Perinatal outcomes after sonographic detection of isolated short femur in the second trimester

[A pragmatic comparison of fetal biometry curves]

INTRODUCTION

The fetal biometrics charts recommended in France for ultrasound screening include measurements of head circumference (HC), biparietal diameter (BIP), abdominal circumference (AC) and femur length (FL). New international growth standards have been recommended since 2022. The aim of this work is to quantitatively describe the differences between these biometric curves.

METHODS

The biometry curves from the French College for Fetal Ultrasound, OMS and INTERGROWTH-21 are pragmatically compared based on their original quantile regression equations (superposition and quantification of differences in millimeters and in proportion) for different percentiles of clinical interest.

RESULTS

Compared with the new charts, CFEF underestimates HC<-3DS and AC<10eP. The proportions of differences between the CFEF and INTERGROWTH-21 or WHO curves always remained <5%. The proportions of difference of the 3rd percentile of HC and FL, 10th and 90th percentile of AC were always lower than 2%, 2%, 5% and 4% respectively, between OMS and INTERGROWTH-21.

CONCLUSION

The switch to prescriptive standards suggests an improvement in the detection of fetuses with AC<10th percentile, an improvement in the detection of prenatal onset microcephaly, with no argument for a decrease in the detection rate of severe constitutional bone disease or modification of obstetrical guidelines.

Long Story of Short Femur: A Single-Center Study with Step-Wise Imaging Approach

PURPOSE

To evaluate the possible outcomes of fetuses diagnosed with short femur length (FL) and to guide diagnosis through a step-wise imaging algorithm.

METHODS

This was a prospective cohort study of 42 pregnancies with fetal femur length (FL) below the 5th centile for gestational age. The cases were divided into two categories of isolated short FL & non-isolated short FL and followed up to determine the etiology.

RESULTS

There were 11 cases of non-isolated short FL with skeletal dysplasia observed in 7 and chromosomal abnormalities in 4 cases. There were 31 cases with isolated short FL in which fetal growth restriction (FGR) occurred in 14/31 (45%) cases; 13 out of 31 (42%) were constitutional (short for gestational age, SGA) whereas 4/31(13%) showed normal interval growth on follow up (false positive).

CONCLUSION

Short femur can be isolated or non-isolated. Short femur length can be a good predictor and early sign of FGR. Serial follow up scan of the all cases of isolated short FL is important since a majority of them are normal and not require any further intervention. Cases of non-isolated short FL require step-wise approach to differentiate into dysplasia or aneuploidy.

The femur too short? 1373 fetuses with short femur during second-trimester screening

Purpose

A short fetal femur in prenatal diagnosis might be an indicator for intrauterine growth retardation (IUGR), a genetically determined small child (SGA) with or without associated fetal malformations and/or an adverse fetal outcome.

Methods

1373 singleton pregnancies with a femoral length < 5th percentile detected between 1999 and 2015 during second-trimester screening in a tertiary prenatal diagnostic center were subjected to a descriptive retrospective analysis with regard to fetal characteristics as well as pregnancy outcome.

Results

685 (49.9%) fetuses presented an isolated short femur, while 688 (50.1%) showed additional abnormalities. 293 (42.6%) of those were SGA babies without any malformation, while 395 (57.4%) had one or more severe anomaly of the following organ systems: 157 (11.5%) cardiovascular, 101 (7.4%) musculoskeletal, 82 (6.0%) urogenital, 72 (5.2%) cerebrocephalic, 50 (3.6%) gastrointestinal, and 5 (0.4%) thoracic. 75 (5.5%) of the fetuses showed chromosomal aberrations of which Trisomy 13, 18 and 21 were found in 2, 13 and 27 of the cases, respectively. Fetuses with associated malformations had a significantly lower live birth rate than those without (64.2% vs. 98.1%, p < 0.001); in addition, a higher rate of preterm births 36.6% vs. 11.3%, p < 0.001) and SGA babies (51.4% vs. 30.4%, p < 0.001) were observed in the first collective.

Conclusion

Diagnosis of a short fetal femur should lead to an extended organ screening; in the case of associated abnormalities, additional genetic testing has to be offered, as well as intensified pregnancy monitoring in pregnancies at risk for IUGR and/or preterm birth.

Prenatal diagnosis of genetic aberrations in fetuses with short femur detected by ultrasound: A prospective cohort study

OBJECTIVES

To investigate the genetic aberrations in fetuses with short femur and explore the relationships with respect to degree of femoral shortening and the initial diagnostic gestational age GA.

