) 67% 50% 50% 18% 50% 25% 40% 35% 0% 0% 0% 0% Ref: Crane JP, LeFevre ML, Winborn RC et al A randomized trial of prenatal ultrrasonographic screening: impact on the detection, management and outcome of anomalous fetuses. Am J Obstet Gynecol 1994;171:392-399 INFECTIONS IN PREGNANCY Infections pose a problem for – mother – baby – both Some infections – antepartum – intrapartum – postpartum VIRUSES Question 4 Genital Herpes: a. Herpes is more likely to result in transmission of the virus to the neonate if it is recurrent as opposed to a primary attack. b. Obvious herpetic lesions on the vulva in labour, is an indication for Caesarean section. Herpes Simplex Recurrent painful genital ulcers HSV 1 & 2 Transmitted to infant at time of delivery More common in primary infection(50%) < 5% with recurrent episodes Neonatal Herpes - acquired perinatally – 95% of cases – localised - eyes, skin, mouth, CNS – disseminated - increased mortality Congenital Herpes - acquired transplacentally – 5% of all cases – skin vesicles, chorioretinits – micro/hydrocephaly, micropthalmia Treatment Antiviral e.g. Acyclovir/famcyclovir Caesarean if lesions present Recurrent attacks now debatable CMV 50% of Austr. population immune(IgG pos) • 2% of births • Acquired by primary or recurrent infections • Primary infection occurs in 4% of pregn Maternal Infection Asymptomatic Mononucleosis like symptoms – fever, fatigue, myalgia, pharyngitis, diarrhoea, lymphadenopathy. Diagnosed by culture or antibody detection Foetal Transplacental transmission Primary infection – 40% risk of infection – 10% symptomatic at birth – 10% symptomatic later Suspicion based on U/S – IUGR, micro/hydrocephaly, periventricular – calcifications, ascites, effusions, oligo/polyhydramnios Recurrent Infection Less insiduous to neonate - usually asymptomatic at birth -10% hearing loss in future Diagnosis - 4 x rise in antibody titre IgG, IgM Foetus - amniotic fluid PCR - umbilical cord sampling Varicella Zoster Maternal infection – – – – may cause severe, possibly fatal chickenpox of all adult chickenpox - 2% in pregnancy 25% of all chickenpox deaths more severe - encephalitis, myocarditis, pneumonitis Prevention – zoster immune globulin in 72 hrs – acyclovir if not given ZIG Congenital malformations Highest risk of foetal damage 13-20 weeks Skin scarring in dermatomal distribution Limb hypoplasia Eye defects - micropthalmia, cataracts Neurological abnormalities Noenatal Chickenpox Occurring within 7 days prior to delivery Transplacental transmission if large amount of virus with no maternal protective antibodies yet present 30% infant mortality Give ZIG to neonate within 72h of birth Toxoplasmosis Protozoan parasite Cat host - passed in cat faeces but must mature in soil prior to becoming infective Undercooked meat, soil, animal contact Prevalence varies France, S. America 80% Australia 30-40% sero +ve Congenital Infection Follows primary maternal infection Chances of transmission 1st trimester - 25% 2nd trimester - 54% 3rd trimester - 65% Magnitude of foetal damage greatest in early pregnancy - Neurological abnormalities, chorioretinitus, jaundice, rash Diagnosis Difficult - maternal infection asymptomatic Demonstrate seroconversion Amniocentesis or foetal blood sample Management Serial IgG and IgM If seroconversion - monitor foetus by serial ultrasound - hydrops foetalis, IUGR Question 5 Which of the following statements regarding Rubella and pregnancy are correct? a. Congenital Rubella Syndrome may occur in patients who are known to be immune to Rubella. b. Rubella infection after 16 weeks of pregnancy results in foetal damage in about 30% of cases. Rubella 90% women immune Vaccine live - give postpartum Congenital Rubella Syndrome - before 16 weeks - cataracts, glaucoma, deafness, cardiac - after 16 weeks