Effect of a standardized maternal meal on fetal middle cerebral artery Doppler indices: A single-blinded crossover study.

OBJECTIVE: Measures of Doppler blood flow velocity profiles are an integral part of monitoring fetal well-being during pregnancy. These examinations are performed at different times of the day and at different maternal meal states. In uncomplicated pregnancies, we assessed the effect of a standardized maternal meal on middle cerebral artery (MCA) and umbilical artery (UA) Doppler blood flow velocity pulsatility indices (PIs) and MCA peak systolic velocity (PSV). METHODS: In this prospective single-blinded crossover study 25 healthy women were examined at 36 weeks of pregnancy. The first examination was performed in the morning following overnight fast, and repeated after extended fast (state A), and after a standard breakfast meal (state B). RESULTS: Irrespective of maternal prandial status, the MCA-PI values were lower in the 2nd compared to the 1st examination (-0.187; p = 0.071, and -0.113; p = 0.099, state A and B, respectively). Compared to the values in the 1st examination, the UA-PI values, were higher after extended fast (0.014; p = 0.436), and lower post-prandially (-0.036; p = 0.070). The difference (state B minus state A) between the meal states were not significant (0.074; p = 0.487 and -0.050; p = 0.058, for MCA-PI and UA-PI, respectively). Adjusting for the possible influence of fetal heart rate on MCA-PI and UA-PI, the differences between meal states remained non-significant (p = 0.179, p = 0.064, respectively). The MCA-PSV values increased after the meal (6.812; p = 0.035), whereas no increase was observed following extended fast (0.140; p = 0.951). The difference in MCA-PSV values between the two meal states was not significant (6.672; p = 0.055). CONCLUSION: Our results demonstrate possible diurnal variations in MCA-PI and UA-PI, with and without adjustment for fetal heart rate, that seem to be unaffected by maternal meal intake in healthy pregnancies.

The impact of umbilical vein blood flow and glucose concentration on blood flow distribution to the fetal liver and systemic organs in healthy pregnancies.

Glucose is a major energy substrate for the fetus, including liver, heart, and brain metabolism. The umbilical vein (UV) blood flow supplies the fetal liver directly from the placenta, whereas a fraction is shunted via ductus venosus (DV) to the fetal systemic circulation bypassing the fetal liver. We hypothesized UV glucose concentration to be a major regulator of the distribution of glucose supply between the fetal liver and DV, and explored the influence of maternal metabolic status on this distribution. We included 124 healthy women with normal singleton pregnancies, scheduled for elective cesarean section. UV and DV blood flow measurements were performed by Doppler ultrasound immediately before, and blood samples were obtained during surgery. UV blood flow was significantly correlated with DV blood flow, liver blood flow, and the DV shunting fraction, while UV glucose concentration was not. For normal-weight mothers, the maternal-fetal glucose gradient was positively correlated with DV shunting fraction, and negatively with liver blood flow. For the fetuses of the overweight mothers no such correlation was found. This indicates that within the normal physiological range the human fetus makes adaptations of blood flow to ensure individual needs related to the offered maternal energy supply.

The effect of a maternal meal on fetal liver blood flow.