METHODS

Singleton pregnancies with fetal short femur who consented to amniocentesis and to single nucleotide polymorphism (SNP) array and Sanger sequencing for G380R mutations in FGFR3 gene were enrolled in this 5-year period prospective study. Clinical follow-up assessments were performed after birth.

RESULTS

Of a total of 161 fetuses, the prevalence of genetic aberrations was 16.2% (26/161), comprised of 65.4% (17/26) with chromosomal abnormalities and 34.6% (9/26) with G380R mutations. All fetuses with chromosomal abnormalities had FL 2-4SDs below GA. Fewer chromosomal abnormalities were detected in fetuses with short femurs presenting in the third trimester. Significantly more FGFR3 mutations were detected in fetuses with FL below -4SDs. All fetuses with FL 2-4SDs below GA diagnosed as achondroplasia were between 22 and 24 gestational weeks, and all of those diagnosed in third trimester had FL below -4SDs.

CONCLUSION

In this small cohort study, we demonstrated that different degrees of femur shortness may be attributed to different genetic aberrations. SNP array should be regarded as the first-tier test for fetuses with FL 2-4SDs below GA. The prognoses for fetuses with FL 2-4SDs below GA was significantly better than those with FL below 4SDs.

Obstetrical and perinatal outcomes in fetuses with early versus late sonographic diagnosis of short femur length: A single-center, prospective, cohort study

OBJECTIVES

The aim of this study was to evaluate obstetrical and perinatal outcomes in fetuses with short femur length diagnosed before or after 24 weeks of gestation.

STUDY DESIGN

This was a prospective cohort study on singleton pregnancies with a diagnosis of fetal femur < 5 centile. Included patients were divided into two groups: patients with a first diagnosis of femur length < 5th percentile at 14-24 weeks (group A) and those with the first diagnosis made at > 24 weeks (group B).

RESULTS

147 patients were included for the analysis. Group A and group B included 66 (44.9%) and 81 (55.1%) cases. Abnormal fetal karyotype and skeletal dysplasia rates were significantly higher (27.3% vs 3.7%,P < 0.001 and 19.7% vs 3.7%, P = 0.002) in group A. Women in group B had a higher incidence of small for gestational age and intrauterine growth restriction (7.6% vs 24.7%, P = 0.007 and 19.7% vs 44.4%, P = 0.002). There was a significant higher incidence of live births in group B (34.9% vs 97.5%, P < 0.001), while the rate of termination of pregnancy was increased in group A (56.1% vs 1.2%, P < 0.001). No significant difference was found in perinatal outcomes of live births, when comparing group A and B.

CONCLUSIONS

The incidence of abnormal karyotype and skeletal dysplasia is higher when short femur length diagnosed earlier in gestation, while the incidence of small for gestational age, intrauterine growth restriction and the rate of live births are significantly increased when short femur length is diagnosed later during pregnancy.

Short Femur in the Second Trimester Scan Is Related to Maternal Preeclampsia and Small for Gestational Age Newborns

OBJECTIVE

To determine the contribution of short femur diaphysis length (FDL) at 19-22 weeks of gestation in the prediction of adverse pregnancy outcomes.

METHODS

The study included singleton pregnant women who underwent a routine anomaly scan at 19-22 weeks of gestation at the Virgen de la Arrixaca University Clinical Hospital (Murcia, Spain) between August 2011 and August 2012. Fetal biometry and Doppler ultrasound of uterine arteries were assessed as part of the anomaly scan, and the mean pulsatility index of both uterine arteries was recorded. Maternal obstetric characteristics, such as ethnicity, age, weight, parity, cigarette smoking, and medical history including hypertension and diabetes mellitus were collected from our database system.

RESULTS

A total of 6,366 women were included in the study after excluding cases with abnormal karyotype, major fetal abnormalities, or termination of pregnancy. There were 88 cases of preeclampsia (PE) (1.4%). Logistic regression was performed including maternal and fetal characteristics. Short FDL at 19-22 weeks was significantly associated with subsequent development of PE (OR = 0.89, 95% CI: 0.80-0.99, p = 0.025). The best model to predict PE from our sample included gestational age at scan, parity, maternal weight, chronic hypertension, mean pulsatility index in the uterine arteries, and FDL (AUC = 0.78, 95% CI: 0.71-0.84). Regarding small for gestational age (SGA) neonates, there were also significant differences in FDL and FDL <5th centile between the control group and SGA newborns below the 3rd, 5th, and 10th centile. In the groups of preterm births (delivery before 32, 34, and 37 weeks), there were no differences in FDL compared with the control group (term births).

