The association between maternal body mass index and severity of neonatal illness in very low birth weight infants

Objective.?To determine the effect of maternal body mass index (BMI) and pregnancy weight gain on neonatal illness severity in very low birth weight infants.

Methods.?Cohort study of infants with birth weight less than 1500 g at a level 3 Neonatal Intensive Care Unit from July 2003 to July 2005, n = 301. The main outcome included neonatal illness severity, as measured by the Score for Neonatal Acute Physiology (SNAP). SNAP was investigated in relationship to maternal BMI and pregnancy weight gain. Statistical analysis included Pearson correlation, ANOVA and multivariable linear regression.

Results.?At delivery and pre-pregnancy, 49 and 54% of mothers were overweight, respectively. Black mothers were more likely to be overweight with less pregnancy weight gain compared with white mothers. After controlling for confounding variables, maternal pre-pregnancy BMI, pregnancy BMI and weight gain were not associated with neonatal illness.

Conclusions.?In our population of very low birth weight infants, maternal BMI was not associated with neonatal illness severity. Black mothers had higher pre-pregnancy BMI and less weight gain than white mothers. The significance of these differences needs further exploration.     

Influence of fetal fat on the ultrasound estimation of fetal weight in diabetic mothers.

Currently available formulas for the estimation of fetal weight assume uniform density of tissue. Because fat tissue is less dense than lean body mass, we hypothesized that the sonographic overestimation of fetal weight in infants of diabetic mothers is the consequence of an elevated proportion of body fat, resulting in a lower body density. We prospectively examined 52 children of diabetic mothers. Each had ultrasound estimation of fetal weight within 7 days of delivery and estimates of neonatal body composition made from anthropometric evaluation within 48 hours of birth. Ultrasound estimates of fetal weight were considered acceptable if they were within 10% of actual birth weight. There was no difference in mean birth weight between those overestimated (N = 22) and those underestimated (N = 8). The sum of skinfolds from two sites, the ponderal index, and percent body fat were all significantly greater in the neonates with sonographic overestimation of fetal weight. Lean body mass was significantly greater (P less than .05) in infants whose sonograms underestimated birth weight. When all subjects were included, a significant correlation was found between the degree of error in the ultrasound estimation of fetal weight and the ponderal index (r = 0.40, P less than .01), the sum of the skinfold measurements (r = 0.29, P less than .05), and the present body fat (r = 0.28, P less than .05). These data suggest that increased body fat in infants of diabetic mothers is associated with sonographic overestimation of fetal weight.     

Pre-pregnancy body mass, gestational weight gain and birth weight

OBJECTIVE: This study was undertaken to determine the effect of pregravid body weight and weight gain during pregnancy on birth weight of term newborns. MATERIALS AND METHODS: The study population consisted of 1443 healthy women, who delivered of singleton, live infants at or beyond 38 weeks of gestation. Maternal pregravid weight was obtained by recall and categorized into quartiles: < or = 53, < or = 58, < or = 65, > 65 (kg). Women were further divided according to their gestational weight gain into quartiles: < or = 10.5; < or = 12.5; < or = 15.5; > 15.5 (kg). Birth weight was measured and recorded at delivery. Newborns were classified as hypotrophic (SGA; < 10th percentile for the study population) and hypertrophic (LGA; > 90th percentile). RESULTS: The mean birth weight in the study population was 3499 +/- 447 g, 8.5% infants met the criteria for SGA, and 9.4%--for LGA. Studies showed that a progressive increase in maternal pregravid weight as well as gestational weight gain effect independently on increase birthweight, although the effect of weight gain during pregnancy was lessened as weight before gestation increased. For example, increasing gestational weight gain from < or = 10.5 kg to > 15.5 kg increased mean birthweight by 385 g (12.1%) for pregravid weight of 53 kg or less, compared with 142 g (4.0%) for weight of more than 65 kg. They were also associated with decreased frequency of hypotrophic infants and increased frequency of hypertrophic neonates. CONCLUSIONS: Both maternal prepregnancy weight and weight gain during gestation are important factors affecting fetal growth and birth weight. Increasing maternal weight before pregnancy diminishes the influence of weight gain on birthweight. As pregravid weight and prenatal weight gain increase, the incidence of LGA also increase, whereas the frequency of SGA decreases.     

