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Biomedical subjects

J Villar

Publications and source records attributed to J Villar.

At least 181 records · Page 10Linked to original sources
PubMed1988

The relationship between calcium intake and pregnancy-induced hypertension: up-to-date evidence.

In 1980 we pointed to a relationship between calcium intake and pregnancy-induced hypertension. The original epidemiologic observations showed an inverse association between calcium intake and incidence of eclampsia after adjusting by several confounding factors. A series of recent randomized clinical trials have demonstrated a reduction in blood pressure with calcium supplementation in animals, in healthy and mildly hypertensive subjects, and in pregnant women. It is hypothesized that parathyroid hormone plays a role since it is affected by calcium intake and can partially regulate the concentration of free cytosolic ionized calcium, thus triggering smooth muscle contraction. Randomized clinical trials showing a reduction in the incidence of pregnancy-induced hypertension with calcium supplementation have not as yet been published. However, preliminary observations appear to support this hypothesis.

Adult↗
PubMed1988

Perinatal data reliability in a large teaching obstetric unit.

In this inter-rater agreement study of antenatal and neonatal variables collected in a large teaching obstetric unit, information routinely collected by hospital staff was compared with that collected by a specially trained physician and a social worker. Agreement between the two sources of data was evaluated using kappa statistics and intraclass correlation coefficients. Excellent agreement was observed for some variables such as maternal and newborn anthropometric measures, and previous birthweight, but there was poor agreement for others such as indicators of physical activity, work during pregnancy and blood pressure measures. Some of the limitations are due to problems in phrasing questions, patients' recall, interviewer bias and abstracting data. We recommend that epidemiological studies should always include a reliability component, proper standardization of personnel and instruments and include, when published, validity data and examples of questions used.

Adult↗
PubMed1988

Nutritional supplementation during two consecutive pregnancies and the interim lactation period: effect on birth weight.

The study consisted of 169 mothers enrolled during two consecutive pregnancies and the intervening lactation period in the Guatemalan Nutritional Supplementation Study. Women were grouped for this analysis according to the levels of caloric supplementation that they received (high or low) during two consecutive pregnancies and the period between them. The supplement also contained minerals and vitamins. Data were analyzed adjusting for maternal height, birth interval, parity, length of lactation, socioeconomic status, birth weight of the first offspring, gestational age of the second offspring, and caloric supplementation, expressed either in continuous fashion (total intake) or as caloric supplementation per week. The adjusted mean birth weights of the second offspring of women with high supplementation during two pregnancies (about an extra 180 kcal/d), and the in-between lactation period (about an extra 245 kcal/d), were up to 301 g greater than that of the low supplementation group. Women with high supplementation while breast-feeding their first offsprings and during their second pregnancies had babies up to 150 g heavier than the reference group; those mothers with high supplementation only during the second pregnancy had infants about 124 g heavier than those of the low supplementation group. Therefore, high supplementation during two consecutive pregnancies and their intervening lactation period among chronically, yet moderately, malnourished women was capable of increasing the mean birth weight to levels closer to those reported for industrialized populations. The mean birth weight increase is between two and three times greater than the effect shown in almost all of the previous studies of this topic.

Birth Weight↗
PubMed1988

Improved lactose digestion during pregnancy: a case of physiologic adaptation?

Loss of intestinal lactase activity among adults could theoretically limit milk consumption and hence dietary availability of calcium during pregnancy. The present study sought to define, using breath hydrogen (H2) production as an index of incomplete carbohydrate absorption, the prevalence during pregnancy of lactose maldigestion of 360 mL of milk (18 g of lactose), and to determine whether lactose digestion improved as pregnancy advanced. The prevalence of lactose maldigestion among 114 pregnant women tested before the 15th week of gestation was 54%. By term, 44% of those originally classified as maldigesters had become digesters. There was a significant reduction in the four-hour sum of the changes in breath H2 concentration from the period before 15 weeks (116.6 +/- 9.6 ppm) to the time after 36 weeks (54.4 +/- 7.3 ppm; P less than .01). This apparent adaptive improvement in intestinal handling of milk lactose during gestation has implications for calcium intake and absorption.

Acidosis, Respiratory↗
PubMed1987

Calcium supplementation reduces blood pressure during pregnancy: results of a randomized controlled clinical trial.

