Influence of gestational age and fetal heart rate on the fetal mechanical PR interval.

OBJECTIVE: The fetal mechanical PR interval obtained via pulsed Doppler has previously been demonstrated to correlate with electrocardiographic PR interval measured in the neonate. We sought to further analyze the influence of fetal heart rate and gestational age upon the fetal mechanical PR interval. METHODS: We searched our database for mechanical PR intervals, which were obtained during fetal echocardiography performed in our antenatal diagnostic unit. We included fetuses with a normal cardiac structural survey. The mechanical PR interval is measured from the A wave of the mitral valve to the beginning of ventricular systole corresponding to the opening of the aortic valve. Linear regression curves were generated to examine the correlation of mechanical PR interval with gestational age and fetal heart rate. Analysis of variance was used to compare the mean variation across three gestational age groups: 17-21.9 weeks (n = 24), 22-25.9 weeks (n = 52) and 26-38 weeks (n = 20). RESULTS: Mechanical PR intervals were measured in 96 fetuses with normal fetal echocardiography. The mechanical PR interval was 123.9 +/- 10.3 ms (mean +/- SD), with a range of 90-150 ms. Linear regression curves correlating mechanical PR interval with fetal heart rate and gestational age demonstrated a flat slope with R2 = 0.016, p = 0.22 and R2 = 0.0004, p = 0.85, respectively. The mechanical PR interval measured over the three gestational ages was as follows (mean +/- SD): 122.3 +/- 10.5 ms for 17-21.9 weeks; 125.0 +/- 9.6 ms for 22-25.9 weeks; and 123.1 +/- 11.9 ms for 26-38 weeks. Analysis of variance revealed no difference among the mechanical PR interval means measured over the three gestational age groups (p = 0.53). CONCLUSIONS: Fetal mechanical PR interval ranges from 90 to 150 ms in fetuses with sonographically normal fetal cardiac structure and rate. The mechanical PR interval appears to be independent of gestational age and fetal heart rate.

Maternal and neonatal morbidity after elective repeat Cesarean delivery versus a trial of labor after previous Cesarean delivery in a community teaching hospital.

OBJECTIVE: To compare maternal and fetal outcomes after elective repeat Cesarean section versus a trial of labor in women after one prior uterine scar. STUDY DESIGN: All women with a previous single low transverse Cesarean section delivered at term with no contraindications to vaginal delivery were retrospectively identified in our database from January 1995 to October 1998. Outcomes were first analyzed by comparing mother-neonate dyads delivered by elective repeat Cesarean section to those undergoing a trial of labor. Secondarily, outcomes of mother-neonatal dyads who achieved a vaginal delivery or failed a trial of labor were compared to those who had elective repeat Cesarean delivery. RESULTS: Of 1408 deliveries, 749/927 (81%) had a successful vaginal birth after a prior Cesarean delivery. There were no differences in the rates of transfusion, infection, uterine rupture and operative injury when comparing trial of labor versus elective repeat Cesarean delivery. Neonates delivered by elective repeat Cesarean delivery were of earlier gestation and had higher rates of respiratory complications (p < 0.05). Mother-neonatal dyads with a failed trial of labor sustained the greatest risk of complications. CONCLUSION: Overall, neonatal and maternal outcomes compared favorably among women undergoing a trial of labor versus elective repeat Cesarean delivery. The majority of morbidity was associated with a failed trial of labor. Better selection of women likely to have a successful vaginal birth after a prior Cesarean delivery would be expected to decrease the risks of trial of labor.

Cost analysis of Down syndrome screening in advanced maternal age.

OBJECTIVE: To analyze the potential cost and efficacy of Down syndrome screening in the population with advanced maternal age. METHODS: Three screening methods defining Down syndrome risk for women with advanced maternal age were analyzed: advanced maternal age; advanced maternal age and maternal serum triple screen; and advanced maternal age, maternal serum triple screen and genetic sonogram. Costs for all tests and procedures were estimated. Procedure-related loss for amniocentesis was assumed to be 1:200. Efficacy was defined as: number of amniocenteses performed, number of Down syndrome cases detected, procedure-related losses, Down syndrome cases detected per fetal loss, cost per Down syndrome case detected and total cost of screening. RESULTS: In 1999 in the USA, there were 530,610 women with advanced maternal age at 16 weeks' gestation carrying an estimated 4,043 fetuses with Down syndrome. Screening by maternal age alone would result in the 100% detection of Down syndrome cases, but would require over 530,000 amniocenteses and result in 2,653 procedure-related losses. Combining age with serum screen and genetic sonogram would detect 97.6% of Down syndrome cases, but would require only 119,791 amniocenteses and result in 599 procedure-related losses. The projected cost per Down syndrome case detected using age screening is 219,109 dollars versus 155,992 dollars using serum screen and genetic sonogram. CONCLUSIONS: The combination of advanced maternal age, maternal serum screen and genetic sonogram would result in the fewest procedure-related losses and lowest cost per Down syndrome case detected.

Extreme second-trimester serum analyte values in down syndrome pregnancies with hydrops fetalis.

OBJECTIVE: To compare second-trimester maternal serum analyte values in Down syndrome pregnancies with, and without, hydrops fetalis. METHODS: Seven hydropic and 85 non-hydropic Down syndrome pregnancies were identified among women with positive second-trimester maternal serum screening results. Values for maternal serum alpha-fetoprotein (MSAFP), human chorionic gonadotropin (hCG), unconjugated estriol and inhibin-A, and risks for Down syndrome were compared using the non-parametric Mann-Whitney statistical test. RESULTS: Hydropic Down syndrome pregnancies had significantly lower MSAFP and estriol concentrations, while hCG levels were higher. For subgroups of five hydropic and 42 non-hydropic cases, no statistically significant difference in the inhibin-A levels could be demonstrated. CONCLUSION: Second-trimester Down syndrome screening risks are significantly higher in affected pregnancies that are complicated by fetal hydrops.