Fetal transabdominal biometry at 11-14 weeks of gestation.

OBJECTIVE: To establish comprehensive transabdominal ultrasonographic reference ranges for viable normal singleton human fetuses at 11-14 weeks' gestation. METHODS: Single transabdominal ultrasound measurements were taken once per pregnancy at a gestational age of between 11+0 and 14+0 weeks (crown-rump length, 45-84 mm), in viable singleton fetuses with nuchal translucency < or = 3 mm and without detectable structural anomalies, using four standard planes: (i) biparietal diameter (BPD) and fronto-occipital diameter (FOD) resulting in head circumference (HC), anterior horn (Va), posterior horn (Vp), and hemisphere (HEM); (ii) transcerebellar diameter (TCD) and cisterna magna (CM); (iii) abdominal anteroposterior (AAP) and abdominal transverse diameter (ATD) resulting in abdominal circumference (AC); and (iv) femur length (FL). The respective ratios Va/HEM, Vp/HEM, HC/AC, BPD/FL, BPD/FOD, FL/CRL, FL/BPD and FL/AC and the estimated weight were derived. Reference ranges were constructed and the mean and 5th and 95th centiles were plotted against gestation. RESULTS: There was a general increase in biometric parameters with gestation. The ratios for the ventricles vs. hemisphere and BPD/FL ratio decreased while the BPD/FOD and HC/AC ratios remained constant. Analysis of the reference range for BPD/FL was performed in both 167 and 664 fetuses and the results showed almost the identical type of equation, indicating a high degree of accuracy for the growth charts. CONCLUSIONS: We have established comprehensive reference ranges for first-trimester fetal biometry by transabdominal sonography. These charts may have a role in the diagnosis of early onset symmetrical or asymmetrical growth restriction and in the interpretation of measurements in chromosomally abnormal fetuses, and they may help in the detection of skeletal dysplasias or acrania/anencephaly.     

Newer ultrasonographic anatomy in the upper abdomen: I. The portal and hepatic venous anatomy

Gray scale ultrasonography has made it possible to identify hepatic and portal venous structures. Single sector sweep scanning is important in depicting these structures. Identification of venous structures is discussed as well as methods for distinguishing large veins from pathologic structures.     

Relationship between nuchal translucency at 11-14 weeks and nuchal fold at 20-24 weeks of gestation.

OBJECTIVES: To examine the relationship between the measurement of nuchal translucency in the first trimester and nuchal fold in the second trimester in normal pregnancy. METHODS: This was a prospective study of 592 singleton pregnancies. Fetal nuchal translucency was measured at 11-14 weeks of gestation and nuchal fold at 20-24 weeks of gestation. Linear regression models were used to assess the relationship between nuchal translucency and nuchal fold after adjustment for gestational age. RESULTS: There was no significant association between nuchal translucency and nuchal fold thickness. CONCLUSION: It is possible that measurement of nuchal translucency and nuchal fold may provide an independent contribution in screening for trisomy 21.     

Reversed end-diastolic flow in the umbilical artery at 10-14 weeks of gestation is associated with absent pulmonary valve syndrome.

OBJECTIVE: To determine the incidence of reversed end-diastolic flow (REDF) in the umbilical artery in high-risk first-trimester pregnancies and evaluate associated conditions. METHODS: This was a prospective evaluation of the umbilical artery Doppler waveforms of 614 consecutive high-risk pregnancies between 10 and 14 weeks of gestation, to determine those with REDF. The associated anomalies and characteristics of these fetuses were then investigated. RESULTS: In 278/614 (45.3%) fetuses, there was positive end-diastolic flow in the umbilical artery; in 331/614 (53.9%) end-diastolic flow was absent and in 5/614 (0.8%) there was REDF. Three of the five fetuses with REDF had tetralogy of Fallot (TOF) with absent pulmonary valve syndrome (APVS) and a patent ductus arteriosus, and all three showed signs of cardiac failure, with reversed blood flow in the ductus venosus during atrial systole and generalized skin edema. Another fetus had a large ventricular septal defect and the remaining fetus had agenesis of the ductus venosus. Three fetuses had trisomy 18 and one had trisomy 13. CONCLUSIONS: REDF in the umbilical artery is very rare in early pregnancy and mostly occurs in association with major fetal vascular anomalies and cardiac defects, particularly TOF with APVS and patent arterial duct. We propose that the patency of the arterial duct in TOF with APVS leads to heart failure with subsequent demise early in pregnancy. Therefore, the frequent absence of the arterial duct observed in APVS in later pregnancy is more likely to be a result of early selection than a prerequisite for the development of this lesion as has been proposed previously.     

