Russell K. Laros

Guidelines for computed tomography and magnetic resonance imaging use during pregnancy and lactation

There has been a substantial increase in the use of computed tomography (CT) and magnetic resonance imaging (MRI) in pregnancy and lactation. Among some physicians and patients, however, there are misperceptions regarding risks, safety, and appropriate use of these modalities in pregnancy. We have developed a set of evidence-based guidelines for the use of CT, MRI, and contrast media during pregnancy for selected indications including suspected acute appendicitis, pulmonary embolism, renal colic, trauma, and cephalopelvic disproportion. Ultrasonography is the initial modality of choice for suspected appendicitis, but if the ultrasound examination is negative, MRI or CT can be obtained. Computed tomography should be the initial diagnostic imaging modality for suspected pulmonary embolism. Ultrasonography should be the initial study of choice for suspected renal colic. Ultrasonography can be the initial imaging evaluation for trauma, but CT should be performed if serious injury is suspected. Pelvimetry now is used rarely for suspected cephalopelvic disproportion, but when required, low-dose CT pelvimetry can be performed with minimal risk. Although iodinated contrast seems safe to use in pregnancy, intravenous gadolinium is contraindicated and should be used only when absolutely essential. It seems to be safe to continue breast-feeding immediately after receiving iodinated contrast or gadolinium. Although teratogenesis is not a major concern after exposure to prenatal diagnostic radiation, carcinogenesis is a potential risk. When used appropriately, CT and MRI can be valuable tools in imaging pregnant and lactating women; risks and benefits always should be considered and discussed with patients.

Risk factors for third-degree and fourth-degree perineal lacerations in forceps and vacuum deliveries

Third- and fourth-degree perineal lacerations occur frequently during operative vaginal deliveries. To identify risk factors for lacerations, 2832 consecutive forceps and vacuum extraction deliveries were analyzed. Third- and fourth-degree lacerations occurred in 30% of deliveries. Multiple logistic regression was used to control for intercorrelation between potential risk factors. Factors associated with increased risk for third- and fourth-degree lacerations were midline episiotomy, nulliparity, second-stage arrest, occipitoposterior position, low or mid station, use of forceps instead of vacuum, use of local anesthesia, and Asian race. When these factors were controlled, there was no effect of birth weight, faculty versus resident operator, gestational age, abnormalities of first-stage labor, or several other factors. Prevention of perineal lacerations requires that the operator identify the patient at risk. Possible options for management of high-risk patients include use of mediolateral episiotomy or no episiotomy, use of vacuum extraction instead of forceps, and use of conduction anesthesia.

Incidence of persistent birth injury in macrosomic infants: association with mode of delivery.

OBJECTIVE Our purpose was to determine the incidence of birth injury in a cohort of macrosomic infants (birth weight >4000 gm) and analyze the association between persistent injury and delivery method. STUDY DESIGN Deliveries of 2924 macrosomic infants were reviewed. Outcomes were compared with those of 16,711 infants with birth weights between 3000 and 3999 gm. RESULTS Macrosomic infants had a sixfold increase in significant injury relative to controls (relative risk 6.7,95% confidence interval 6.5 to 6.9). Risk of trauma correlated with delivery mode: forceps were associated with a fourfold risk of clinically persistent findings compared with spontaneous vaginal delivery or cesarean section. However, the overall incidence of persistent cases remained low (0.3%); a policy of elective cesarean section for macrosomia would necessitate 148 to 258 cesarean sections to prevent a single persistent injury. Avoidance of operative vaginal delivery would require 50 to 99 cesarean sections per injury prevented. CONCLUSIONS These findings support a trial of labor and judicious operative vaginal delivery for macrosomic infants.

Forceps compared with vacuum: Rates of neonatal and maternal morbidity

OBJECTIVE: To compare perinatal outcomes between forceps- and vacuum-assisted deliveries. Our hypothesis was that the force vectors achieved in forceps delivery will lead to fewer shoulder dystocias, but greater perineal lacerations. METHODS: This was a retrospective cohort study of 4,120 term, cephalic, singleton, nonrotational operative vaginal deliveries at a single institution. Outcomes examined included rates of neonatal trauma, shoulder dystocia, and perineal lacerations. Potential confounders, including maternal age, birthweight, ethnicity, parity, station at delivery, episiotomy, attending physician, anesthesia, and length of labor, were controlled for using multivariate logistic regression. RESULTS: Among the 2,075 (50.4%) forceps- and 2,045 (49.6%) vacuum-assisted deliveries, the rate of shoulder dystocia was lower among women undergoing forceps delivery (1.5% compared with 3.5%, P < .001), as was the rate of cephalohematoma (4.5% compared with 14.8%, P < .001), whereas the rate of third- or fourth-degree perineal laceration was higher (36.9% compared with 26.8%, P < .001). These differences in perinatal complications persisted when controlling for the confounders listed above. The adjusted odds ratio for shoulder dystocia was 0.34 (95% confidence interval [CI] 0.20–0.57), for cephalohematoma was 0.25 (95% CI 0.19–0.33), and for third- or fourth-degree lacerations was 1.79 (95% CI 1.52–2.10) when comparing forceps to vacuum. CONCLUSION: Vacuum-assisted vaginal birth is more often associated with shoulder dystocia and cephalohematoma. Forceps delivery is more often associated with third- and fourth-degree perineal lacerations. These differences in complications rates should be considered among other factors when determining the optimal mode of delivery. LEVEL OF EVIDENCE: II-2

Obstetric Complications With GDM: Effects of Maternal Weight

Obstetric complications recorded prospectively were assessed retrospectively in 150 women with gestational diabetes mellitus (GDM) and 305 control subjects matched for age, parity, and ethnicity. Intensive diet therapy and self-monitoring of capillary blood glucose were used to obtain postprandial euglycemia; 22% of GDM subjects required insulin. GDM and control subjects were grouped by body mass index to detect any influence of maternal prepregnancy weight on outcome. Polyhydramnios, preterm labor, and pyelonephritis were not more frequent in GDM, but hypertension without proteinuria (7.3 vs. 3.3%) and preeclampsia (8 vs. 3.9%) were more frequent in GDM. The frequency of hypertensive complications in GDM was not totally attributable to being overweight. Abnormalities of labor, birth trauma, and fetal macrosomia were not more common in GDM; 6.7% of the infants of mothers with GDM weighed >4200 g at birth compared with 3.6% of control infants (NS), and 10% were large for gestational age and sex compared with 6.6% of control infants (NS). Despite this, cesarean delivery was more common in GDM (35.3 vs. 22%, P < 0.01), mostly due to significantly more cesarean births without labor.

Supportive nurse-midwife care is associated with a reduced incidence of cesarean section

OBJECTIVE Our purpose was to examine whether care by a certified nurse-midwife, including personal labor support, was associated with a reduced risk of cesarean delivery. STUDY DESIGN A retrospective cohort study comparing 3551 physician-managed patients with 1056 certified nurse-midwife-managed patients in a university hospital with a mixed socioeconomic and ethnic population was performed. Regression analysis was used to estimate the risk of labor abnormalities, diagnosis of fetal distress, and cesarean delivery in patients delivered by a certified nurse-midwife vs a physician and to control for maternal age, race, parity, fetal size, and delivery year. Subjects included were women having at least five prenatal visits who were delivered of term, singleton, liveborn infants without congenital anomalies with occiput presentation. RESULTS Odds ratio for cesarean section for women delivered by certified nurse-midwives versus those delivered by physicians was 0.71 (95% confidence interval 0.55, 0.91). Midwifery care was associated with a lower risk of abnormal labor (adjusted odds ratio 0.70, 95% confidence interval 0.60, 0.83) and diagnosis of fetal distress (adjusted odds ratio 0.50, 95% confidence interval 0.32, 0.77). CONCLUSION This work demonstrates that labor abnormalities and diagnosis of fetal distress are less frequent in patients cared for by nurse-midwives, and there is an association with a lower incidence of cesarean section.

Oral ritodrine maintenance in the treatment of preterm labor

Seventy patients with preterm labor and intact membranes were initially treated with ritodrine hydrochloride to delay preterm delivery. Tocolysis beyond 24 hours was achieved in 59 patients. Fifty-five of the 59 patients were then placed on either oral ritodrine or placebo as maintenance therapy in a randomized double-blind manner. If preterm labor recurred, the sequence of intramuscular and then oral treatment was repeated. The number of days gained after initiation of intramuscular treatment was similar in both groups (oral ritodrine = 34 days, oral placebo = 36 days). In those 55 patients receiving oral treatment, there was a smaller number of relapses requiring repeat intramuscular treatment in the oral ritodrine group (1.11 in the ritodrine patient vs. 2.71 in the placebo patient, p less than 0.05), and the mean interval between beginning oral treatment and the first relapse/delivery was 5.8 days in the oral placebo group and 25.9 in those receiving oral ritodrine (p less than 0.05). Cardiovascular side effects, notably maternal tachycardia and palpitations were frequent but well tolerated. The results suggest that oral ritodrine maintenance will decrease the incidence of recurrent preterm labor in patients who have had initial successful tocolysis.

Management of term breech presentation

Abstract The management of 716 cases of singleton breech presentation occurring at 37 or more weeks of gestational age is reviewed. Beginning in 1980 a trial of external version was offered if the breech was identified before active labor. Only 433 (61%) breeches were identified before active labor. Of these, 171 (44%) underwent an attempt at external version and 83 (48%) were successful. The 623 cases remaining as breech presentation were stratified into three groups: (1) cesarean section without labor (379),(2) trial of labor with cesarean section (69), and (3) trial of labor with vaginal delivery (175). The criteria for allowing a trial of labor are detailed. Careful review of maternal and fetal variables indicates that a trial of labor in selected patients will result in vaginal delivery in 72% and that this can be achieved without an increase in fetal or maternal mortality or morbidity. Furthermore, successful external version followed by a trial of labor in selected cases is highly cost-effective.

A comparison of methods for quantitating fetal heart rate variability

Fetal heart rate (FHR) variability is thought to be an important index of fetal health. In the presence of normal variability, the fetus is vigorous, but lack of beat-to-beat variability may be associated with fetal compromise. A distinction between short-term variability (STV) (beat-to-beat changes between successive beats) and long-term variability (LTV) (rhythmic fluctuations in FHR) has not been made to date. We have utilized computer programs to compare three pairs of mathematical indices and one visual index of FHR variability. Among the three pairs of indices designed for detection of STV and LTV, de Haans short-term and long-term indices exhibited the least interdependence, and the long-term index was completely insensitive to artifically generated pure STV. Yehs short-term and long-term indices exhibited substantial positive interdependence. Hons visual index appears to detect LTV primarily rather than STV. When the effect of progression of labor on FHR variability was examined, no conclusions were possible because of inconsistencies between patients. Ultimately, the clinical value of any one of these indices awaits testing of their ability to define fetal well-being or fetal distress.

Management of twin pregnancy: The vaginal route is still safe

To investigate the effect of method of delivery on the outcome of twin pregnancies, we reviewed all deliveries at our institution over the 10 years from 1976 to 1985. Two hundred six pairs were delivered, with a mean gestational age of 34 weeks (range 20 to 43 weeks) and a mean weight of 2116 gm (range 220 to 3800 gm). The mean gestational age at diagnosis of the twin pregnancy was 23 weeks. Nineteen (4.6%) infants were stillborn, and 36 (8.7%) died in the neonatal period. Cesarean section was used to deliver both twins in 66 cases. The method of delivery for the remaining 142 cases was vaginal-vertex, 85 (61%), vaginal-breech, 40 (29%), cesarean section, 13 (9%), and version and extraction, 2 (1%). The four most common indications for cesarean section for both twins were previous cesarean section, breech presentation, abnormal labor, and fetal distress. The indications for the 13 cesarean sections after vaginal delivery of twin A were fetal distress, cord prolapse, high presenting part, and footling breech. The impact of the method of delivery was investigated by comparing outcome variables between twin pairs. No significant differences were noted for perinatal mortality, need for resuscitation, duration of newborn hospital stay, and trauma. There were significant differences in the 1- and 5-minute Apgar scores in the vaginal delivery group. These differences were clinically minor, tending toward mild acidemia, and were unaffected by route or method of delivery.