A controlled trial of puncture sites for amniocentesis. The role of hexoprenaline in suprapubic amniocentesis during late pregnancy. A pilot study. A randomized study to assess two different techniques of aspiration while performing transabdominal chorionic villus sampling. A randomised trial of progesterone prophylaxis after midtrimester amniocentesis.
A controlled trial to determine a better site for amniocentesis was carried out over a 6-month period, involving 98 obstetric patients. The suprapubic and nuchal puncture site for amniocentesis were compared. The failure rate was found to be lower when the suprapublic site was used, and no significant difference in morbidity was found in the two groups. Suprapubic amniocentesis is often complicated by the fetal head being fixed in the pelvis, oligohydramnios or a hyperirritable myometrium. These factors limit the success rate associated with the procedure. If the myometrium is relaxed with a beta 2-stimulant, a higher success rate may be achieved. This was investigated in a randomized, prospective, double-blind pilot study using hexoprenaline. When four- or five-fifths of the fetal head was palpable above the pelvis, hexoprenaline (17 amniocenteses) showed no advantage over a placebo (16 amniocenteses). However, when three-fifths or less of the fetal head was palpable above the brim, 4 dry taps were obtained in the control group using a placebo (17 amniocenteses), while none occurred in the study group (19 amniocenteses) (P less than 0,05). Elevation of the fetal head was less difficult in the study group, but this difference was not statistically significant. These results suggest that hexoprenaline is not indicated for routine use during amniocentesis. When a dry tap is obtained or when marked difficulty is encountered in lifting the fetal head from the pelvis, 10 micrograms hexoprenaline administered intravenously 5 minutes before amniocentesis appears to facilitate successful completion of the procedure. However, a larger series is necessary to confirm this observation. The technique used to perform transabdominal chorionic villus sampling (CVS) is not standardized, but aspiration of villi is generally obtained by discontinuous vacuum created in a syringe, manually or by a hand-grip device. We evaluated the feasibility of a new method of performing CVS which employs a 4-mL Vacutainer connected to the needle, producing a continuous negative pressure.
                Two hundred pregnant women, whose gestational age ranged from 10 + 2 to 16 + 2 (mean, 12 + 1) weeks, entered the randomized study, which was powered to detect with 90% probability the absence of any difference in the size of chorionic samples obtained by using a 20-mL syringe with the vacuum obtained by a hand-grip device (Group 1) or by a vacutainer (Group 2). Four operators with different levels of experience performed all the procedures, which were done transabdominally using a freehand technique with a 20-gauge needle under ultrasound guidance.
                Maternal age, body mass index, gestational age and the way the needle was inserted within the chorion were similar in the two groups. The median amount of villi sampled was 20 mg, with no differences between the two groups. The rate of fetal loss was 1.7%. All losses occurred in women of Group 1 who had only one needle insertion. A second needle insertion was required more frequently while using the vacutainer.
                This new technique for performing transabdominal CVS uses a readily available device and is as effective as traditional sampling systems to aspirate villi. It has the advantage of being a one-operator procedure. Midtrimester amniocentesis to investigate fetal karyotype carries a small risk of fetal loss.
                To test the hypothesis that progesterone prophylaxis may reduce this.
                A randomised controlled trial comparing a short prophylactic treatment with progesterone after amniocentesis with untreated controls.
                There were no differences in frequency of miscarriage, preterm delivery or neonatal outcome.
                Prophylactic progesterone treatment after amniocentesis does not improve obstetric outcome.
Overall, the quality of evidence summarised in this review is not of sufficient quality to change current clinical practice. In the absence of clear evidence, the operators should continue to use methods and technique modifications with which they are most familiar with.
Any randomised trials of technique modifications that are performed to high standard with adequate safety outcomes and power to detect important clinical differences would be clearly welcome.