Implications of a high placental ratio in pregnancies with appropriate-for-gestational age neonates

OBJECTIVE: To determine the relationship between the placental weight to birth weight ratio (placental ratio) with maternal pre-pregnancy weight, gestational weight gain, and neonatal outcome in non-diabetic pregnancies resulting in appropriate-for-gestational age (AGA) infants. METHODS: A retrospective study was performed on 593 patients with singleton pregnancies, normal results in the 75-gram oral glucose tolerance test and who delivered AGA newborns within a 1-year period. The patients were categorized into high placental ratio (> mean +1 SD based on previous data, n = 113 or 19.1%) and normal ratio groups for the comparison of maternal and neonatal anthropometric parameters. RESULTS: The high placental ratio group had a higher pre-pregnancy weight, body mass index, placental weight, and incidence of low Apgar score, but decreased absolute and percentage gestational weight gain, gestational age, and birth weight. After controlling for pre-pregnancy weight and gestational age, only the correlation between placental weight and percent weight gain remained significant. CONCLUSION: Our finding suggests that a high placental ratio can identify AGA newborns who are disproportionately small relative to maternal size, and may reflect some form of fetal growth impairment.     

Hemodynamic changes in underweight pregnant women.

Twelve normal-weight and 12 underweight women were compared to test whether fetal growth retardation in underweight gravidas is related to inadequate maternal hemodynamic adjustments. Plasma volume (+/- standard error) was 3227 +/- 103 mL in normal-weight and 2731 +/- 84 mL in underweight women (P less than .002). Cardiac output was 6340 +/- 167 mL/minute in controls and 5689 +/- 213 mL/minute in underweight women (P less than .03). Total peripheral vascular resistance was lower in controls than in underweight subjects (1025 +/- 31 versus 1198 +/- 58 dyne/second/cm5). Mean birth weight was 2837 +/- 125 g in underweight women and 3362 +/- 106 g in controls (P less than .005). Similarly, placental weight was reduced in the underweight group. All infants delivered by control mothers had a normal birth weight, whereas six infants from underweight gravidas were growth-retarded. In all cases combined, maternal plasma volume correlated significantly with both birth weight (r = 0.6, P less than .002) and placental weight (r = 0.56, P less than .01); total peripheral vascular resistance also correlated significantly and inversely with newborn weight and placental weight. Cardiac output correlated only with placental weight (r = 0.54, P less than .02). These results are consistent with the hypothesis that underweight mothers are at higher risk of fetal growth retardation because of a smaller plasma volume and lower cardiac output.     

Impact of maternal anthropometry and smoking on neonatal birth weight

The purpose of this study was to determine the effect of maternal pre-pregnancy body mass index (BMI) and maternal smoking habits on neonatal birth weight. We reviewed 10,240 normal singleton term pregnancies between 1985 and 1995 at the University Department of Obstetrics and Gynecology, Vienna. Birth weights of infants of overweight smokers were greater than those of smokers in general and similar to birth weights of nonsmokers, but smoking did have a fetal growth-retarding effect in overweight smoking mothers. Infants of underweight mothers who increased their daily cigarette consumption during pregnancy had significantly lowest birth weight. Our results suggest that the negative effects of smoking during pregnancy cannot be mitigated by a higher pre-pregnancy BMI and/or an improved weight gain during pregnancy. Especially the infants of underweight mothers benefit from their mothers' decision to cease smoking.     

