Birthweights in consecutive pregnancies

Birthweight of the subsequent singleton pregnancy following a first twin or singleton pregnancy

INTRODUCTION

Birthweight is an important pregnancy indicator strongly associated with infant, child, and later adult life health. Previous studies have found that second-born babies are, on average, heavier than first-born babies, indicating an independent effect of parity on birthweight. Existing data are mostly based on singleton pregnancies and do not consider higher order pregnancies. We aimed to compare birthweight in singleton pregnancies following a first twin pregnancy relative to a first singleton pregnancy.

MATERIAL AND METHODS

This was a prospective registry-based cohort study using maternally linked offspring with first and subsequent pregnancies registered in the Medical Birth Registry of Norway between 1967 and 2020. We studied offspring birthweights of 778 975 women, of which 4849 had twins and 774 126 had singletons in their first pregnancy. Associations between twin or singleton status of the first pregnancy and birthweight (grams) in subsequent singleton pregnancies were evaluated by linear regression adjusted for maternal age at first delivery, year of first pregnancy, maternal education, and country of birth. We used plots to visualize the distribution of birthweight in the first and subsequent pregnancies.

RESULTS

Mean combined birthweight of first-born twins was more than 1000 g larger than mean birthweight of first-born singletons. When comparing mean birthweight of a subsequent singleton baby following first-born twins with those following first-born singletons, the adjusted difference was just 21 g (95% confidence interval 5-37 g).

CONCLUSIONS

Birthweights of the subsequent singleton baby were similar for women with a first twin or a first singleton pregnancy. Although first twin pregnancies contribute a greater combined total offspring birthweight including more extensive uterine expansion, this does not explain the general parity effect seen in birthweight. The physiological reasons for increased birthweight with parity remain to be established.

Parental age and child growth and development: child health check-up data

BACKGROUND

The aim of the present study was to determine whether parental age has any influence on child health.

METHODS

Well-baby check-up data at 1 month and at 12 months of age were used. The trends of parental age in association with growth measurements, incidence of physical and developmental abnormalities, occurrence of low birthweight, and maternal history of spontaneous abortion were analyzed.

RESULTS

Associations between increasing paternal age and incidence of psychomotor developmental delay at 12 months, increasing paternal and maternal age and increasing birthweight, and increasing parental age and higher incidence of history of spontaneous abortion were found. The incidence of low-birthweight infants was significantly decreased with increasing paternal age.

CONCLUSIONS

Not only increasing maternal age but also increasing paternal age have influences on child development and growth in the general population.

Reduced birthweight in short or primiparous mothers: physiological or pathological?

OBJECTIVE

Customisation of birthweight-for-gestational-age standards for maternal characteristics assumes that variation in birth weight as a result of those characteristics is physiological, rather than pathological. Maternal height and parity are among the characteristics widely assumed to be physiological. Our objective was to test that assumption by using an association with perinatal mortality as evidence of a pathological effect.

DESIGN

Population-based cohort study.

SETTING

Sweden.

POPULATION

A total of 952 630 singletons born at > or =28 weeks of gestation in the period 1992-2001.

METHODS

We compared perinatal mortality among mothers of short stature (<160 cm) versus those of normal height (> or =160 cm), and primiparous versus multiparous mothers, using an internal reference of estimated fetal weight for gestational age. The total effects of maternal height and parity were estimated, as well as the effects of height and parity independent of birthweight (controlled direct effects). All analyses were based on fetuses at risk, using marginal structural Cox models for the estimation of total and controlled direct effects.

MAIN OUTCOME MEASURES

Perinatal mortality, stillbirth, and early neonatal mortality.

RESULTS

The estimated total effect (HR; 95% CI) of short stature on perinatal death among short mothers was 1.2 (95% CI 1.1-1.3) compared with women of normal height; the effect of short stature independent of birthweight (controlled direct effect) was 0.8 (95% CI 0.6-1.0) among small-for-gestational-age (SGA) births, but 1.1 (95% CI 1.0-1.3) among non-SGA births. Similar results were observed for primiparous mothers.