Ear length in trisomy 21 fetuses at 11-14 weeks of gestation.

OBJECTIVE: To determine the value of measuring fetal ear length at 11-14 weeks of gestation in screening for chromosomal defects. METHODS: The fetal ear length was measured in 450 fetuses immediately before chorionic villus sampling for karyotyping at 11-14 weeks of gestation. RESULTS: The median gestational age was 12 (range, 11-14) weeks. The fetal ear was successfully examined in all cases. The fetal karyotype was normal in 409 cases and abnormal in 41, including 32 cases of trisomy 21. In the chromosomally normal group the fetal ear length increased significantly with crown-rump length from a mean of 3.7 mm at 45 mm to 6.9 mm at 84 mm. In the trisomy 21 fetuses the median ear length was significantly below the normal mean for crown-rump length by 0.45 mm (P = 0.013) but it was below the 5(th) centile of the normal range in only two (6.3%) of the cases. There was no significant association between the delta score of ear length and delta nuchal translucency in either the chromosomally normal (r = - 0.015, P = 0.753) or the trisomy 21 fetuses (r = - 0.014, P = 0.94). CONCLUSIONS: At 11-14 weeks of gestation the ear length in trisomy 21 fetuses is significantly reduced but the degree of deviation from normal is too small for this measurement to be useful in screening for trisomy 21.     

Absent nasal bone at 11-14 weeks of gestation and chromosomal defects.

OBJECTIVE: To examine the association between absence of the nasal bone at the 11-14-week ultrasound scan and chromosomal defects. METHODS: Ultrasound examination was carried out in 3829 fetuses at 11-14 weeks' gestation immediately before fetal karyotyping. At the scan the fetal crown-rump length (CRL) and nuchal translucency (NT) thickness were measured and the fetal profile was examined for the presence or absence of the nasal bone. Maternal characteristics including ethnic origin were also recorded. RESULTS: The fetal profile was successfully examined in 3788 (98.9%) cases. In 3358/3788 cases the fetal karyotype was normal and in 430 it was abnormal. In the chromosomally normal group the incidence of absent nasal bone was related firstly to the ethnic origin of the mother (2.8% for Caucasians, 10.4% for Afro-Caribbeans and 6.8% for Asians), secondly to fetal CRL (4.6% for CRL of 45-54 mm, 3.9% for CRL of 55-64 mm, 1.5% for CRL of 65-74 mm and 1.0% for CRL of 75-84 mm) and thirdly, to NT thickness, (1.8% for NT < 2.5 mm, 3.4% for NT 2.5-3.4 mm, 5.0% for NT 3.5-4.4 mm and 11.8% for NT > or = 4.5 mm. In the chromosomally abnormal group the nasal bone was absent in 161/242 (66.9%) with trisomy 21, in 48/84 (57.1%) with trisomy 18, in 7/22 (31.8%) with trisomy 13, in 3/34 (8.8%) with Turner syndrome and in 4/48 (8.3%) with other defects. CONCLUSION: At the 11-14-week scan the incidence of absent nasal bone is related to the presence or absence of chromosomal defects, CRL, NT thickness and ethnic origin.     

Vesicocentesis at 10-14 weeks of gestation for treatment of fetal megacystis.

This report of four cases shows that fetal vesicocentesis at 10-14 weeks of gestation is a useful treatment option in some cases with megacystis. Although megacystis at this gestation has been reported, there are few studies examining the role of early vesicocentesis. The natural history of the condition and outcome following treatment is reviewed with reference to the literature.     

Fetal exomphalos at 11 to 14 weeks of gestation.

In an ultrasonographic screening study at 11 to 14 weeks' gestation involving 9885 singleton pregnancies, the prevalence of exomphalos was 0.11% (11 cases) and the prevalence of trisomy 18 or 13 was 0.35% (35 cases). The mean maternal age of the screened population was 35 years (range, 15 to 47 years) and a significant association was found between maternal age and both the prevalence of trisomies and the prevalence of exomphalos. Because the frequency of exomphalos in fetuses with trisomy 18 or 13 was 17% and in those with no evidence of these trisomies it was 0.05%, the risk for trisomies in fetuses with exomphalos is 340 times higher than in those without exomphalos.     

