Ultrasound indications for maternal STORCH testing in pregnancy

DOI: https://doi.org/10.4414/smw.2017.14534

Introduction

Materno-fetal infections may cause severe fetal disease, intrauterine fetal demise (IUFD), and long-term manifestations. The acronym TORCH was established in 1971 to describe a group of congenital infections with similar clinical features. The term initially included Toxoplasma gondii, others (syphilis), rubella virus, cytomegalovirus (CMV), and herpes simplex virus 1 and 2 (HSV-1, HSV-2) [1] and has since then been extended to include several other infectious agents that may cause congenital infections [2]. Most recently, the addition of zika virus should be considered in the light of its strong association with fetal microcephaly if maternal infection develops in the first trimester [3–5]. Due to the recent increase in syphilis rates, use of the term STORCH in this paper seems appropriate (the “S” denoting syphilis). The epidemiology of STORCH infections varies geographically. In low-income and middle-income countries, STORCH infections are major contributors to prenatal, perinatal, and postnatal morbidity and mortality. Cytomegalovirus infection is the most common viral infection in pregnancy, affecting 0.4 to 2.3% of live-born infants, and is more common than other well-known diseases such as Down syndrome, which affects about 1 out of 730 live born infants [6–8]. While most STORCH infections cause only mild symptoms in the mother, fetal infection has a broad spectrum of manifestations. Infection in utero may be asymptomatic or may cause severe fetal malformations, central nervous system damage, or fetal death. Affected neonates can be asymptomatic at birth, and late manifestations may become apparent only years after birth. Obvious fetal abnormalities are usually detected on routine ultrasound examinations during pregnancy and prompt a diagnostic work-up including a panel of serological tests to detect possible STORCH infections. For many years, the STORCH test has been used as a panel upon the detection of various ultrasound findings, and during recent decades, questions have been raised concerning the indications and cost-effectiveness of STORCH testing [9–11]. The aim of this study was to review the ultrasound indications for STORCH panels at the university hospital of Basel during a five-year period.

Materials and methods

Practice at the University Women’s Hospital in Basel during the time period of this study included routine screening in every pregnancy for human immunodeficiency virus (HIV) infection, syphilis, and hepatitis B, checking for anti-varicella zoster virus (VZV), IgG antibodies if prior varicella infection could not be confirmed by the patient, and verifying rubella vaccinations by checking anti-rubella antibodies. Routine screening for toxoplasmosis was stopped about two years into the study period according to the revised national guidelines [12]. Testing for any other STORCH agents is requested for specific indications only and includes serologies for Borrelia burgdorferi, cytomegalovirus, herpes simplex virus, Toxoplasma gondii, parvovirus B19, enterovirus, and leptospires. Laboratory results were provided by the Division of Clinical Microbiology at the University Hospital of Basel, and the Division of Infection Diagnostics at the Department Biomedicine at the University of Basel, a fully accredited and licensed medical microbiology laboratory according to ISO17025 (SAS219). The women’s hospital’s ultrasound database system was used to retreive the pathological ultrasound findings that led to serological testing. The main ultrasound findings considered to be associated with congenital infection were noted. Patient records were obtained by the Children’s Hospital of Basel in case of confirmed fetal infection with admission to the neonatal unit. For Borrelia burgdorferi, CMV, Toxoplasma gondii, rubella virus, parvovirus B19, HSV and VZV, IgM and IgG antibodies were tested. When required, additional CMV and toxoplasma IgG avidity testing was performed. Reactive borrelia IgG and/or IgM serology was confirmed by performing line immunoblotting. Detection of HBV surface antigen was used to screen for hepatitis B infection, anti-HCV antibodies for hepatitis C, and a 4th generation test combining the detection of both p24 antigen and anti-HIV-1/2 antibodies was used to screen for HIV. Antibodies of enteroviruses and leptospires were detected by complement-binding reaction. Quantitative polymerase chain reaction (PCR) of amniotic fluid was performed to confirm fetal infection with CMV and parvovirus, and the detection of CMV-DNA in urine was used to confirm CMV infection in a newborn. Maternal CMV infections were diagnosed by seroconversion (case 5), low IgG avidity indices (case 4 and case 7), and increasing IgG avidity indices (from low/medium to high indices) (case 1 and case 6). Two maternal serologies were inconclusive (case 2 and case 3), but fetal infection was confirmed by PCR of amniotic fluid (case 2) and by placental immunohistochemistry (case 3). Maternal parvovirus infections were diagnosed based on the presence of IgM antibodies (case 1, cases 3–6), and based on a positive PCR of amniotic fluid (case 2). Tests for CMV were performed in 344 (87.8%) patients, parvovirus B19 in 316 (80.6%), HSV in 309 (78.8%), Toxoplasma gondii in 301 (76.8%), Borrelia burgdorferi in 290 (74%), VZV in 286 (73%), HBV in 276 (87.8), Treponema pallidum in 270 (68.9%), HCV in 266 (67.9%), rubella virus in 252 (64.3%), HIV in 244 (62.2%), enterovirus in 231 (58.9%), and leptospires in 227 (57.9%) (fig. 1). The study was approved by the ethics committee of north-western and central Switzerland (reference numbers: 2013/142, 2014/143). No informed consent was necessary for the execution of this study.

