American Journal of Obstetrics and Gynecology (2005) 193, 1208–12
First trimester uterine artery Doppler abnormalities
predict subsequent intrauterine growth restriction
Lorraine Dugoff, MD,a Anne M. Lynch, MD, MSPH,a Darleen Ciofﬁ-Ragan, BA,a
John C. Hobbins, MD,a Lisa K. Schultz, RN,a Fergal D. Malone, MD,b
Mary E. D’Alton, MD,b for the FASTER Trial Research Consortium
Department of Obstetric and Gynecology, University of Colorado Health Sciences Center,a Denver, CO;
Department of Obstetrics and Gynecology, Columbia University College of Physicians and Surgeons,b New York, NY
Received for publication March 1, 2005; revised June 2, 2005; accepted June 13, 2005
KEY WORDS Objective: This study was undertaken to evaluate the association between uterine artery Doppler
First trimester velocimetry performed between 10 and 14 weeks gestation and intrauterine growth restriction
Uterine artery (IUGR).
Doppler Study design: Uterine artery Doppler velocimetry data were collected on 1067 women enrolled in
Intrauterine growth the FASTER trial at the University of Colorado site. The data were analyzed by using univariate
restriction and multivariable logistic regression analysis.
Results: The uterine artery mean resistance index (RI) for the entire cohort was equal on the right
and left sides (0.59 G 0.14). Of the 1067 women, 34.2% had unilateral or bilateral diastolic
notches, 1 notch was observed in 23.8%, and bilateral notches in 10.4%. Women with a high
uterine artery mean RI (R75th percentile) were 5.5 times more likely to have IUGR (95% CI
1.6-18.7). There was no significant relationship between notching and IUGR.
Conclusion: Elevated first trimester uterine artery mean RI is significantly associated with IUGR.
Ó 2005 Mosby, Inc. All rights reserved.
Blood ﬂow through the uteroplacental circulation can pathology from pregnancies diagnosed with preeclamp-
be studied noninvasively with the use of Doppler ultra- sia and intrauterine growth restriction (IUGR) shows
sound. The impedance to ﬂow in the uterine arteries failure of the normal transition of maternal placental
progressively decreases during the ﬁrst 2 trimesters of arteries into low resistance vessels.2,3 A subsequent
normal pregnancies. This observation has been attrib- histologic study on tissue obtained from women under-
uted to a direct eﬀect of trophoblastic invasion on the going elective ﬁrst trimester pregnancy termination
musculoelastic coat of uterine spiral arteries.1 Placental conﬁrmed that Doppler resistance index (RI) was
inversely related the percentage of vessels demonstrating
trophoblastic invasion.4 This observation appears to
support the thesis that a relationship between tropho-
Funded by the National Institute of Child Health and Human blastic invasion and RI can be demonstrated early in
Development, Grant Number RO1 HD 38652.
Presented at the Twenty-Fifth Annual Meeting of the Society for
pregnancy, and gives credence to the possibility that this
Maternal Fetal Medicine, Reno, Nev, February 7-12, 2005. technique may prove useful in predicting adverse ob-
Reprints not available from the author. stetric outcome, speciﬁcally IUGR, later in pregnancy.
0002-9378/$ - see front matter Ó 2005 Mosby, Inc. All rights reserved.
Dugoff et al 1209
Previous studies have shown an association between the few cases in which more than 1 measurement was
increased uterine artery impedance to ﬂow measured obtained, we used the waveform that appeared to be the
by Doppler velocimetry in the second trimester and best quality.
subsequent IUGR.5-8 It has also been previously demon- Relevant information on select maternal risk factors
strated that the uterine artery RIs obtained transabdomi- (maternal age, body mass index, nulliparity, prior pre-
nally at 10 to 14 weeks are repeatable and reproducible term birth, and gestational age at the time of the ﬁrst
measurements.9 These investigators showed that notch- trimester ultrasound) was included in this study. This
ing was positively correlated with birth weight, whereas information was collected at the time of enrollment in
RI was negatively correlated.10 However, there are lim- the FASTER trial. Postdelivery follow-up was per-
ited data describing the relationship between uterine formed by telephone interview or medical record review.
artery blood ﬂow in early pregnancy and IUGR. The The primary outcome we investigated was IUGR.
