Early prenatal diagnosis of triploidy

Ultrasound detection of first trimester malformations: a pictorial essay

Knowledge of normal and abnormal anatomy in the first trimester aids in early detection of anomalies and the avoidance of potential pitfalls.

Increased fetal nuchal translucency at 11-14 weeks

Nuchal translucency (NT) is the sonographic appearance of a subcutaneous collection of fluid behind the fetal neck. The measurement of fetal NT thickness at the 11-14-week scan has been combined with maternal age to provide an effective method of screening for trisomy 21; for an invasive testing rate of 5%, about 75% of trisomic pregnancies can be identified. When maternal serum free-beta human chorionic gonadotrophin (beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A) at 11-14 weeks are also taken into account, the detection rate of chromosomal defects is about 90%. Increased NT can also identify a high proportion of other chromosomal abnormalities and is associated with major defects of the heart and great arteries, and a wide range of skeletal dysplasias and genetic syndromes. In monochorionic twins, discordancy for increased NT is an early marker of twin-to-twin transfusion syndrome (TTTS). As with the introduction of any new technology into routine clinical practice, it is essential that those undertaking the 11-14-week scan are adequately trained and their results are subjected to rigorous audit.

Fetal nuchal translucency: a prenatal screening tool

During fetal nuchal translucency screening, ultrasonography is used to assess for a fluid collection at the nape of the fetal neck. An abnormal fluid collection may be related to genetic disorders and/or physical anomalies. This screening is most accurate when performed between 10 and 14 weeks gestation. Analyzing maternal serum beta-hCG and pregnancy-associated plasma protein A levels increases the accuracy of 1st trimester screening. Nurse practitioners, midwives, and physicians can be certified in performing fetal nuchal translucency screening.

First trimester diagnosis of holoprosencephaly and cyclopia with triploidy by transvaginal three-dimensional ultrasonography

We present the prenatal three-dimensional (3D) ultrasound findings in a case of holoprosencephaly and cyclopia at 11 weeks gestation. Only holoprosencephaly with missing cyclopia were initially diagnosed because suboptimal views of the fetal face were obtained with transvaginal two-dimensional (2D) ultrasonography due to fetal position. Chromosomes identified by analysis of a fluid sample from early amniocentesis demonstrated a triploidy (69, XXX), spontaneous fetal demise occurred at 12 weeks and the pregnancy was terminated. This case demonstrated the usefulness of transvaginal 3D ultrasonography in establishing the final diagnosis.

Sonographic markers of fetal aneuploidy

A variety of ultrasound findings can be identified in fetuses with fetal aneuploidy. Typical findings vary with both the chromosome abnormality and gestational age at time of the ultrasound examination. Increased NT is the primary marker during the first trimester, whereas a variety of markers may be seen during the second trimester. The presence of ultrasound markers increases the risk for fetal aneuploidy, whereas a normal ultrasound reduces the risk. Optimal risk assessment includes consideration of other risk factors including maternal age, family history, and biochemical markers. It is expected that combined risks, incorporating ultrasound findings and biochemistry, will be available in the near future. How first-trimester screening is integrated with second-trimester screening remains to be determined.

Fetal heart rate in chromosomally abnormal fetuses

OBJECTIVES

To determine the effects of chromosomal defects on fetal heart rate at 10-14 weeks of gestation.

METHODS

Fetal heart rate at 10-14 weeks of gestation in 1061 chromosomally abnormal fetuses was compared to that from 25,000 normal pregnancies. The chromosomally abnormal group included 554 cases of trisomy 21, 219 cases of trisomy 18, 95 of trisomy 13, 50 of triploidy, 115 of Turner syndrome and 28 of sex chromosome abnormalities other than Turner syndrome.

RESULTS

In the normal group, fetal heart rate decreased from a mean value of 170 beats per minute (bpm) at 35 mm of crown-rump length to 155 bpm at 84 mm crown-rump length. In trisomy 21, trisomy 13 and Turner syndrome fetal heart rate was significantly higher, in trisomy 18 and triploidy the heart rate was lower and in other sex chromosome defects it was not significantly different from normal. Fetal heart rate was above the 95th centile of the normal range in 10%, 67% and 52% of fetuses with trisomy 21, trisomy 13 and Turner syndrome, respectively. The fetal heart rate was below the 5th centile in 30% of fetuses with triploidy and 19% of those with trisomy 18.

