Accuracy of fetal lung volume assessed by three-dimensional sonography

OBJECTIVE

To determine the accuracy and precision of prenatal three-dimensional (3D) ultrasound in estimating fetal lung volume using the rotational multiplanar technique (VOCAL) by comparing it to postmortem volume measurements.

METHODS

Fetal lung volume was measured during 3D ultrasound examination using a rotational multiplanar technique in eight cases of congenital diaphragmatic hernia (CDH) (six left and two right-sided) and in 25 controls without pulmonary malformation, immediately before termination. Prenatal 3D sonographic estimates of fetal lung volume were compared with postmortem measurement of fetal lung volume achieved by water displacement.

RESULTS

The intraclass correlation coefficient of fetal lung volume estimated by 3D ultrasound and measured at postmortem examination was 0.95 in CDH cases and 0.99 in controls. Based on Bland-Altman analysis, the bias, precision and limits of agreement were, respectively, 0.35 cm(3), 1.46 cm(3) and between -2.51 and + 3.21 cm(3) in cases with CDH and 0.08 cm(3), 2.80 cm(3) and between -5.41 and + 5.57 cm(3) in controls. The mean relative error of 3D ultrasound fetal lung volume measurement was -7.19% (from -42.70% to + 18.11%) in CDH cases and -0.72% (from -30.25% to + 19.22%) in controls, while the mean absolute error of 3D ultrasound fetal lung volume measurement was 1.40 (range, 0.71-2.52) cm(3) and 2.12 (range, 0.05-4.98) cm(3), respectively. Accuracy of 3D ultrasound for measuring fetal lung volumes was 84.86 (range, 57.30-99.48)% in cases with CDH and 91.38 (range, 69.75-99.45)% in controls. The mean intraobserver variability for lung volume estimated by 3D ultrasound was 0.28 cm(3) in controls and 0.17 cm(3) in CDH cases.

CONCLUSION

Prenatal 3D ultrasound can estimate accurately fetal lung volume using the rotational multiplanar technique for volume measurements (VOCAL), even in fetuses with very small lungs, such as cases with isolated CDH.

The impact of 3-dimensional ultrasonography on perinatal management of a large epignathus teratoma without ex utero intrapartum treatment

We report a case of epignathus teratoma diagnosed at 22 weeks of gestation in which 3-dimensional ultrasound (3DUS) was useful to plan perinatal management. A significant enlargement of the tumor, associated with polyhydramnios and preterm labor, was observed at 35 weeks of gestation. After amniotic fluid evacuation, 3DUS was performed in the presence of pediatricians, obstetricians, and otolaryngologists. Three-dimensional ultrasound revealed that great part of the tumor was located outside the fetal mouth and anterior to fetal mandible, suggesting that the newborn could breathe spontaneously by nasal via. A cesarean section with longitudinal hysterotomy was performed at 36 weeks followed by an immediate extirpation of the tumor and the intubation of the newborn. The management of this rare case illustrates that the ex utero intrapartum treatment (EXIT) procedure is not always necessary in this situation. Besides, the actual prenatal goal consists on carefully selecting fetuses with epignathus teratoma that will need the EXIT procedure from those that will not. Three-dimensional ultrasound and magnetic resonance imaging in association with 2DUS can be helpful in this prenatal selection.

Correlation between ultrasound and anatomical findings in fetuses with lower urinary tract obstruction in the first half of pregnancy

OBJECTIVE

The prognosis of fetal lower urinary tract obstruction (LUTO) depends upon renal function and also upon the underlying etiology. Precise identification of the latter remains a challenge antenatally. Our objective was to examine the underlying pathology in male fetuses with sonographic evidence of severe and isolated LUTO.

METHODS

Detailed postmortem examination was carried out after termination of pregnancy in 24 male fetuses presenting before 25 weeks of gestation with ultrasound evidence of isolated severe LUTO.