goal of this study was to evaluate the association between IUGR was deﬁned as birth weight less than the 10th
uterine artery Doppler velocimetry performed between percentile for gestational age in Colorado women
10 and 14 weeks’ gestation and IUGR. using the Lubchenco Colorado intrauterine growth
Material and methods
This is a study performed at a single site within the Statistical analysis
FASTER trial, a prospective multicenter observational
study whose goal was to compare the diagnostic per- The data were analyzed in SAS 8.2 (SAS Institute, Cary,
formance of several ﬁrst and second trimester screening NC). Initially, univariate analyses were conducted on
markers for Down syndrome that has been described the primary explanatory variables (exposures) and select
elsewhere.11 Women at the University of Colorado maternal risk factors to determine general descriptive
Health Sciences Center who consented to enroll in the statistics. The mean RI for the right and left sides was
FASTER trial between July 18, 2001, and December 3, determined by calculating the sum of the RI values from
2002, were asked if they would agree also to undergo all the patients divided by the number of patients. This
uterine artery Doppler investigation for this study. This was performed by using the data from each patient for
prospective pilot study included all women enrolled in the right and then the left uterine artery. We also
the FASTER trial at the University of Colorado Health determined the mean RI for each subject in the cohort
Sciences Center site who agreed to participate in this (sum of the uterine artery RI for the right and left side
study and for whom bilateral uterine artery RI and divided by 2). We then looked at the distribution of the
notching data were obtained. Our analysis excluded all mean uterine artery resistance for the entire cohort. We
women carrying a fetus with a chromosomal or struc- deﬁned an elevated mean uterine artery RI as a value
tural abnormality or a genetic syndrome, women with a above the 75th, 90th, and 95th percentile for the entire
pregnancy that resulted in a fetal demise at less than 24 cohort. An early diastolic notch was categorized as
weeks’ gestation, those with a known congenital uterine present or absent.
malformation, and those for whom pregnancy outcome The relative risk (RR) was used as a measure of
data were unavailable. association to test the relationship between these pri-
Ultrasound examinations were performed with the mary explanatory variables and IUGR. The RR was
use of a Voluson 730 and 730 MT (Medison, Cyprus, deﬁned as the cumulative incidence of IUGR among
Calif) equipped with a 3.5-MHz curvilinear transabdo- mothers with the primary exposures divided by the
minal probe. To perform the uterine artery Doppler cumulative incidence of IUGR among mothers without
interrogation, we followed a standard protocol that has the primary exposures. The incidence of IUGR in the
been used in the second trimester. Both uterine arteries subjects with the exposures was compared with the
were identiﬁed with color Doppler at the point at which incidence IUGR among women without the exposures.
they appeared to cross the external iliac artery. Pulse Measures of association between dichotomous variables
waved Doppler was used to obtain the waveforms. The were tested by using the c2 or Fisher exact test. Statistics
RI and the presence of an early diastolic notch were are presented with 95% CI (P ! .05). We conducted
assessed for both uterine arteries. All measurements multivariable logistic regression analysis if there was a
were performed by the same ultrasonographer and signiﬁcant relationship between either explanatory var-
reviewed by a single investigator. A notch was consid- iable or the outcome from the univariate stage of the
ered to be present when there was a clearly deﬁned analysis. In the multivariable logistic regression analysis,
upturn of the ﬂow velocity waveform at the beginning of the odds ratio (OR) was used as an approximation of
diastole. The number of measurements obtained on each the RR and we estimated the OR of the primary
side was determined by the sonographer. In the majority explanatory variable for IUGR adjusted for other
of cases, 1 measurement was obtained on each side. In covariates. Lastly, the performance characteristics for
1210 Dugoff et al
Table I Clinical Characteristics of the cohort (n = 1008) Table III Multivariable logistic regression analysis showing
Risk factors and outcomes the crude and adjusted ORs of mean RI R75th percentile for
Mean maternal age G SD 33 G 5
Nulliparity n (%) 502 (49.8) OR
Race Risk factor Crude Adjusted 95% CI*
White n (%) 857 (85.0) Mean RI R75th 6.0 5.5 1.6-18.7
Black n (%) 25 (2.5) percentile
Hispanic n (%) 82 (8.1) Maternal age 1.2 1.2 1.0-1.4
Other n (%) 44 (4.4) Body mass index 1.0 1.0 0.8-1.2
Body mass index (mean G SD) 23.3 G 4.0 Nulliparous 1.4 2.6 0.6-10.0
Cigarette smoker during current 39 (3.9) Prior preterm birth 3.2 4.8 0.7-30.8
pregnancy n (%) Gestational age 1.0 1.0 0.9-1.1
Prior preterm birth n (%) 61 (6.1) at ultrasound
IUGR, Intrauterine growth restriction.
IUGR 12 (1.2%)
* For the adjusted OR.
