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Objective: To determine whether some offspring of women with diabetes are intrinsically more active than others in utero and whether those who are active are able to normalize their birth weight despite maternal hyperglycemia.
Research Design and Methods: We conducted a three-phase study to view the relationship between fetal movements and subsequent birth weight in women with diabetes. Phase I was designed to assess maternal perception of fetal movements in a population of 10 women with diabetes. To improve our fetal monitoring techniques, in phase II we analyzed fetal movements using the Card Guard home fetal monitoring device (CG 900P) in a population of 13 women with gestational diabetes mellitus (GDM). To apply our observations of fetal movements to a larger population, during phase III we conducted a retrospective analysis of fetal monitoring strips (HP 8041A) from 46 women with GDM to examine the relationship between fetal heart rate (FHR) accelerations and percentile birth weight, corrected for gestational age.
Results: Phase I confirmed that there is little variability in fetal movements (i.e., fetal kicks did not significantly deviate from one another on a day-to-day basis). In phase II, the fetal monitoring strips illustrated that the active fetuses (defined as ≥4 FHR accelerations in a 20-min period) were always active, and the inactive fetuses were always inactive. The mean birth weight percentile, corrected for gestational age, in the active group was 37 vs. 63% in the inactive group (P = 0.05). In phase III, the fetal monitoring strips showed an inverse correlation between the mean number of FHR accelerations and the birth weight of the fetus, corrected for gestational age. The mean birth weight percentile in the active group was 37 vs. 62% in the inactive group (P = 0.0017).
Conclusions: The fetus appears to play a role in determining its own destiny. Increased fetal activity may minimize the impact of hyperglycemia on subsequent birth weight. The inactive fetus appears to be at a higher risk for glucose-mediated macrosomia.
Maternal glucose concentration plays a major role in the birth weight of infants born to women with gestational diabetes mellitus (GDM). deVeciana et al. reported that women with GDM who only monitor preprandial glucose have a 42% risk of neonatal macrosomia, whereas those who monitor both preprandial and 1-h postprandial glucose decrease their risk of neonatal macrosomia to near normal. Macrosomia, defined as birth weight >90th percentile for gestational age, ethnicity, and sex, is associated with an increased risk of birth trauma, including shoulder dystocia, death, and cesarean deliveries. Literature also reports macrosomia in offspring of women with GDM, despite documentation of maternal normoglycemia. Using continuous glucose sensors in women with GDM has shown that continuous monitoring detects postprandial glucose elevations not detected by intermittent fingerstick blood glucose determinations. Perhaps the previous notion "macrosomia despite normoglycemia" is in reality "macrosomia due to undetected hyperglycemia."
Recent reports suggest that although postprandial hyperglycemia plays a major role in increasing the risk of macrosomia, it does not explain why the other 58% of the fetuses are not macrosomic. The "fidgety fetus hypothesis" seeks to explain this paradox, suggesting that fetal activity is an intrinsic trait that plays a role in determining subsequent birth weight. We hypothesize that some offspring of women with GDM may be intrinsically more active in utero, and those that are active may be able to compensate for the hyperglycemia and thus minimize their risk of macrosomia. We conducted a three-phase study to observe the relationship between fetal movements and subsequent birth weight of the fetus in women with diabetes. The first phase assessed fetal movements by maternal perception of fetal kicks. The second phase was designed to improve fetal monitoring techniques by home telemetry monitoring of fetal heart rate accelerations. The third phase applied our observations of fetal movements to a larger population of women with GDM who performed fetal heart rate (FHR) monitoring at clinic visits. This report describes all three phases and shows the relationship between fetal movement and subsequent birth weight.
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