CONCLUSIONS

The effect of maternal short stature or primiparity on perinatal mortality is partly mediated through SGA birth. Thus, birthweight differences resulting from these maternal characteristics appear not only to be physiological, but also to have an important pathological component.

Are babies born to short, primiparous, or thin mothers "normally" or "abnormally" small?

OBJECTIVES

To examine whether the smaller size of infants born to primiparous, short, or thin mothers is associated with increased risks of perinatal mortality.

STUDY DESIGN

We compared gestational age-specific patterns of "revealed" small-for-gestational-age (SGA) birth (number of SGA births expressed as a proportion of fetuses remaining in utero at each gestational age) with the patterns for perinatal mortality among singleton late fetal deaths and live births (n = 791,523) to Swedish mothers in 1992 to 2001.

RESULTS

Based on a single standard for SGA, primiparae were at substantially higher risk of revealed SGA throughout gestation, paralleling the pattern for perinatal mortality. However, for short and thin women, risks of revealed SGA were much more consistent with those for perinatal mortality when SGA was based on height-specific or body mass index-specific standards, respectively, rather than on the single standard. Overweight and obese mothers had lower revealed SGA rates based on either standard but higher perinatal mortality rates.

CONCLUSIONS

Slower fetal growth due to maternal short stature or low prepregnancy body mass index appears to be physiologic, whereas the slower growth of fetuses born to primiparous women is associated with higher risks of perinatal death.

Perinatal and reproductive factors: a report on haematological malignancies from the UKCCS

The United Kingdom Childhood Cancer Study was designed to examine the potential aetiological role of a range of perinatal and reproductive factors. Our use of clinical records permitted a more exact characterisation of reproductive events than is possible in investigations that rely on self-reporting; and the increased specificity with which antecedent events were measured produced more precise risk estimates, albeit ones based on progressively smaller numbers. Information on the conduct of this component of the study and results for 1485 children with haematological malignancies and 4864 controls are presented. The 'find' rate for obstetric records was high at 86% for cases, with 81% having information on both matched controls. Associations were seen for severe hyperemesis (Odds Ratio=3.6, 95%Confidence Interval=1.3-10.1, for all leukaemias), polyhydramnios (OR=4.0, 95%CI=1.5-10.3, for acute myeloid leukaemia (AML)), anaemia (haemoglobin <10 g, OR=2.6, 95%CI=1.7-4.1, for AML), and pre-eclampsia (OR=1.7, 95%CI=1.1-2.7, for non-Hodgkin's lymphoma). Babies who developed leukaemia were heavier at birth (>4000 g, OR=1.2, 95%CI=1.0-1.4), as were their older siblings (>4000 g, OR=1.4, 95%1.0-1.9). Mothers' whose children developed common B-cell precursor acute lymphoblastic leukaemia (ALL) were more likely to have had a previous molar pregnancy (OR=5.2, 95%CI=1.9-14.7). Gender-specific analysis revealed that findings often differed markedly for boys and girls; and, in common with other reports, strong associations with Down's syndrome were seen for both ALL and AML.

Fraternal birth order and birth weight in probably prehomosexual feminine boys

The purpose of this study was to confirm a previous finding that homosexual males with older brothers weigh less at birth than do heterosexual males with older brothers. The subjects comprised 250 feminine boys referred to a child psychiatry service because of extreme cross-gender wishes or behavior and assumed, on the basis of previous research, to be prehomosexual, plus 739 control boys and 261 control girls referred to the same service for reasons unrelated to sexual orientation or gender identity disorder and assumed, from base-rate probabilities, to be preheterosexual. The feminine boys with two or more older brothers weighed 385 g less at birth than did the control boys with two or more older brothers (P = 0.005). In contrast, the feminine and control boys with fewer than two older brothers did not differ in birth weight. This finding suggests that the mechanism by which older brothers increase the odds of homosexuality in later-born males operates prior to the individual's birth. We hypothesize that this mechanism may be immunologic, that antimale antibodies produced by human mothers in response to immunization by male fetuses could decrease the birth weight of subsequent male fetuses as well as increase their odds of homosexuality.