Reference values for fetal limb biometry at 10-14 weeks of gestation.

OBJECTIVES: To calculate reference ranges for fetal limb measurements obtained by transabdominal ultrasound at 10-14 weeks of gestation. METHODS: Six hundred and six normal fetuses were examined transabdominally in a cross-sectional study by a single observer. The crown-rump length of the fetuses ranged from 31 to 78 mm. Measurement of the length of the humerus, ulna, femur, tibia and foot was attempted from the longest section of each structure. To assess intraobserver repeatability, three sets of repeated measurements were obtained in 26 fetuses. RESULTS: An appropriate ultrasound measurement was obtained in a percentage of cases ranging from 93.2% to 97.9%. A significant correlation was found between crown-rump length measurements and humerus length (r = 0.74, P < 0.001), ulna length (r = 0.70, P < 0.001), femur length (r = 0.77, P < 0.001), tibia length (r = 0.69, P < 0.001) and foot length (r = 0.58, P < 0.001). Crown-rump length-specific reference ranges for each measurement were calculated with the method of scaled absolute residuals. The study of intraobserver variability showed coefficients of variation ranging from 7.9 to 10.0% and intraclass correlation coefficients ranging from 0.89 to 0.94. CONCLUSIONS: Fetal limb size is strongly correlated with crown-rump length. Despite a significant biological variability of the measurements, the availability of reference ranges could be of help in the early diagnosis of fetal skeletal dysplasias.     

Uterine artery Doppler at 11-14 weeks of gestation in chromosomally abnormal fetuses.

OBJECTIVE: To determine whether the major chromosomal abnormalities are associated with impaired placentation in the first trimester of pregnancy. METHODS: This was a prospective study of 692 singleton pregnancies undergoing fetal karyotyping at 11-14 weeks of gestation. Uterine artery Doppler was carried out and the mean pulsatility index was calculated just before chorionic villus sampling. RESULTS: The fetal karyotype was normal in 613 pregnancies and abnormal in 79, including 39 cases of trisomy 21, 11 of trisomy 18, 11 of trisomy 13, eight of Turner syndrome and 10 with other defects. There were no significant differences in the median value of uterine artery mean PI between any of the individual groups. Although in the combined group of trisomy 18, trisomy 13 and Turner syndrome fetuses, the median pulsatility index (1.60) was significantly higher than in the chromosomally normal group (median pulsatility index, 1.51; P = 0.021), in the majority of abnormal fetuses (24 of 30) mean pulsatility index was below the 95th centile of the normal group (mean pulsatility index, 2.34). There was no significant association between uterine artery mean pulsatility index and fetal nuchal translucency thickness or fetal growth deficit. CONCLUSIONS: The high intrauterine lethality and fetal growth restriction associated with the major chromosomal abnormalities are unlikely to be the consequence of impaired placentation in the first trimester of pregnancy.     

Femur and humerus length in trisomy 21 fetuses at 11-14 weeks of gestation.

OBJECTIVE: To determine the value of measuring fetal femur and humerus length at 11-14 weeks of gestation in screening for chromosomal defects. METHODS: Femur and humerus lengths were measured using transabdominal ultrasound in 1018 fetuses immediately before chorionic villus sampling for karyotyping at 11-14 weeks of gestation. In the group of chromosomally normal fetuses, regression analysis was used to determine the association between long bone length and crown-rump length (CRL). Femur and humerus lengths in fetuses with trisomy 21 were compared with those of normal fetuses. RESULTS: The median gestation was 12 (range, 11-14) weeks. The karyotype was normal in 920 fetuses and abnormal in 98, including 65 cases of trisomy 21. In the chromosomally normal group the fetal femur and humerus lengths increased significantly with CRL (femur length = - 6.330 + 0.215 x CRL in mm, r = 0.874, P < 0.0001; humerus length = - 6.240 + 0.220 x CRL in mm, r = 0.871, P < 0.0001). In the Bland-Altman plot the mean difference between paired measurements of femur length was 0.21 mm (95% limits of agreement - 0.52 to 0.48 mm) and of humerus length was 0.23 mm (95% limits of agreement - 0.57 to 0.55 mm). In the trisomy 21 fetuses the median femur and humerus lengths were significantly below the appropriate normal mean for CRL by 0.4 and 0.3 mm, respectively (P = 0.002), but they were below the respective 5th centile of the normal range in only six (9.2%) and three (4.6%) of the cases, respectively. CONCLUSION: At 11-14 weeks of gestation the femur and humerus lengths in trisomy 21 fetuses are significantly reduced but the degree of deviation from normal is too small for these measurements to be useful in screening for trisomy 21.     

