Development of gastric emptying in the human fetus

Influences of breast milk composition on gastric emptying in preterm infants

OBJECTIVES

The aim of the present study was to determine whether specific biochemical and energy concentrations influence gastric emptying of unfortified and fortified mother's own milk (MOM) in stable preterm infants, and whether gastric emptying differs between feeds of unfortified MOM and feeds fortified with S-26 or FM 85 human milk fortifier (HMF) when infants are fed the same volume under similar conditions. Influences of infant gestation, age, and weight, and feed characteristics were also explored.

METHODS

Stomach volumes of 25 paired unfortified and fortified MOM feeds were monitored prefeed and postfeed delivery and at 30-minute intervals thereafter. For each feed, MOM samples were analyzed to determine concentrations of total protein, casein, whey, carbohydrate, lactose, fat, and energy. Fortified feed compositions were calculated by adding fortifier biochemical and energy concentrations to unfortified MOM concentrations. Ultrasound images were used to calculate infant stomach volumes. Statistical comparisons were made of paired stomach volume measurements.

RESULTS

Higher feed concentrations of casein were associated with faster gastric emptying during feed delivery (P = 0.007). When compared with unfortified MOM, S-26 fortified feeds emptied similarly, whereas FM 85 fortified feeds emptied more slowly both during feed delivery and during the postprandial period (P = 0.002, <0.001, respectively). Gastric emptying was slower for 2-hourly feeds compared with that for 3-hourly feeds (P = 0.003) and in supine position compared with that in prone (P = 0.001).

CONCLUSIONS

Breast milk composition influences gastric emptying in stable preterm infants, with feeds of higher casein concentration emptying faster during feeding than otherwise equivalent feeds, and FM 85 fortified MOM emptying more slowly than unfortified MOM.

Three-dimensional sonographic volume measurement of the fetal stomach

The objective of this study was to measure the fetal gastric volume using three-dimensional (3-D) ultrasound during pregnancy. Three-dimensional sonographic examinations were performed involving 35 pregnant women from 12 to 38 weeks of gestation. The fetal gastric volume was monitored every 5 min for a minimum of 40 min (40-60 min) in each woman. The rotational technique with Virtual Organ Computer-aided AnaLysis (VOCAL) was used to calculate the fetal gastric volume. Maximum and minimum gastric volumes were curvilinearly associated with the gestational age, respectively (R(2) = 0.611, p < 0.0001, and R(2) = 0.407, p < 0.0001, respectively). A curvilinear relationship was noted between the functional capacity (maximum volume - minimum volume) of the fetal stomach and gestational age (R(2) = 0.531, p < 0.0001). The maximum volume change [(maximum volume - minimum volume/maximum volume) × 100] did not change during pregnancy (mean and standard deviation, 64.1% ± 16.1%). However, gastric emptying cycles could not be determined in this study because of the short observation period and small number of subjects. Our findings suggest that the fetal gastric volume calculated by conventional two-dimensional ultrasound in previous investigations is approximately one-third of the maximum volume using 3-D ultrasound in the present study and that 3-D ultrasound is a superior means of evaluating the fetal gastric volume in utero. However, the data and their interpretation in the present study should be viewed with some degree of caution because of the small number of subjects. Further studies involving a larger sample size are needed to confirm these findings.

Ontogeny of gastric emptying patterns in the human fetus

OBJECTIVE

Fetal swallowing and gastric emptying contribute importantly to amniotic fluid (AF) homeostasis and fetal gastrointestinal development. We speculated that fetal gastric emptying must be functional early in gestation to prevent rapid increases in AF. We sought to determine the human fetal ontogenic pattern of gastric emptying.

STUDY DESIGN

Gastric emptying of eighty normal fetuses at 12-39 weeks was studied. Real-time ultrasound of the fetal stomach was continuously recorded for 1 hour. The gastric area ratio (GAR) was defined as the gastric area divided by the abdominal transverse area. The delta GAR was defined as the change between the maximum and the minimum gastric area ratiox100 (expressed as percent). A change of the fetal gastric area more than the 10th percentile of the delta GAR at 36-39 weeks was used to define gastric emptying.

