To the Editor:-Realizing the substantial variation in fetal growth in the second trimester, experienced obstetrical sonologists have, for many years, questioned the validity of most second trimester methods for sonographic determination of gestational age. Thus, according to Brenner et al, 1 at 23 weeks the tenth percentile for fetal weight is 370 g, while the ninetieth percentile is 990 g. An average fetal weight of 370 g is found in the 20th week of pregnancy, whereas 90 g compares to 27 weeks. Hadlock et al, have now demonstrated that dating by a combination of parameters (biparietal diameter, head circumference, abdominal circumference, and femur length), which are the parameters used in a number of equations to determine fetal weight, is better than using the head circumf erence only. We may, therefore, conclude that the biological variation in fetal growth to its full extent affects sonographic determination of gestational age in the second trimester. Hadlock et al compared nonlinear dating functions from cross-sectional studies based on menstrual age with linear equations based on serial studies of individual fetuses from pregnancies with known date of ovulation.3·4 A table containing misleading information with regard to the systematic errors of the linear equations was used (example, correct mean value for the mean head diameter is -0.95 days, not 6.7 days), giving the reader the impression that the linear functions were inferior to the nonlinear polynomials. It was also kept a secret for the reader that the main topic of the Rossavik and Fishbume4 article was the observation that, because of the biological variation in growth rate, a single sonographic measurement to determine gestational age in the second trimester does not provide the needed accuracy for high quality prenatal care. Thus, none of the Rossavik equations given in the table mentioned are actually used to determine gestational age after 14 weeks of gestation. For any single scan procedure, the biological variaassessed by the systematic error. A significant systematic error means that no support was obtained for the method. 6 The amazing precision observed for the present study cannot change this fact. The conclusions were supported neither by the data nor by the citations. Although longitudinal studies by now have provided overwhelming evidence that linear dimensions of the fetal body grow linearly in the first two trimesters, clinicians continue to use curvilinear functions for dating purposes. The discussion today is, however, not linear versus curvilinear, but linear versus which one of the multiple differently shaped curvilinear functions in current use. This question cannot be answered unless the presentation or test of each curvilinear function is accompanied by a deviation plot.

Amrinone, a bipyridine derivative, has both vasodilating and positive inotropic properties. The cardiovascular effects of amrinone and dopamine were evaluated in eight acutely instrumented normotensive gravid baboons anesthetized with Ketamine. Amrinone was compared with dopamine, both infused systemically in random sequence and two randomly varying concentrations (8 or 40 μg/kg/min). Dopamine at 40 μg/kg/min produced a significant increase in mean arterial pressure, systemic vascular resistance, and left ventricular stroke work index. Amrinone at 40 μg/kg/min resulted in a significant increase in both heart rate and cardiac output, while significantly decreasing systemic vascular resistance. Other cardiac parameters were not significantly altered. We conclude that, in the gravid baboon, intravenous dopamine elicited the expected cardiovascular changes noted above, while amrinone proved to be an effective vasodilating agent that increases cardiac output without significantly altering left ventricular work.

Journal of Ultrasound in MedicineVolume 11, Issue 3 p. 74-74 Letter to the Editor Growth in twin gestations I K Rossavik, I K RossavikSearch for more papers by this author I K Rossavik, I K RossavikSearch for more papers by this author First published: 01 March 1992 https://doi.org/10.7863/jum.1992.11.3.74AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume11, Issue3Mar 1992Pages 74-74 RelatedInformation

Resistance to the passage of the fetus during parturition has been estimated indirectly by calculation of the active contraction area during the first stage of labor until the cervix reaches a dilatation of 5 cm--the period of cervical resistance. Parturients with a high total uterine impulse in this period were studied. Two different patterns of cervical resistance with corresponding clinical pictures were found. Type I had a high frequency of cesarean sections with a good correlation to the resistance. With high resistance there also was a tendency to low Apgar scores at 1 minute. Type II had normal 1 minute Apgar scores and only vaginal deliveries.

Continuous fetal heart rate (FHR) recordings from 200 parturients in first stage of labour were evaluated according to conventional systems and compared with the Apgar scores at one minute. The results were disappointing, but they indicate that an improvement could be achieved by taking into consideration the periodical total uterine impulse (TUI) in the first stage of labour.

The resistance to the passage of the fetus during labour has been estimated indirectly by calculation of the total area below the intrauterine pressure curve (total uterine impulse) in two periods during the first stage of labour. A good correlation was found between the total uterine impulse from a cervical dilatation of 5 to 10 cm, the outcome of the second stage of labour and the Apgar score at one minute.