CONCLUSIONS

Trisomy 21, trisomy 13 and Turner syndrome are associated with fetal tachycardia, whereas in trisomy 18 and triploidy there is fetal bradycardia. Inclusion of fetal heart rate in a first-trimester screening program for trisomy 21 by a combination of maternal age and fetal nuchal translucency thickness is unlikely to provide useful improvement in sensitivity.

Triploid pregnancy after ICSI of frozen testicular spermatozoa into cryopreserved human oocytes: case report

Although freezing oocytes is ethically more acceptable than cryopreservation of embryos, variable oocyte survival, fertilization rate and possible risk of increased ploidy after cryopreservation have precluded the widespread clinical application of oocyte cryopreservation in assisted reproduction techniques. We report a triploid pregnancy from intracytoplasmic sperm injection of recombinant FSH-stimulated frozen/thawed testicular spermatozoa into cryopreserved oocytes in a hormone replacement cycle. To our knowledge, this is the first report of a pregnancy where both gametes have been frozen. It illustrates the need for further research when applying new techniques in assisted reproduction.

Advances in antenatal screening for Down syndrome

Antenatal screening for Down Syndrome using maternal age alone is no longer an adequate standard of care. Screening in the early second trimester of pregnancy (between 15 and 20 weeks of pregnancy) using the quadruple test can identify 76% of affected pregnancies with a 5% false-positive rate. Screening in the first trimester of pregnancy (between 10 and 13 weeks of pregnancy) is possible using two biochemical markers (PAPP-A and free beta-hCG) together with an ultrasound marker nuchal translucency measurement; using these three markers together with maternal age can identify 85% of affected pregnancies, with a 5% false-positive rate. While there is debate over issues involved in choosing between first and second trimester screening, the most effective screening test for Down Syndrome is the integrated test based on the integration of the first trimester and the second trimester markers. This has a 94% detection rate for a 5% false-positive rate. If the false-positive rate were set at 1%, the detection rate would be 85%. No other screening test for Down Syndrome can detect such a high proportion of affected pregnancies with such a low false-positive rate.

The 11-14 week scan

Fetal nuchal translucency thickness (NT) at the 11-14 week scan has been combined with maternal age to provide an effective method of screening for trisomy 21; for an invasive testing rate of 5%, about 75% of trisomic pregnancies can be identified. When maternal serum free-beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A at 11-14 weeks are also taken into account, the detection rate of chromosomal defects is about 90%. Increased NT can also identify a high proportion of other chromosomal abnormalities and is associated with major defects of the heart and great arteries, and a wide range of skeletal dysplasias and genetic syndromes. Other benefits of the 11-14 week scan include early diagnosis of major fetal defects and the detection of multiple pregnancies, as well as reliable identification of chorionicity. As with the introduction of any new technology into routine clinical practice, it is essential that those undertaking the 11-14 week scan are adequately trained and that their results are subjected to rigorous audit.

Screening for triploidy by fetal nuchal translucency and maternal serum free beta-hCG and PAPP-A at 10-14 weeks of gestation

In 25 cases of triploidy at 10-14 weeks of gestation, compared with 947 controls, the median multiple of the median (MoM) fetal nuchal translucency (NT) thickness was significantly increased (1.89 MoM), and maternal serum total and free beta-human chorionic gonadotrophin (hCG) were increased (3.13 MoM and 4.59 MoM respectively), alpha fetoprotein (AFP) was increased (2.14 MoM), and pregnancy associated plasma protein A (PAPP-A) was decreased (0.12 MoM). There are two types of triploidy. In type I, where the additional chromosome set is of paternal origin, the placenta is partially molar and the fetus is relatively well-grown. Type II, where the extra chromosome set is of maternal origin, is characterized by a small normal looking placenta and severe asymmetrical fetal growth restriction. In type I triploidy there was increased fetal NT (2.76 MoM), maternal serum total hCG (4.91 MoM), free beta-hCG (8.04 MoM), and AFP (3.22 MoM), and mildly decreased PAPP-A (0.75 MoM). In type II triploidy fetal NT was not increased (0.88 MoM), and there was a decrease in maternal serum total hCG (0.16 MoM), free beta-hCG (0.18 MoM), PAPP-A (0.06 MoM) and AFP (0.77 MoM). We conclude that a large proportion of triploidy cases of both phenotypes could be identified in the first trimester using NT, maternal serum free beta-hCG and PAPP-A with a combination of trisomy 21 risk and an atypicality approach.