DISCUSSION

Our results suggest that FDL at 19-22 weeks of gestation is an independent predictor of PE and SGA newborns.

Midtrimester isolated short femur and perinatal outcomes: A systematic review and meta-analysis

INTRODUCTION

Fetal femur length below the expected value has been described as a marker of aneuploidy, skeletal dysplasia, intrauterine growth restriction and small-for-gestational-age neonate. The aim of this systematic review and meta-analysis was to evaluate the strength of association between isolated short femur length and intrauterine growth restriction or small-for-gestational-age, and perinatal adverse outcomes.

MATERIAL AND METHODS

PubMed, EMBASE and Medline were searched from the inception of each database to May 2018. Selection criteria included prospective and retrospective cohort studies of singleton pregnancies between 18 and 28 weeks of gestation, with sonographic finding of isolated short femur length, without any structural chromosomal abnormality. The meta-analysis was performed by computing odds ratios using both fixed and random-effects models. Quality assessment of the included studies was performed using the Newcastle-Ottawa Scale.

RESULTS

Six studies including 3078 cases of isolated short femur length (study group) and 222 303 normal femur length (control group) were included. The prevalence of intrauterine growth restriction or small-for-gestational-age in the study group was 14.2%, compared with 5.2% in the control group (odds ratio of 4.04, 95% confidence interval 3.63-4.50). Isolated short femur length was associated with a higher incidence of low birthweight (study group: 22.10% vs control group: 8.57%, odds ratio 3.24, 95% confidence interval 2.34-4.48), Apgar <7 at 5 minutes (study group: 3.98% vs control group: 1.79%, odds ratio 3.56, 95% confidence interval 1.87-6.77), preterm birth (study group: 12.16% vs control group: 8.16%, odds ratio 3.09, 95% confidence interval 1.57-6.08), fetal death (study group: 1.83% vs control group: 0.44%, odds ratio 6.48, 95% confidence interval 3.70-11.35) and neonatal intensive care unit admission (study group: 15.34% vs control group: 14.81%, odds ratio 2.11, 95% confidence interval 0.56-7.93).

CONCLUSIONS

There is a significant association between isolated short femur length and intrauterine growth restriction or small-for-gestational-age and poor perinatal outcome.

The impact of third-trimester genetic counseling

OBJECTIVE

To evaluate the impact of genetic counseling (GC) during the third trimester by analyzing changes in pregnancy management and the correlation with postnatal findings.

METHODS

This was a retrospective study. Pregnancy course and neonatal follow-up were analyzed according to the reason for referral and implementation of recommendations.

RESULTS

The records of neonates born to 181 women were retrieved. Fifty-two women (group 1-29%) qualified for pregnancy termination under Israeli guidelines and laws, and 129 (group 2-71%) were not at the time they were referred. By another division: 104 women (group 3-57%) followed the physician's diagnostic recommendations completely after counseling including amniocentesis, fetal MRI, targeted ultrasound scans, fetal echocardiography. Seventy-seven declined amniocentesis (group 4-43%). Additional abnormalities were detected postpartum in all groups without statistically difference: 3/52 (10%) in group 1, 9/129 (7%) in group 2, 6/104 (6%) in group 3, and 6/77 (8%) in group 4).

CONCLUSION

GC in the third trimester of pregnancy provided the couple with a sharper more focused picture and assisted them to perceive the significance of new, significant fetal findings which attest to the value of the GC.

Prognosis of 591 fetuses with ultrasonic soft markers during mid-term pregnancy

The present study aimed to examine the value of ultrasonic soft markers in prenatal screening by analyzing the clinical outcome of fetuses with ultrasonic soft markers during the second trimester of pregnancy. A retrospective analysis was performed to evaluate the outcome of 591 fetuses with ultrasonic soft markers from January 2015 to August 2016 in Zhongnan Hospital of Wuhan University, China. It was found that 591 fetuses showed ultrasonic soft markers in 4927 cases with the occurrence rate being 12.0%. Among them, 564 fetuses (95.4%) were delivered and the remaining 27 cases (4.6%) were aborted. Five hundred and sixty-seven cases had single ultrasonic soft marker, including echogenic intracardiac focus (n=343), mild renal pelvis dilatation (n=116), short long bones (n=72), single umbilical artery (n=31), mild lateral ventriculomegaly (n=21), choroid plexus cysts (n=19), and echogenic bowel (n=13), with the disappearing rates in pregnancy being 97.1% (333/343), 77.6% (90/116), 0% (0/72), 0% (0/31), 57.1% (12/21), 89.5% (17/19) and 61.5% (8/13) respectively. The rate of pregnancy termination due to single ultrasonic soft marker was 3.4% (19/567), and that was 33.3% (8/24) due to two ultrasonic soft markers with the difference being statistically significant (P<0.05). The reasons of pregnancy termination included malformations (polycystic kidney, cleft lip and palate, congenital heart diseases, pcromphalus, hypospadias, hydrocephalus), chromosome abnormality, and stillbirth. It was concluded that single ultrasonic soft marker is usually transient manifestation in pregnancy. Without the other structural defects, single ultrasonic soft marker usually disappears spontaneously with favorable prognosis in a low-risk population. It is suggested that ultrasonic soft markers should be appropriately interpreted to avoid unnecessary invasive examination.

