Fetal arterial and venous Doppler parameters in the interpretation of oligohydramnios in postterm pregnancies.

OBJECTIVE: The objective of the current study was to evaluate fetal arterial and venous Doppler parameters in postterm pregnancies with oligohydramnios and those with normal amniotic fluid. STUDY DESIGN: A cross-sectional study was performed in 38 pregnancies beyond 41 weeks' gestation. Pulsed Doppler imaging was used to determine the pulsatility index (PI) for the fetal middle cerebral artery (MCA), renal artery, umbilical artery, inferior vena cava (IVC) and ductus venosus. The amniotic fluid index (AFI) was used for semiquantitive assessment of amniotic fluid volume. Oligohydramnios was defined as an AFI < 5 cm. RESULTS: Oligohydramnios was detected in 10 cases, and a normal AFI was present in 28 cases. In the presence of oligohydramnios the PI of the MCA was decreased, while the renal artery PI and the MCA PI/UA PI ratio were found to be elevated. In cases of oligohydramnios the PI in the IVC was increased but was unchanged in the ductus venosus. CONCLUSION: Oligohydramnios in post-term pregnancies is associated with arterial redistribution of fetal blood flow typifying the brain sparing effect and with decreased resistance in the MCA and increased resistance in the fetal IVC.     

Prediction of fetal anemia in rhesus disease by measurement of fetal middle cerebral artery peak systolic velocity.

OBJECTIVE: In red blood cell (RBC) isoimmunized pregnancies fetal anemia is associated with a hyperdynamic circulation. The aim of the present study was to examine further the possible value of fetal middle cerebral artery peak systolic velocity (MCA-PSV) in the management of affected pregnancies. METHODS: A reference range of fetal MCA-PSV with gestation was constructed from the study of 813 normal singleton pregnancies at 20-40 weeks' gestation. Fetal MCA-PSV was also measured in 58 fetuses from RBC isoimmunized pregnancies, with maternal hemolytic antibody concentration of >15 IU/mL at 19-38 weeks' gestation and within 10 days of measurement of fetal hemoglobin concentration in blood obtained either by cordocentesis (n = 43) or at delivery (n = 15). In the RBC isoimmunized pregnancies each of the measured MCA-PSV and hemoglobin concentrations was expressed as a delta value (difference in SDs from the normal mean for gestation). Regression analysis was used to determine the significance of the association between delta MCA-PSV and delta fetal hemoglobin concentration. RESULTS: In the normal pregnancies there was a significant increase in fetal MCA-PSV with gestation (mean MCA-PSV = 10(0.0223 x GA + 0.963)). In RBC isoimmunized pregnancies the fetal MCA-PSV was increased and there was a significant association between delta MCA-PSV and delta hemoglobin concentration (delta hemoglobin = (delta MCA-PSV + 0.093)/-0.356; R(2) = 0.638, P < 0.0001). An MCA-PSV of mean + 1.5 SDs detected 96% of severely anemic fetuses, with a hemoglobin deficit of at least 6 SDs, for a false-positive rate of 14%. CONCLUSION: Measurement of fetal MCA-PSV is a useful method of assessing fetal anemia. In the clinical management of isoimmunized pregnancies a cut-off in MCA-PSV of mean + 1.5 SDs can identify nearly all severely anemic fetuses with a low false-positive rate.     

High perinatal survival in monoamniotic twins managed by prophylactic sulindac, intensive ultrasound surveillance, and Cesarean delivery at 32 weeks' gestation.