RESULTS

The 10th, 50th and 90th percentile of delta GAR at 36-39 weeks' was 5.2, 6.5 and 8.7%, respectively. Fetal gastric emptying was detected as early as 12 5/7 weeks of gestation. The proportion of fetuses demonstrating gastric emptying (>10th percentile delta GAR) increased with gestational age: 4/33 (12.1%) 12-23 weeks, 3/9 (33.3%) at 24-27 weeks, 8/11 (72.7%) at 28-31 weeks, 12/14 (85.7%) at 32-35 weeks, and 11/13 (84.6%) at 36-39 weeks.

CONCLUSIONS

Fetal gastric emptying occurs by the beginning of the second trimester, contributing to AF regulation. The increased frequency of gastric emptying in late gestation is likely secondary to increased swallowing, altered fetal behavioral state or endogenous production of gastrointestinal motility factors.

TTX-sensitive and TTX-insensitive control of spontaneous gut motility in the developing zebrafish (Danio rerio) larvae

Spontaneous regular gut motility in zebrafish begins around 4 days post fertilisation (d.p.f.) and is modulated by release of acetylcholine and nitric oxide. The role of intrinsic or extrinsic innervation for initiating and propagating the spontaneous contractions, however, is not well understood. By creating spatiotemporal maps, we could examine spontaneous motility patterns in zebrafish larvae in vivo at 4 and 7 d.p.f. in more detail. Tetrodotoxin (TTX) was added to elucidate the importance of nervous control. Anterograde and retrograde contraction waves originated in the same region,just posterior to the intestinal bulb. This area correlates well with the distribution of Hu (human neuronal protein C/D)-immunoreactive nerve cell bodies. Whereas numerous immunoreactive nerve cells were present in the mid and distal intestine at both 4 and 7 d.p.f., fewer cells were seen anterior to the origin of contractions. The overall frequency of contractions(1.16±0.15 cycles min–1, N=14 at 4 d.p.f.;1.05±0.09 cycles min–1, N=13 at 7 d.p.f.) and the interval between individual anterograde contraction waves (54.8±7.9 s at 4 d.p.f., N=14; 56.9±4.4 s, N=13 at 7 d.p.f.)did not differ between the two stages but the properties of the contractions were altered. The distance travelled by each wave increased from 591.0±43.8 μm at 4 d.p.f. (N=14) to 719.9±33.2 μm at 7 d.p.f. (N=13). By contrast, the velocity decreased from 4 d.p.f.(49.5±5.5 μm s–1, N=12) to 7 d.p.f.(27.8±3.6 μm s–1, N=13). At 4 d.p.f., TTX did not affect any of the parameters whereas at 7 d.p.f. anterograde frequency(control 1.07±0.12 cycles min–1, N=8; TTX 0.55±0.13 cycles min–1, N=8) and distance travelled (control 685.1±45.9 μm, N=8; TTX 318.7±88.7 μm, N=6) were decreased. In conclusion, enteric or extrinsic innervation does not seem to be necessary to initiate spontaneous contractions of the gut in zebrafish larvae. However, later in development,nerves have an increasingly important role as modulators of intestinal activity.)

Two-dimensional fast imaging employing steady-state acquisition (FIESTA) cine acquisition of fetal non–central nervous system abnormalities

PURPOSE

To evaluate the value of two-dimensional fast imaging employing steady-state acquisition (2D FIESTA) cine MR with parallel imaging techniques in the diagnosis of fetal non-central nervous system (CNS) anomalies.

MATERIALS AND METHODS

A total of 28 pregnant women were referred for further MR evaluation on fetuses after abnormal sonographic results. A total of 33 fetal MR examinations were performed by a 1.5 T MR scanner with eight-channel phase-arrayed body coils. Single-shot fast spin-echo (SSFSE(R), GE) of three orthogonal planes and 2D FIESTA for cine fetal MR of three sagittal planes (midsagittal and 10 mm off midline on left and right) were routinely acquired. Additional planes on target organs with variable imaging frames were added if indicated.

RESULTS

Nine of the 33 examinations (9/33; 27.3%) had motion artifacts obscuring the detail in SSFSE imaging; 2D FIESTA imaging provided motion-artifact-free imaging in all of them. Cine 2D FIESTA imaging provided additional information on the visceral peristalsis. The information helped in differentiating dilated gastrointestinal (GI) tract from other intraabdominal cystic lesions and in confirming the nature and level of GI tract obstruction.