Figure 1 Total amount of births during study period, percentage of performed STORCH panels, incidence of maternal and fetal infections.

Results

Indications

In the five-year study period, the number of deliveries was 10,729, of which 392 (3.7%) had STORCH tests performed because of abnormal ultrasonographic findings. A detailed list of these findings and the frequency of maternal STORCH infections are shown in table 1. The most common abnormal ultrasound finding leading to STORCH testing was intrauterine growth restriction (IUGR) (30.4%), followed by polyhydramnios (14.8%) and intrauterine fetal death (13.3%). 46% of the ultrasounds showed multiple abnormalities, while in 54% of cases, a STORCH test was performed because of a single suspicious finding. All seven confirmed congenital infections were associated with multiple rather than isolated ultrasonographic abnormalities. Three maternal infections showed a single abnormality (polyhydramnios), and fetal infection was not confirmed in any of these cases. The most common findings associated with maternal infection were hyperechogenic bowel, IUGR, ventricular septum defect (VSD), polyhydramnios and oligohydramnios, prominent cerebral lateral ventricles, fetal hydrops, and cardiomegaly, in descending order. Of the seven confirmed congenital infections, 43% were associated with IUGR, hyperechogenic bowel, and VSD, while 29% were associated with oligohydramnios, prominent lateral ventricles, fetal hydrops, and cardiomegaly. Each of these findings occured in combination with other abnormalities. Microcephaly was reported in 1.5% of cases (table 1).

Maternal infections

There were seven confirmed maternal CMV infections (7/392 = 1.8%), six confirmed maternal parvovirus infections (6/392 = 1.5%), and one of these six patients reported a history of varicella primary infection during early pregnancy in addition to a parvovirus infection (1/392 = 0.3%). Furthermore, there was one suspected case of peripartal enterovirus infection and none of the other infections. Two patients suffered from a chronic hepatitis C infection and one patient from a chronic hepatitis B infection. One woman had been diagnosed with HIV prior to pregnancy. Reactive anti-HSV IgM were observed in 19 patients and reactive anti-borrelia IgM were observed in 31 patients. Follow-up studies revealed no IgG seroconversions and no increases of IgM or IgG. PCRs of amniotic fluid to detect Borrelia burgdorferi or HSV were not performed. In conclusion, the reactive IgM results were considered to be polyclonal antibodies occuring in the context of pregnancy. There were no cases of primary syphilis. Seroprevalence rates were 78, 66 and 62% for HSV, parvovirus, and CMV, respectively. Immunisation rates were 94.4 and 98.4% for varicella zoster virus and rubella virus, respectively. Ultrasonographic findings and detailed pregnancy outcomes of confirmed maternal STORCH infections are listed in table 2.

Fetal outcome

Four of the seven maternal CMV infections were transmitted to the fetus (transmission rate 57%). Diagnosis was confirmed either by autopsy (one case), by detection of CMV-DNA in amniotic fluid (two cases), or chorionic villus sampling (one case). Congenital CMV was excluded by testing newborns’ urine (one case) or by amniocentesis (one case). It is unclear whether the remaining case of maternal CMV was transmitted to the fetus because testing was not performed. All four confirmed congenital CMV infections displayed multiple ultrasonographic abnormalities. Two of the mothers wished termination of pregnancy after confirmation of congenital infection. Two children had severe symptomatic CMV disease at birth, one of which died on the second day of life. One woman had elevated enterovirus titres at 31 weeks of gestation, when polyhydramnios was seen on ultrasound. No further data concerning diagnostics were found. There were three congenital parvovirus infections (transmission rate 50%). Two of them were confirmed by amniocentesis, and one was likely based on ultrasound findings but was not confirmed by invasive fetal testing. All of the congenital parvovirus infections showed multiple sonographic abnormalities and displayed fetal anemia. Intrauterine transfusions were administered in all three cases. There was one IUFD, in the same woman who had a history of varicella infection in pregnancy. The two other cases of fetal anaemia resolved over the course of pregnancy, but IUGR was severe enough to require premature delivery of one baby.

