Vacuum extraction in modern obstetric practice: a review and critique.

The practice of obstetric vacuum extraction is controversial. This article discusses several issues concerning vacuum extraction including maternal and fetal injury risks, failure rates, indications and technique. Recently published articles on these topics are presented and summarized. Throughout this review, vacuum extraction is evaluated against its principal alternatives, forceps and cesarean delivery.

Nitroglycerin for rapid tocolysis: development of a protocol and a literature review.

OBJECTIVE: A protocol for nitroglycerin (NTG) use based on experiences with regard to new and previously described obstetric cases is presented. The efficacy of NTG tocolysis for obstetric emergencies is clinically evaluated. STUDY DESIGN: Hemodynamically stable parturients requiring acute tocolysis were treated with intravenous NTG and closely monitored. Clinical information was subsequently abstracted from medical records and compared with data from previous reviews. RESULTS: Tocolytic treatment was successful in all cases (22 of 22, 100%). Complications were clinically insignificant. The most common problem was transient hypotension, which occurred in 9 of 22 (41%) cases. CONCLUSION: NTG is an effective tocolytic with minimal complications, rapid onset, and a brief half-life. These characteristics favor its use during select obstetric procedures. However, strict adherence to protocols for administration is advised.

Prenatal diagnosis and clinical features of an individual with tetrasomy 18p and trisomy 18q mosaicism.

Prenatal diagnosis and clinical follow up of a patient with mosaicism for anomalies of chromosome 18 are reported. The fetus appeared on ultrasound to have multiple anomalies, including clubbed feet, abnormal hand positioning, edema of the scalp, cleft palate, and polyhydramnios. The karyotype on amniocytes was 47,XY,+i(18p). Postnatally, the peripheral blood karyotype was 46,XY,+i(18q), whereas the skin fibroblast karyotype was 47,XY,+i(18p). The infant had many features consistent with those previously described in cases of tetrasomy 18p and some that were consistent with trisomy 18q.

Assessment of computed tomographic pelvimetry within a selective breech presentation management protocol.

A vital component of selective protocols in term breech presentation management is exclusion of the gravida with borderline pelvic dimensions. Computed tomographic (CT) pelvimetry was employed to evaluate potential candidates for a trial of labor with a breech fetus at term. Thirty-seven of 39 women who underwent labor after this selection had a successful assisted vaginal breech delivery. Adequate pelvic dimensions by CT pelvimetry reliably predicted a safe vaginal delivery in patients managed within a standard breech protocol.

Amniotic fluid surfactant-albumin ratio as a screening test for fetal lung maturity. Two years of clinical experience.

An automated amniotic fluid surfactant-albumin ratio (SAR) test was performed as a screening test for pregnancies requiring fetal pulmonary maturity testing. Of the 178 neonates delivered within 3 days of the testing, respiratory distress syndrome (RDS) developed in 21 (11.8%) and transient tachypnea of the newborn infant (TTN) in 11 (6.1%). A positive test was defined as one which predicted RDS or TTN. Sensitivity was interpreted as the proportion of neonates with RDS or TTN detected by SAR less than 70 mg/gm. Sensitivity was 90.7% with a specificity of 76.1%. The positive predictive value was 45.3%; the negative predictive value 97.4%. The interassay coefficient of variability was 3.5%. The SAR test has proven to be a rapid, precise laboratory tool. Our combined testing protocol uses the SAR as an initial screening test with the lecithin/sphingomyelin ratio used as backup if the SAR did not predict maturity (SAR < 70 mg/gm). This protocol has markedly lowered the use of lecithin/sphingomyelin ratios while maintaining necessary clinical accuracy.

Effect of maternal carbon dioxide inhalation on human fetal breathing movements in term and preterm labor.

Induced maternal hypercapnia is a potent stimulus to fetal breathing movements in nonlaboring pregnant women. To determine the effect of maternal CO2 administration on fetal breathing movements during spontaneous labor, 14 healthy pregnant volunteers at term and 34 in preterm labor were recruited. If fetal breathing movements were markedly decreased or absent, the subjects were administered a prepared gas mixture of 3% CO2 in air. In term labor and in true preterm labor, fetal breathing movements were markedly decreased and could not be induced by maternal hypercapnia. Among women with suspected preterm labor, initial absence of fetal breathing movements and failure to evoke this response by maternal hypercapnia predicted delivery within 48 hours with a sensitivity of 80% and specificity of 95.5%. Induced maternal hypercapnia fails to stimulate fetal breathing movements in true term and preterm labor and may assist in distinguishing between true and false preterm labor.

Infant survival following delayed postmortem cesarean delivery.

A 19-year-old multipara was delivered of a living infant by postmortem cesarean 22 minutes after documented maternal cardiac arrest and 47 minutes from the fatal injury. Neonatal follow-up at 18 months of age demonstrated no evidence of neurologic damage.

Evaluation of fetal renal function: unreliability of fetal urinary electrolytes.

In the fetus with bilateral hydronephrosis it has been reported that a normal volume of amniotic fluid, absence of renal cortical cysts, urinary sodium less than 100 mEq./l., chloride less than 90 mEq./l. and osmolarity less than 210 mOsm. are prognostic factors indicative of good renal function, whereas oligohydramnios, cortical cysts and higher urinary levels of sodium, chloride or osmolarity suggest irreversible renal dysplasia. We report 5 cases in which the fetal urinary electrolytes were not predictive of ultimate renal function. In 3 instances fetal urinary electrolytes and osmolarity were abnormally elevated but the infants survived without ventilatory support. In 2 of these 3 patients the volume of amniotic fluid was normal. Diagnoses included posterior urethral valves, prune belly variant and bilateral ureteropelvic junction obstruction. In 2 cases with oligohydramnios fetal urinary electrolytes were suggestive of satisfactory renal function but the infants died of pulmonary hypoplasia and had bilateral renal dysplasia, prune belly syndrome and urethral atresia. Presently, the volume of amniotic fluid remains the most important prognostic sign in the fetus with bilateral hydronephrosis. Further work is necessary to identify other factors that may be more reliable as prognostic indexes of fetal renal function.

Diffusion permeability of cyanocobalamin in human placenta.

The molecular weight of cyanocobalamin is well suited to distinguish the two patterns of size discrimination found in the hemochorial and epitheliochorial placentas. The concentrations of cyanocobalamin that were used ensured that nondiffusional transport was negligible, and experiments on guinea pigs confirmed that the diffusion permeabilities measured with cyanocobalamin were the same as those expected for inert hydrophilic substances of similar molecular weight. All human studies were performed on volunteers who were scheduled for elective cesarean section under spinal or epidural anesthesia. Endogenous plasma concentrations of cobalamin were measured in 10 pregnant volunteers and their newborns. Ten additional volunteers were given 1 mg of cyanocobalamin by intramuscular injection 44 min before delivery. Placental permeability, calculated as the ratio of fetal uptake and the concentration-time integral between maternal and fetal plasmas, was 14.3 microliter X min-1 X g placental wt-1. The permeability of the human placenta parallels that of the histologically similar guinea pig placenta, at a slightly higher level, up to molecular weights of 1,355.

External cephalic version: a clinical experience.

Eighty-five normal women underwent external cephalic version (ECV) for breech presentation in the late 3rd trimester. The protocol included real time ultrasonic scanning and pre- and post-procedure electronic fetal monitoring. Subcutaneous terbutaline sulfate (0.25 mg.) was administered to (43/85 or 50.5%) of ECV candidates and rendered the procedure easier for patient and operator. A single operator, head-over-heels technique assisted by supine Trendelenberg's position was used. Rh negative women were routinely administered 300 mcg of immune globulin. Successful ECV (53/85, 62.5%) was related to maternal parity, but not to gestational age nor eventual delivery weight. In this series only engagement of the breech was reliable in predicting ECV failure. Fifty of 51 (98.1%) successfully verted women delivered a cephalic presentation infant at term. Cesarean section was performed in 5/51 of these patients (9.8%) for routine obstetrical indications. In one case, compound presentation at term resulting in dystocia and eventual cesarean section was believed related to prior successful version. In contrast, 15/30 (50%) of the ECV failure patients went on to operative delivery despite a liberal institutional policy toward term vaginal breech trials. In addition, the only serious fetal complication in this series, meconium aspiration, occurred in a vaginally delivered breech infant. It is unlikely that late 3rd trimester ECV will impact on out overall rate of cesarean delivery. In North America prematurity is the greatest risk factor in malpresentation and our policy increasingly is to permit attempts at term breech vaginal delivery. Nonetheless, ECV deserves serious consideration. When successful, ECV avoids the costs and/or risks of either cesarean section or vaginal trial of breech.(ABSTRACT TRUNCATED AT 250 WORDS)

Fetal breathing movements and the response to carbon dioxide in patients on methadone maintenance.

Fetal breathing movements were monitored on six methadone maintenance patients and ten healthy control patients, studied while breathing room air and while breathing a prepared gas mixture with 5% carbon dioxide, both before and 2 hours after either the usual daily dose of methadone or a diet drink. There was no difference before and after the diet drink in control patients, who showed a significant increase in the incidence of fetal breathing movements from 37.1% +/- 5.9% (SEM) on room air to 69.4% +/- 2.8% while breathing 5% carbon dioxide (p less than 0.01). In the patients studied on room air before receiving methadone, fetal breathing movements were significantly decreased from those of the control group, 4.7% +/- 1.2% (p less than 0.01), with a further decrease when studied after receiving methadone, 1.3% +/- 0.7%. Fetal breathing movements did increase significantly in response to 5% carbon dioxide both before and after receiving methadone; however, in both instances the incidence was significantly less that that of the control group. The findings of the present study on methadone subjects demonstrate that abnormal function of the respiratory control network is evident in utero, which may be predictive of subsequent neonatal respiratory development.