Families with a perinatal death: is there an association between the loss and the birthweight of surviving siblings?

Our objective was to study birthweight among surviving siblings in families with and without a perinatal loss, and to evaluate whether different causes of death were associated with the results. Data were for 1967-98 from the Norwegian Medical Birth Registry. Births were organised with the mother as the observation unit through the personal identification number, providing sibship files. We analysed 550 930 sibships with at least two singletons, 208 586 sibships with at least three singletons and 45 675 sibships with at least four singleton births. We compared mean birthweight and gestational age between infants in sibships with and without a perinatal loss, total losses and the different causes of death. Surviving siblings in families with a perinatal loss had significantly lower mean birthweights than their counterparts in unaffected families, after adjusting for gestational age, interpregnancy interval, time period and marital status. An exception was found when cause of death was a birth defect, when growth retardation among surviving siblings was not found on average. We conclude that families who have lost an infant because of a birth defect do not appear to have an increased risk of adverse birth outcome associated with growth restriction.

Multivariate analysis of determinants of fetal growth retardation

OBJECTIVE

To analyse the relative effect of the risk factors related to fetal growth retardation (FGR) in the central area of Spain.

STUDY DESIGN

This is a case-control survey of 370 full-term gestations. Of the 370 women, 185 were diagnosed with intrauterine growth retardation, and 185 were in the normal group. All came from a central region of Spain. We took into account 25 possible risk factors.

RESULTS

In the FGR group we found 12 risk factors with statistical significance in the univariate analysis (tobacco, drugs, low pre-pregnancy weight, low maternal height, little gestational weight gain, excessive physical activity during pregnancy, low socioeconomic status, low educational level, unmarried, urinary infection, mother's haematological changes, and previous infertility). After the multiple logistic regression analysis, five factors were shown to exist as independent risks (tobacco: OR, 23.50; 95% CI, 3.01-183.18; P < 0.01; low pre-pregnancy weight: OR, 4.01; 95% CI, 2.14-7.51; P < 0.001; low socioeconomic status: OR, 2.91; 95% CI, 1.72-4.90; P < 0.001; little gestational weight gain: OR, 2.52; 95% CI, 1.21-5.22; P < 0.05; and urinary infection: OR, 3.83; 95% CI, 1.49-9.87; P < 0.01).

CONCLUSIONS

(i) Tobacco, low pre-pregnancy weight and low socioeconomic status are the three main cause-effect factors of relative importance in our sanitary zone for FGR. (ii) Disproportionate FGR is related more to older mothers and maternal previous illness than to the proportionate FRG.

Classification of small-for-gestational age births: weight-by-gestation standards of second birth conditional on the size of the first

Percentiles of weight-by-gestational age were constructed for first and second births, based on linked sibship-data from the Medical Birth Registry of Norway. Standards were made for weight-by-gestational age of second births conditional on whether the first birth was small-for-gestational age (SGA) or large-for-gestational age (LGA). These standards were compared with the conventional, cross-sectional standard of all second births. The relevance of the conditional standards was assessed on the basis of perinatal mortality, using logistic regression analyses. When applying cross-sectional standards of second births, more than 30% of the births following a SGA first birth were classified as SGA, compared with only 1.7% following an LGA first births. The overall risk for a perinatal loss in second births following a SGA first birth was twice that among second births following a LGA first birth. When second births were themselves categorised as SGA or non-SGA using the cross-sectional standards, the mortality among the SGA second births was such that the risk was 4 to 5 times higher following LGA first births compared with SGA first births. When conditional standards were applied to define SGA among second births, the risk relation between the subgroups (defined by classification of first birth) corresponded to the observed overall risk pattern. An unconditional SGA classification conceals important differences between clinically distinct subgroups.