Patterns of maternal weight gain in pregnancy

A retrospective study of 1145 pregnant women showed that trends in mean maternal weight gain from the time of booking until delivery were not linear. Statistically significant lower rates of maternal weight gain were seen before 16 weeks, after 36 weeks and between 28 and 32 weeks gestation (P less than 0.05). The mean maternal weight gain was 10.71 kg (SD 4.3) and the mean weekly weight gain was 0.38 kg (SD 0.16). A wide variation of maternal weight gain was seen in women with a normal outcome. The mean weight gain in heavy (greater than 68 kg) and light (less than 55.4 kg) women was less than that in women whose weight was in the third quartile (60-68 kg, P less than 0.05). The mean maternal weight gain was less in young (less than 20 years) women than in older women (greater than 25 years; P less than 0.05), less in parous than in primigravid women from week 37 onwards (P less than 0.05), less in smokers than in non-smokers from 20 weeks onwards (P less than 0.05), and greater in hypertensive women (BP less than 140/90) than in normotensive women (P less than 0.05) from week 24 onwards. The mean weight gain in women who had small for gestational age (SGA) infants was not significantly different from that in women who had infants that were of appropriate size for gestational age. After taking into account infant and placental weight using multiple regression analysis, the factors that were associated with statistically significant differences in average weekly weight gain were parity, body mass index, smoking habit and raised blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Maternal weight gain rate in the second trimester are associated with birth weight and length of gestation

BACKGROUND: Low total weight gain during pregnancy has been widely accepted as a valid risk factor for small-for-gestational-age infants and pre-term births. However, it is not obvious in which trimester the weight gain rate most affects birth weight and length of gestation. METHOD: Using logistic regression analysis and Pearson's correlation coefficient test, data from 472 women who had vaginally delivered an infant at term without any complications were analyzed retrospectively. RESULTS: Pre-pregnancy underweight and low total maternal weight gain were significant independent predictors of small-for-gestational-age infants and shortened gestations. Pre-pregnancy weight was significantly related to the birth weight and length of gestation (r = 0.18, p < 0.0001; r = 0.10, p = 0.04, respectively), and total weight gain was also significantly related to those (r = 0.17, p = 0.0003; r = 0.11, p = 0.03, respectively). Significant correlations between maternal weight gain rate in the second trimester and the birth weight and length of gestation were found (r = 0.32, p = 0.005; r = 0.40, p = 0.0003, respectively), while such correlations were not found in the first or third trimester. CONCLUSION: The most sensitive period of maternal weight gain for the birth weight and length of gestation was the second trimester.     

Maternal weight and weight gain in pregnancy and obstetric outcome

We studied 3002 antenatal patients to assess the relationship between maternal weight at booking in the first trimester and the total weight gain during the pregnancy and the birth weight of infants, pregnancy complications and mode of delivery. We found if the weight of the mother in the first trimester was lower or higher by 20% as compared with the standard weight, and the weight gain was more than 16 kg and less than 2.5 kg, there was higher incidences of maternal and fetal morbidity (P less than 0.01).     

Maternal hemoglobin F levels may have an adverse effect on neonatal birth weight in pregnancies with sickle cell disease

A total of 26 patients with sickle cell disease were followed up through 32 pregnancies. There was no correlation between days in hospital or number of painful crises and either birth weight or birth weight percentile. The number of dense irreversibly sickled and least deformable cells was negatively correlated with birth weight percentile (r = -0.63, p less than 0.01). Patients' initial hemoglobin levels were positively correlated with birth weight percentile (r = 0.52, p less than 0.004). Hemoglobin F, on the other hand, was significantly inversely correlated with birth weight percentile. Nine pregnancies with small-for-gestational-age infants had an average hemoglobin level of 9.1% +/- 4.5%. In contrast, patients who were delivered of appropriate-for-gestational-age infants (23 pregnancies) had an average hemoglobin F level of 3.6% +/- 2.9% (p less than 0.01). We conclude that total hemoglobin levels and dense cells are correlated with birth weight percentile; moreover, the higher the maternal hemoglobin F levels the higher the risk of small-for-gestational-age infants. We speculate that although high hemoglobin levels may be beneficial to the fetus, high maternal hemoglobin F levels could increase the desaturation of non-F cells and induce placental obstruction.     