Reproducibility of ductus venosus Doppler flow measurements at 11-14 weeks of gestation.

OBJECTIVES: To assess the intra- and interobserver repeatabilities of fetal ductus venosus Doppler measurements at 11-14 weeks of gestation. DESIGN: Flow velocity waveforms were recorded transabdominally. Intraobserver repeatability was studied in 22 fetuses in whom four repeated measurements were performed by the same observer. Interobserver repeatability was assessed in 54 fetuses in each of whom two observers performed two repeated measurements. The pulsatility index for veins (PIV), peak velocity during ventricular systole (S wave), peak velocity during atrial contraction (A wave) and time-averaged maximum velocity (TAMV) were recorded. Reproducibility of the Doppler measurements was analyzed by calculating repeatability coefficient, coefficient of variation (CV), intraclass correlation coefficient (ICC), mean differences and their limits of agreement. Cohen's k-coefficient was used for categorical data. RESULTS: Intraobserver repeatability was good with a CV of 10%, 13%, 22% and 13% and an ICC of 0.85, 0.94, 0.94 and 0.95, respectively, for PIV, S wave, A wave and TAMV. Interobserver repeatability was also good, and no bias between the observers was detected. A CV of 8.8%, 14%, 27% and 15% and an ICC of 0.86, 0.84, 0.87 and 0.84, respectively, for PIV, S wave, A wave and TAMV were obtained. There was 100% agreement for the detection of normal/abnormal blood flow. CONCLUSIONS: Intra- and interobserver repeatability of all parameters was acceptable, allowing for the detection of moderate to large changes in Doppler measurements.     

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.     

Intra- and interoperator variability in fetal nasal bone assessment at 11-14 weeks of gestation.

OBJECTIVES: Examination of the fetal nasal bones by ultrasound between 11 and 14 weeks of gestation has been proposed as an additional tool in the detection of trisomy 21 in a high-risk population. However the variability in the identification of fetal nasal bones by ultrasound has not yet been investigated. The aim of this study was to assess the intraobserver and interobserver reproducibility of fetal nasal bone identification by ultrasound between 11 and 14 weeks of gestation. METHODS: A total of 1040 consecutive ultrasound examinations were performed at 11-14 weeks of gestation for nuchal translucency (NT) measurement and nasal bone identification by ultrasound. A total of 657 consecutive video-loops were assessed by three experienced operators. Each operator assigned cases to one of three categories, namely present, uncertain or absent nasal bones, and the results were compared between operators. To assess the intraoperator variability each operator reviewed 100 randomly selected videos out of the 657 loops and again used the same classification. Results were compared by pairwise unweighted and weighted Kappa index to evaluate the inter- and intraoperator variability. RESULTS: Among the 1040 fetuses, there were 51 (4.9%) with an NT measurement above the 95th centile. Nasal bones were identified by ultrasound in 948, not seen in eight and impossible to assess in 84 fetuses. Four fetuses had trisomy 21 including three with absent nasal bones and increased NT and one with present nasal bones and normal NT. The Kappa and weighted Kappa values for interoperator variability between the three operators were between 0.26 and 0.37 and 0.33 and 0.44, respectively. The Kappa and weighted Kappa values for intraoperator variability were between 0.35 and 0.48 and 0.43 and 0.55, respectively. CONCLUSION: The assessment of fetal nasal bones is only fairly reproducible. Although the performance of the test in fetuses at high risk for trisomy 21 has been reported to be good, its implementation as an additional screening technique in the general population must be accompanied by teaching and quality control programs.     

Assessment of the fetal nasal bone at 11-14 weeks of gestation by three-dimensional ultrasound.