OBJECTIVES: Increased perinatal mortality in monoamniotic twin pregnancies is attributed to cord accidents in utero and at delivery. We evaluated the following parameters in monoamniotic pregnancies: (1) the incidence of cord entanglement; (2) the effect of sulindac on amniotic fluid volume and stability of fetal lie; and (3) the perinatal outcome with our current management paradigm. METHODS: This is a retrospective review of monoamniotic pregnancies of >or=20 weeks' gestation managed with serial ultrasound surveillance, medical amnioreduction and elective Cesarean delivery at 32 weeks' gestation. Mean amniotic fluid index (AFI) and change in AFI in monoamniotic pregnancies managed with oral sulindac was compared with 40 gestation-matched monochorionic-diamniotic controls. RESULTS: Among 44 monoamniotic pregnancies, 20 with two live structurally normal twins at 20 weeks' gestation satisfied the inclusion criteria. All fetuses survived to 28 days postnatally despite early prenatal cord entanglement in all but one case. Whereas AFI remained stable throughout gestation in the controls, the AFI fell in those patients on sulindac from a mean value of 21.0 cm (95% CI, 18.5-23.6 cm) at 20 weeks to a mean of 12.4 cm (95% CI, 10.1-14.6 cm) at 32 weeks (ANOVA P across gestation = 0.001) but mainly remained within normal limits. Fetal lie was stabilized in 11/20 cases in the monoamniotic group compared with 13/40 in the control group (P < 0.0001). CONCLUSIONS: Cord entanglement appears unpreventable, as it typically occurs in early pregnancy. Sulindac therapy reduces AFI, leads to more stable fetal lie, and may prevent intrauterine death by diminishing the risk of constricting cords that are already entangled. Perinatal survival in monoamniotic pregnancies managed by a regime of sulindac from 20 weeks' gestation, close ultrasound surveillance and elective abdominal delivery at 32 weeks' gestation seems empirically higher than that in the literature.     

Fetal loss following ultrasound diagnosis of a live fetus at 6-10 weeks of gestation.

OBJECTIVE: To examine prospectively the value of demographic characteristics and ultrasound findings in the prediction of subsequent fetal loss in pregnancies with live fetuses at 6-10 weeks of gestation. METHODS: Transvaginal ultrasound examination was performed in 866 pregnancies at 6-10 weeks of gestation. The relation of demographic data and ultrasound findings at the time of the initial assessment to subsequent fetal loss was examined. RESULTS: In the 668 singleton pregnancies with live fetuses and complete follow-up there were 50 (7.5%) fetal losses. The incidence of fetal loss increased significantly with maternal age and decreased with gestation. In the pregnancies resulting in fetal loss, compared to those with live births, the incidence of vaginal bleeding and cigarette smoking was higher, the fetal heart rate was significantly lower and the gestation sac diameter was smaller but the yolk sac diameter was not significantly different. CONCLUSION: In pregnancies with a live fetus at 6-10 weeks' gestation the rate of subsequent fetal loss is related to maternal age, gestation, cigarette smoking, history of vaginal bleeding and the ultrasound findings of small gestation sac diameter and fetal bradycardia, relative to crown-rump length.     

First trimester diagnosis of monoamniotic twin pregnancies.

This study reports the ultrasound findings and pregnancy outcome for a series of monoamniotic twin pregnancies diagnosed at 11-14 weeks' gestation. Of 315 monochorionic twin pregnancies examined, there were 12 (3.8%) monoamniotic, including four sets of conjoined twins (1.3%). The parents opted for termination of pregnancy in all cases of conjoined twins. In four other cases, there was discordancy for major structural fetal abnormality (kyphoscoliosis, anencephaly, body stalk defect, diaphragmatic hernia), and the cotwin was structurally normal. In the four cases in which both twins were structurally normal, ultrasound examination demonstrated normal nuchal translucency thickness in all cases but cord entanglement was demonstrated from the first trimester. Two cases were managed expectantly; one resulted in livebirth of both twins at 31 weeks' gestation and the second in intrauterine death of both fetuses at 21 weeks. Two pregnancies were treated with Sulindac; one resulted in a single intrauterine death at 30 weeks and delivery of a normal cotwin, the other, in intrauterine death of both fetuses at 31 weeks'. Monoamniotic twin pregnancies are associated with a high risk of fetal abnormalities and perinatal death and the mortality rate is higher than previously reported from series with recruitment later in gestation.     

Prediction of preterm birth by second trimester cervical sonography in twin pregnancies.