Leptin levels in maternal and cord serum: relationship with fetal development and placental weight

OBJECTIVE: To test the hypothesis that the circulating levels of leptin in the maternal and cord serum correlate with the birthweight of the newborns and with the weight of the placenta. METHODS: In a population of 85 women from northern Greece who gave birth to an equal number of full-term infants, we calculated the concentration of leptin in the maternal serum as well as in the cord serum, right after delivery, by using an immunoradiometric assay. The correlation between these values, the maternal BMI before pregnancy and at the time of delivery, the neonatal BMI, Ponderal Index, and the placental weight was studied. RESULTS: Mean maternal leptin showed a statistically significant difference from mean cord serum leptin (14.7 and 7.07 ng/ml, respectively) and was positively correlated to the maternal BMI at the time of delivery (r = 0.3, P = 0.016), but not to neonatal BMI. A positive correlation between the mean cord serum leptin and the BMI of the neonates (r = 0.26, P = 0.031 ) was found. There was no correlation between the maternal BMI at the time of delivery and the neonatal BMI. Similarly, no correlation could be established between the placental weight and the levels of leptin in the maternal or in the cord serum but a positive correlation between placental weight, neonatal BMI and weight, and mothers' BMI was observed. Finally, although a noteworthy difference between the mean leptin levels of neonates of two different sexes was observed (male 5.9 ng/ml, female 7.8 ng/ml), that difference never reached a statistically significant level. CONCLUSIONS: The maternal leptin level could not be used as a reliable marker of fetal growth but a positive correlation between cord serum leptin and fetus growth is suggested.     

Excessive maternal weight and pregnancy outcome.

OBJECTIVES: This study was undertaken to determine the influences of increased maternal prepregnancy weight and increased gestational weight gain on pregnancy outcome. STUDY DESIGN: This was a longitudinal retrospective study of 7407 term pregnancies delivered from 1987 through 1989. After excluding cases with multiple fetuses, stillbirths, fetal anomalies, no prenatal care, selected medical and surgical complications, and those with incomplete medical records, 3191 cases remained for analyses by determination of odds ratios for obstetric outcomes, by chi 2 tests for significant differences and by adjustment for risk factors with stepwise logistic regression. RESULTS: Both increased maternal prepregnancy weight (body mass index) and increased maternal gestational weight gain were associated with increased risks of fetal macrosomia (p less than 0.0001), labor abnormalities (p less than 0.0001), postdatism (p = 0.002), meconium staining (p less than 0.001), and unscheduled cesarean sections (p less than 0.0001). They were also associated with decreased frequencies of low birth weight (p less than 0.001). The magnitude of the last was less than that of the other outcomes. CONCLUSIONS: Increased maternal weight gain in pregnancy results in higher frequencies of fetal macrosomia, which in turn lead to increased rates of cesarean section and other major maternal and fetal complications. Because these costs of increased maternal weight gain appear to outweigh benefits, weight gain recommendations for pregnancy warrant careful review.     

Antenatal dexamethasone and decreased birth weight

OBJECTIVE: To test the hypothesis that antenatal dexamethasone treatment to promote fetal lung maturation results in decreased birth weight corrected for gestational age. METHODS: The birth weights of all dexamethasone-treated, singleton, live-born infants delivered at our hospital were compared with our overall obstetric population; a group of untreated infants frequency matched approximately 3:1 according to maternal race, infant sex, and gestational age at delivery; and an historical cohort of infants with an indication for dexamethasone but delivered in the 12 months before the introduction of corticosteroid therapy at our hospital. RESULTS: Dexamethasone-treated infants (n = 961), when compared with either the overall population (n = 122,629) or matched controls (n = 2808), had significantly lower birth weights after adjustment for week of gestation (P <.001). Compared with the historical cohort of infants, the average birth weight of dexamethasone-treated infants was smaller by 12 g at 24-26 weeks, 63 g at 27-29 weeks, 161 g at 30-32 weeks, and 80 g at 33-34 weeks' gestation. CONCLUSION: Antenatal dexamethasone administered to promote fetal maturation is associated with diminished birth weight.     