RESULTS

All fetuses had megacystis and hyperechogenic kidneys. There was anhydramnios/oligohydramnios and pelvicalyceal dilatation in 20 and 15 cases, respectively. Posterior urethral valves (PUV) were suspected antenatally in 20 cases and urethral atresia was not suspected antenatally. However, postmortem examination of the urethra demonstrated atresia in six cases, severe stenosis in eight cases, PUV in nine cases and an apparently normal urethra in one case. Renal dysplasia was found in all cases but one. Urethral atresia was the most common urethral anomaly at 12-17 weeks. Hydronephrosis was more frequent in cases with PUV (8/9) and urethral stenosis (6/8) than with urethral atresia (0/6). In LUTO presenting in the first and second trimester, hyperechogenic kidneys were predictive of renal dysplasia in 95% of cases. The association of a sagittal diameter of the bladder of at least 40 mm with hydronephrosis before 28 weeks was predictive of PUV with a positive (PPV) and negative (NPV) predictive value of 44.4% and 66.6%, respectively. Absence of hydronephrosis and a sagittal diameter of the bladder of less than 40 mm were predictive of urethral atresia or stenosis with a PPV and NPV of 100% and 47.6%, respectively. The absence of hydronephrosis was predictive of urethral atresia with a PPV and NPV of 66.6% and 100%, respectively.

CONCLUSION

LUTO in a male fetus presenting with megacystis in the first or second trimester of pregnancy is as likely to reflect urethral atresia or stenosis as it is PUV. The size of the bladder and the presence of hydronephrosis should be considered in order to improve prenatal diagnosis and counseling.

Fetal RhD genotyping by maternal serum analysis: a two-year experience

OBJECTIVE

The purpose of this study was to determine the accuracy of the none-invasive prenatal determination of polymerase chain reaction (PCR)-based fetal RhD genotyping.

STUDY DESIGN

A prospective case series was undertaken on all RhD-negative pregnant women presenting for genetic counseling in our prenatal diagnosis center from January 2001 until December 2002. Results were compared with serologic RhD typing of the newborns.

RESULTS

Among the 285 pregnant women who participated in the study, fetal RhD status could be determined for 283 patients. In 2 cases, the RhD-negative phenotype of the mother was not the result of a complete RHD gene deletion, and therefore, the status of the fetus could not be determined. Neither false-negative nor false-positive results were observed.

CONCLUSION

The present report demonstrates that a reliable fetal RHD genotype determination can be achieved with 100% accuracy. It is therefore possible to consider that such an assay could be systematically proposed to all RhD-negative pregnant women in order to more effectively utilize RhD prophylaxis.

Surfactant phospholipids and proteins are increased in fetal sheep with pulmonary hypertension secondary to fetal systemic arteriovenous fistula

To determine whether prenatal surfactant storage was altered in a model of systemic arteriovenous fistula (SAVF) with pulmonary hypertension, a fistula was created between the internal jugular vein and the carotid artery in 120-day fetal lambs, and surfactant material was explored at 134 days. Total phospholipids (TPL) and disaturated phosphatidylcholine (DSPC) were increased in whole lung tissue. Phospholipid analysis of isolated lamellar body fraction evidenced a specific increase of surfactant pool size: TPL and DSPC in this fraction were enhanced 1.9 and 2.9 times, respectively, when referred to DNA. Although the steady-state level of transcripts of surfactant protein (SP)-A and SP-B was not found to be changed at the time of death, semiquantitative Western blot analysis revealed elevated SP-A and SP-B protein contents three- and twofold, respectively. These findings indicate markedly enhanced accumulation of surfactant material in the presence of surgically induced prenatal pulmonary hypertension. Although total lung cell number was increased by 26%, SP-B immunolabeling indicated that increased surfactant amount did not result from an increased alveolar type II cell proportion, but rather from an increased rate of storage. Whether similar changes in surfactant are encountered in human neonates with persistent pulmonary hypertension is worthy of investigation.

