Several studies have established a relationship between indications for prenatal diagnosis and abnormal cytogenetic test results of sex chromosome abnormalities [5,7,9]. Thus, Brun et al. [7] found abnormal ultrasonog­raphy findings in 41 out of 96 fetuses with sex chromosome aneuploidy cases, and Baena et al. [9] reported that the most frequent abnormal ultrasonography findings were cystic hygroma (59.5%) and hydrops fetalis (19%) in 125 TS cases. Bronshtein et al. [5] have shown that cystic hygroma, hydrops fetalis and subcutaneous edema were highly predictive of TS in early pregnancy. Our smaller study confirms that the most common indications for fetal chromosomal analysis are cystic hygroma and hydrops fetalis, however, the frequency of fetuses having these abnormalities is slightly lower, probably because of the number of cases available.
Drummond et al. [10] found nine fetuses with chromosomal abnormality among 130 pregnancies that underwent invasive testing after 28 weeks gestation. One of these fetuses with a chromosomal abnormality had the 45,X0 karyotype and hydrops fetalis, with a cardiac abnormality as the ultrosonographic findings.
Among our TS cases, 82.35% had a non mosaic karyotype. The frequency of non mosaic karyotypes has been reported at 60 to 81% of TS diagnosed prenatally [2,3,9,11].
Turner’s syndrome cases with a mosaic karyotype do not usually show abnormal prenatal ultrasonography findings [4,5,11]. Thus, Huang et al.[11] observed intrauterine growth retardation in only one of the 17 mosaic fetuses with TS. None of our three mosaic TS fetuses showed prenatal ultrasonography findings supporting the previous reports.
Most cases of 45,X0/46,XY mosaicism are thought to be caused by nondisjunction of the Y chromosome after normal disomic fertilization [12,13]. In over 90% of such cases, diagnosed prenatally, a normal male phenotype was found by several authors [14,15,16]. Genetic counseling for such mosaic patients is problematic as there is a 10% risk of abnormality [17]. Unfortunately, our case of 45,X0/ 46,XY mosaicism was lost to follow-up.
Most prenatally diagnosed fetuses with TS are legally aborted in most countries [3,7,8].The termination rate can be changed by the genetic counseling given by professionals [7]. Higher termination rates have been observed among couples with a higher mean number of previous children [8]. The termination rate in our pregnancies diagnosed with 45,X0 were 100% after genetic counseling. One of the mosaic cases spontaneously aborted after amniocentesis, while the other two cases were lost to follow-up. We suggest that fetal karyotyping be performed in pregnancies in which there are abnormal ultrasound findings.