Mean gestational age at delivery G SD 38.8 G 2
!37 wks n (%) 77 (7.6)
%32 wks n (%) 14 (1.4) Table IV Multivariable logistic regression analysis showing
Intrauterine fetal death n (%) 3 (0.3) the crude and adjusted ORs of mean RI for IUGR
Risk factor Crude Adjusted 95% CI*
Table II Relative risk of uterine artery mean RI for IUGR
Mean RI 75th-90th 5.1 4.8 1.2-19.8
Percentile cut-off Above Below RR percentile
level for mean RI cut-off cut-off (95% CI) Mean RI O90th 7.3 6.4 1.6-26.7
R75th (0.70*) 8/256 (3.1) 4/752 (0.5) 5.9 (1.8-19.3) percentile
R90th (0.78*) 4/106 (3.8) 8/902 (0.9) 4.3 (1.3-13.9) Maternal age 1.2 1.2 1.0-1.3
R95th (0.81*) 2/51 (3.9) 10/957 (1.0) 3.8 (0.8-16.7) Body mass index 1.0 1.0 0.8-1.1
* Value of RI. Nulliparous 1.4 2.6 0.6-10.2
Prior preterm birth 3.2 4.7 0.7-30.3
Gestational age 1.0 1.0 0.9-1.1
the prediction of IUGR by RI were calculated by using at ultrasound
sensitivity, speciﬁcity, and the positive and negative * For the adjusted OR.
The mean uterine artery RI for the entire cohort of
Results patients was equal on both sides (0.59 G 0.14). A total
of 663 women (65.8%) had no early diastolic notch on
A total of 1066 women agreed to participate in this the uterine artery waveform, 210 (20.8%) had a right
study. Fifty-eight women were excluded from the study notch only, 240 (23.8%) had a left notch only, and 105
for the following reasons: fetal chromosomal abnormal- (10.4%) had bilateral notches.
ity (n = 6), fetal structural abnormality (n = 12), fetal The RR of mean uterine artery RI for IUGR at
genetic syndrome (n = 3), fetal demise less than 24 diﬀerent cut-oﬀ values is shown in Table II. Women
weeks (n = 11), patient diagnosed with a congenital whose mean RI was the 75th percentile or greater (0.70)
uterine malformation (n = 1), and pregnancy outcome were 5.9 times more likely to have a fetus aﬀected by
data were unavailable (n = 25). Thus, a total of 1008 IUGR, whereas women whose mean RI was the 90th
cases were included in our ﬁnal analysis. percentile or greater (0.78) were 4.3 times more likely to
Demographic characteristics of the women and have an aﬀected fetus. There was no signiﬁcant associ-
pregnancy outcome are shown in Table I. Less than ation between notching (unilateral or bilateral) and
2% of the cohort had IUGR. Two of these pregnancies development of IUGR.
resulted in a fetal demise with severe IUGR. The mean The multivariable logistic regression analysis showing
uterine artery RI in these cases of fetal death were 0.76 the crude and adjusted ORs of mean RI R75th percentile
and 0.78 (80th and 90th percentiles, respectively). The for IUGR is shown in Table III. Women who had a
most severe and earliest onset case of IUGR in our mean RI R75th percentile were 5.5 times more likely to
cohort had a uterine artery mean RI of 0.82 (O95th have a growth-restricted infant when adjusted for ma-
percentile) and required delivery at 25 weeks for fetal ternal age, body mass index, nulliparity, prior preterm
indications. birth, and gestational age at the time of the ﬁrst trimester
Dugoff et al 1211
early stage could allow more aggressive monitoring or
Table V Performance characteristics for IUGR
even initiation of therapy.
Mean RI Sensitivity Speciﬁcity PPV NPV The presence of notching has been suggested to be
cut-off (%) (%) (%) (%)
another predictor of adverse fetal outcome. Part of the
R75th (0.70) 66.7 75.1 3.1 99.5 diﬃculty in assessing this relationship relates to the
R90th (0.78) 33.3 89.8 3.8 99.1 subjectivity inherent in the qualitative identiﬁcation of
R95th (0.81) 16.7 95.1 3.9 99.0 notching. Martin et al13 observed notching in 75% of
IUGR, Intrauterine growth restriction; PPV, positive predictive value; 3324 women scanned in the ﬁrst trimester, and dis-
NPV, negative predictive value. missed this criterion as unimportant because of its
frequency. Notching is generally thought to be less
common with increasing gestational age, but was nev-
ultrasound was performed. Older women were also at a ertheless observed in 55.6% of women scanned between
signiﬁcantly increased risk of having a growth-restricted weeks 12 and 16 in the study by Harrington et al.15
infant. Table IV shows the results of a multivariable Again, the high prevalence of this ﬁnding would sug-
logistic regression analysis using 2 categories of mean RI. gest that it would be unlikely to be of signiﬁcant
This analysis demonstrates that the risk for IUGR predictive value for adverse obstetric outcome. Using
increases as the mean RI goes up. The performance our criteria, we observed a 34.2% incidence of notching
characteristics for the prediction of IUGR by RI are but found no association between notching and IUGR.