OBJECTIVES: To determine the predictive value of sonographic cervical length and of funneling for spontaneous preterm delivery (PTD) in twin pregnancies under 26 weeks' gestation. METHODS: Women with twin pregnancies were studied prospectively with transvaginal or translabial ultrasound of the cervix from 18 to 26 weeks' gestation. Exclusion criteria were: signs of preterm labor, prophylactic cervical cerclage, placenta previa, or severe congenital fetal anomaly. The primary outcome was spontaneous preterm birth at < 35 weeks' gestation. RESULTS: Sixty-five twin pregnancies were analyzed, of which 23% (15/65) delivered preterm. Cervical ultrasound examination was performed by 22 weeks' gestation in 75% and by 24 weeks' gestation in 91% of women. Cervical length < or = 25 mm and < or = 30 mm was associated with sensitivities of 27% and 53%, respectively, and with 67% and 62% rates of PTD, respectively (R.R. 4.6, C.I. 2.0-10.3 and R.R. 3.6, C.I. 1.6-7.8, respectively). A cervical length > 35 mm was associated with only a 4% rate of PTD (R.R 0.13; C.I. 0.02-0.93). Of 10 women (15%) with any cervical funneling, 70% delivered preterm, all under 32 weeks' gestation. By logistic regression analysis, both short cervix < or = 30 mm and any funneling were strongly predictive of PTD. CONCLUSIONS: Both cervical length < or = 30 mm and cervical funneling in twin pregnancies under 26 weeks' gestation are independently and strongly associated with high risk for preterm birth. A long cervix, of length > 35 mm, is associated with very low risk (4%) for preterm birth.     

Failures of intravenous Rh immune globulin prophylaxis: an analysis of the reasons for such failures

Universal administration of an ion exchange column prepared Rh immune globulin (RhIG-IV) antepartum at 28 weeks' gestation and postpartum to 9,295 Rh negative women delivering Rh positive babies has reduced the prevalence of Rh immunization from the expected 601 to 25 (a protection rate of 95.9%). Rh immunization, despite universal Rh prophylaxis, developed in 25 women; eight before antenatal prophylaxis was administered, 17 after antenatal prophylaxis was administered. Residual Rh immunization is caused by small fetal transplacental hemorrhages (TPH) (greater than or equal to 0.01 mL of fetal blood) before antenatal prophylaxis (15%) and by significant fetal TPH (greater than or equal to 0.05 mL of fetal blood) between 30 and 38 weeks' gestation (18%); TPH was too great, in some instances, for residual passive Rh antibody to give protection. Although a reduction of 62% (five of eight) of early Rh immunization and 82% (14 of 17) of later Rh immunization might be achieved by addition of 16 weeks' to 20 weeks' gestation and 34 weeks' gestation Rh prophylaxis; and a reduction of 84% overall (21 of 25) might be achieved by universal fetal TPH screening every 2 weeks from 10 weeks' gestation until delivery, with administration of RhIG when a small early fetal TPH or a significant later fetal TPH is detected, all of these programs are costly in terms of prevention of perinatal mortality and in terms of cost per quality adjusted life year gained. We believe that the costs outweigh the benefit that would be achieved. Therefore, a residual Rh immunization prevalence of 0.24% to 0.31% during or after each Rh positive pregnancy in patients at risk is to be expected despite universal 28 weeks' gestation antenatal and postnatal Rh prophylaxis.     

孕妇外周血中胎儿有核红细胞数量与胎儿窘迫的关系

目的:探讨孕妇外周血中胎儿有核红细胞(nucleatedredbloodcells,NRBC)数与胎儿窘迫的关系。方法:对54名孕龄32～42周,年龄19～35岁(包括19名急性胎儿窘迫,15名慢性胎儿窘迫)的孕妇外周血进行不连续密度梯度离心,对分离后的细胞进行制片、染色,显微镜下进行NRBC计数,比较组间差异。结果:15名慢性胎儿窘迫孕妇外周血中NRBC数目为(23.26±6.75)个/7mL;同孕龄正常妊娠妇女外周血中NRBC数目为(9.43±4.01)个/7mL,两者间差异有显著性(P<0.05)。19名急性胎儿窘迫孕妇外周血中NRBC数目为(10.87±4.29)个/7mL,与正常妊娠间差异无显著性(P>0.05)。结论:慢性胎儿窘迫孕妇外周血中NRBC数目明显升高,为胎儿窘迫的临床预测和评估提供了一条新思路。     

Fetal lung development in pregnancies of diabetic women assessed by quantitative ultrasonic tissue characterization.