CONCLUSION

With sub-half-second temporal resolution of the 2D FIESTA sequences, fetal movement is no longer problematic. In addition to the anatomical information also provided by conventional SSFSE sequences, 2D FIESTA demonstrates information on motility and peristalsis of hollow organs and helps the diagnosis of fetal visceral anomalies.

The effects of endogenous and exogenous nitric oxide on gut motility in zebrafish Danio rerio embryos and larvae

Using motion analysis, the ontogeny of the nitrergic control system in the gut was studied in vivo in zebrafish Danio rerio embryos and larvae. For the first time we show the presence of a nitrergic tonus,modulating both anterograde and retrograde contraction waves in the intestine of developing zebrafish. At 4 d.p.f. (days post fertilisation), the nitric oxide synthase (NOS) inhibitor l-NAME (three boluses of 50–100 nl, 10–3 mol l–1) increased the anterograde contraction wave frequency by 0.50±0.10 cycles min–1. Subsequent application of the NO donor sodium nitroprusside (SNP; three boluses of 50–100 nl, 10–4mol l–1) reduced the frequency of propagating anterograde waves (–0.71±0.20 cycles min–1). This coincided with the first appearance of an excitatory cholinergic tonus, observed in an earlier study. One day later, at 5 d.p.f., in addition to the effect on anterograde contraction waves, application of l-NAME increased(0.39±0.15 cycles min–1) and following SNP application reduced (–1.61±0.36 cycles min–1) the retrograde contraction wave frequency. In contrast, at 3 d.p.f., when no spontaneous motility is observed, application of l-NAME did not induce contraction waves in either part of the gut, indicating the lack of a functional inhibitory tonus at this early stage. Gut neurons expressing NOS-like immunoreactivity were present in the distal and middle intestine as early as 2 d.p.f., and at 1 day later in the proximal intestine. In conclusion, the present study suggests that a nitrergic inhibitory tonus develops shortly before or at the time for onset of exogenous feeding.

Fetal abdominal magnetic resonance imaging

This review deals with the in vivo magnetic resonance imaging (MRI) appearance of the human fetal abdomen. Imaging findings are correlated with current knowledge of human fetal anatomy and physiology, which are crucial to understand and interpret fetal abdominal MRI scans. As fetal MRI covers a period of more than 20 weeks, which is characterized not only by organ growth, but also by changes and maturation of organ function, a different MR appearance of the fetal abdomen results. This not only applies to the fetal intestines, but also to the fetal liver, spleen, and adrenal glands. Choosing the appropriate sequences, various aspects of age-related and organ-specific function can be visualized with fetal MRI, as these are mirrored by changes in signal intensities. Knowledge of normal development is essential to delineate normal from pathological findings in the respective developmental stages.

Gastric emptying cycles in the human fetus

OBJECTIVE

Fetal swallowing contributes greatly to amniotic fluid homeostasis and fetal somatic development. Despite the absorption and recirculation of significant volumes of amniotic fluid, little is known about the rates of fetal gastric emptying or gastrointestinal absorption. We sought to determine the patterns of human fetal gastric emptying cycles across gestation.

STUDY DESIGN

The gastric emptying cycle of 80 normal human fetuses at 12 to 39 weeks of gestation was studied. Real-time ultrasound examination of the fetal stomach (defined as the largest gastric area inclusive of the pylorus) was recorded continuously for a minimum of 1 hour (60-112 minutes). Images were replayed with measurements of gastric size every minute. The gastric area ratio was defined as the ratio of the fetal gastric area divided by the area of the fetal abdominal transverse section. The changes in gastric area ratio of all subjects were analyzed with the discrete Fourier transform method. The calculable maximum cycle was 60 or 112 minutes, and the minimum cycle was 2 minutes. The highest and second highest peaks of all power spectrum were recorded, and each cycle was converted from frequency of each peak.

RESULTS

The gastric emptying cycles of the highest peak before 24 weeks of gestation were scattered between 30 and 100 minutes with low power. At 32 to 35 weeks of gestation, cycles were focused at approximately 40 minutes with increased power. At term, the cycles increased to >80 minutes. The gastric emptying cycles of the second highest peak were constant at 20 minutes, with stronger power after 24 weeks of gestation.