listed in Table V. These data suggest that we would be On the basis of these data, we believe that the presence
able to predict two thirds of IUGR cases by using the of notching identiﬁed at the ﬁrst trimester ultrasound
75th percentile RI as a cut-oﬀ. cannot be viewed as a clinically useful predictor of the
development of IUGR, at least based on present
Comment We had a relatively low incidence of adverse out-
comes such as IUGR because of the low-risk population
In this pilot study we found that an elevated ﬁrst enrolled in our study. This limited the statistical power
trimester mean uterine artery RI was signiﬁcantly asso- of our analysis to a large extent. The outcome we chose
ciated with developing IUGR later in pregnancy. The to evaluate, birth weight less than the 10th percentile for
highest quartile of our cohort contained 67% of the gestational age, included a spectrum of severity in terms
women who subsequently had IUGR develop. We did of fetal growth impairment. The cases ranged from
not ﬁnd any association between the presence of uterine healthy infants delivered at term with birth weight less
artery notching and IUGR. than the 10th percentile to infants with severe early
Three previous studies13-15 have examined the asso- onset growth restriction requiring early delivery, and in
ciation between ﬁrst trimester uterine artery Doppler 2 cases, resulting in fetal demise. Clearly, the severe
velocimetry and IUGR. In 1995 a Dutch group14 cases are the ones we are interested in identifying early
showed that women with a high pulsatility index (PI), in pregnancy, and the relatively low number of cases of
an alternative measurement of uterine artery impedance, this severity prevented us from stratifying our ﬁrst
had a 2.4-fold increase in the rate of IUGR. In 2001 trimester data to analyze this possibility. Present data
Martin et al13 also found that high PI was associated suggest that second trimester Doppler studies are eﬀec-
with the development of both IUGR and preeclampsia. tive at predicting the most severe cases of IUGR and
Harrington et al15 reported similar ﬁndings in patients preeclampsia.16,17 We speculate that, at the very least,
who underwent measurement of uterine artery imped- ﬁrst trimester Doppler screening may allow us to iden-
ance between 12 and 16 weeks’ gestation. The predictive tify those patients who may be at higher risk and should
importance of notching was not clearly established by be followed up with a second trimester scan.
any of these studies. Our obvious goal is to increase the sensitivity and
Similar to Martin’s study, we found a relatively low positive predictive value of Doppler velocimetry in
sensitivity for the mean uterine artery impedance cut-oﬀ detecting patients at risk of IUGR in the ﬁrst trimester.
of the 95th percentile or greater, though we measured RI We have previously reported on the association between
rather than PI. However, we found that the sensitivity low maternal serum levels of pregnancy associated
was increased to 67% when the mean RI cut-oﬀ was plasma protein-A (PAPP-A) levels and low free beta
lowered to the 75th percentile or greater. Although a human chorionic gonadotropin levels at 10 3/7 weeks
speciﬁcity of 75.1% (false-positive rate of 25%) might be to 13 6/7 weeks and birth weight less than the 10th
less than optimal, we believe it would still be very useful percentile.18 In the future we hope to have suﬃcient
if we could identify two thirds of women in the ﬁrst cases to evaluate these multiple associations and to
trimester of pregnancy who were destined to have a fetus develop a composite predictive panel that will increase
aﬀected by IUGR. Identifying these women at such an our sensitivity as well as positive predictive value.
1212 Dugoff et al
Acknowledgments 9. Hollis B, Mavrides E, Campbell S, Tekay A, Thilaganathan B.
Reproducibility and repeatability of transabdominal uterine artery
We acknowledge V. Faber, BA, and L. Sullivan, PhD, Doppler velocimetry between 10 and 14 weeks of gestation.
Ultrasound Obstet Gynecol 2001;18:593-7.
(DM-STAT, Inc, Medford, Mass) for their assistance 10. Hollis B, Prefumo F, Bhide A, Rao S, Thilaganathan B. First-
with coordination of data and outcome results. trimester uterine artery blood ﬂow and birth weight. Ultrasound
Obstet Gynecol 2003;22:373-6.
11. Malone FD, Canick JA, Ball RH, Nyberg DA, Comstock CH,
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