OBJECTIVE: To evaluate the benefit of three-dimensional (3D) ultrasound in the examination of the fetal nasal bone at 11-14 weeks of gestation. METHOD: We examined the fetal nasal bone in 120 stored volumes acquired transabdominally with a 3D scanner from singleton pregnancies at 11-14 weeks of gestation. The volume acquisition had been performed following conventional ultrasound examination that had demonstrated presence of the fetal nasal bone. The volumes were obtained with two-dimensional (2D) start images in transverse, coronal mid-sagittal, parasagittal and oblique longitudinal sections of the fetal head. RESULTS: In the transverse and coronal sections, a satisfactory image demonstrating presence of the nasal bone was achieved in only three and one, respectively, of the 20 volumes that we obtained. In mid-sagittal sections, the nasal bone was always visible when the angle was within a range of 30-60 degrees, without the need for sectional image analysis. None of the images with an angle >60 degrees or <30 degrees was satisfactory. In the parasagittal sections with the fetal profile at 45 degrees, a good-quality image of the nasal bone was possible in all cases that were examined, irrespective of the distance from the mid-sagittal plane. In the oblique longitudinal sections with the fetal profile at 45 degrees, there were 10 volumes where the 2D start section was at 0-25 degrees from the midline and in all these cases the nasal bone was successfully visualized. In contrast, only 5/20 cases where the 2D start section was at 25-90 degrees from the midline provided a satisfactory image demonstrating the nasal bone. In 5/10 volumes obtained with the fetus facing downwards the nasal bone was visible in both the 2D and 3D images. CONCLUSION: In a 3D volume the extent to which the nasal bone can be demonstrated to be present in a given reconstructed section is entirely dependent on obtaining a good initial 2D view.     

Umbilical cord diameter at 11-14 weeks of gestation: relation to chromosomal defects.

OBJECTIVE: To determine the potential value of measuring umbilical cord diameter (UCD) at 11-14 weeks of gestation in screening for chromosomal defects. METHODS: The UCD was measured in 1323 fetuses immediately before chorionic villus sampling for karyotyping at 11-14 weeks of gestation. In the group of chromosomally normal fetuses, regression analysis was used to determine the association between UCD and crown-rump length (CRL). UCD was compared in normal fetuses and those with chromosomal abnormalities. RESULTS: The median gestation was 12 (range, 11-14) weeks. The UCD was successfully measured in all cases. The fetal karyotype was normal in 1150 pregnancies and abnormal in 173, including 97 cases of trisomy 21. In the chromosomally normal group the UCD increased significantly with CRL from a mean of 2.9 mm at a CRL of 45 mm to 4.4 mm at a CRL of 84 mm. The UCD in the group of fetuses with trisomy 21 was significantly smaller than normal. Conversely, there were no significant differences from normal in the UCD of fetuses with other chromosomal abnormalities. CONCLUSION: At 11-14 weeks of gestation the UCD of fetuses with trisomy 21 is significantly smaller than normal but the magnitude of the difference is too small for useful inclusion of this measurement in screening.     

Reference values for ductus venosus Doppler flow measurements at 10-14 weeks of gestation.

OBJECTIVES: To calculate reference ranges for ductus venosus Doppler measurements obtained transabdominally at 10-14 weeks of gestation. DESIGN: Two hundred and one normal fetuses with a crown-rump length (CRL) ranging from 38 to 88 mm were examined in a cross-sectional study. The pulsatility index for veins (PIV), peak velocity during ventricular systole (S-wave), lowest forward velocity during atrial contraction (A-wave) and time-averaged maximum velocity (TAMXV) were recorded from the ductus venosus. Flow velocity waveforms were also classified as normal or abnormal according to the presence (normal) or absence or reversal (abnormal) of frequencies during atrial contraction. RESULTS: Three of 201 fetuses showed an abnormal flow pattern (1.5%; 95% exact confidence interval, 0.3-4.3%). In the 198 fetuses with a normal flow pattern, the mean PIV ranged from 1.07 at a CRL of 38 mm to 1.00 at a CRL of 88 mm (r = -0.093; P = 0.19). A significant increase in mean blood flow velocity with increasing CRL was noted for the S-wave (27.0 cm/s to 33.6 cm/s; r = 0.17; P = 0.02), the A-wave (5.9 cm/s to 7.8 cm/s; r = 0.14; P = 0.04) and the TAMXV (19.4 cm/s to 25.3 cm/s; r = 0.19; P < 0.01). Crown-rump length-specific reference ranges for each parameter were calculated using the method of scaled absolute residuals. CONCLUSIONS: Abnormal ductus venosus flow patterns could be observed in normal fetuses, even if they ocurred with a low prevalence. Reference values for Doppler measurements were established in fetuses with normal patterns of flow.     