Risk of Adverse Outcomes in Euploid Pregnancies With Isolated Short Fetal Femur and Humerus on Second-Trimester Sonography

OBJECTIVES

The purpose of this study was to evaluate pregnancies with isolated short fetal femur and humerus on second-trimester sonography. Short fetal long bones are known to be associated with aneuploidy and structural anomalies. In this study, we wanted to show the risk of adverse pregnancy outcomes in euploid and nonanomalous pregnancies.

METHODS

Singleton pregnancies with short femur and humerus were included. Pregnancies with normal fetal bone lengths and age-matched mothers were selected as controls.

RESULTS

The study group included 30 pregnancies with short fetal femur and humerus, and the control group included 60 normal pregnancies. The overall odds ratio for an adverse pregnancy outcome in the study group was 24.9. Preterm delivery occurred significantly more frequently (odds ratio, 20.8; P < .001), and one-third of pregnancies were complicated by preeclampsia. In the group with short long bones, the odds ratio for a pathologic umbilical Doppler flow pattern was 45.2 (P < .001), and birth weight was significantly lower (P < .001). Also, 3 (10.3%) stillbirths and 4 (13.3%) cases of early neonatal death were recorded in this group. These complications were not recorded in the control group. The risk of emergency cesarean delivery was significantly higher in the group with short long bones (odds ratio, 11.8; P < .001).

CONCLUSIONS

The risk of adverse pregnancy outcomes is significant in euploid and nonanomalous pregnancies with isolated short long bones. Close follow-up is needed during pregnancy.

Isolated Short Fetal Femur Length in the Second Trimester and the Association with Adverse Perinatal Outcome: Experiences from a Tertiary Referral Center

Objective

To determine the association between isolated mid-trimester short fetal femur length and adverse perinatal outcome.

Methods

This is a retrospective cohort study of patients with singleton gestations routinely assessed by second trimester ultrasound examination during 2006-2013. A fetal isolated short femur was defined as a femur length (FL) below the 5^th percentile in a fetus with an abdominal circumference greater than the 10^th percentile. Cases of aneuploidy, skeletal dysplasia and major anomalies were excluded. Primary outcomes of interest included the risk of small for gestational age neonates, low birth weight and preterm birth (PTB). Secondary outcome parameters were a 5-min Apgar score less than 7 and a neonatal intensive care unit admission. A control group of 200 fetuses with FL ≥ 5th percentile was used to compare primary and secondary outcome parameters within both groups. Chi-square and Student’s t-tests were used where appropriate.

Results

Out of 608 eligible patients with a short FL, 117 met the inclusion criteria. Isolated short FL was associated with an increased risk for small for gestational age (19.7% versus 8.0%, p = 0.002) neonates, low birth weight (23.9% versus 8.5%, p<0.001), PTB (19.7% versus 6.0%, p<0.001) and neonatal intensive care unit admissions (13.7% versus 3.5%, p = 0.001). The incidence of a 5-min Apgar score less than 7 was similar in both groups.

Conclusion

Isolated short FL is associated with a subsequent delivery of small for gestational age and Low birth weight neonates as well as an increased risk for PTB. This information should be considered when counseling patients after mid-trimester isolated short FL is diagnosed.