Prenatal diagnosis of pulmonary sequestration using three-dimensional power Doppler ultrasound

OBJECTIVE

To investigate the contribution of three-dimensional power Doppler ultrasound to the prenatal diagnosis of pulmonary sequestration.

METHODS

Prenatal three-dimensional power Doppler ultrasound was used to screen for an abnormal pulmonary blood supply in eight fetuses with hyperechogenic lung lesions and to image the pulmonary blood supply in 50 normal controls. A comparison was made with postnatal findings.

RESULTS

Postnatally the eight pulmonary lesions were found to be an isolated pulmonary sequestration (n = 3), a microcystic congenital adenomatoid malformation (n = 4), and a mixed (macrocystic and microcystic) congenital adenomatoid malformation (n = 1). Prenatal three-dimensional power Doppler ultrasound demonstrated an abnormal blood supply in all cases of pulmonary sequestration and in none of the other cases. Among the three cases that turned out to be pulmonary sequestrations, conventional two-dimensional ultrasound failed to identify the feeding vessel in one case and identified it at a later stage of gestation than did three-dimensional power Doppler in the other two.

CONCLUSION

Prenatal three-dimensional power Doppler ultrasound may be useful in identifying the feeding vessel and thus establishing the diagnosis of pulmonary sequestration in the presence of a hyperechogenic pulmonary lesion, allowing its differentiation from congenital cystic adenomatoid malformation.

Thoracoamniotic shunting for fetal pleural effusions with hydrops

OBJECTIVE

The purpose of this study was to evaluate perinatal outcome after thoracoamniotic shunting for fetal pleural effusions with hydrops.

STUDY DESIGN

This was a retrospective study.

RESULTS

Shunting was performed immediately after diagnosis and was successful in all 54 of the cases that were attempted. There were 7 pregnancy terminations, 9 in utero deaths, and 38 live births, of which 7 children died in the neonatal period and 31 children survived. Among the liveborn infants, 27 infants were delivered preterm (71%), of whom 7 infants (15%) had preterm premature rupture of membranes and 4 infants (8.5%) had chorioamnionitis. Perinatal death (23/54 infants; 43%) was related to underlying anomalies (7 cases), pulmonary hypoplasia (5 cases), chorioamnionitis (2 cases), or treatment failure for unknown reasons (9 cases). All 31 survivors had chylothorax; for 28 of the survivors, the chylothorax was primary, and for 3 survivors, the chylothorax was the result of right congenital diaphragmatic hernia, pulmonary sequestration, or Noonan syndrome.

CONCLUSION

After the shunting, pleural effusion with hydrops has a 57% survival rate; premature delivery is the leading source of morbidity.

Sonography in prenatal diagnosis of congenital adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder with an incidence of 1/15 000. More than 90% of CAH cases result from mutations of CYP21, leading to 21-hydroxylase deficiency. In its classical form, CAH is severe and consists of the virilizing (increase of androgens) and salt-wasting (lack of aldosterone) phenotype. When a proband exists, early prenatal diagnosis for CAH can be performed by direct molecular analysis in the first trimester. We describe herein two cases suggesting that the prenatal diagnosis of CAH can be initiated by the sonographic appearance of the adrenal gland at the second-trimester scan in the absence of a family history.

Fetal home monitoring for the prenatal management of gastroschisis

BACKGROUND

Fetal distress is a frequent complication of gastroschisis, and could be screened for by home monitoring, as many pregnant women expecting an affected child live far away from a specialized perinatal center. This study was undertaken to audit a policy of fetal home monitoring (FHM) to achieve early detection of fetal heart rate (FHR) abnormalities in gastroschisis.

METHODS

Daily FHM was started at a median age of 30 weeks in 31 pregnant women referred following prenatal diagnosis of isolated gastroschisis. Monitoring was considered abnormal in cases with decelerations, tachycardia, bradycardia, decreased baseline variability or absence of accelerations. When an ominous FHR was detected and confirmed by in-hospital monitoring, an emergency cesarean section (C-section) was indicated. Otherwise, an elective C-section was planned.

