Fetal size charts for the Italian population. Normative curves of head, abdomen and long bones.

OBJECTIVE: To describe size charts developed from fetuses of Italian couples. METHOD: Prospective cross-sectional investigation conducted in three referral centers for prenatal diagnosis. The population of the study included fetuses between the 16th and the 40th week of gestation recruited prospectively and examined only once for the purpose of this study. Exclusion criteria comprised all maternal and/or fetal conditions possibly affecting fetal biometry. The following biometric variables were measured: biparietal diameter, head circumference, abdominal circumference, femur, tibia, humerus, ulna and radio length. The statistical procedure recommended for analyzing this type of data set was employed to derive normal ranges and percentiles. Birthweight was also recorded. Our centiles were then compared with results from other studies. RESULTS: The best-fitted regression model to describe the relationships between head circumference and abdominal circumference and gestational age was a cubic one, whereas a simple quadratic model fitted BPD, and length of long bones. Models fitting the SD were straight lines or quadratic curves. Neither the use of fractional polynomials (the greatest power of the polynomials being 3) nor the logarithmic transformation improved the fitting of the curves. CONCLUSION: We have established size charts for fetuses from Italian couples using the recommended statistical approach. Since the mean birthweight in this study is not statistically different from the official birthweight reported for the Italian population, these reference intervals, developed according to the currently approved statistical methodology, can be employed during second- and third-trimester obstetric ultrasound of fetuses from Italian couples.

Fetal DNA detection in maternal plasma throughout gestation.

The presence of fetal DNA in maternal plasma may represent a source of genetic material which can be obtained noninvasively. We wanted to assess whether fetal DNA is detectable in all pregnant women, to define the range and distribution of fetal DNA concentration at different gestational ages, to identify the optimal period to obtain a maternal blood sample yielding an adequate amount of fetal DNA for prenatal diagnosis, and to evaluate accuracy and predictive values of this approach. This information is crucial to develop safe and reliable non-invasive genetic testing in early pregnancy and monitoring of pregnancy complications in late gestation. Fetal DNA quantification in maternal plasma was carried out by real-time PCR on the SRY gene in male-bearing pregnancies to distinguish between maternal and fetal DNA. A cohort of 1,837 pregnant women was investigated. Fetal DNA could be detected from the sixth week and could be retrieved at any gestational week. No false-positive results were obtained in 163 women with previous embryo loss or previous male babies. Fetal DNA analysis performed blindly on a subset of 464 women displayed 99.4, 97.8 and 100% accuracy in fetal gender determination during the first, second, and third trimester of pregnancy, respectively. No SRY amplification was obtained in seven out of the 246 (2.8%) male-bearing pregnancies. Fetal DNA from maternal plasma seems to be an adequate and reliable source of genetic material for a noninvasive prenatal diagnostic approach.