Midtrimester Isolated Short Femur Length as a Predictor of Adverse Pregnancy Outcome

Objective: The aim of this study was to investigate whether midtrimester isolated short femur length is associated with pregnancy complications. Study Design: Retrospective analysis of pregnancies with a midtrimester femur length <5th percentile for gestational age compared to controls with a femur length ≥5th percentile. Outcome measures included hypertensive disorders, being small for gestational age, oligohydramnios and preterm delivery. Results: 2,105 women were eligible for this study, 85 (3.45%) of whom were in the study group and 2,020 were controls. Birth weight <10th percentile for gestational age (OR 4.4, 95% CI 2.5-7.8), birth weight <3rd percentile for gestational age (OR 31.0, 95% CI 13.3-72.3) and severe preeclampsia (OR 6.3, 95% CI 1.4-28.6) were significantly associated with midtrimester isolated short femur length. Conclusions: Midtrimester isolated short femur length is associated with higher rates of being small for gestational age and preeclampsia.

Outcome of fetuses with short femur length detected at second-trimester anomaly scan: a national survey

OBJECTIVE

To assess the relationship between the finding of fetal femur diaphysis length (FL) below the 5(th) percentile at the second-trimester scan and pregnancy outcome, in a population in which more than 90% of women attend first-trimester screening.

METHODS

This was a retrospective study of all Danish singleton pregnancies with a 17-22-week anomaly scan between 1 January 2008 and 30 June 2011. Information on FL and gestational age (GA) at anomaly scan, on birth weight and GA at delivery and on chromosomal abnormalities was obtained from the Danish Fetal Medicine Database.

RESULTS

Short FL was identified in 2718 (1.8%) of 147,766 fetuses and was present in 11 (16.2%) of the 68 fetuses affected by trisomy 21 (positive likelihood ratio (LR+) 8.8 (95% CI, 5.1-15.2)). Trisomy 13/18 and unbalanced autosomal structural abnormalities were also associated with a short FL in three (12.0%, LR+ 6.5 (95% CI, 2.3-18.9)) and eight (32.0%, LR+ 17.4 (95% CI, 9.8-30.9)) of the cases, respectively. The risk of a fetus having trisomy 21, trisomy 18, trisomy 13 or an unbalanced autosomal structural abnormality was 1 : 123 (95% CI, 79-192), given a short FL. Pregnancies with a fetus with short FL were more often affected by early preterm delivery (before 34 weeks) (5.6%; odds ratio (OR) = 4.2 (95% CI, 3.5-4.9)) and small-for-gestational-age (SGA) infants (13.9%; OR = 4.3 (95% CI, 3.8-4.8)).

CONCLUSION

Short FL at the second-trimester anomaly scan is associated with a significantly higher relative risk of chromosomal abnormalities, and a substantially higher absolute risk for SGA and early preterm delivery.

Tracking of fetal growth characteristics during different trimesters and the risks of adverse birth outcomes

BACKGROUND

Fetal growth characteristics are used to identify influences of several maternal characteristics and to identify individuals at increased risk of adverse outcomes. The extent to which fetal growth characteristics track in different trimesters is not known.

METHODS

In a population-based prospective cohort study among 8636 pregnant women, we examined the extent to which fetal growth characteristics track, are influenced by maternal socio-demographic and lifestyle related determinants and are associated with birth outcomes. Fetal growth was assessed in each trimester and at birth.

RESULTS

Correlation coefficient between first-trimester crown-rump length and birthweight was r = 0.12 (P-value < 0.05). Correlation coefficients for fetal-head circumference, (femur) length and (estimated) fetal weight ranged from r = 0.16 to r = 0.30 (all P-values < 0.05) between second trimester and birth and from r = 0.36 to r = 0.58 (all P-values < 0.05) between third trimester and birth, and were highest for (estimated) fetal weight. Correlation coefficients for (estimated) fetal weight tended to be lower among overweight mothers, as compared with normal weight mothers, but were not influenced by other maternal characteristics. First, second and third-trimester fetal growth characteristics were associated with risks of preterm birth and small size for gestational age at birth,with the strongest associations present in third trimester.

CONCLUSION

Fetal growth characteristics track moderately throughout gestation, with stronger tracking coefficients present in later pregnancy. Tracking coefficients were not materially influenced by maternal socio-demographic and lifestyle characteristics. First, second and third trimester fetal growth characteristics were associated with the risk of adverse birth outcomes.

Effects of embryo culture media do not persist after implantation: a histological study in mice

STUDY QUESTION

Is post-implantation embryonic development after blastocyst transfer affected by exposure to different assisted reproduction technology (ART) culture media?

SUMMARY ANSWER

Fetal development and placental histology of ART embryos cultured in vitro in different ART media was not impaired compared with embryos grown in vivo.