RESULTS

In 20 cases FHM remained normal. There were 16 elective C-sections, two emergency C-sections for FHR abnormalities detected by in-hospital monitoring, and two spontaneous premature vaginal deliveries. In 11 cases, an abnormal FHM was detected. There was one intrauterine death with acute ischemic necrosis of the large bowel. The other abnormalities consisted of decreased baseline variability with tachycardia (n = 7) or without tachycardia (n = 3) and were confirmed by in-hospital follow-up in nine cases, leading to emergency C-section.

CONCLUSION

The high rate of abnormal FHR patterns picked up by FHM in gastroschisis led to a rate of emergency C-sections of 9/31. However, this strategy failed to prevent one intrauterine death due to acute bowel necrosis.

A novel PCR approach for prenatal detection of the common NEMO rearrangement in incontinentia pigmenti

OBJECTIVES

Incontinentia pigmenti (IP) is a rare X-linked dominant genodermatosis that is usually lethal in males in the prenatal period. Largely 80% of cases are accounted for by a large-scale deletion encompassing exons 4 to 10 of the NEMO gene. The aim of this work was to facilitate prenatal diagnosis of IP by devising a novel test for detection of the prevalent NEMO deletion.

METHODS

We devised a sensitive and reproducible multiplex PCR test enabling simultaneous amplification of the deleted and wild-type NEMO genes in IP female individuals.

RESULTS

Combination of this DNA test, with Xq28 linkage analysis and X-inactivation pattern study enabled us to offer an IP prenatal diagnosis in 15 of the 16 couples at a 50% risk to have an affected offspring.

CONCLUSION

A current approach to IP prenatal diagnosis is proposed on the basis of the previously mentioned molecular tools.

Analyse génétique du fœtus à partir du sang maternel

Circulating fetal DNA in maternal plasma and serum was first demonstrated by Lo et al. in 1997 and has become a useful tool for prenatal diagnosis less than five years later. There is more and more evidence that the trophoblastic cells act as the major source of this circulating fetal DNA. Contrary to fetal cells analysis in maternal blood which requires isolation and enrichment procedures, fetal DNA analysis is relatively easy to perform with the use of real-time PCR. Non-invasive fetal sex and fetal RHD genotype determination are, to date, the two main clinical indications. Those newly offered possibilities have changed the management of pregnant women who are carriers for X-linked genetic disorders; prenatal diagnosis by choriovillous sampling could only be performed for male fetuses avoiding an unnecessary risk of fetal loss for female fetuses. Moreover, fetal RHD genotyping by maternal blood analysis could be useful in RhD-negative women at risk of immunization in order to adapt prophylactic anti-D injection.

Three-dimensional ultrasonographic assessment of fetal lung volume as prognostic factor in isolated congenital diaphragmatic hernia

OBJECTIVE

To evaluate the potential of three-dimensional ultrasound to predict outcome in congenital diaphragmatic hernia.

DESIGN

Prospective observational study.

SETTING

Tertiary care centre.

POPULATION

Twelve cases of isolated congenital diaphragmatic hernia (11 left-sided, 1 right-sided) and 109 controls.

METHODS

Fetal lung volume was assessed by three-dimensional ultrasound using the technique of rotation of the multiplanar imaging. In the control fetuses, a logistic transformation was performed to correlate fetal lung volume with gestational age, and the confidence interval was obtained with a bootstrap resampling. A mathematical equation was then obtained allowing calculation of the expected fetal lung volume as a function of gestational age. In fetuses with congenital diaphragmatic hernia, the observed/expected lung volume ratio was compared with postnatal outcome.

MAIN OUTCOME MEASURES

Neonatal mortality and pulmonary hypoplasia, which was defined as lung/body weight ratios less than 0.012.

