Influence of gestational age and maternal height on fetal femur length calculations.

OBJECTIVE: To determine whether current methods of detecting Down syndrome based on fetal femur length calculations are influenced by gestational age or maternal height. METHODS: Four formulas were used to calculate expected femur length (FL) based on the fetal biparietal diameter (BPD) between 15 0/7 weeks' gestation and 19 6/7 weeks' gestation. For each gestational age, the BPD:FL ratio for women shorter than one standard deviation (SD) below the mean height was compared with the ratio for women taller than one SD above the mean height. A measured:expected FL ratio of 0.91 or less and a BPD:FL ratio greater than 1.5 SD above the mean was considered abnormal. RESULTS: The four formulas used to calculate measured:expected FL ratios were significantly more likely to be abnormal at 15--16 weeks' gestation, compared with 18-19 weeks' gestation (P <.05). Maternal height correlated with femur lengths at 18 and 19 weeks' gestation (P <.05) but not at earlier gestational ages. At 18 and 19 weeks' gestation, women shorter than one SD below the mean were twice as likely to have an abnormal BPD:FL ratio compared with women taller than one SD above the mean (relative risk 2.38; 95% confidence interval 1.21, 4.69). CONCLUSION: Early gestational age increases a woman's risk of having an abnormal measured:expected FL ratio, whereas short stature increases a woman's risk of having an abnormal BPD:FL ratio at later gestational ages. These findings indicate that risk assessment for fetal Down syndrome for such patients might be inaccurate. (Obstet Gynecol 2001;97:742-6.

The effects of hypoxia and hyperoxia on fetal-placental vascular tone and inflammatory cytokine production.

OBJECTIVE: To determine the effects of fetal hypoxia and hyperoxia on placental vascular tone and production of interleukin-6 and tumor necrosis factor-alpha. STUDY DESIGN: The maternal and fetal circulation of 2 cotyledons from 5 human placentas were perfused for 4 hours. The fetal circulation of 1 cotyledon was perfused with hypoxic Hanks' balanced salt solution; the other was perfused with hyperoxic Hanks' balanced salt solution. Fetal vascular pressures were recorded every 10 minutes, and fetal vein effluents were collected hourly. RESULTS: Fetal-placental vascular perfusion pressure was reduced from baseline during hypoxic conditions. Cytokine concentrations were elevated during hyperoxic conditions compared with hypoxic conditions, with significant differences achieved at 2, 3, and 4 hours for interleukin-6 and at 4 hours for tumor necrosis factor-alpha. CONCLUSION: Fetal-placental vasodilation may be a compensatory mechanism to improve hypoxic conditions. Supraphysiologic oxygenation may contribute to the fetal inflammatory response syndrome and to the development of cerebral palsy.

Perinatal outcome following fetal single umbilical artery diagnosis.

OBJECTIVE: We report the frequency of associated congenital abnormalities in fetuses with a single umbilical artery as well as the sensitivity, specificity, positive predictive value and negative predictive value of ultrasound for detecting these abnormalities. We also report the pregnancy outcome of fetuses complicated by single umbilical artery, both isolated and with other congenital anomalies. METHODS: All pregnancies complicated by fetal single umbilical artery from 1995 to 1999 were identified. A retrospective chart review was performed on both the prenatal records and the ultrasound records of these pregnancies, determining the nature and incidence of other congenital abnormalities. Delivery data were collected to include gestational age at delivery, Apgar score, birth weight, mode of delivery, fetal gender and any complications. RESULTS: Ninety-two pregnancies were identified with a fetal single umbilical artery, of which outcome data were available for 65. Forty-eight (74%) cases were identified as isolated single umbilical artery. Seventeen (26%) cases had other congenital abnormalities. High-resolution ultrasound had 100% sensitivity and specificity for identifying single umbilical artery and an 85% sensitivity and 98% specificity for detecting other congenital abnormalities. Compared to isolated single umbilical artery, pregnancies complicated by single umbilical artery with other abnormalities had a statistically significantly increased rate of fetal aneuploidy, lower birth weight, preterm delivery and Cesarean delivery. CONCLUSION: Pregnancies complicated by fetal single umbilical artery, especially when associated with other congenital abnormalities, are at increased risk for adverse pregnancy outcome.

Hypoperfusion causes increased production of interleukin 6 and tumor necrosis factor alpha in the isolated, dually perfused placental cotyledon.

OBJECTIVE: Our purpose was to determine whether exposure of the isolated, perfused human placental cotyledon to different fetal circuit perfusion rates, and to concomitant pressure differences, alters placental production of interleukin 6 and tumor necrosis factor alpha. STUDY DESIGN: The maternal and fetal circulations of 2 cotyledons from 5 placentas were perfused for 4 hours. The fetal circulation of 1 cotyledon was perfused at a low rate of 1 mL/min, and the other at a high rate of 10 mL/min. The maternal circulation of each cotyledon was perfused at 10 mL/min. Effluents from the fetal circulation were collected at hourly intervals, and concentrations of interleukin 6 and tumor necrosis factor alpha were determined by enzyme-linked immunosorbent assay. Concentrations of interleukin 6, obtained from a prior study with an estimated physiologic fetal circulation rate of 4 mL/min, were compared with the low and high perfusion rate results. RESULTS: Concentrations of interleukin 6 and tumor necrosis factor alpha were greater at the perfusion rate of 1 mL/min, in comparison with the perfusion rate of 10 mL/min, with statistically significant differences achieved at 2 and 4 hours for interleukin 6 and at 4 hours for tumor necrosis factor alpha. Concentrations of both cytokines increased exponentially with time. Placental perfusion pressures were significantly greater at the perfusion rate of 10 mL/min. CONCLUSION: Placental hypoperfusion results in an increased production of both interleukin 6 and tumor necrosis factor alpha. This finding links placental perfusion abnormalities to the myriad of disorders associated with elevated concentrations of inflammatory cytokines, including cerebral palsy.