CONCLUSION

Fetal gastric emptying cycles normalize during the early third trimester. The near-term evidence of delayed emptying may contribute to newborn infant feeding satiation.

Correlation between fetal gastric size and amniotic fluid volume

PURPOSE

Since abnormal conditions of the fetal digestive tract may alter both amniotic fluid volume and fetal gastric volume, we sought to determine whether amniotic fluid volume is correlated with fetal gastric volume in normal pregnancy.

METHODS

A total of 280 fetal gastric size measurements were made prospectively from routine sonographic examinations of women with normal singleton pregnancies between 16 and 42 weeks of gestation. The fetal stomach was defined as the largest area including the pyloric site on transverse or oblique real-time sonographic scans. Gastric volume was calculated according to the formula for a prolate ellipsoid. The amniotic fluid index (AFI) was used for the evaluation of amniotic fluid volume.

RESULTS

Both fetal gastric volume and AFI were significantly correlated with gestational age (R2= 0.422 and R2= 0.128, respectively). Only a weak correlation was found between gastric volume and AFI (R2= 0.036, p <0.001). On multivariate linear regression analysis adjusting for gestational age and fetal biometric measurements, gastric volume was not an independent and significant predictor of AFI.

CONCLUSIONS

Although sonographically determined fetal gastric volume measurements appear to be useful in the assessment of fetal digestive tract anomalies, fetal gastric volume has no clinically significant effect on the amniotic fluid volume in normal pregnancy.

Fetal duodenal obstructions: increased risk of prenatal sudden death

OBJECTIVES

The aim of this study was to describe the outcome of fetuses with duodenal obstruction diagnosed prenatally and to compare the outcome with the results of studies of newborns.

METHODS

All fetuses with a prenatal diagnosis of duodenal obstruction were registered and evaluated prospectively from January 1985 to December 2000.

RESULTS

Duodenal obstruction was found in 29 fetuses at a mean gestational age of 29+2 weeks. Polyhydramnios was found in 24 cases (83%). Six fetuses (21%) had trisomy 21. Associated anomalies, including trisomy 21, were found in 18 cases (62%). Four fetuses with normal karyotype died in utero at 31-35 gestational weeks. Two of them had associated anomalies, but the anomalies could not explain the prenatal deaths and the deaths occurred suddenly and unexpectedly. Three infants died postnatally; all three had associated anomalies. Four infants with normal karyotype had neurological impairment suggesting that they might have had intrauterine asphyxia.

CONCLUSIONS

The present study indicates that duodenal obstruction is a more serious condition than previously believed, with an increased risk of prenatal asphyxia and death, even when the karyotype is normal and no associated anomalies are present. We consider the possibility that it could be caused by bradycardia/asystole following vagal overactivity due to distension of the upper gastrointestinal tract.

Fetal gastric size in normal and abnormal pregnancies

OBJECTIVE

The aim of this observational study was to construct an ultrasound index of fetal gastric size for the prenatal detection of congenital digestive tract obstruction.

SUBJECTS

A total of 386 fetal measurements were performed in routine ultrasonographic examinations of women with normal singleton pregnancies between 18 and 39 weeks of gestation. Gastric measurements were also performed in 13 fetuses with digestive tract obstruction.

METHODS

The ultrasound plane which included the pylorus and which provided the largest stomach area was used for definition and measurement of gastric area and maximal longitudinal dimension. The transverse section at the center of the gastric corpus was used for transverse and anteroposterior dimensions. Gastric volumes were calculated as a prolate ellipsoid. The gastric area ratio was defined as the gastric area divided by the transverse abdominal area. Biparietal diameter (BPD) and abdominal transverse area were also measured.

RESULTS

The fetal gastric area was significantly correlated with fetal gastric volume (r = 0.91) and gestational age (r = 0.74). However, the correlation coefficient for gastric area with gestational age was smaller than those of the BPD (r = 0.97) with gestational age and abdominal transverse area with gestational age (r = 0.97). Gastric area ratio decreased slightly towards term. The gastric area ratio was below the 95% confidence intervals for the predicted values in all five fetuses with esophageal atresia, and exceeded the 95% confidence intervals in seven of the eight fetuses with duodenal atresia or intestinal tract obstruction.

CONCLUSION

Fetal gastric area correlates with ultrasound-determined gastric volume measurements and appears to be useful in the assessment of digestive tract anomalies.