Ultrasound examination and measurement of fetal biometry have become an integral part of recent obstetric care. These measurements can serve for measuring the gestational age (GA) or assessment of fetal development. Selection of the appropriate reference charts is of great importance to ensure accurate diagnosis ( Ayad et al., 2016). Some published reference charts are blemished (Altman & Chitty, 1994). It is well known that ethnicity has a significant influence on fetal biometry ( Yeo et al., 1994) & ( Jacquemyn et al., 2000).
A Pilot study was done by Zaki et al in National Research Centre, Giza Governorate in Egypt to compare the Egyptian fetal biometric measurements with those of other Western populations. This study was a limited pilot study applied on only 71 pregnant women between 14 & 24 weeks of gestation, not through the whole pregnancy and did not include a wide range, diverse and a large number of Egyptian population from different governorates. They found that Egyptian data are totally different from other western data and they recommended the development of a national fetal ultrasound biometric reference charts that can be used for the assessment of fetal growth and in clinical practice (Zaki et al., 2012).
Accordingly this study was designed to provide fetal biometric charts and regression equations for biometric measurements of pregnant women between 12 and 42 weeks of gestation living in Ismailia and Port Said Governorates in Egypt as a first step in creating Egyptian growth curve and there is need for more data from other governorates in Egypt to help in establishing the final Egyptian growth curve including all data from whole Egyptian Governorates . Our sample size, a sample of several hundred is sufficient to give a reasonable estimate of extreme centiles.We chose a lower gestational age limit of 12 weeks because the nomograms for BPD and FL are useful at such early gestational ages when an ideal fetal position for measurement of the crown-rump length cannot be obtained.
Several authors have emphasized the value of using customized fetal biometry charts that consider variables such as maternal weight, parity, and race (Pang et al., 2003). Cross-sectional and longitudinal ultrasound studies have demonstrated racial variations in fetal growth (Drooger et al., 2005; Jacquemyn et al., 2000; Salomon et al., 2006). It was reported that the fetus of Turkish and Moroccan women had a shorter femur, smaller abdominal and HCs than Belgian women, and in Africa, Nigerian AC and biparietal diameter were found to be smaller than those of the British population (Jacquemyn et al., 2000; Okonofua et al., 1988).
We compared the mean of fetal biometric measures (BPD, HC, AC, FL) of our results with that of other different countries as United Kingdom ( Snijders & Nicolaides, 1994), Korea ( Jung et al., 2007) and North America ( Lessoway et al., 1998). BPD was quitely higher in the UK women, while in Korean and North American were lower than Egyptian women, HC was higher in the UK and North American people than Egyptian ones while in Korean people there was an unremarkable variability. This may be attributed to the method or the way BPD and HC measures were taken, ethnic, racial factors and the shape of the head. In abnormal head shapes, the cephalic index (CI) defined by the equation BPD × 100/occipito?frontal diameter is used. The CI ranges from 75% to 85%. It is lower in dolichocephalic fetuses and higher in brachycephalic fetuses. The accuracy of BPD in determining GA between 14 and 26 weeks is + 9 days is 95% of cases.
AC was higher in UK and North American women than Egyptian ones especially in third trimester, while there was an unstable variability between Korean and Egyptian women, although the AC requires more quality assurance to ensure accurate level of measurement compared with the HC and BPD in the third trimester, the fetal abdomen is more accessible to scan than the head, particularly late in the pregnancy. As such, the AC measurement is faster and easier to obtain than the expected fetal weight in a term pregnancy, where the engaged head can make the HC and BPD measurements technically difficult and less reliable (Nesbitt-Hawes et al., 2014).
Lastly, there was no remarkable variability regarding FL of UK, North American and Egyptian women, while regarding Korean women they had shorter femur than that of Egyptian women. The difference in FL measurements among the different populations illustrates the importance of selecting charts appropriate for one’s own population. These differences may be attributed to the difference in methodology, racial variation, or both. A short femur has been reported as one of the soft markers associated with Down syndrome. Hence, it might be important to pay more attention to ethnic variation in the fetal FL. ( Zaki et al., 2012).
It has been shown that the fetal femur length can be underestimated by obtaining oblique images of the femur or overestimated by including the non-ossified portions of the femur ( Shipp et al., 2001). We do not think that there was a systematic bias with regard to measuring the femur length, because we included only the ossified portion of the femur shaft, and all the measurements were done in the same way on all patients. The difference in FL measurements among the different populations illustrates the importance of selecting charts appropriate for one’s own population.
Our new Egyptian fetal measurements charts for fetal biometry and reference equations have clinical relevance since they provide sonographers new reference equations in the obstetrical practice.