INTRODUCTION: During the third trimester of development, the human fetus accumulates fat, an important energy reservoir during the early postnatal period. The fetal liver, perfused by the nutrient-rich and well-oxygenated blood coming directly from the placenta, is assumed to play a central role in these processes. Earlier studies have linked fetal liver blood flow with maternal nutritional status and response to the maternal oral glucose tolerance test. Our aim was to explore the effect of a regular maternal meal on fetal liver blood flow at two timepoints during the third trimester, representing the start and towards the end of the fetal fat accretion period. We also sought to explore the influence of prepregancy body mass index on how the maternal meal affects fetal liver blood flow. METHODS: Using ultrasound Doppler, we examined 108 healthy women with singleton pregnancies in gestational weeks 30 and 36. At each visit, the first examination was performed with the participant in a fasting state at 08.30 a.m., followed by a standard breakfast meal of approximately 400 kcal. The examination was repeated after 105 minutes. Umbilical vein and ductus venosus blood flow was estimated from diameter and blood flow velocity measurements. Fetal liver flow was calculated as umbilical vein flow minus ductus venosus flow, and change in liver blood flow as flow after minus before the meal. The total group was divided into a normal-weight group (prepregancy body mass index 18.5-25.0 kg/m2; n = 83) and an overweight group (prepregancy body mass index >25.0 kg/m2; n = 21). Four women with prepregancy body mass index <18.5 kg/m2 were excluded from these analyses. Non-parametric statistical hypothesis tests were used for group comparisons. RESULTS: For the total group, we observed a significant increase in median (10th - 90th percentile) liver flow 28.9 (‒67.9-111.6) ml/min (p = 0.002) following the meal in week 36, but not in week 30, ‒2.63 (‒53.2-65.0) ml/min (p = 0.91). This result in turn yielded a statistically significant increase in delta liver flow from weeks 30 to 36 of 26.0 (‒107.1-146.6) ml/min (p = 0.008). The increase in postprandial liver flow was observed only in the normal-weight group in week 36. Accordingly, the delta liver flow values between the two weight groups were significantly different in week 36 (p = 0.006) but not in week 30 (p = 0.155). Among the normal-weight women, the increase in delta liver blood flow from weeks 30 to 36 was 39.3 (‒83.0-156.1) ml/min (p<0.001); in contrast, we observed no statistically significant change in the overweight group (‒44.5 (‒229.0-123.2) ml/min; p = 0.073). As a substitute for liver size, we divided the delta liver flow values by abdominal circumference and found no changes in the statistical significance results within or between the two weight groups. CONCLUSION: In our healthy study population, we observed a statistically significant difference in liver blood flow after maternal intake of a regular meal. This effect depended on gestational age and maternal prepregancy body mass index, but apparently was independent of liver size, based on abdominal circumference as a proxy measure.

A maternal meal affects clinical Doppler parameters in the fetal middle cerebral artery.

INTRODUCTION: Middle cerebral artery (MCA) and umbilical artery (UA) Doppler blood flow pulsatility indices (PIs) and MCA peak systolic velocity (PSV) are essential variables for clinically evaluating fetal well-being. Here we examined how a maternal meal influenced these Doppler blood flow velocity variables. METHODS: This prospective cohort study included 89 healthy Caucasian women with normal singleton pregnancies (median age, 32 years). Measurements were performed at gestational weeks 30 and 36, representing the start and near the end of the energy-depositing period. Measured variables included the MCA-PI, UA-PI, fetal heart rate (FHR) and MCA-PSV. The cerebroplacental ratio (CPR) was calculated as the ratio of MCA-PI to UA-PI. The first examination was performed in the fasting state at 08:30 a.m. Then participants ate a standard breakfast (approximate caloric intake, 400kcal), and the examination was repeated ~105 min after the meal. RESULTS: Without adjustment for FHR, fetal MCA-PI decreased after the meal at week 30 (‒0.115; p = 0.012) and week 36 (‒0.255; p < 0.001). All PI values were negatively correlated with FHR. After adjustment for FHR, MCA-PI still decreased after the meal at week 30 (‒0.087; p = 0.044) and week 36 (‒0.194; p < 0.001). The difference between the two gestational weeks was non-significant (p = 0.075). UA-PI values did not significantly change at week 30 (p = 0.253) or week 36 (p = 0.920). CPR revealed significant postprandial decreases of -0.17 at week 30 (p = 0.006) and -0.22 at week 36 (p = 0.001). Compared to fasting values, MCA-PSV was significantly higher after food intake: +3.9 cm/s at week 30 (p < 0.001) and +5.9 cm/s at week 36 (p < 0.001). CONCLUSION: In gestational weeks 30 and 36, we observed a postprandial influence that was apparently specific to fetal cerebral blood flow.