Israel Medical Association Journal

Background: While the ratio of male to female births (sex-ratio at birth [SRB]) in humans is remarkably stable on the population level, there are many families with multiple same-sex offspring.

Objectives: To identify a putative sub-population with skewed SRB and explore potential factors affecting the SRB.

Methods: A retrospective cohort study including 66,054 families with up to nine same-sex offspring evaluated between 2003 and 2015 at Hadassah-Hebrew University Medical Center. Outcome measures were observed prevalence and SRB of families with up to nine same-sex offspring in a single family. Analyses included the effect of parity, month and year of delivery, inter-delivery interval, and presence of a sequence of previous same-sex offspring on the SRB.

Results: The study comprised 193,411 live-born babies with SRB of 1.057 in favor of males. The proportion of SRB in families with up to nine same-sex offspring did not differ from the calculated presumed proportion. Furthermore, none of the tested factors (parity, month and year of delivery, inter-delivery interval, and the sequence of previous same-sex offspring) were significantly associated with SRB.

Conclusions: SRB was not associated with any of the tested demographic characteristics. We could not identify a skew in SRB even in families with up to nine consecutive same sex offspring. This finding suggests that in the majority of the population the chance of a male or female fetus in each pregnancy remains similar in every pregnancy, regardless of any of the tested variables.

Background: Sonographic estimation of birth weight may differ among evaluators due to its operator-dependent nature.

Objectives: To compare the accuracy of estimation of fetal birth weight by sonography between ultrasound-certified physicians and registered diagnostic medical technicians.

Methods: The authors reviewed ultrasound examinations that had been performed by either technicians or ultrasound-certified obstetricians between 2010 and 2017, and within 2 days of delivery. Inclusion criteria were: singleton viable pregnancy, details of four ultrasound measurements (abdominal circumference, bi-parietal diameter, head circumference, and femur length), and known birth weight. The estimated fetal weight (EFW) was calculated according to the Hadlock formula, incorporating the four ultrasound measurements. The mean percentage error (MPE) was calculated by the formula: (EFW-birth weight) x100 / birth weight.

Results: Technicians performed 9741examinations and physicians performed 352 examinations. The proportion of macrosomic neonates was similar in both groups. Technicians were more accurate than physicians in terms of the MPE, absolute MPE, proportion of estimates that fell within ± 10% of birth weight, and Euclidean distance (P < 0.0001 for all comparisons). They were also more accurate in terms of sensitivity, specificity, positive predictive value, negative predictive value, and area under the receiver operating curve. Furthermore, for fetuses weighing more than 4000 grams the technicians had a lower total false prediction rate.

Conclusions: Medical technicians in our institute performed better than physicians in estimating fetal weight. Further studies are warranted to confirm our findings and better delineate the role of repeat physician’s examination after an initial estimation by an experienced technician.