OBJECTIVES: This study was performed to compare quantitative ultrasonic tissue characterization of the fetal lung at different gestational ages in uncontrolled diabetic patients with that in normal uncomplicated pregnancies. METHODS: A total of 44 women at 24-37 weeks' gestation with the diagnosis of diabetes in pregnancy were enrolled. Data were compared to those of the control group, which consisted of 140 women with uncomplicated pregnancies of the same gestational age. Longitudinal and transverse sections of the fetal thorax and upper abdomen were examined. A region of interest of constant size was defined and the tissue-specific gray scale was determined by using interactive software. RESULTS: Compared with normal pregnancies, fetal lungs of diabetic pregnancies have a higher echogenicity between 28 and 37 weeks of gestation. The lung mean gray values (MGV) only differed significantly between 30 and 31 weeks of gestation in the group with diabetes (P = 0.033) compared to the control group. The MGV of the liver in diabetic and normal pregnancies is similar during pregnancy, significant differences being found only at 30-31 weeks of gestation (P = 0.038). The lung-to-liver ratio in the control group showed a significant increase from 24 to 31 weeks and a slight non-significant decrease after 31 weeks. The ratio in the group with diabetes increased slightly up to week 33 and decreased slightly afterwards. CONCLUSION: Fetal lung MGV in uncontrolled diabetic pregnancies compared to that in uncomplicated pregnancies differs significantly only between 30 and 31 weeks of gestation.     

The role of transvaginal sonography in the early detection of congenital heart disease.

The antenatal diagnosis of congenital heart disease by fetal echocardiography is rarely achieved before 18-20 weeks' gestation. Transvaginal sonography allows examination of fetal anatomy at earlier gestations than the transabdominal approach. In a screening study of 270 low-risk women between 8 and 14 weeks' gestation using a 5 MHz vaginal transducer, it was possible to obtain adequate four-chamber views in over 70% from 12 weeks. In a second study of 32 women at high risk of congenital heart disease scanned between 14 and 15 weeks' gestation, satisfactory views were obtained transvaginally in 21 women. Seven of the remainder had normal cardiac anatomy confirmed by transabdominal scanning. In three of the four where normal cardiac anatomy could not be demonstrated by either transvaginal or transabdominal scanning, severe congenital heart disease was diagnosed and later confirmed.It is unlikely that transvaginal sonography will replace abdominal scanning for the screening of low-risk pregnancies, but it is a valuable addition to the early examination of those women identified as being at high risk of congenital heart disease.     

Unusual amniotic fluid spectral analysis in Rh sensitization.

In our experience delta 450 millimicron OD measurements have shown a progressive decline during the latter half of gestation in pregnancies unaffected by fetal hemolytic disease. However, we have seen two Rh-negative patients in whom there was a rise in delta 450 millimicron OD between 24 and 27 weeks' gestation and who subsequently bore Rh-negative infants. In these two cases the increase between 24 and 27 weeks was from approximately 0.140 to about 0.200. Both infants were unaffected with fetal hemolytic disease. Therefore, we recommend caution in interpreting modest increases in delta 450 millimicron OD during this period of gestation.     

Chorionicity determination in twin pregnancies: how accurate are we?

