Prenatal diagnosis of pelvic kidney

A 30-year-old woman had serial ultrasound scans from 28 weeks' gestation which revealed the presence of a cystic area in the fetal pelvis. The ‘cyst’ remained unchanged until delivery at 41 weeks. Fetal growth and amniotic fluid volume were normal throughout. A pelvic kidney was confirmed at birth. The differential diagnosis and antenatal management of this ‘cyst’ are discussed.     

Mosaicism of 46,XX/47,XX,+9/47,XX,+?mar in the same amniotic fluid with apparent loss of one cell line after delivery

A 46,XX; 47,XX,+9; 47,XX, + ?mar karyotype was detected in an amniotic fluid cell culture and confirmed in a subsequent fetal blood sample from a 40-year-old woman. After termination of the pregnancy, none of the 186 mitoses obtained from a second blood sample was trisomic for chromosome 9 (p<0.001). Selection against cells containing trisomy 9 is postulated to explain the disappearance of the lymphocyte clone.     

A rare case of de novo structural rearrangement of X chromosome diagnosed by amniocentesis

A dicentric X chromosome was found in a female fetus during cytogenetic studies performed on amniotic cells. Blood samples from the parents showed normal karyotypes and the pregnancy was terminated. The mechanism for the formation of this ‘de novo’ rearrangement is discussed.     

Prenatal diagnosis using deletion studies in Duchenne muscular dystrophy

Accurate carrier testing and prenatal diagnosis in Duchenne muscular dystrophy (DMD) families is facilitated when an Xp21 deletion is found to be segregating within a family. We discuss the results of the DNA testing in two families, one in which DNA from affected males was available for study and the other in which no DNA from an affected male was available. Factors complicating the counselling of DMD deletion families are outlined.     

Effects of mid-trimester induced abortion on the subsequent pregnancy

The outcome of the pregnancy following (a) a mid-trimester termination of pregnancy (TOP) for fetal neural tube defect (NTD) (77 women=group 1); (b) mid-trimester TOP for fetal Down's syndrome (13 women=group 2); (c) delivery of a baby with NTD (119 women=group 3) was studied. The prenatal fetal loss was relatively high in all groups. In group 1 it was similar to that found in other studies after first trimester TOP, in group 2 it was associated with advanced maternal age and the unexpected finding in group 3 was not attributable to advanced maternal age. It is suggested that a previous NTD per se might increase the risk of fetal loss in the next pregnancy. A previous mid-trimester TOP for NTD was not associated with an increase in premature labour, small for dates babies or congenital abnormality in the next pregnancy, but there was a slight increase in the number of babies weighing less than 2500 g.     

Is maternal alpha-fetoprotein screening still of value in a low-risk area for neural tube defects?

Estimation of maternal serum alpha-fetoprotein (AFP) was used as a screening method for the detection of neural tube defects (NTDs) in 6344 women over three years. Of 88 (1.4 per cent) who had one or more serum AFP levels equal to, or greater than, 2.5 multiples of the median (MoM) for the relevant gestational age, 43 (0.68 per cent) underwent amniocentesis. There were eight NTDs. Four of these were screened by serum AFP, and all cases of spina bifida had serum AFP levels greater than 3.0 MoM, including one small open defect which was not seen on ultrasound. The other four cases of NTD, which were not screened, were identified by ultrasound. Of 64 singleton pregnancies 32 (50 per cent) had serum AFP levels between 2.5 and 3.0 MoM, and low birthweight (⪕2500 g) occurred in 29 per cent. Because of improvements in ultrasound techniques and the apparent falling incidence of NTD, the role of serum AFP as the primary screening procedure should be regularly reviewed. Effective screening is dependent on mothers booking early.     

Prenatal diagnosis of the hurler syndrome: Report on 40 pregnancies at risk

In 40 pregnancies at risk for the Hurler syndrome 13 affected fetuses were detected by the demonstration of an α-L -iduronidase deficiency and an increased level of ³⁵S-sulphate incorporation. The diagnoses were confirmed by the analysis of fetal tissues and/or cultured fetal skin fibroblasts. Microassays for α-L -iduronidase, using phenyl α-L -iduronide and more recently 4–methyl-umbelliferyl α-L -iduronide, enabled a reliable diagnosis to be made within 15 to 18 days after amniocentesis. ³⁵S-sulphate incorporation has been a valuable adjunct in cases with a low (heterozygote) enzyme activity.     

Detection of fetal HLA-DQα sequences in maternal blood: A gender-independent technique of fetal cell identification

The objective of this study was to detect fetal HLA-DQα gene sequences in maternal blood. HLA-DQα genotypes of 70 pregnant women and their partners were determined for type A1. We specifically sought couples where the father, but not the mother, had genotype A1. In 12 women, maternal blood samples were flow-sorted. Candidate fetal cells were isolated and amplified by using PCR primers specific for a paternal HLA-DQα A1 allele. Fetal HLA-DQα A1 genotype was predicted from sorted cells; amniocytes or cheek swabs were used for confirmation. Six of twelve sorted samples had amplification products indicating the presence of the HLA-DQα A1 allele; 6/12 did not. Prediction of the fetal genotype was 100 per cent correct, as determined by subsequent amplification of amniocytes or cheek swabs. We conclude that paternally inherited uniquely fetal HLA-DQα gene sequences can be identified in maternal blood. This system permits the identification of fetal cells independent of fetal gender, and has the potential for non-invasive prenatal diagnosis of paternally inherited conditions.     

Maternal age-specific risks for trisomies at 9—14 weeks' gestation

This study provides data on the incidence of fetal trisomies 21, 18, and 13 at 9–14 weeks' gestation in women aged 35–45 years and estimates of maternal age-specific risks in women aged 20–45 years. Our data from 5814 singleton pregnancies undergoing first-trimester karyotyping for the sole indication of maternal age ⩾ 35 years were combined with those from two previous reports and the incidence of the trisomies was calculated from a total of 15 793 pregnancies. Comparison of incidences at 9–14 weeks' gestation with published data at 15–20 weeks' gestation and in livebirths demonstrated that at birth the maternal age-specific incidence of trisomy 21 is 33 per cent lower than at 15–20 weeks' gestation and 54 per cent lower than at 9–14 weeks' gestation. Furthermore, the relative frequency of trisomies 18 and 13 decreases from 30 per cent at 9–14 weeks to 22 per cent at 15–20 weeks and 14 per cent at birth.