RESULTS

The expected fetal lung volume was derived from the mathematical equation: Fetal lung volume (mL) = exp (4.72/(1 + exp ((20.32 - gestational age in weeks)/6.05))). The observed/expected fetal lung volume ratio was significantly lower in the congenital diaphragmatic hernia group (median: 0.34, range: 0.16-0.66), than in the control group (median: 1.02, range: 0.62-1.97, P < 0.0001). The distribution of this ratio was significantly downshifted in the infants with congenital diaphragmatic hernia who died (median: 0.19, range: 0.18-0.66) compared with survivors (median: 0.44, range: 0.36-0.66, P= 0.04). The observed/expected fetal lung volume ratio was also correlated with the postmortem lung/body weight ratio.

CONCLUSION

In isolated congenital diaphragmatic hernia, fetal lung volume measurement by three-dimensional ultrasound is a potential predictor for pulmonary hypoplasia and postnatal outcome.

Volume contrast imaging: A new approach to identify fetal thoracic structures

OBJECTIVE

To assess the potential of volume contrast imaging for evaluation of fetal intrathoracic structures.

METHODS

Volume contrast imaging is a new ultrasonographic method that increases the contrast between tissues. It consists of a 5- to 10-mm-thick slice-shaped volume image projected on a 2-dimensional screen. The rendering process applied on the slice smoothens the speckle pattern of the image by filling up the gaps with tissue information from the adjacent layers. To evaluate the potential of volume contrast imaging for enhancing the contrast between fetal lungs and surrounding tissues, we compared the ability of volume contrast imaging and conventional ultrasonography to image the fetal thymus in 50 controls. We also applied volume contrast imaging to prenatal imaging of 6 thoracic abnormalities (2 left congenital diaphragmatic hernias, 1 right diaphragmatic hernia, 2 congenital adenomatoid lung malformations, and 1 lung sequestration).

RESULTS

In controls, the thymus was identified in all cases by volume contrast imaging and in 42 cases (84%) by conventional 2-dimensional ultrasonography. Clear images of macrocystic and microcystic congenital adenomatoid malformations were obtained by volume contrast imaging, which provided precise contouring of the lesions. In cases with congenital diaphragmatic hernias, volume contrast imaging provided clear images of the limits of the lungs ipsilateral to the hernia.

CONCLUSIONS

Volume contrast imaging may enhance the contrast between fetal lungs and surrounding organs and can be applied to prenatal imaging of intrathoracic structures in cases with thoracic fetal abnormalities.

Fetal lung volume estimated by 3-dimensional ultrasonography and magnetic resonance imaging in cases with isolated congenital diaphragmatic hernia

OBJECTIVE

To assess the agreement of 3-dimensional ultrasonography and magnetic resonance imaging in estimating fetal lung volume in cases with isolated congenital diaphragmatic hernia.

METHODS

Fetal lung volume was measured in 11 cases of congenital diaphragmatic hernia (10 left and 1 right) by 3-dimensional ultrasonography and magnetic resonance imaging. These examinations were performed during the same week. The operators were blinded to each other's results. Intraclass correlation was used to evaluate the agreement between 3-dimensional ultrasonography and magnetic resonance imaging estimations of the ipsilateral, contralateral, and total fetal lung volume. A Bland-Altman graph was plotted to detect possible discordant observations.

RESULTS

The global intraclass correlation coefficient between magnetic resonance imaging and 3-dimensional ultrasonographic measurement of fetal lung volume was 0.94 (95% confidence interval, 0.78-0.98) with no outliers observed on the Bland-Altman plot.

CONCLUSIONS

There is a good agreement between 3-dimensional ultrasonography and magnetic resonance imaging for fetal lung volume estimation in cases with congenital diaphragmatic hernia.

Prenatal sonographic diagnosis of congenital hiatal hernia

OBJECTIVES

To report a rare case of congenital hiatal hernia illustrating the importance of its prenatal diagnosis as well as to discuss the prenatal sonographic criteria.

