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.     

Prenatal diagnosis of a rare heteropagus

The prenatal diagnosis by ultrasound of an unusual case of supernumerary head is reported. The problems of differential diagnosis, the pathological findings after voluntary interruption of the pregnancy, and the problems of obstetric management are presented.     

Cystic hygroma: Prenatal diagnosis and genetic counselling

Six cases of cystic hygromas detected during second trimester ultrasound examination are reported: 4 fetuses (67 per cent) had a 45, X karyotype, 1 fetus had trisomy 18, 1 fetus had a normal karyotype (46,XX) and at autopsy multiple anomalies were observed. In the latter case the family history suggested an autosomal recessive pattern of inheritance. In order to reach a definite diagnosis and give proper genetic counselling when a fetus is found to have cystic hygroma, a fetal karyotype as well as a family and reproductive history should be obtained.     

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.     

The safety of fetoscopy: (I). Effect of umbilical vessel puncture on the fetal heart rate and cord histology

The fetal heart rate (FHR) was continuously monitored during 42 umbilical vessel punctures performed at the placental insertion of the cord in 24 diagnostic fetoscopies in which pure fetal blood was obtained. In only one patient did a deceleration first appear during puncture and aspiration of fetal blood. In two patients decelerations preceded fetoscopy and in two others they began during the fetoscopy but before puncture of an umbilical vessel. In 19 patients, the FHR did not change at all during the procedure. Fetal haemorrhage after sampling was either absent or minimal. Six pregnancies were terminated because a positive diagnosis had been made and 18 healthy babies were born. Umbilical cords were examined after 7 terminations of pregnancy and after 6 deliveries. In the former group the puncture could just be seen with the naked eye and the needle track was demonstrated histologically in 6. No traces of the puncture or other abnormalities were found in the cords after delivery. Fetal blood sampling from umbilical cord vessels, particularly at the placental insertion of the cord, is the technique of choice since pure fetal blood can be obtained without increasing the risk of fetoscopy.     

DNA-based carrier detection and prenatal diagnosis of tyrosinase-negative oculocutaneous albinism (OCA1A)

We describe molecular prenatal diagnosis and carrier detection of tyrosinase-negative oculocutaneous albinism (OCA1A) in two families. In one family, we carried out DNA-based prenatal diagnosis of OCA1A. In the other family, mutation analysis and carrier detection obviated the need for prenatal diagnosis. Molecular analysis is safer and probably more accurate than fetoscopy and fetal scalp biopsy, and should become the method of first choice for prenatal diagnosis of OCA1.     

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.     

MSAFP levels and oesophageal atresia

This study was undertaken to evaluate the relationship between maternal serum alpha-fetoprotein (MSAFP) levels and oesophageal atresia (OA). OA occurred in 16 fetuses of mothers who had an MSAFP test in the study interval. The multiple of the median (MOM) value for MSAFP averaged 1·54 ± 0·65 (range 0·5–2·9 MOM), which was significantly higher than the value seen in controls. The median MOM was 1·35. Using a cut-off of 2·5 MOM, the sensitivity of MSAFP for detecting OA was 19 per cent. Although OA should be considered in the differential diagnosis of an elevated MSAFP level, MSAFP cannot be considered an appropriate screening test for OA given the low sensitivity.