Discussion

A variety of ultrasonographic findings are associated with fetal infection. Most of these findings are non-specific and can be caused by several other conditions. In our study, a maternal STORCH infection was found in 5.2, 3.4, and 1.9% of the three findings with the largest case numbers, polyhydramnios, IUGR, and IUFD.

Most infections were caused by cytomegalovirus and parvovirus, and all seven confirmed fetal infections displayed multiple sonographic abnormalities. Interestingly, the classic ultrasound findings that are associated with fetal STORCH infections, such as abdominal or intracranial calcifications, were rarely found.

It is believed that congenital infections account for approximately 5–10% of all cases of IUGR [13]. The association of IUGR with congenital infections and the cost-effectiveness of STORCH testing in growth-restricted fetuses have been examined by a number of studies. Khan et al. found that the yield of TORCH testing in cases of IUGR (birth weight, height, and/or head circumference <10th%ile for gestational age) is poor and does not justify its costs, as most cases of IUGR in their study were caused by maternal conditions other than infections [10]. Yamamoto et al analysed the systematic screening for Toxoplasma gondii, rubella virus, CMV, and HSV among 319 women carrying a fetus with fetal growth restriction and concluded that a complete maternal STORCH test in growth-restricted fetuses appeared unneccessary. The decision to perform a STORCH test should instead be based on ultrasonographic signs and on previous obstetric history [11]. The second most common indication was polyhydramnios. In the absence of maternal signs or symptoms, isolated polyhydramnios is rarely caused by congenital infection [14]. Most causes of polyhydramnios in singleton pregnancies remain idiopathic [15]. In a retrospective study among 860 singleton pregnancies with polyhydramnios, serological evidence of recent STORCH infection was found in 25 women with isolated polyhydramnios (2.9%). The two most common infections were CMV (12 cases) and parvovirus (9 cases). Based on these results, the authors suggested performing a TORCH test following the detection of polyhydramnios [16]. On the other hand, Abdel-Fattah et al. analysed 462 STORCH tests in the UK and out of the 11 confirmed cases of maternal CMV infection, none was associated with polyhydramnios [9]. Fayyaz et al. and Pasquini et al. concluded that STORCH testing is not beneficial in cases of isolated polyhydramnios [14, 17]. The third most common indication was intrauterine fetal demise. Infection accounts for 10 to 25% of all stillbirths in high-income countries [18]. A review of 25 studies found that the prevention and treatment of syphilis and possibly malaria had the clearest evidence of impact in stillbirth reduction [19]. Parvovirus and CMV infection are relatively common and should be considered in stillbirths of unknown etiology after autopsy. Among viral infections leading to stillbirths, parvovirus B19 caused two thirds and CMV one third of all stillbirths [20]. A prospective case-control study that examined the incidence of CMV, parvovirus B19, and HSV-1/2 in intrauterine fetal death showed that CMV-DNA was found in 16% of placentas with IUFD compared to 3% of the control placentas [21]. Iwasenko et al. found CMV-DNA in 15% of examined fetal tissues of 130 singleton stillbirths [22]. Cytomegalovirus is the most common congenital viral infection [23] and is a significant cause of birth defects and developmental disabilities [24–26]. This is contrasted by the limited knowledge pregnant women in Switzerland have about the hazards of CMV infection in pregnancy [27]. In the absence of established maternal treatment that improves perinatal outcome [28, 29], the value of prenatal testing (including invasive fetal testing) is questionable. There is evidence from randomised controlled trials that postnatal treatment with intravenous ganciclocvir or oral valganciclovir prevents hearing deterioration and improves neurodevelopmental outcome in children with symptomatic congenital infections [30–32], but testing could be limited to a urine PCR in the first weeks of life. Maternal treatment with intravenous immunoglobulins (IVIG) was shown to decrease the severity of disabilities caused by fetal CMV infection [33] and was associated with a smaller risk of intrauterine CMV transmission in retrospective studies [34]. However, a randomised trial showed no significant impact on the course of primary CMV infection during pregnancy after the administration of immunoglobulins [29]. A larger randomised trial is currently recruiting patients and results can be expected by May 2018. Treatment with IVIG was offered to all affected women in our study. In the meantime, pregnant women or women trying to get pregnant should be educated about preventive measures [35, 36]. Acute parvovirus infection occurs in about 3.3 to 3.8% of pregnancies with a transmission rate of 25% [37, 38]. Parvovirus is not considered a teratogen, and most congenital infections have a favorable outcome [38, 39]. Typical ultrasound abnormalities are fetal anemia, fetal hydrops, and fetal death due to hydropic changes. Testing could thus be limited to these ultrasound findings, also with regard of available effective treatment in reducing fetal death [40]. Congenital varicella and rubella infections are rather rare. Only about 5% of pregnant women in Europe are susceptible to VZV infection during pregnancy [41, 42], and varicella embryopathy occurs in approximately 2% of maternal primary infections before 20 weeks of gestation [43]. The incidence of rubella infections has been monitored by the Swiss paediatric surveillance unit (SPSU) since 1995. Until 2012, three cases of congenital rubella syndrome, one congenital rubella infection and six rubella infections during pregnancy have been reported [44]. Leptospirosis is known to cause spontaneous abortion in animals, and cases of spontaneous abortions in humans due to leptospirosis in pregnancy have been reported [45]. However, the rate of fetal transmission is unknown and there is a lack of information about the outcome of surviving neonates [46]. Although rare cases of intrauterine fetal death due to enterovirus infection have been reported [47], it does not readily cross the placenta or cause fetal disease [48], and vertical transmission most likely occurs in the perinatal period [49]. Maternal infection is not thought to cause congenital damage, although congenital anormalities have been reported [50, 51]. In conclusion, STORCH testing based on abnormal ultrasonography could be limited to the two most common infections, CMV and parvovirus, considering (1) the presence of multiple rather than isolated ultrasonographic abnormalities, (2) a history of symptoms and/or exposure, and (3) results of previous serologies. The incidence of STORCH infections in our sample probably underestimates the real incidence. First, our sample is not representative of all pregnant patients with abnormal ultrasound findings. As we lack data concerning the number of abnormal ultrasounds and only included abnormal ultrasounds that were followed by a STORCH serology, we cannot make a statement about the percentage of all abnormal ultrasounds that were possibly caused by fetal infection. Second, not all fetal infections displayed abnormal ultrasound findings. It it therefore very likely that there were some fetal infections that were never detected prenatally because there were no ultrasound abnormalities and therefore no indications to perform a STORCH test. It is important to be aware of the limitations of ultrasound, as most abnormalities are not specific and can occur in the absence of underlying disease [52–54]. A retrospective cohort study found that among 154 fetuses with congenital CMV infections, only 14.9% showed abnormal ultrasonographic findings [55]. Most importantly, normal ultrasonography of infected fetuses does not exclude symptomatic disease or manifestations in later life [56–60]. Third, serology results might be misleading depending on the timing of the sample and require careful interpretation. Negative CMV IgM and high CMV IgG avidity indices during late pregnancy do not exclude early intrauterine transmission caused by periconceptional primary infection or CMV reactivation. The latency for the development of ultrasound abnormalities is accompanied by the disappearance of IgM and the maturation from low- to high-avidity IgG indexes in CMV infection. Similarly, by the time fetal hydrops due to parvovirus infection becomes apparent, maternal IgM might have already dropped below the limit of detection [61].

STORCH infections remain an important cause of congenitally acquired disease and the recent outbreak of the zika virus gives this topic new relevance [62]. A few imported cases of zika infections have already been reported in Switzerland [63]. Although the risk of a local epidemic is low, the possibility of sexual transmission in addition to acquiring the infection in epidemic regions makes the spread of the virus to pregnant women an important concern [64]. Further studies concerncing the cost-effectiveness of STORCH testing for specific ultrasound findings are needed. However, in the light of the results reported by us and others, and the success of screening pregnant women for HIV infection and syphilis in preventing mother-to- child transmission, our study raises the questions about optimal testing for the risk of CMV and parvovirus B19 testing. Clearly, studies with higher case numbers are needed to determine the value of specific combinations in predicting the probability of fetal infection.

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