CASE REPORT

A case of congenital hiatal hernia was diagnosed by ultrasound at 33 weeks of gestation. After a normal second-trimester morphologic ultrasound examination, a hypoechogenic mass was detected in the posterior mediastinum juxtaposed to the vertebral body and seemed to be in continuity with the intra-abdominal stomach bubble. Congenital hiatal hernia was suspected mainly because of the dynamic position of the stomach during the examination, without mediastinal shift, and normal appearance of the diaphragm on parasagittal sections of the thorax. Postnatal management was planned with no urgency and surgery was successfully performed, confirming the diagnosis.

CONCLUSION

This rare case illustrates the importance of prenatal diagnosis of congenital hiatal hernia for prenatal counseling and postnatal management. The ultrasound criterion for prenatal diagnosis is the presence of a herniated stomach in the posterior mediastinum, sometimes having a dynamic position during examination, with no mediastinal shift associated with normal diaphragm appearance on parasagittal sections of the thorax.

Antenatal manifestations of Smith-Lemli-Opitz (RSH) syndrome: A retrospective survey of 30 cases

Smith-Lemli-Opitz (SLO) syndrome or RSH syndrome is an autosomal recessive multiple malformation, and mental retardation syndrome ascribed to 7-dehydrocholesterol reductase deficiency, and usually diagnosed in the early postnatal period. Reviewing a series of 30 cases of SLO, we have investigated the variable antenatal expression of the disorder. Intrauterine growth retardation (IUGR) was the most frequent detectable trait (20/30). IUGR was either isolated (9/20) or associated with at least one other anomaly (11/20), including nuchal edema, renal, cardiac, cerebral malformations, genital anomalies, or polydactyly. In this last group, 3/11 presented with multiple malformations (> or =3 anomalies). In 5/30 cases, isolated nuchal edema (3/30), and isolated cardiac (1/30) or renal malformations (1/30) were the only detectable anomalies. Ultrasound findings were considered normal in 5/30 cases and were abnormal in 25/30 cases (83%), but early detection of multiple malformations was rare (3/30, 10%). We suggest giving consideration to a more systematic sterol analysis when dealing with IUGR, especially when associated anomalies are detected.

Can Three-Dimensional Ultrasound Be Used for the Assessment of the Fetal Lung Volume in Cases of Congenital Diaphragmatic Hernia?

We report on 2 fetuses with congenital diaphragmatic hernia (CDH) in whom the fetal lung volumes were estimated by three-dimensional ultrasound and the results compared with the postmortem lung volume measurements. Both examiners (sonographer and pathologist) were blinded to each other's results. The 1st case was a right CDH diagnosed at 20 weeks of gestation. The 2nd case was a left CDH diagnosed at 22 weeks of gestation. Both pregnancies were terminated upon request of the parents. Three-dimensional ultrasound estimation of the fetal lung volume was performed 1 day before termination of pregnancy using the technique of rotation of the three perpendicular planes. The left and right lung volumes estimated by three-dimensional ultrasound were 3.88 and 1.87 cm(3), respectively, in the 1st case and 0 and 5.52 cm(3), respectively, in the 2nd case. On postmortem examination, the left and right lung volumes were 3.0 and 2.2 cm(3), respectively, in case 1 and 1.1 and 5.6 cm(3), respectively, in case 2. This suggests that a three-dimensional estimation of pulmonary volumes may be correlated with postmortem findings in cases with CDH.

Perinatal three-dimensional color power Doppler ultrasonography of vein of Galen aneurysms

OBJECTIVE

To present the prenatal and postnatal three-dimensional color power Doppler ultrasonographic features in cases of vein of Galen aneurysmal malformation.

METHODS

Prenatal three-dimensional color power Doppler ultrasonography was used to image the neurovascular malformations in 3 fetuses with vein of Galen aneurysms and in unaffected control fetuses at the same gestational age. Postnatal transfontanel three-dimensional power Doppler ultrasonography was also performed in the third affected case and in an unaffected control neonate. The feeding and drainage vessels were analyzed in the three-dimensional rendering mode.

