# Invasive Prenatal Diagnostics: A Cornerstone of Perinatal Management
## 2 Techniques of Invasive Diagnostics
### Amniocentesis
#### 2.1.3 TORCH Infections
_Rublella_--Following the Global Vaccine Action Plan (GVAP) introduced by the WHO [133], rubella infection has been declared eradicated in 51% of countries. It resulted in an increase in the percentage of infants vaccinated from 40% to 68%, according to the latest report by [PERSON] et al. [134]. However, as a result of insufficient access to the rubella-containing vaccine (RCV) in low-income countries, more than 32,000 children are born with congenital rubella syndrome (CRS) each year [135]. This number is suspected to be underestimated because of the lack of surveillance of CRS in certain countries. Typically, neonates with CRS are growth-restricted and present symptoms depicted as Gregg Triad, which include the following: sensorineural deafness, cataracts and other ocular abnormalities, and cardiac anomalies [136]. Humans are the only source of infection, and the infectious period lasts from 8 days before the onset of the rash to 8 days after [137]. Maternal screening is based on anti-RBV IgG and IgM examination. Anti-RBV IgM antibodies are usually detected only for 2 months after the immunisation; hence, their presence strongly implies a primary infection. It was reported that some patients have the persistent presence of anti-RBV IgM antibodies; however, the prevalence is unknown because of the lack of population-based studies [138; 139; 140] Anti-RBV IgG avidity reaches a level considered high after around 13 weeks [141]. Therefore, it can be useful in specifying the risk of transmission. In order to diagnose a foetal infection, amniocentesis and amniotic fluid PCR tests are recommended [142]. Upon isolating the viral DNA in amniotic fluid, the patient should be properly counselled. Termination of pregnancy should be offered because of the high risk of neonatal impairment. Otherwise, pregnancy should be continued with strict ultrasound monitoring and postnatal management. No treatment has yet been proven to limit transplacental transmission. _Parovovirus B19_ is a leading cause of rash illness among school-age children [143]. Its prevalence is seasonal and is observed to be highest in late winter and early spring [144]. Teachers and nursery workers are at the greatest risk. If a pregnant woman develops a B19 infection, the risk of transplacental transmission is 30% [145]. Most foetuses exposed to parvovirus B19 do not present any abnormalities [146]. However, it may lead to lethal consequences, such as severe foetal anaemia, myocarditis, congestive heart failure, and nonimmune hydrops foetals [147]. The reason is its high affinity for human erythroid progenitor cells and cardiac myocytes. This leads to increased erythrocyte apoptosis in the bone marrow and liver, which results in high-output cardiac failure, general oedema, and still-birth within a median of 3 weeks [148] if not treated. The incidence of prenatal infection is rare; hence, routine screening is not advised. Therefore, diagnosis usually begins with ultrasound findings, such as polyhydramnios, cardiomegaly, pleural effusion, placentomegaly, and ascites. The IgM assay is used to detect a recent infection for about 2-3 months [149]. IgG antibodies are present 10-14 days after contact and last for life [150]. However, definite confirmation of transmission is established with PCR of amniotic fluid [151]. Most mild to moderate cases of foetal anaemia are generally well-tolerated and tend to resolve without invasive intervention [152]. Severe cases usually require treatment. Cordocentesis allowsfor assessing foetal haematocrit, enhancing the severity of foetal anaemia, and transfusing packed red blood cells [153]. This regimen increases the survival rate of compromised footuses to 82%, compared with 55% if not transfused. However, transfusions after the 35 th week of gestation carry a greater foetal risk than immediate delivery [154]. _Other_--in 2016, [PERSON] et al. [155] first reported the presence of Zika virus DNA in the amniotic fluid of a foetus with severe central nervous abnormalities.