Psychosocial stress in pregnancy and its relation to the onset of premature labour.

A modified life events inventory was presented over a four-month period to 132 consecutive women going into spontaneous labour in Hull and Manchester. Three study groups were identified according to the duration of pregnancy. The levels of psychosocial stress in pregnancy were found to be particularly high in the mothers whose babies were born preterm. Stressful events may precipitate preterm labour in some women. The concept of antenatal care may have to be broadened if the incidence of premature labour and resulting perinatal mortality are to be reduced.     

Chromosome breakage in low birth weight newborns.

The frequency of chromosome aberrations in cells cultured from umbilical cord blood was determined for 50 low birth weight (LBW) and 50 normal birth weight (NBW) euploid newborns matched for sex, race, and maternal age. The metaphase spreads had been prepared in the course of an earlier study of frequency of aneuploidy and results are from 72-h cultures, i.e., presumably, at the second division in vitro. There were no significant differences between the two groups in the frequency of cells with chromosome breakage, chromosome gaps, or hyperdiploid cells. There was, however, a significantly higher frequency of hypodiploid cells in the LBW group. The present findings differ from those of others who have reported an increase in chromosome breakage in premature newborns.     

Organic-solvent water pollution and low birth weight in Michigan.

This pilot study explored the association between a measure of water pollution caused by benzene or chlorinated solvents and the incidence of low birth weights for white residents of Michigan counties. A positive relationship between water pollution by these contaminants and the per cent of low-weight births (less than 2,500 grams, or about 5.5 pounds) resulted despite controls for the incidence of teenaged childbearing, infrequent prenatal care, and mean household income from wages or salaries. Water pollution showed an association with the incidence of low birth weight that was as strong as that between low birth weight and low prenatal care. While correlation cannot prove causation, the finding suggests that impure water may impair fetal growth in Michigan.     

Oxidative stress in very low birth weight infants as measured by urinary 8-OHdG

Very low birth weight (VLBW) infants can be subjected to oxidative stress in the course of intensive care. We measured 8-hydroxydeoxyguanosine (8-OHdG), a biomarker of oxidative stress, and estimated the degree of oxidative stress in such infants. We also examined if the administered oxygen was related to oxidative stress. Urine samples of 50 Japanese VLBW infants [birth weights: 956.3+/-277.6g, and gestational ages: 28.0+/-2.6 weeks (mean +/- SD)] were collected on various postnatal days and 8-OHdG levels were determined using an ELISA kit. Sixteen term infants served as normal controls. As body weights at sampling increased, the average levels of urinary 8-OHdG decreased. 8-Hydroxydeoxyguanosine levels were: infants under 1000g, 29.5+/-16.4 micromol/mol creatinine (n = 24); 1000-1500g, 23.8+/-14.9 (n = 12); over 1500g, 16.1+/-8.5 (n = 14); and control, 10.9+/-7.2 (n = 16). Significant differences were found between <1000g group and > or = 1500g group (p = 0.0030), <1000g group and control (p < 0.0001), and 1000-1500g group and control (p = 0.0108). Also as postconceptional age at sampling increased, the average levels of 8-OHdG decreased. 8-Hydroxydeoxyguanosine levels were: infants before 252 days (36 weeks) of postconception: 27.4+/-15.5 micromol/mol creatinine (n = 34); after 252 days, 18.2+/-12.5 (n = 16). Differences between <252 days group and control (p < 0.0001), and <252 days group and > or = 252 days groups (p = 0.0253) were statistically significant. Among the three groups based on ambient oxygen concentration (21%, 22-29%, and > or = 30%) there was no significant difference (p = 0.417). The more premature the infants were, the more intense was the oxidative stress, hence, it is the prematurity rather than the administered oxygen which causes oxidative stress in VLBW infants. Drury et al. ["Urinary 8-hydroxydeoxyguanosine in infants and children" Free Radic. Res. 28 (1998) 423-4281 measured urinary 8-OHdG of 28 infants (24-40 weeks gestation) and found no gestation or birthweight related differences. This discrepancy seemed to be because of difference in birth weights and sampling period of the subjects.     

Social adversity,low birth weight,and preterm delivery.

