Mục tiêu nghiên cứu

Chương 4: DISCUSSION

In compare with other foreign studies, the mean birth weight in this study lower than result of Alex in America on 1996. At the GA of 33-34 week, the difference was highest, up to 500gr. However, that difference steadily decreased at late preterm and term. It all had been shown that the mean birth weight by all week of GA of White mothers is higher than Asian mothers. When compare with Kerean and HongKong birth weight, the Vietnamese birth weight was lower, although the level of difference was not as high as those of White infant.

It was demonstrated clearly about the ethical characteristic of birth weight and other percentile chart. So it is needed to have a growth chart for own Vietnamese infant. To assess the neonate IUGR and size which relate to nutrition and disease, it is unappropriate to use foreign birth weight percentile chart, even use the other Asia growth charts as Korean or Chinese chart.

Indeed, the application of higher mean birth weight growth chart of foreign countries would lead to overestimated the IUGR newborns as well as underestimated the large fo GA fetus.

The birth lenght was measured during 24 hours after birth. As birth weight, the birth lenght is diffrent between races. It was recognized by all studies that the European and American birth lenght was longer 1cm than Asian birth lenght at all week of GA.

The male birth lenght at 50th percentile by 28th week of GA in this study was approximate to other studies. After 28th week of GA, the growth speed of foreign birth lenght was higher than that of us (ie, between 28-29 weeks of GA, the speed of lenght growth in our study was 1.4 cm, that of Israel was 3,3cm, of HongKong was 2.5cm and of America was 1.5cm) so at the GA from 30-37 week, the foreign birth lenght, even Asian ethnical birth lenght, was higher than those of us about 1-1.5cm. However, to late preterm, the foreign birth lenght growth speed was slower so there was little diffirence between those of Viet nam and other countries.

4.3.3. Discussion on birth head cicurmference percentile charts by GA.

The birth head circumference is one of basic measurement to evaluate the clinical status of the babies. The birth head percentile chart allow to assess whether babies' head normal or not. An excessive large head circumference suggest to a hydrocephalus or an extremly small head circumference suggest to a microcephaly. The ratio of head circumference to weight allow assess fetal nutrition status. Example, if birth weight is small for GA and the head circumference is normal, it is suggest to IUGR caused by undernutrition due to insufficial function of placeta at late months.

Compare to those of America, Vietnamese birth head circumference is 0,5 cm smaller by all preterm weeks. This difference was unremarkable at term. Vietnamese birth head circumfernce at all weeks of GA in this study is approximate to those of other Asian countries. As well as other anthropometric indices, the head circumference is diffirent between sexes and races. By which, the Eropean birth head circumference is larger than that of Asian ethnics, the male birth head circumference is larger than of female. However, the head circumference not always reflect cranial capacity and not affect the intelligence between races.

4.3.4. The birth ponderal index by GA.

The our results was sa same as other reseachers. Lubchenco (1966) found that the birth weight strongly increased by lenght at the age of 30-31 weeks, then steadly increased at the age from 34-38 week. After GA of 38 week, the PI was relatively constant.

For a long time the researchers have found fetal IUGR is an important factor related to the medical condition of the infant after birth. Compared to newborn appropriate for GA, newborn small for GA have mortality and morbidity is higher. Chart of growth for GA newborn is applied to determine the child IUGR for both clinical purposes and research. Often clinicians select the 10 percentile as the threshold weight to diagnose as underweight children (small - for - GA), however underweight infants for GA is not necessarily that infants IUGR

merely that the children perfectly healthy baby but due to constitutional factors (genetic or hereditary). So we need to find a weight threshold at which children increased morbidity and mortality in order to warn the obstetric and pediatric to pay an attention on care and intervention.

As the results of table 3.6, we choose a threshold weight below 1650g is to identify IUGR for valuable diagnostic with sensitivity of 87%, specificity of 80%, positive predictive value was 67 % and negative predictive value was 93%. Compared with the percentile chart 3.1, below 1650g threshold corresponding to 10 percentile line at 33 weeks gestation . Such results suggest that the line is 10 percentile threshold morbidity with valuable diagnostic sensitivity and specificity of the most acceptable in low birthweight for GA.

In clinical practice, it is needed to identify children at risk of fetus growth retardation to the timely intervention before birth. The diagnosis of low birth weight for GA may alert clinicians how to prevention and have an early treatment of neonatal complications and 33 -week is appropriate time point before fast fetus growth and is early time for treatment management.