Effects of obesity and weight gain during pregnancy on obstetrical factors

The relationship between the body weight or weight gain during pregnancy and various obstetrical factors was investigated in 731 patients who delivered in San-ikukai Hospital for in the year 1986. The patients were classified into three groups according to their body weight in non-pregnant states: slender (n = 214), ordinary (n = 379) and obese (n = 138), according to the standard for "The decision diagram for the estimation of obesity and emaciation in Japanese" published in 1986 by the Ministry of Health and Welfare, Japan. Each of these groups was further divided into two groups according to the degree of weight gain during pregnancy (more or less than 15kg). Then, the duration of labor, the blood loss during delivery, the birth weight, the placental weight and the obstetrical abnormalities (prolonged labor, arrested labor, blood loss of more than 500 ml, fetal distress and toxemia of pregnancy) were investigated in these groups. The blood loss, the neonatal birth weight and the placental weight in the obese groups were much greater than those in the ordinary or the slender group (p less than 0.005). However, there was no significant difference in the duration of the labor among these groups. The incidence of obstetrical abnormalities in the obese group was significantly higher than in the ordinary or the slender group (chi 2 = 4.37, p less than 0.05, chi 2 = 5.27, p less than 0.025).(ABSTRACT TRUNCATED AT 250 WORDS)     

Smoking, human placental lactogen and birth weight.

Human placental lactogen (HPL) was measured in 525 serum samples from 144 pregnant women and related to smoking habits and the birth weight of their infants. Women smoking during pregnancy were found to have a level of HPL significantly lower than the non-smokers (p less than 0.05). A significant correlation between HPL and birth weight was found (r=0.38); p less than 0.001) which remained significant when smoking was held constant (r=0.35; p less than 0.001). There was no relationship between birth weight and smoking when HPL was held constant.     

Relation between umbilical artery flow velocity and prostanoid production in the feto-placental vascular bed

The maintenance of adequate maternal-fetal circulation is essential for fetal growth. The circulation appears to be controlled by local prostanoid synthesis which may affect the vascular tone. With a view to examining this possibility, the present study was designed to evaluate the umbilical circulation serially in vivo by means of pulse doppler flowmetry. After delivery, the cord vasculature and the placenta were studied in vitro for the synthesis and release of prostacyclin (PGI2) and thromboxane A2 (TxA2). The resistance index (RI) showed a significant negative correlation to the birth weight (n = 15, r = - 0.70, p less than 0.01) and a positive correlation to the maternal arterial pressure (r = 0.56, p less than 0.05). PGI2 synthesis was highest in the umbilical artery, then in the umbilical vein, and lowest in the placenta. TxA2 tended to be higher in the umbilical artery of light-for-date neonates, showing a negative correlation with the birth weight (r = - 0.56, p less than 0.05). RI showed a significant correlation with the PGI2/TxA2 ratio. These results indicate that the balance between PGI2 and TxA2 influences cord circulation and in turn fetal growth.     

Increased umbilical cellular fibronectin concentrations are associated with a decreased prevalence of growth restriction in preeclampsia.

OBJECTIVE: Cellular fibronectin (cFN), a marker of endothelial activation, is elevated in maternal and cord blood in preeclampsia. We tested whether maternal or fetal cFN is related to fetal growth restriction in preeclampsia, in the context of gestational age at delivery. METHODS: Cellular fibronectin was measured in maternal and cord blood of 29 preeclamptic women and their infants delivered at Magee-Womens Hospital at 25-41 weeks of gestation. Relationships among maternal and cord cFN, birth weight, birth weight percentile, and ponderal index were evaluated using Pearson correlation and regression analyses controlled for gestational age. RESULTS: Cord cFN was not significantly related to maternal cFN (r = -.34, P = .08) or gestational age (r = -.32, P = .09). The relationship of maternal cFN to each index of infant size was not significant. By contrast, higher cord cFN predicted higher birth weight, birth weight percentile, and ponderal index (P < .05). CONCLUSION: Elevated maternal and cord cFN concentrations have been reported in pregnancy complicated by preeclampsia. This study assessed the relationship among maternal cFN, cord cFN, and indices of fetal growth in preeclampsia. Elevated cord cFN was associated with measures of better fetal growth.     