OBJECTIVES: To determine the accuracy of antenatal prediction of chorionicity in twin pregnancies in our institution. METHODS: Antenatal chorionicity was determined using the number of placental masses, the presence or absence of a twin peak sign and the fetal sex. The gestational age at assessment was documented. Postnatal diagnosis of chorionicity was determined by neonatal sex and placental pathology. RESULTS: Chorionicity was correctly determined in 95% of cases (n = 131); 91% of the monochorionic and 96% of the dichorionic pregnancies were correctly determined. If chorionicity was assessed prior to 14 weeks' gestation (n = 96) the correct diagnosis was made in all except one case. CONCLUSIONS: Ultrasound assessment of chorionicity has a high sensitivity and specificity. This is further improved if the assessment is performed prior to 14 weeks' gestation.     

Relationship of isolated fetal intracardiac echogenic focus to trisomy 21 at the mid-trimester sonogram in women younger than 35 years.

OBJECTIVE: To determine whether an isolated echogenic intracardiac focus in the fetal heart in the mid-trimester (16-24 weeks) in women aged 18-34 years of age is associated with trisomy 21. METHOD: This was a prospective population-based observational study. A search of all obstetric sonograms performed in our region from January 1997 to December 1999 was carried out. From 12,373 pregnancies we identified 267 cases of echogenic foci in the fetal heart. Trisomy 21 was detected in 38 deliveries (0.31%). An echogenic focus was seen in 193 of the 9167 women < 35 years of age who had an obstetric sonogram at 16-24 weeks' gestation, and an echogenic focus was seen in 67 of the 1968 women > 35 years. The study group comprised the 149 women aged 18-34 years who had an echogenic focus in the fetal heart as the only abnormality at an obstetric sonogram performed at 16-24 weeks' gestation. RESULTS: There were no abnormal outcomes or cases of trisomy 21 among the 149 pregnancies with an echogenic focus as an isolated finding in women aged 18-34 years (0% (95% confidence interval, 0.00-2.43)). The prevalence of isolated echogenic focus was 1.6% for women < 35 and 1.8% for women >or= 35 years old. Of the 25 fetuses with trisomy 21 undergoing an obstetric sonogram at any gestational age, five (20%) had an echogenic focus. An isolated echogenic focus was present in one fetus with trisomy 21 seen at 26 weeks' gestation in a 17-year-old mother. Echogenic foci were single and in the left ventricle in 84.7% of cases. CONCLUSION: An isolated echogenic focus in the fetal heart at mid-trimester ultrasound in women aged 18-34 years is not associated with increased risk for trisomy 21.     

Fetal outcome in pregnancies defined as post-term according to the last menstrual period estimate, but not according to the ultrasound estimate.

OBJECTIVE: To study the risk of adverse fetal outcome in fetuses that were post-term according to the last menstrual period estimate but not according to the ultrasound estimate. DESIGN: A total of 11,510 women with singleton pregnancies, reliable last menstrual period and delivery after 37 weeks were divided into four groups: women who delivered at term, i.e. within 259-295 days according to both the ultrasound and the last menstrual period estimate; women who delivered post-term according to the last menstrual period estimate but not according to the ultrasound estimate; women who delivered post-term according to the ultrasound estimate but not according to the last menstrual period estimate; and women who delivered post-term according to both the ultrasound and the last menstrual period estimates. Stepwise logistic regression was used to test whether the risk of Apgar score of < 7 after 5 min and transfer to the neonatal intensive care unit increased in any of the post-term groups. RESULTS: There was no significant difference in mortality between the term group and the three study groups. There was no significant increase in the risk for Apgar score of < 7 after 5 min or transfer to the neonatal intensive care unit for pregnancies that were defined as post-term according to the last menstrual period estimate but not according to the ultrasound estimate. There was, however, an increased risk for Apgar score of < 7 after 5 min in the group that was post-term according to the ultrasound estimate but not according to the last menstrual period estimate. There was also an increased risk for transfer to the neonatal intensive care unit in the group that was post-term according to both estimates. CONCLUSION: The effect of ultrasound in changing the estimated day of delivery to a later date leading to pregnancies becoming post-term according to the last menstrual period estimate but not according to the ultrasound estimate does not have any adverse consequences for the fetal outcome. However, there seems to be an increased risk for adverse consequences for pregnancies that are post-term according to the ultrasound estimate.     