Fifty-two healthy pregnant women were enrolled in a double-blind, randomized, controlled clinical trial. After the 26th week of gestation, the women were given either 1.5 g of elemental calcium per day or a placebo. Subjects in the calcium group, after adjustment for race and initial blood pressure (BP), had a term mean systolic and diastolic BP value of 4-5 mmHg lower than those in the placebo group (P less than .05). The incidence of pregnancy-induced hypertension was 11.1% in the placebo group and 4.0% in the calcium group, a nonsignificant difference. Combining these values with previous data, we found a dose-effect relationship between calcium intake and BP reduction during the third trimester of pregnancy. Further research should be directed at understanding the mechanism of this effect and trying to demonstrate a reduction in pregnancy-induced hypertension with calcium supplementation in a larger population.

Blood Pressure↗
PubMed1986

Differences in the epidemiology of prematurity and intrauterine growth retardation.

Although both preterm (PT) and intrauterine growth retarded (IUGR) infants can have similar birth weights, they are known to show different neonatal and post-neonatal features. Newborns (n = 623) from the Guatemalan longitudinal study of nutritional supplementation during pregnancy were studied. There were 61 PT (less than or equal to 37 wk) and 173 IUGR (less than or equal to 10th percentile) infants. Simultaneous adjustment using the long-linear model showed that calorie and/or protein supplementation during pregnancy lowered the risk of PT (adjusted odd ratios (OR) = 0.52, 95%, CI = 0.40-0.77, and 0.43 CI = 0.36-0.59, respectively), but did not affect the incidence of IUGR. Low maternal head circumference and weight increased the risk of IUGR only (OR = 1.4, CI = 1.02-1.8 and 2.3 CI = 1.8-2.7, respectively). Male fetuses were at higher risk of both PT and IUGR. These data confirm the differential effect of maternal characteristics and nutritional supplementation during pregnancy on both PT and IUGR, and strongly suggest the need to include both gestational age and birth weight as outcome measures in epidemiological studies, thus avoiding the exclusive use of LBW (less than or equal to 2500 g).

Birth Weight↗
PubMed1986

The evaluation of the methods used in the diagnosis of intrauterine growth retardation.

Several methods used in the diagnosis of intrauterine growth retardation (IUGR) were evaluated with epidemiologic techniques. The strong effect of IUGR prevalence on the positive predictive and false-positive values of these methods is discussed. If correctly used, the combination of clinical measurements and perinatal risk factors can have a predictive power as high as any of the other more sophisticated techniques. The data reviewed show that at present biparietal diameter measurements, nonstress test/oxytocin challenge test or hormone values do not contribute to a better IUGR prediction than when the above mentioned methods are applied. For IUGR detection, ultrasound evaluation should include ratios of anthropometric measurements and may be complemented with amniotic fluid volume assessment. It is suggested that these procedures be reserved to a selected high risk population. Efforts should be made to evaluate new technologies through randomized controlled trials before they are introduced to the general population, particularly in developing countries.

Anthropometry↗
PubMed1985

Amniotic fluid prolactin and fetal lung maturation.

Concentrations of prolactin in amniotic fluid, fetal plasma, and maternal plasma were determined in 34 rhesus monkeys delivered by hysterotomy under general anesthesia at gestational ages of 110 to 160 days (term, 165 days). Included were 15 cases (gestational ages 110 to 143 days) in which the mothers received 2 mg of betamethasone intramuscularly daily for 3 days prior to delivery. Fetal lung maximum volumes were determined in addition to the following indices of fetal lung surfactant: lung alveolar stability, lung phosphatidylcholine concentrations, lung extract surface tensions, and amniotic fluid lecithin to sphingomyelin ratios. Amniotic fluid prolactin was found to correlate significantly with lung alveolar stability (r = 0.51; p less than 0.01), lung phosphatidylcholine (r = 0.51; p less than 0.01), lung extract surface tension (r = -0.39, p less than 0.05) and amniotic fluid lecithin/sphingomyelin ratio (r = 0.50; p less than 0.01). These correlations remained statistically significant even when the effects of gestational age were taken into account. These findings suggest that amniotic fluid may modulate fetal production of surfactant via its prolactin content.

Amniotic Fluid↗