Birth dimensions in Melanesian and Indian Fijians and their relationships with maternal and socio-economic factors

Fifty-nine Melanesian (MF) and 39 Indian (IF) Fijian full-term newborns were studied within 5 days of birth. Dimensions recorded included birthweight, length, crown-rump length, head circumference, upper limb length, bycondylar humeral and femoral diameters and four skinfolds (triceps, subscapular, suprailiac and thigh). Data from previous pregnancies of the presenting newborns' mothers were added to presenting birthweights, giving a total of 160 MF and 84 IF birthweights. In all birthweight and linear dimensions MFs were the bigger. Sex differences were significant in respect only of head circumference and the two bicondylar diameters. Multiple regression analysis showed dimensions in MF newborns to have few significant relationships with the maternal and socio-economic variables of age, parity, stature and years of education, but IFs had many more significant relationships. When covariance correction was made for the significant maternal and socio-economic variables (maternal age and parity) little effect on racial differences was seen. All linear dimensions except length could be subsumed into birthweight. MFs had greater triceps and subscapular skinfold thicknesses than IFs, a difference which was not much changed by covariance correction for significant maternal and socio-economic variables (maternal stature and years of education). Measurements of shape, expressed as ratios of linear dimensions, showed few racial differences but males had relatively broader limbs. For upper limb shape only, this difference was maintained after covariance correction for significant maternal and socio-economic variables (parity, stature and education). The greater size of MF infants at birth is associated with lower peri- and neonatal death rates. However this advantage is reversed during the remainder of the first year of life. It is suggested that better standards of infant care among IFs are responsible for this change.

Birth weights in three Norwegian cities, 1860-1984. Secular trends and influencing factors

Data from birth records from three maternity hospitals in Norway have been used to study the trend in birth weight in this country from 1860-1984. The investigation is based on a sample of 200-300 records taken at random from 2 to 5 years around every 10th year, from each of the three maternity hospitals--amounting to a total sample of 9152 women. Besides describing the trend in birth weight, I have analysed the different factors influencing birth weight--using multivariate linear regression methods. The results show that the mean birth weight has changed remarkably little throughout this period of 120 years. The total increase has only been just below 200 g. From Montreal, Ward and Ward (1984) have reported a decrease in mean birth weight of about 430 g during the second half of the last century. The Norwegian data indicates a simultaneous fall in mean birth weight of about 70 g. This fall is, however, found mainly among unmarried women. Thus, the great decline in birth weight which is found in Montreal, is not apparent in our material from Norway, despite the fact that Oslo was industrialized at approximately the same time as Montreal. Of the various independent variables used in the multiple regression analyses, only the following variables appear to be of any importance: the year when the birth took place, the mother's menarcheal age, her marital status, the sex of the child and the parity number. In this material, I have found a linearly increasing birth weight from birth number 2 up to at least parity 8, and a larger increase from parity 1 to 2. The birth weight shows a significant increase in the case of married women as opposed to unmarried. This effect is most marked before 1900, indicating that the social conditions gradually became less unequal after the turn of the century. The birth weights have a decreasing tendency with higher ages of menarche. This tendency is constant throughout the whole period of time. Boys appear to be about 112 g heavier than girls, this difference being largely the same throughout the investigated period.

Birth weight before and after a spontaneous abortion

A survey of pregnancies occurring in 3502 women doctors provided an opportunity to examine the relationship between early fetal loss and birth weight. This was found to be complex. The most important observations were that the mean birth weight of babies preceding a spontaneous fetal loss was lower than that of livebirths preceding another livebirth, and that in the subgroup of women with repeated early losses, mean birth weight fell with increasing pregnancy order. In contrast, mean birth weight of the first livebirth following a single spontaneous abortion was higher, though not significantly, than that of livebirths in the first pregnancy.