Single Motherhood and Neonatal Survival of Twins: Comment
In this study, when we adjusted for several con-founders (excepting gestational age), we observed an elevated risk for neonatal mortality among twin births to unmarried mothers regardless of the racial group. Loading the gestational age variable into the model confirmed that shortened gestation was the pathway (intermediary variable) through which the preponderance of neonatal mortality among twins of single mothers was mediated. While some studies did not find single motherhood to be linked to adverse perinatal events, other population-based reports observed higher-than-expected levels of adverse birth outcomes in unmarried gravidas in consonance with our results. However, our investigation differs from previous reports in that our analysis was restricted to the neonatal period, with birth population limited to twins. Our findings strengthen the case that single motherhood is an obstetric risk factor that deserves extra attention.
A plausible pathway that could link single motherhood to adverse birth outcomes is the supportive role of the male partner, the absence of which may be equated with lack of sufficient social buffer against stress in general. It is reasonable to speculate that stress may lead to adverse fetal outcome through the increased release of stress hormones (e.g., corti-cotropin-releasing hormone), which have been associated with shortened gestation. A shortcoming in this study is our inability to determine the role of stress as an intermediary in the causal pathway of neonatal mortality due to the absence of information on measures of stress levels of mothers in the dataset.
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Another frequently advanced explanation for the negative outcomes associated with single motherhood is socioeconomic disadvantage. Both the extent and severity of socioeconomic deprivation tend to be longer and deeper in families with female householders, a proxy for single motherhood. Poverty correlates with other acute and chronic life stresses, such as poor housing, acute and continuous exposure to environmental hazards, crime victimization, disease and barriers to healthcare services. These factors may act either in isolation or in concert to precipitate untoward pregnancy events, such as preterm delivery and LBW, two of the most important precursors of early infant demise. However, incriminating poverty as the predominant cause of adverse obstetric outcomes among uniquely defined sociodemographic entities may be too simplistic and erroneous. A good example is the “Hispanic paradox,” whereby the Hispanic population with poor educational achievement levels and highly suboptimal income indices still show comparable pregnancy outcomes to their richer white counterparts. After controlling for educational status, a proxy for socioeconomic well-being, we found higher mortality estimates among single mothers, suggesting that perhaps socioeconomic disadvantage does not explain a substantial portion of the disparity attributed to being unmarried.
When the neonatal period was further dichotomized into early and late neonatal mortality, we found that the late neonatal period was more critical and accounted for most of the disparity between twins of married and those of single mothers in neonatal survival probabilities. This information is potentially useful in formulating intervention strategies and allocation of resources aimed at dampening the neonatal survival disadvantage experienced by twins born to single mothers. Care providers involved in counseling mothers that are identified as obstetrically high-risk may find these results useful as well. It is also noteworthy that in both races when gestational age was adjusted for, the association between single motherhood and neonatal demise vanished, highlighting the importance of the preponderance of preterm births among twins of single mothers as being responsible for the higher mortality experienced by same.
Another important result in this study is the divergence in the estimates by race. