ACOG practice bulletin: Clinical management guidelines for obstetrician-gynecologists

Customised antenatal growth charts.

Objective. —To quantitate the potential effectiveness and monetary costs of a policy of elective cesarean delivery for fetal macrosomia diagnosed by ultrasound. Design. —A decision analytic model was constructed to compare 3 policies: (1) management without ultrasound; (2) ultrasound and elective cesarean delivery for estimated fetal weight of 4000 g or more (4000-g policy); and (3) ultrasound and elective cesarean delivery for estimated fetal weight of 4500 g or more (4500-g policy). The impact of maternal diabetes was analyzed separately. Probability data used in the decision analytic model were summarized from the literature and supplemented with unpublished data from the Collaborative Trial of Preterm Birth Prevention. Costs were estimated from the literature, regional reimbursements, and clinical practice data. Main Outcome Measures. —Rates of shoulder dystocia and permanent brachial plexus injury, and both the number of additional cesarean births and monetary costs per permanent brachial plexus injury averted. Results. —In the baseline analysis for nondiabetic women, the ultrasound policies increased both the cesarean delivery rate and costs, while decreasing the rate of shoulder dystocia and brachial plexus injury. For each permanent brachial plexus injury prevented by the 4500-g policy, 3695 cesarean deliveries were performed at an additional cost of $8.7 million, vs 2345 cesarean deliveries and $4.9 million with the 4000-g policy. In the baseline analysis for diabetic women, with all 3 policies, rates of cesarean delivery, shoulder dystocia and brachial plexus injury, and total costs were higher than for nondiabetic women. However, more favorable ratios for both cesarean deliveries and cost per permanent injury avoided were observed: 443 deliveries and $930 000, respectively, with the 4500-g policy, and 489 deliveries and $880 000, respectively, with the 4000-g policy. Sensitivity analysis confirmed the general robustness of these findings. Conclusions. —For the 97% of pregnant women who are not diabetic, a policy of elective cesarean delivery for ultrasonographically diagnosed fetal macrosomia is medically and economically unsound. In pregnancies complicated by diabetes, such a policy appears to be more tenable, although the merits of such an approach are debatable.

https://jamanetwork.com/HttpHandlers/ArticlePdfHandler.ashx?journal=jama&articleId=410522&pdfFileName=jama_276_18_030.pdf

The Effectiveness and Costs of Elective Cesarean Delivery for Fetal Macrosomia Diagnosed by Ultrasound

Copyright © 2009 Massachusetts Medical Society. A healthy 29-year-old woman who has been trying to conceive presents with vaginal spotting for the past 5 days and intermittent crampy abdominal pain in her left lower quadrant for the past 3 days. Although she normally has regular menstrual cycles, her last menstrual period was 6 weeks and 2 days before presentation. She has had a spontaneous vaginal delivery and an anembryonic gestation treated by dilation and curettage. How should this patient be evaluated and treated?

Clinical practice. Ectopic pregnancy.

Acute myocardial infarction associated with pregnancy.

Conceptual age and ultrasound measurements of gestational sac and crown-rump length in in vitro fertilization pregnancies.

In this investigation the weight estimation procedure of Rossavik was reassessed with particular emphasis on parameter estimation and performance over a wide weight range. Using a cross-sectional data set (193 patients), a longitudinal data set (20 patients), and an iterative procedure, parameter estimates were obtained based solely on regression analysis. Comparison of weight estimates obtained using a function based on these parameter values with actual birth weights indicated virtually no systematic errors over a 250-g to 4750-g weight range and random errors (+/- 1 SD) of 10% to 13% below 200 g and 6% to 8% above 2000 g. The weights of small- and large-for-gestational age fetuses were systematically overestimated (4.1%) and underestimated (-3.0%), respectively, but systematic errors were not found in average-for-gestational age fetuses. No differences in random errors were seen in these three growth categories. Comparison with other weight estimation procedures indicated that the Rossavik procedure gives weight estimates that are at least as accurate as those obtained with other methods over a wide range of weight and growth categories. However, the Rossavik procedure can be used to generate individual growth curve standards for weight estimates, a characteristic not shared with other weight estimation procedures.

Development of individual growth curve standards for estimated fetal weight. I: Weight estimation procedure

Using a weight estimation procedure based of the Rossavik growth model, we have evaluated the possibility of establishing individual growth curve standards for fetal weight estimates and of predicting birth weights in the second trimester. In 20 normal fetuses delivered at term, 95% of the weight estimates obtained after 26 weeks' menstrual age (MA) were within +/- 22% of the predicted weight estimates. In these same fetuses the mean difference between birth weight estimates based on growth patterns before 26 weeks, MA, and actual birth weights was 1.2%, with 95% of the percent deviations being between 13.3% and - 8.8%. In a similar prospective study, the mean percent difference was -1.7%, with a range of 9.6% to -13.6%. Direct comparison of weight estimates obtained during the last week before delivery with birth weight projections indicated that birth weight estimates obtained 14 weeks before delivery had smaller systematic and random errors than those obtained within a week of delivery. These results indicate that individual growth curve standards for fetal weight estimates and the growth potential of individual fetuses can be determined from growth patterns in the second trimester.

Development of individual growth standards for estimated fetal weight: II. Weight prediction during the third trimester and at birth.

It has been claimed that sonographic techniques offer no advantages over palpation of the maternal abdomen for detection of macrosomatia. We studied a group of 498 pregnant patients, 36 (7.2%) of whom gave birth to infants having macrosomatia. A sensitivity of 67%, specificity of 97%, and positive predictive value of 67% was obtained using our method without significant systematic error. Three problems that could reduce the value of ultrasonography in the detection of macrosomatia were detected: (1) use of equations with systematic errors; (2) human bias; and (3) use of ultrasonography machines/transducers with insufficient capacity.

Ivar K. Rossavik

Papers

Conceptual age and ultrasound measurements of gestational sac and crown-rump length in in vitro fertilization pregnancies.

Development of individual growth curve standards for estimated fetal weight. I: Weight estimation procedure

Development of individual growth standards for estimated fetal weight: II. Weight prediction during the third trimester and at birth.

Macrosomatia and Ultrasonography: What Is the Problem?

Effects of amrinone and dopamine on uterine blood flow and vascular responses in the gravid baboon.