Folate, vitamin B12, and homocysteine levels in South Asian women with growth-retarded fetuses

OBJECTIVE. To investigate whether intrauterine growth retardation (IUGR) and preterm delivery in a poor population of South Asia was associated with altered maternal and fetal levels of folate, vitamin B12, and homocysteine. SUBJECTS AND METHODS. Hundred and twenty-eight pregnant women from a low socio-economic strata in the city of Lahore, Pakistan were followed with ultrasound of fetal growth from the 12th week of pregnancy. Blood samples were drawn from the woman and the cord at delivery. Serum was analyzed by a chemiluminescent immunoassay for folate and vitamin B12 and by fluorescence polarization immunoassay for total homocysteine (tHcy). RESULTS. Fourty-six infants showed IUGR. In term, but not preterm, deliveries with IUGR, maternal and cord blood folate levels were half of those in deliveries of normal birth weight infants (P=0.004 and P=0.005). The risk of IUGR was reduced among women with folate levels in the highest quartile (OR 0.31, 95% CI 0.10--0.84). There was no association between vitamin B12 and IUGR. Total homocysteine levels were higher in women delivering IUGR infants (P=0.02). There was an inverse correlation between cord blood folate and tHcy levels (r=-0.26, P=0.006). We also found increased risks for hypertensive illness (OR 3.5, 95% CI 1.4--8.6) and premature delivery (OR 2.5, 95% CI 1.1--6.2) in women in the highest quartile of tHcy. CONCLUSIONS. The occurrence of IUGR increased with low maternal and cord concentrations of folate and high maternal levels of tHcy. Further studies on the effects of vitamin B supplementation through pregnancy are warranted.     

Birth weight of Hausa infants in Northern Nigeria.

The birth weight of 1460 Hausa singleton infants was recorded and analysed. The birth weight of Hausa infants (Mean +/- SD) was 3.03 +/- 0.45 kg, being higher in males (3.08 +/- 0.47 kg) than females (2.97 +/- 0.48 kg). The difference was significant (P less than 0.001). The mean birth weight of first born children was significantly lower than the subsequent born, and increasing birth order was associated with higher birth weight irrespective of maternal age. The birth weight was influenced more by the parity as compared to maternal age. The incidence of low birth weight was 15.8 per cent, being lower in males (13.6 per cent) as compared to females (18.1 per cent). Comparison were made with studies from other parts of the country as well as from other countries.     

Growth hormone, somatomedin C, and nonsuppressible insulin-like activity levels compared in premature, small, average birth weight, and large infants

We have investigated the relationship between growth hormone, somatomedin C, nonsuppressible insulin-like activity, weight, gestational age, and 1-minute Apgar score in newborn infants. The 153 infants were categorized as small for gestational age (n = 19), average for gestational age (n = 59), large for gestational age (n = 60), and premature (gestational age at birth, 36 weeks or less (n = 15). Our study showed that (1) growth hormone levels were elevated in premature infants and correlated with Apgar scores and birth weights; (2) somatomedin C and nonsuppressible insulin-like activity levels were significantly lower in premature than in term infants; and (3) the birth weight of all infants studied had a significant overall effect on both somatomedin C and nonsuppressible insulin-like activity levels, suggesting that these factors may be involved in fetal growth. However, because in small for gestational age infants somatomedin C and nonsuppressible insulin-like activity were similar to levels in average for gestational age infants, it is suggested that other factors may inhibit fetal growth.