Real-time B-scan-directed amniocentesis

Traditional Prenatal Diagnosis: Past to Present

In the nearly 60 years since prenatal diagnosis for genetic disease was first offered, the field of prenatal diagnosis has progressed far past rudimentary uterine puncture to provide fetal material to assess gender and interpret risk. Concurrent with the improvements in invasive fetal sampling came technological advances in cytogenetics and molecular biology that widened both the scope of genetic disorders that could be diagnosed and also the resolution at which the human genome could be interrogated. Nowadays, routine blood work available to all pregnant women can determine the risk for common chromosome abnormalities; chorionic villus sampling (CVS) and amniocentesis can be used to diagnose nearly all conditions with a known genetic cause; and the genome and/or exome of a fetus with multiple anomalies can be sequenced in an attempt to determine the underlying etiology. This chapter will discuss some of the major advances in prenatal sampling and prenatal diagnostic laboratory techniques that have occurred over the past six decades.

Management of serious alloimmunization in pregnancy

In the past 40 years, tremendous advances in the treatment of hemolytic disease have been made. The perinatal mortality has been reduced considerably. Rh immunoprophylaxis has decreased the incidence of Rh immunization to around 6 per 100,000 live births. Nevertheless, treatment of severe hemolytic disease is still essential. Increased reliability of diagnostic procedures have made early detection and optimal treatment of hemolytic disease possible. Treatment by plasmapheresis is still controversial. Although believed to be beneficial by some authors, conclusive evidence of its efficacy has not been obtained. With preterm induction of birth at 32 weeks of gestation, the chances for survival are 95%. Improvement of techniques and the use of modern real-time ultrasound equipment have made intrauterine intraperitoneal transfusion, in experienced hands, a relatively safe and successful procedure. Intravascular transfusion appears beneficial in early pregnancy. Combination of both techniques will probably be the answer for the future. The development of neonatal intensive care facilities has made a major contribution to the survival of children with haemolytic disease. The relative low incidence of haemolytic disease has made it imperative that treatment should take place in centers where experience and special skill are available.

Conservative management of pregnancy in diabetic women

In 1979 the obstetric management of pregnancies in diabetic women in Cardiff was changed from elective delivery at 37-38 weeks to delivery at term. This change was facilitated by home monitoring of blood glucose concentrations and improved techniques for assessing fetal wellbeing. There were 35 pregnancies in insulin dependent diabetics in 1972-8 and 45 in 1979-82. The quality of diabetic control during pregnancy was equally good in both periods. The average gestation at final admission to hospital increased from 30 to 37 weeks. Amniocentesis to assess fetal pulmonary maturity was necessary in 26 patients (74%) in the first period of study and in only four (9%) in the second. Gestational age at delivery increased from 37.4 to 39.4 weeks after the change in policy. The proportion of mothers entering spontaneous term labour and delivering vaginally increased from 14.3% to 37.8%. The mean birth weight of live born, singleton infants increased from 3090 g to 3650 g, the feeding pattern improved, and respiratory problems were less common. Morbidity was reduced and perinatal mortality was not increased with conservative management of pregnancy in diabetic women.

The use of ultrasound in evaluating problems and complications of genetic amniocentesis

A prospective study of 460 midtrimester amniocenteses performed with ultrasonic guidance was made to determine the problems that occur during amniocentesis and the causes of dry or bloody taps. In 27 instances the needle was seen piercing the fetus. Thickening of the uterine wall, tenting of the membranes, and blocking of flow by the fetus were also observed. The dangers of advancing the needle blindly when no fluid is obtained at the predetermined depth is stressed. The use of active real-time ultrasonic guidance during amniocentesis is advocated.

Effect of blood in amniotic fluid on the detection of phosphatidylglycerol

Samples of amniotic fluid were mixed with serum or red blood cells (RBC) in order to determine the effect of blood contamination on the detection of phosphatidylglycerol (PG). Samples of amniotic fluid was obtained from patients in the second trimester of pregnancy and at term, PG standard was added to half of the aliquots of the second-trimester fluid. The samples of fluid were tested before and after the addition of maternal or fetal serum or RBC in concentrations up to 20%. Two-dimensional thin-layer chromatographic procedures were performed to determine the presence or absence of PG. The results obtained showed that serum of RBC contamination of amniotic fluid without PG did not result in the appearance of a PG spot on the chromatographic plate. Neither serum nor RBC contamination interfered with the detection of PG in those fluids in which it was present. Maternal and fetal blood were similar in their failure to affect the detection of PG. These data suggest that PG determination for fetal lung maturity is a reliable test in the presence of bloody amniotic fluid.

Amniotic fluid phosphatidylglycerol and real-time ultrasonic cephalometry

The fetal biparietal diameter (BPD) was measured at the time of real-time ultrasound-directed amniocentesis in 159 cases and a phospholipid profile was obtained from the amniotic fluid. BPD measurements of 9.0, 8.7, and 9.2 cm were then compared with a lecithin/sphingomyelin (L/S) ratio greater than or equal to 2.0 for the ability to predict the presence of phosphatidylglycerol (PG) in the profile. The data from the diabetic and nondiabetic patients were analyzed separately. The results demonstrated that in the presence of a L/S ratio greater than or equal to 2.0 the BPD does not aid in the identification of amniotic fluid samples which contain PG in either the diabetic or nondiabetic groups. The data also confirmed previous findings that the BPD is not a reliable predictor of the L/S ratio. It is concluded that for the detection of PG in amniotic fluid, the use of real-time ultrasonic cephalometry cannot substitute for the performance of the phospholipid profile.