Normal cardiac flow velocities at 14-16 weeks of gestation measured by transvaginal ultrasound.

OBJECTIVE: Doppler ultrasound has been used to study the flow velocities through the valves and arteries of the fetal heart. Using transvaginal sonography, we sought to determine normal values for flow velocities through the fetal heart valves at 14-16 weeks of gestation. METHODS: Eighty-seven normal fetuses were examined. The flow velocity waveforms were visualized using Doppler ultrasound with the sample volume calipers placed just distally to the four fetal valves. Peak E- and A-wave velocities were recorded for the tricuspid and mitral valves and peak systolic flow velocities were recorded for the ascending aorta and pulmonary arteries. Linear regression for comparison of flow velocities with gestational age was performed. RESULTS: There was no significant correlation between any of the velocities and gestational age. CONCLUSIONS: Flow velocities through the fetal cardiac valves remain unchanged at 14-16 weeks of gestation as measured by transvaginal Doppler sonography.     

Single umbilical artery at 11-14 weeks' gestation: relation to chromosomal defects.

OBJECTIVE: To determine the possible association between single umbilical artery (SUA) at 11-14 weeks of gestation and the incidence of chromosomal abnormalities. METHODS: Color flow imaging of the fetal pelvis was used to determine the number of umbilical arteries in 717 fetuses immediately before chorionic villus sampling for karyotyping at 11-14 weeks' gestation. RESULTS: Single umbilical artery (SUA) was diagnosed in 21/634 (3.3%) chromosomally normal fetuses, in 5/44 (11.4%) with trisomy 21, 14/18 (77.8%) with trisomy 18 and 2/21 (9.5%) with other chromosomal defects. In the chromosomally normal group there was no significant difference in median fetal crown-rump length or nuchal translucency (NT) between those with a single and those with two umbilical arteries. In the 42 fetuses with SUA the expected number of cases of trisomy 21, estimated on the basis of maternal age, gestational age and fetal NT, was 4.7, which was not significantly different from the observed 5. The corresponding numbers for trisomy 18 were 2.0 for expected and 14 for observed (Fisher's exact test P = 0.0016). CONCLUSION: A SUA at 11-14 weeks' gestation has a high association with trisomy 18 and other chromosomal defects.     

探讨正常孕11~14周子宫动脉及螺旋动脉的多普勒超声特征

目的 分析正常孕11～14周子宫动脉及螺旋动脉的多普勒超声的特征.方法 选取410名正常孕11～14周孕妇,根据孕周分为Ⅰ组(≥11周且＜12周)、Ⅱ组(≥12周且＜13周)和Ⅲ组(13周～14周),按胎盘位置分为居中胎盘组、左侧胎盘组和右侧胎盘组;根据阻力指数(RI)分为＜0.60组、0.60～0.69组、0.70～0.74组、0.75～0.79组及≥0.80组;分析不同孕周、不同胎盘位置的子宫动脉和螺旋动脉的多普勒超声参数特征,以及子宫动脉不同RI值舒张早期存在α切迹的情况.结果 Ⅲ组子宫动脉平均RI值低于Ⅰ组(P＜0.05);Ⅲ组平均搏动指数(PI)值低于其他两组(P均＜0.05).居中胎盘组右侧子宫动脉PI低于左侧胎盘组(P＜0.05),左、右侧胎盘组子宫动脉收缩期最大血流速度/舒张末期血流速度(S/D)及RI差异无统计学意义(P均＞0.05).左侧胎盘组左侧子宫动脉S/D、RI及PI均低于右侧胎盘组(P均＜0.01);右侧胎盘组右侧子宫动脉S/D、RI及PI均低于左侧胎盘组(P均＜0.01).在子宫动脉RI≥0.75的孕妇中,右侧α切迹发生率79.49％(31/39),左侧89.80％(44/49).螺旋动脉各项多普勒超声参数在不同孕周、不同胎盘位置孕妇间差异均无统计学意义(P均＞0.05).结论 正常孕11～14周子宫动脉、螺旋动脉多普勒参数及胎盘位置存在一定特征,可为临床早期诊疗提供参考.