WHAT IS KNOWN ALREADY

The application of different in vitro culture (IVC) media for human ART has an effect on birthweight of newborns. In the mouse model, differences in blastocyst formation were reported after culture in different ART media. Moreover, abnormalities in the liver and heart have been detected as a result of suboptimal IVC conditions.

STUDY DESIGN, SIZE, DURATION

Fertilized oocytes from inbred and outbred breeding schemes were retrieved and either immediately transferred to foster mothers or incubated in control or human ART culture media up to the blastocyst stage prior to transfer. Placental and fetal anatomy and particularly bone development were evaluated.

PARTICIPANTS/MATERIALS, SETTING, METHODS

B6C3F1 female mice were used as oocyte donors after ovulation induction. C57Bl/6 and CD1 males were used for mating and CD1 females as foster mothers for embryo transfer. Fertilized oocytes were recovered from mated females and incubated in sequential human ART media (ISM1/ISM2 and HTF/Multiblast), in control media [KSOM(aa) and Whitten's medium] or grown in utero without IVC (zygote control). As in vivo, control B6C3F1 females were superovulated and left untreated. Fetuses and placentae were isolated by Caesarean section and analysed at 18.5 days post-coitum (dpc) for placenta composition and at 15.5 dpc for body weight, crown-rump length (CRL), fetal organ development, morphological development, total bone length and extent of bone ossification.

MAIN RESULTS AND THE ROLE OF CHANCE

No major differences in the number of implantation sites or in histological appearance of the placentae were detected. CRL of KSOM(aa) fetuses was higher compared with zygote control and Whitten's medium. Histological analysis of tissue sections revealed no gross morphological differences compared with the in vitro groups or in vivo controls. Furthermore, no changes in skeletal development and degree of ossification were observed. However, fibula and tibia of ISM1/ISM2 fetuses were longer than the respective ones from in vivo fetuses.

LIMITATIONS, REASONS FOR CAUTION

Findings in the mouse embryo and fetus may not be fully transferable to humans. In addition to skeletal development and placentation, there may be other parameters, e.g. on the molecular level which respond to IVC in ART media. Some comparisons have limited statistical power.

WIDER IMPLICATIONS OF THE FINDINGS

Our data suggest that once implantation is achieved, subsequent post-implantation development unfolds normally, resulting in healthy fetuses. With mouse models, we gather information for the safety of human ART culture media. Our mouse study is reassuring for the safety of ART conditions on human embryonic development, given the lack of bold detrimental effects observed in the mouse model.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Deutsche Forschungsgemeinschaft (BO 2540/4-1 and SCHL 394/9-1) and by the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (S.L.G.); Bilateral grant NWO-DFG 63-258. None of the authors has any conflict of interest to declare.

TRIAL REGISTRATION NUMBER

Not applicable.

Isolated short femur length on second-trimester sonography: a marker for fetal growth restriction and other adverse perinatal outcomes

OBJECTIVES

To estimate the association between isolated second-trimester short femur length and fetal growth restriction as well as other adverse perinatal outcomes.

METHODS

We conducted a retrospective cohort study of patients with singleton gestations presenting for sonography between 16 and 24 weeks' gestation from 1990 to 2009. Cases of aneuploidy, skeletal dysplasia, and major anomalies were excluded. Short femur length was defined as length below the 10th percentile for gestational age and was considered isolated when both the estimated fetal weight and abdominal circumference were above the 10th percentile for gestational age. Isolated short femur length below the 5th percentile was also evaluated. The primary outcome was fetal growth restriction, defined as birth weight below the 10th percentile. Secondary outcomes included preeclampsia and preterm birth before 37 and 34 weeks. Univariable and multivariable logistic regression analyses were used to estimate the risk of these outcomes in fetuses with isolated short femur length.

RESULTS

Of 73,884 patients, 569 (0.8%) had a fetus with a femur length below the 10th percentile, of which 268 (47.1%) were isolated; 210 patients (0.3%) had a fetus with a femur length below the 5th percentile, of which 34 (16.2%) were isolated. Isolated short femur lengths below the 10th and 5th percentiles were associated with an increased risk of fetal growth restriction (<10th: adjusted odds ratio [aOR], 3.4; 95% confidence interval [CI], 2.4-4.6; <5th: aOR, 4.6; 95% CI, 2.0-10.7) and also with an increased risk of preterm birth before 37 and 34 weeks. There was no significant association between isolated short femur length and preeclampsia.

CONCLUSIONS

Isolated short femur length on second-trimester sonography is associated with a greater than 3-fold increased risk of fetal growth restriction and an increased risk of preterm birth. Serial growth assessment may be warranted in these cases.