Early prenatal sonographic diagnosis of twin triploid gestation presenting with fetal hydrops and theca-lutein ovarian cysts

The presence of theca-lutein ovarian cysts in the early second trimester of pregnancy is highly suspicious for a complete hydatidiform molar pregnancy but can be seen in association with a partial mole. Theca-lutein cysts may occur following hormonal stimulation for assisted reproductive techniques or in association with multiple gestations. Rare causes include immune and nonimmune fetal hydrops, maternal hypothyroidism, and triploid gestations. We report a case of a monochorionic twin gestation in which prenatal sonography demonstrated multiple anomalies and hydrops in each twin and bilateral theca-lutein ovarian cysts. Triploidy in both twins and a partial hydatidiform mole were confirmed at pathologic examination.

Hydatidiform mole coexistent with a twin live fetus: a national collaborative study in Japan

A national collaborative study was conducted in Japan to evaluate the clinical course and the sequelae of patients with hydatidiform mole coexistent with twin live fetus (HMTF). Seventy-two cases of HMTF were diagnosed based on gross appearance and histopathological criteria. In 18 cases, the molar parts were cytogenetically confirmed to be of androgenetic origin (complete mole). The overall incidence of persistent trophoblastic tumour (PTT) in patients with HMTF was 30.6%, and it increased to 50.0% in the 18 patients with proven androgenetic complete mole coexistent with twin live fetus (CHMTF). Among these patients, the mean gestational age at termination of pregnancy or delivery in those who developed PTT (n = 9) and those who did not (n = 9) were 20.6 and 19.4 weeks respectively. The incidence of severe maternal complications was significantly higher in patients who subsequently developed PTT (P < 0.05). The rate of subsequent development of PTT in patients with CHMTF was found to be considerably higher than in a previous study of patients with single complete mole (50 and 12.5% respectively). However, since the risk of malignancy is unchanged with advancement of gestational age, continued pregnancy may be allowed in patients with HMTF provided that severe maternal complications are controlled and fetal karyotype and development are normal.

First trimester ultrasonography of multiple gestations: a review

The objective was to review current literature pertaining to first trimester ultrasonography of multiple gestations. To this goal, all manuscripts published in the English language regarding this topic were selected and reviewed in a MEDLINE search from 1966 through May 1998. Additional sources were identified through cross-referencing. Current widespread application of first trimester ultrasonography and especially transvaginal sonography has introduced a new dimension in both diagnostic and management aspects of multiple gestations. Application of first trimester ultrasonography in multiple gestations enables an earlier and more precise depiction of important anatomical details regarding fetal viability, chorionicity, pregnancy outcome, structural abnormalities, pathophysiology of developmental disorders (such as twin reverse arterial perfusion [TRAP] sequence), early sonographic signs associated with fetal aneuploidy (nuchal translucency and abnormal crown-rump length), and potential fetal growth discordancy. First trimester ultrasonography also assists in guiding operative procedures including: amniocentesis, chorionic villus sampling, and selective fetal reduction. Enhanced information obtained with high-resolution, first trimester transvaginal ultrasonography is rapidly becoming a standard for establishing critical information that will assist clinicians to stratify management of multiple gestations. Given the increasing incidence of multiple gestations because of various assisted reproductive technology modalities, it is important that obstetricians become aware of the potential advantages of first trimester ultrasonography in clinical management of multiple gestations.

Diagnosis and management of early non-immune hydrops fetalis

Fetal hydrops is a common symptom of fetal disease at any stage of gestation. The aetiological mechanisms leading to non-immune fetal hydrops are complex and their impact variable at different stages of gestation. In early pregnancy, primary or secondary intra-uterine cardiac failures due to major cardiovascular defects are more often linked to a chromosomal abnormality than during the second half of gestation. In these cases, an increase of the nuchal translucency thickness is probably the first stage of fetal hydrops. Depending on the severity of the underlying defect, the next stage is generalized skin oedema with eventual placental oedema, ascites and pleural effusion. The natural history of fetal hydrops remains poorly understood and thus the prognostic factors determining fetal outcome are still unknown. Examination of the fetal nuchal anatomy between 10 and 15 weeks of gestation and the follow-up of these pregnancies offer an opportunity for an early screening in most aneuploidies and cardiovascular defects, and a better understanding of the aetiopathology of fetal hydrops.