Time domain measurement of blood flow in the human fetal aorta during normal pregnancy.

OBJECTIVE: To evaluate blood-volume flow-rate measurement in the fetal descending thoracic aorta using a non-invasive, non-Doppler, ultrasound technique. METHODS: This was a cross-sectional, observational study. Volume flow measurements were obtained from the descending thoracic aorta in 59 human fetuses between 20 and 40 weeks' gestation. These were uncomplicated pregnancies that resulted in the live births of appropriately grown infants. The measurements were obtained using a time domain processing technique: color velocity imaging quantification (CVI-Q). RESULTS: The blood-volume flow rate increased consistently from the second trimester until term. The mean values ranged between 100 mL/min at 20 weeks' gestation and approximately 350 mL/min at term. The normalized (weight-adjusted) volume flow rates decreased with increasing gestation, from a maximum of 626 mL/min/kg at 23 weeks to a minimum of 45.6 mL/min/kg at 37 weeks. CONCLUSIONS: The regular measurement of blood-volume flow in the descending fetal thoracic aorta is feasible using CVI-Q. Although there is a considerable learning curve, with adequate training there are potential clinical applications for this non-Doppler technique. However, limitations exist with the currently available technology for clinical use in fetal vascular studies.     

Sonographic detection of undescended testes in the third trimester.

OBJECTIVE: To assess the sonographic detection rate of fetal undescended testes among a low-risk population during the third trimester. METHODS: A sonographic evaluation, which included biometric studies and a detailed examination of the fetal genitalia, was performed prospectively on 332 male fetuses of singleton pregnancies between 34 and 40 weeks' gestation. A qualified neonatologist examined the presence of the testes within the scrotum within 3 days after birth. RESULTS: The scrotum was visible in 294 (89%) of the 332 fetuses who were examined. It was visible in all fetuses evaluated between 34 and 36 weeks' gestation. Nine cases of undescended testes were detected (3%). Of these, the diagnosis of 1 case, examined at 34 weeks' gestation, was revealed after birth to be false-positive. There were no false-negative results. CONCLUSIONS: Sonographic examination during the late third trimester of pregnancy appears to allow accurate diagnosis of undescended testes prenatally. This early identification will alert the neonatologist of the possibility of cryptorchidism and will permit early postnatal identification and treatment.     

Ultrasound examination at 37 weeks' gestation in the prediction of pregnancy outcome: the value of cervical assessment.

OBJECTIVE: To examine the potential value of routine measurement of cervical length in singleton low-risk pregnancies at 37 weeks of gestation in the prediction of onset and outcome of labor. METHODS: Cervical length was measured by transvaginal sonography at 37 weeks in 1571 singleton low-risk pregnancies. Outcome measures were gestation at spontaneous onset of labor, post-term delivery, duration of labor and mode of delivery. RESULTS: The median cervical length at 37 weeks was 30 mm and there was a significant association between cervical length and gestation at delivery, which increased from a mean of 38 weeks for cervical length of 10 mm to 41 weeks for cervical length of 35 mm. The incidence of delivery after 40 weeks and 10 days was 296 (18.8%) and the incidence increased with cervical length at 37 weeks from 0% to 6%, 35% and 68% for respective cervical lengths of < 20, 21-30, 31-40 and 41-50 mm. In the pregnancies with spontaneous onset of labor the incidence of Cesarean section for failure to progress increased from 3.6% to 6.0%, 6.4% and 11.8% for cervical lengths of < 20, 21-30, 31-40 and 41-50 mm, respectively. In the pregnancies requiring induction for post-term the incidence of Cesarean section for failed induction or failure to progress increased from 7.5% to 20.1% to 25.0% for cervical lengths of 21-30, 31-40 and 41-50 mm, respectively. CONCLUSION: Measurement of cervical length at 37 weeks can define the likelihood of spontaneous delivery before 40 weeks and 10 days and the risk of Cesarean section in those requiring induction for prolonged pregnancy.     