RESULTS

The first case was complicated by porencephaly and fetal heart failure, and the pregnancy was terminated. The other 2 cases were uncomplicated prenatally, but 1 of the infants died after aneurysmal embolization due to acute cerebral ischemia. The angioarchitecture of the arteriovenous fistula was characterized in greater detail by three-dimensional color power Doppler ultrasonography than by two-dimensional ultrasonography, especially regarding the anatomic features of the feeding and drainage vessels and their connections with the dilated vein of Galen.

CONCLUSIONS

Three-dimensional color power Doppler ultrasonography provided detailed images of the aneurysmal malformation and its vascular connections. Further studies are needed to correlate three-dimensional vascular imaging patterns with outcome.

Pericardial teratoma complicated by hydrops: successful fetal therapy by thoracoamniotic shunting

Pericardial teratoma is a potentially curable lesion that may become life threatening when it induces mediastinal compression and fetal hydrops. So far, cases with fetal hydrops have been managed by elective delivery or pericardial needle decompression. We report a case in which pericardial teratoma resulted in fetal hydrops. Following transpleural needling of the fetal pericardium at 29 weeks and 6 days, pericardial effusion decreased but hydrops persisted, while major unilateral pleural effusion appeared. A thoracoamniotic shunt was placed at 30 weeks and 5 days. Hydrops resolved, although incompletely. The baby was delivered at 32 weeks and was operated upon on day 3. This observation suggests that fetal hydrops associated with pericardial teratoma may improve following thoracoamniotic shunting. Fetal therapy may limit the risks of respiratory distress arising from the combined effect of airways compression and lung immaturity.

Kinetics of SRY gene appearance in maternal serum: detection by real time PCR in early pregnancy after assisted reproductive technique

BACKGROUND

Fetal DNA circulating in maternal serum offers a possibility for non-invasive prenatal diagnosis but its kinetics during very early pregnancy is still unclear. In order to clarify this point, the studies on the kinetics of fetal DNA appearance in maternal serum were conducted on patients undergoing assisted reproduction.

METHODS

Using a quantitative real time PCR assay, the presence of SRY gene sequences was evaluated in the serum of patients at the onset of pregnancy.

RESULTS

Twenty-seven patients were originally studied but first trimester abortion occurred in five cases. Among the 22 ongoing pregnancies, ten were found to bear at least one male fetus and all sera from these women gave positive results for SRY gene detection. The SRY gene was found to be detectable as soon as day 18 after embryo transfer in one case and it had been found in the other nine patients by day 37.

CONCLUSIONS

Fetal DNA is found in maternal serum even before the fetal circulation is established, which is highly suggestive that it is released, at least in part, from the trophoblast. Detection of fetal DNA in maternal serum very early in pregnancy may have clinical implications such as with the management of pregnant women carrying a fetus at risk for congenital adrenal hyperplasia.

Fetal DNA in maternal serum: does it persist after pregnancy?

Fetal DNA and cells present in maternal blood have previously been used for non-invasive prenatal diagnosis. However, some fetal cells can persist in maternal blood after a previous pregnancy. Fetal rhesus status and sex determination have been performed by using amplification by real-time polymerase chain reaction (PCR) of fetal DNA sequences present in maternal circulation; no false-positive results related to persistent fetal DNA from a previous pregnancy have been reported. This idea has recently been challenged. An SRY real-time PCR assay was performed on the serum of 67 pregnant women carrying a female fetus but having previously given birth to at least one boy and on the serum of 30 healthy non-pregnant women with a past male pregnancy. In all cases, serum was negative for the SRY gene. These data suggest that fetal DNA from a previous pregnancy cannot be detected in maternal serum, even by using a highly sensitive technique. Therefore, non-invasive prenatal diagnosis by fetal sex determination for women at risk of producing children with X-linked disorders, and fetal RHD genotyping is reliable and secure as previously demonstrated.