Jennifer M. Mitchell

The Prevalence of Polycystic Ovaries on Ultrasound Scanning in a Population of Randomly Selected Women

Summary: Polycystic ovaries (PCO) diagnosed by ultrasound have been commonly reported amongst healthy women. The study aimed to determine the prevalence of PCO in a population of women from the community, and to relate it to clinical and endocrinological data. Twelve hundred women chosen randomly from electoral rolls were invited to take part in the study. Two hundred and fifty five women (21%) who met eligibility criteria agreed to participate and 183 women (16%) finally completed the study. Seventy two women did not attend. An ultrasound scan and blood tests were taken on day 5–9 of their menstrual cycles. Data about their menstrual periods and reproductive history was collected. The prevalence of PCO was 21% (39 of 183). No differences existed between women with PCO and normal ovaries with respect to uterine size, body mass index, luteinizing hormone levels, serum hormone binding globulin levels and fertility status. Hirsutism (Ferriman Gallwey score >7), elevated testosterone levels and irregular menstrual cycles were significantly more frequent amongst women with PCO. Mean ovarian volume was larger in women with PCO irrespective of the use of hormonal contraception. Fifty nine per cent of women with PCO had irregular menstrual cycles or elevated Ferriman Gallwey scores or both. There was no detectable effect of PCO on parity or miscarriage although only 70% of women with PCO had evidence of an adequate ovulation compared to 95% of women with normal ovaries.

Fetal liver length in normal and isoimmunized pregnancies.

The length of the right lobe of the fetal liver was measured by means of ultrasound examined on 53 occasions in 21 isoimmunized pregnancies. Fetal blood samples were taken in all patients within 24 hours. Comparisons were made with 350 measurements of liver length in normal pregnancies. A good correlation was found between liver length and fetal hemoglobin level (r = 0.794, p less than 0.001) and between liver length and reticulocyte count (r = 0.721, p less than 0.001). At the time of first sample, all fetuses with a hemoglobin of less than 100 gm/L had a liver length that was greater than the ninetieth percentile. Liver length measurement seems to be a useful indicator of the degree of fetal anemia in isoimmunized pregnancies.

Transabdominal scanning of the cervix at the 20-week morphology scan: Comparison with transvaginal cervical measurements in a healthy nulliparous population

Background:  Healthy, nulliparous women at low risk for preterm birth would not usually undergo transvaginal scanning at the 20‐week morphology scan. The study aimed to determine whether transabdominal cervical measurement would be sufficient to exclude a short cervix in this population.

Ultrasonographic measurement of liver length in the small-for-gestational-age fetus

OBJECTIVE Our purpose was to measure fetal liver size in small-for-gestational-age fetuses diagnosed by ultrasonography and to determine whether the small abdominal circumference used to diagnose small for gestational age is the result of a small liver. STUDY DESIGN Ninety-eight pregnant women who were diagnosed as having a fetus that was small for gestational age were included. All had a fetal ultrasonographic measurement of abdominal circumference <10th percentile for gestational age. Measurements were made of the length of the right lobe of the fetal liver within 2 weeks of delivery. The liver length measurements were compared with data collected from a normal population that had been previously published by the authors. The group of fetuses with liver length measurements <10th percentile for gestational age were compared with those with liver length measurements within normal limits. RESULTS Liver length measurements were >10th percentile in 80 fetuses (82%). Eighteen fetuses (18%) had small liver lengths, and this group had significantly smaller antenatal ultrasonographic measurements of head, abdomen, and femur. They were smaller at birth with smaller placentas and they had a higher perinatal mortality rate. CONCLUSION The small abdominal circumference measurement that is the mainstay of ultrasonographic diagnosis of small for gestational age is thought to be a reflection of fetal liver size. This study questions that assumption. The majority of small-for-gestational-age fetuses in this small study did not have small liver lengths. The small abdominal circumference measurement may reflect a reduction in size of other intra-abdominal organs, reduced amounts of fat, or possibly an elevated diaphragm because of poor lung growth.

Pulmonary hypoplasia and fetal breathing in preterm premature rupture of membranes

Forty-eight patients with premature rupture of membranes prior to 24 weeks gestation (PPROM) were studied to investigate whether there was any difference in fetal breathing movements in those fetuses that did or did not develop pulmonary hypoplasia. The diagnosis of pulmonary hypoplasia was made on the basis of ultrasound measurement of fetal lung length. A control group of fetuses with intact membranes and normal pregnancies at the same gestation was also studied. The group that developed pulmonary hypoplasia had significantly less breathing movements than those that did not develop pulmonary hypoplasia and controls. This reduction in breathing movements may contribute to the development of pulmonary hypoplasia.

Thickness of tissues intervening between the transducer and fetus and models for fetal exposure calculations in transvaginal sonography

In transvaginal scanning the tissues intervening between the fetus and transducer are relatively thin. The average thickness in the first trimester is 25 mm and reduces to 15 mm by the third trimester; the minimum thicknesses are 14 and 8 mm, respectively. Two models are proposed for calculating exposure in transvaginal scanning. The models are considered in terms of the overlying tissues and the target tissues. A fixed path, constant attenuation of 0.3 dB/MHz describes the properties of the overlying tissues throughout pregnancy. In the model used in first-trimester scanning, the target tissues of the embryo/fetus are considered to have properties similar to those of soft tissues, and they attenuate the energy at the same rate as the overlying tissues. In the model used in second- and third-trimester scanning, the bony structures of the fetus are the target tissues. These reflect 30% of the incident energy and attenuate all of the transmitted energy at their surface.