The world is still controversial in the selection of traits to identify low birth weight for GA . If mortality is selected for study variables would correspond to percentile lines < 3 and at that time it was too late to intervene. Just had one in disorders such as in our study is also dangerous to the health and lives of children. So the selection of pathology that we have yet to find the threshold on weight-related diseases in relation to fetus growth retardation and partly contrinbute for prevention in early pregnancy complications due to fetus growth retarded. Thus, the percentage of diseases in our study had higher than other authors . Although this is our threshold weight is also recommended as line at 10 percentile, similar to international researchers.

We calculate the index weight- length of 124 newborn subjects above. Of the 124 children, 46 of them had weight- length index below the 10th percentile (≤ 2.06 ). That's consistent with the study subjects was 50% of the cases severe maternal preeclampsia disease, pathological condition caused mainly asymmetrical IUGR in the third trimester. When put on the sensitivity, specificity threshold index of weight-length for diagnose of pathology involving fetus growth reatardation, chart 3.28 shows the threshold cutoff point ≤ 2.06 index weight – length for high sensitivity and high specificity for the diagnosis of disease.

Threshold corresponding to this index as a diagnostic sensitivity of 85 %, a specificity of 85.7% with a positive predictive value was 73.9% and the negative predictive value was 92.3 % (table 3.7). The results showed that with the weight, the weight and length index has a high value in the pathologic diagnosis related to fetus growth retardation and this should take into clinical applications to classify children with asymmetrical IUGR or not, and also in meaningful diagnostic and prognostic condition of the child after birth.

4.4.3. Determine the weight threshold for diagnosing overweight infants

The definition is based on the conception to birth weight infants at birth varies greatly between races. For example, the average weight of babies born at 40 weeks is American 3495g ± 290g, 4000g infants ≥ 9.8%, 1.5% infants ≥ 4500g. In Vietnam, the average number of babies born 40 weeks is 3270g ± 280g, including children ≥ 4000g proportion accounted for 2.78%. So how much weight limits are pregnant to determine the need for each country to have valuable clinical applications. In this study, selected cases of full-term gestation of 38 weeks or older and weigh between 3300g or more (weight corresponding to the 15th percentile on the line in week 38 of gestation). Such cases are the terms and conditions on 600 cases. 293 cases of normal delivery (48.8%) and 297 cases of cesarean section (49.5%), others are forceps. We chose the case of a cesarean section may be related to pregnancy as the cervix open to all not caught early, experimental methods fail fall vertex, difficult head position and slow the progression of cervical, uterine contractions and forceps because his mother did not push switch is selected as pathological variables difficult to measure fetal macrosomia (accounting for 79 cases). 3650 weight threshold corresponding to the 90 percentile line at 40 weeks GA threshold for the diagnosis of dystocia due to fetal macrosomia in Vietnamese women with sensitivity of 77%, specificity of 78%, positive predictive value is 48 % and the negative predictive value was 92.3 %. The international authors take the weight threshold on line 97 percentile as the threshold to cause fetal neonatal pathology. In this study we choose the weight threshold corresponding to lines 90 percentile threshold is troublesome. Because of the different pathologies should be selected threshold weight also cause various diseases. Moreover, because of the height and especially the pelvis (factors directly related to the birth) of Vietnamese women is lower than the European women should weigh the absolute cause of dystocia also much lower (3650g in Vietnam women than European women at 4500g ) .

nn S, ole T, Preece M, et al. Growth charts for ethnic populations in CONCLUSIONS
1. To define the percentile values of some anthropometry of newborn infant by GA:

1.1. There were 2 stage of growth of birth weight by GA from 28-42 week: the first stage from 28-34 week and the second stage from 35-42 week shown as follow:

1.2. The growth of birth lenght and birth head circumference as follow:

1.3. The birth ponderal index percentile chart by GA from 28-42 weeks as shown in the chart 3.7.

1.4. The male birth weight, birth lenght and birth head circumference were higher than those of female, particularly at near term and full term

2. To assess the application value of percentile chart: defining the abnormal cut-off of anthropometric measurement.

2.1. The abnormal birth weight thresol related to IUGR at the GA of 33 week was below 1650gr, correspond to 10th percentile. At this cut - off, the values to diagnosis newborn IUGR were: sensitivity: 87,5% and specificity: 80%

2.2. The abnormal PI thresol related to IUGR at the GA of 33 week was below 2.06, correspond to 10th percentile with the values to diagnosis newborn IUGR were: sensitivity: 85% and specificity: 85,7%.

2.3. The abnormal birth weight thresol related to dystocia caused by fetal large for GA was above 3650gr, corespond to 90th percentile of 40 week with the values to diagnosis were: sensitivity: 77% and specificity: 78%.

The percentile charts of birth weight, birth lenght, birth head circumference and birth PI should be applicated to diagnosis the abnormal growth of newborn. Particularly, birth weight growth chart should be used as a main tool to classify fetal appropriate for GA, small for GA or large for GA.