Outcome of pregnancies after non-amniocentesis-induced premature rupture of membranes at 14 to 23 weeks' gestation

OBJECTIVE: To evaluate the outcome of singleton pregnancies after non-amniocentesis-induced premature rupture of membranes (PROM) at 14 to 23 weeks' gestation. STUDY DESIGN: We reviewed the hospital records of 53 consecutive pregnant women with PROM at 14 to 23 weeks' gestation at our institution from 1991 to 1996; the pregnancies were not associated with amniocentesis or multiple gestation. RESULTS: The median interval between PROM and delivery was 1 day (range 0-90; mean 5.2 days). Fifty-two (98%) of the 53 neonates were stillborn or died within 4 days. One neonate (2%), a 720-gram male delivered vaginally at 23 weeks' gestation, survived. The infant had Apgar scores of 6 at 1 minute and 2 at 5 minutes, and showed normal physical and neurological development at age 5 months. CONCLUSION: The outcome of pregnancies with non-amniocentesis-induced PROM at 14 to 23 weeks' gestation is almost uniformly poor.     

Determination of gestational age after the 24th week of gestation from fetal kidney length measurements.

OBJECTIVE: To evaluate the application of kidney length measurement to the determination of gestational age between the 24th and 38th weeks and to compare its accuracy with that of other fetal biometric indices. STUDY DESIGN: Seventy-three women with singleton uncomplicated pregnancies underwent standard ultrasound fetal biometry and kidney length measurement every 2 weeks between 24 and 38 weeks' gestation. These measurements were used to date the pregnancies relative to crown-rump length dating between 8 and 10 weeks' gestation. Linear regression models for estimation of gestational age were derived from the biometric indices and kidney length. In addition, stepwise regression models were constructed to determine the best model for determining gestational age between 24 and 38 weeks. Comparisons were then made between the accuracy of these models in the determination of gestational age. RESULTS: The best model for estimating gestational age in late pregnancy included the variables kidney length, biparietal diameter, head circumference, femur length and abdominal circumference. This model accurately predicted gestational age with a standard error of +/- 8.48 days. A model including kidney length, biparietal diameter, head circumference and femur length accurately predicted gestational age with a standard error of +/- 8.57 days. These models were slightly more accurate than models derived from the biometric indices of biparietal diameter, head circumference and femur length (+/- 9.87 days), biparietal diameter, head circumference, femur length and abdominal circumference (+/- 9.45 days) and biparietal diameter and femur length (+/- 9.9 days). Kidney length and femur length were the most accurate single parameters for predicting gestational age using simple linear regression models (+/- 10.29 and 10.96 days, respectively); the abdominal circumference was the least accurate (+/- 14.54 days). CONCLUSION: Kidney length is a more accurate method of determining gestational age than the fetal biometric indices of biparietal diameter, head circumference, femur length and abdominal circumference between 24 and 38 weeks' gestation. When combined with biparietal diameter, head circumference and femur length, the precision of dating is improved by 2 days. This measurement is easy to make and could therefore be easily incorporated into the model for dating pregnancies after 24 weeks of gestation, in particular when measurements of the biparietal diameter and head circumference are difficult.     

Doppler sonographic study of fetal brachial and umbilical artery blood flow during pregnancy

PURPOSE: The purpose of this study was to evaluate the fetal brachial artery resistance index (RI), its changes throughout gestation, and its relationship to the umbilical artery RI. METHODS: One hundred fifty-four sonographic examinations of the brachial and umbilical arteries in 71 fetuses were performed between 12 and 40 weeks' gestational age in 71 women with normal pregnancies. For each week of gestational age, the mean, standard deviation, range, and t-distribution 95% confidence interval of the fetal brachial artery RI were calculated. RESULTS: The fetal brachial artery RI, although relatively lower at the beginning of gestation, showed a pattern of high resistance, with a slight increase until term, whereas the fetal umbilical artery RI decreased progressively. CONCLUSIONS: The brachial artery RI is high in normal fetuses with good oxygenation. Umbilical artery RIs showed a progressive decrease until the end of term.