A prospective study to compare serum human placental lactogen and menstrual dates for determining gestational age.

In a group of 575 healthy pregnant women with certain menstrual dates the estimation of the length of gestation from maternal serum human placental lactogen concentrations has been compared with gestational age calculated from the last menstrual period and ultrasonic measurements of the fetal biparietal diameter. In 412 of these patients labor started spontaneously, and the estimated dates of delivery determined by these three methods were also compared. In the range of 9 to 17 weeks of pregnancy, gestational age can be determined by human placental lactogen measurement to within 7 days (+/- 1 SD) which compares favorably with other methods. Regarding the prediction of the expected date of delivery, 88% were delivered within 2 weeks of the date predicted by last menstrual period, 82% within 2 weeks of the sonar date, and 80% by the date determined by human placental lactogen assessment. Prediction of delivery in a further group of 139 women with uncertain dates gave 73% within 2 weeks by sonar date and 69% within 2 weeks by human placental lactogen determination. We suggest human placental lactogen measurements should become part of routine antenatal care complementing rather than replacing the role of ultrasonic scanning. For those doctors and patients who wish to avoid more exposure to ultrasonic scanning than absolutely necessary, human placental lactogen estimates offer an alternative method for assessing the length of gestation.

Changes in plasma solutes after food.

In experiments on 8 healthy young male volunteers, the ingestion of a large meal was found to cause plasma osmolality to rise from 288.8 +/- 0.8 (mean +/- s.e. mean) to 295.6 +/- 0.9 mmol/kg at 4 hours (P less than 0.001). There was an accompanying rise in plasma sodium (Na) from 141.9 +/- 0.8 to 144.6 +/- 0.8 mmol/l, also at 4 hours (P less than 0.01), but little change in other plasma electrolytes. Serum total amino acids rose slightly, non-esterified fatty acid fell minimally and changes in blood glucose concentrations were unremarkable. Thirst was experienced at plasma osmolality of 294.8 +/- 0.7 mmol/kg. Repeating the experiment either without food, or with the salt content of the meal only, was without effect on plasma Na, other solutes or osmolality. Postprandial hypersomolality and hypernatraemia is probably due to movement of water from the vascular compartment to the gut, or into cells. Plasma osmolality is best measured in the fasting state.