A prospective study of 483 pregnant women was undertaken to examine possible associations of social and psychiatric factors with both low birth weight (less than 2500 g) and preterm delivery (less than 37 weeks'' gestation). As few babies were born before term (n = 14) or with a low birth weight (n = 14) further analyses were conducted to investigate predictors of absolute birth weight and gestational age. Low income was found to be an independent predictor of birth weight when birth weight was treated both as a dichotomous and as a continuous variable. Unemployment was found to be associated with absolute birth weight. Although this effect was statistically accounted for by low income, a low income was frequently caused by unemployment. Smoking independently predicted absolute birth weight and tended to be associated with preterm delivery. None of the factors investigated was associated with gestational age. In contrast with previous findings, factors such as social class, adverse life events, and psychiatric state were not associated with birth outcome. The mechanism underlying the association between low income and low birth weight requires further investigation.     

Maternal exposure to exogenous sex hormones in relation to birth weight of offspring

Birth weight was analyzed among singleton live births (N = 665) in Upstate New York in 1974 to women who used oral contraceptives (OC) in comparison to live births to women who used no contraceptives (N = 716), within 11 months prior to last menstrual period (LMP). In addition, birth weight was examined among live births to women who received hormone support therapy (N = 97) and hormone pregnancy tests (N = 75) during pregnancy. There was no evidence for a reduction in mean birth weight, or an increase in frequency of lower weights, among births to OC users, including those who stopped using OC within 2 months of LMP. Generally similar findings held within three maternal age groups (less than 25, 25-29, and 30-39 years). There was no evidence for a reduction in birth weight among offspring of women who received hormone pregnancy tests. Mean birth weight was relatively low among male and female births to women who received hormone therapy for "threatened abortion," but this may reflect the selection of women for such treatment rather than an effect of exogenous hormones on fetal growth.     

Maternal and neonatal factors influencing premature birth and low birth weight in Australia

This study identified the influences of neonatal and maternal factors on premature birth and low birth weight in New South Wales, Australia. Bivariate and multivariate analyses were used to explore the association of selected neonatal and maternal characteristics with premature birth and low birth weight. The findings of this study showed that premature birth and low birth weight rate significantly varied by infant sex, maternal age, marital status, Aboriginality, parity, maternal smoking behaviour during pregnancy and maternal hypertension. First-born infants, and infants born to mothers aged less than 20 years, or who were single, separated/divorced, Aboriginal or who smoked during the pregnancy, were at increased risk of being premature or of low birth weight. This study also found that risk factors for premature births and low birth weight were similar in both singleton and multiple births. Gestational age was confirmed to be the single most important risk factor for low birth weight. The findings of this study suggest that in order to reduce the incidence of low birth weight and premature births, health improvement strategies should focus on anti-smoking campaigns during pregnancy and other healthcare programmes targeted at the socially disadvantaged populations identified in the study.     

Effect of birthplace on infants with low birth weight.

From December 1983 to June 1985, 162 infants of less than 32 weeks'' gestation or weighing less than 1,500 g, or both, were cared for at the regional neonatal intensive care unit in Leeds. Of the 162, 64 (40%) were born in the unit because their mothers had received antenatal care there, 58 (36%) were born in another hospital and subsequently transferred, and 40 (25%) were transferred in utero because of potential complications. The overall mortalities for each group were 14%, 38%, and 18% respectively. These differences were significant, but when they were corrected for gestation, birth weight, and mode of delivery there was no difference in either the mortality or the incidence of intraventricular haemorrhage in the three study populations. Although there seem to be no distinct advantages of in utero transfer in terms of mortality and morbidity, there are other psychological and emotional advantages.     

Race and the inheritance of low birth weight

This paper uses intergenerational data from the Panel Study of Income Dynamics (PSID) to address the black-white difference in propensities toward low birth weight (LBW). We determine that socioeconomic conditions account for some variation in low birth weight across race. Further, while race differences in the risk of low birth weight cannot be explained entirely, we find that the inheritance of parental birth weight status dramatically reduces the black-white gap in low birth weight. Intergenerational legacies of poor infant health explain the largest share of racial disparities in filial birth weight. We then try to assess whether this intergenerational transmission of low birth weight is indeed genetic by using grandparent-fixed effects models to factor out, to a great extent, family socioeconomic circumstances. We find that even within this framework, both father's and mother's birth weight status have an important impact on filial outcomes. However, the degree of inheritance is weaker for African Americans than for other races. Finally, we theorize that the importance of paternal birth weight status implies a genetic association that does not work through the uterine environment but rather through the fetus itself.