The significance of fetal sacral length in the ultrasonographic assessment of gestational age

The morphometrical and topographical evaluation of the superior gluteal nerve in the prenatal period

Introduction

Advances in medical science are helping to break down the barriers to surgery. In the near future, neonatal or in utero operations will become the standard for the treatment of defects in the human motor system. In order to carry out such procedures properly, detailed knowledge of fetal anatomy is necessary. It must be presented in an attractive way not only for anatomists but also for potential clinicians who will use this knowledge in contact with young patients. This work responds to this demand and presents the anatomy of the superior gluteal nerve in human fetuses in an innovative way. The aim of this work is to determine the topography and morphometry of the superior gluteal nerve in the prenatal period. We chose the superior gluteal nerve as the object of our study because of its clinical significance—for the practice of planning and carrying out hip surgery and when performing intramuscular injections.

Material and methods

The study was carried out on 40 human fetuses (20 females and 20 males) aged from 15 to 29 weeks (total body length v-pl from 130 to 345 mm). Following methods were used: anthropological, preparatory, image acquisition with a digital camera, computer measurement system Scion for Windows 4.0.3.2 Alpha and Image J (accuracy up to 0.01 mm without damaging the unique fetal material) and statistical methods.

Results

The superior gluteal nerve innervates three physiologically significant muscles of the lower limb’s girdle: gluteus medius muscle, gluteus minimus muscle and tensor fasciae latae muscle. In this study the width of the main trunk of the nerve supplying each of these three muscles was measured and the position of the nerve after leaving the suprapiriform foramen was observed. A unique typology of the distribution of branches of the examined nerve has been created. The bushy and tree forms were distinguished. There was no correlation between the occurrence of tree and bushy forms with the body side (p > 0.05), but it was shown that the frequency of the occurrence of the bushy form in male fetuses is significantly higher than in female fetuses (p < 0.01). Proportional and symmetrical nerve growth dynamics were confirmed and no statistically significant sexual dimorphism was demonstrated (p > 0.05).

Conclusions

The anatomy of the superior gluteal nerve during prenatal period has been determined. We have identified two morphological forms of it. We have observed no differences between right and left superior gluteal nerve and no sexual dimorphism. The demonstrated high variability of terminal branches of the examined nerve indicates the risk of neurological complications in the case of too deep intramuscular injections and limits the range of potential surgical interventions in the gluteal region. The above research may be of practical importance, for example for hip surgery.

Second and third trimester estimation of gestational age using ultrasound or maternal symphysis-fundal height measurements: A systematic review

Many vulnerable women seek antenatal care late in pregnancy. How should gestational age be determined? We examine all available studies estimating GA >20 weeks. Ultrasound is much better than fundal height, and using cerebellar measurement appears to be the most accurate.

Linked article: This article is commented on by Philip J. Steer, pp. 1459 in this issue. To view this minicommentary visit https://doi.org/10.1111/1471‐0528.17127 .

Sonographic Assessment of Fetal Growth Abnormalities

Fetal growth abnormalities have significant consequences for pregnancy management and maternal and fetal well-being. The accurate diagnosis of fetal growth abnormalities contributes to optimal antenatal management, which may minimize the sequelae of inadequate or excessive fetal growth. An accurate diagnosis of abnormal fetal growth depends on accurate pregnancy dating and serial growth measurements. The fetal size at any given stage of pregnancy is either appropriate or inappropriate for the given gestational age (GA). Pregnancy dating is most accurate in the first trimester, as biologic variability does not come into play until the second and third trimesters. The authors describe the determination of GA with use of standard US measurements and how additional parameters can be used to confirm dating. Once dates are established, serial measurements are used to identity abnormal growth patterns. The sometimes confusing definitions of abnormal growth are clarified, the differentiation of a constitutionally small but healthy fetus from a growth-restricted at-risk fetus is described, and the roles of Doppler US and other adjunctive examinations in the management of growth restriction are discussed. In addition, the definition of selective growth restriction in twin pregnancy is briefly discussed, as is the role of Doppler US in the classification of subtypes of selective growth restriction in monochorionic twinning. The criteria for diagnosing macrosomia and the management of affected pregnancies also are reviewed. The importance of correct pregnancy dating in the detection and surveillance of abnormal fetal growth and for prevention of perinatal maternal and fetal morbidity and mortality cannot be overstated. The online slide presentation from the RSNA Annual Meeting is available for this article. ^©RSNA, 2020.

Normal development of sacrococcygeal centrum ossification centers in the fetal spine: a postmortem magnetic resonance imaging study

PURPOSE

To describe the temporal pattern of the appearance of the S1-Co1 centrum ossification centers (COCs) and provide reference data for the S1-S5 COCs and sacral length at various gestational ages (GAs).

METHODS

Postmortem magnetic resonance imaging (MRI) was performed on 71 fetuses (GA, 17-42 weeks) using the 3D dual-echo steady-state with water excitation T2 sequence in the sagittal plane. To confirm the reliability of this sequence, the MRI data were compared with the CT and histologic data obtained from two fetuses (GAs, 21 and 30 weeks). The presence or absence of each sacrococcygeal COC was recorded. Sacral length and S1-S5 COC height, sagittal diameter, transverse diameter, cross-sectional area, and volume were measured.

RESULTS

All fetuses showed S1-S3 COCs by 17 weeks, S4 COCs by 19 weeks, and S5 COCs by 28 weeks. The S4, S5, and Co-1 COCs were visualized in 70 (98.59%), 51 (71.83%), and 21 (29.58%) fetuses, respectively. Sacral length, height, sagittal, and transverse diameters increased linearly, while cross-sectional area and volume increased exponentially with advancing GA. Mean growth rates of the sagittal and transverse diameters, cross-sectional area, and volume, but not of height, significantly differed among the S1-S5 vertebrae.

CONCLUSION

We have presented the timing of appearance of individual sacrococcygeal COCs and the age-specific, normative MRI reference values for sacral length and the morphometric parameters of the sacral COCs, which are of clinical importance in the diagnosis of congenital sacral abnormalities and skeletal dysplasia.

Fetal kidney length as a useful adjunct parameter for better determination of gestational age

OBJECTIVES

To determine the validity of fetal kidney length and amniotic fluid index (AFI) in labor dating. 

METHODS

This prospective study included 180 pregnant women followed up in the outpatient clinic at the Department of Obstetrics and Gynecology, Gaziantep University, Turkey, between January 2014 and January 2015. The gestational age (GA) was estimated by early fetal ultrasound measures and last menstrual period. Routine fetal biometric parameters, fetal kidney length, and amniotic fluid index were measured. We studied the correlation between fetal kidney length, amniotic fluid index, and gestational age. 

RESULT

The mean gestational age depending on last menstrual period and early ultrasound was 31.98±4.29 (24-39 weeks). The mean kidney length was 35.66±6.61 (19-49 mm). There was a significant correlation between gestational age and fetal kidney length (r=0.947, p=0.001). However, there was a moderate negative correlation between GA and AFI. Adding fetal kidney length to the routine biometrics improved the effectiveness of the model used to estimate GA (R2=0.965 to R2=0.987). 

CONCLUSION

Gestational age can be better predicted by adding fetal kidney length to other routine parameters.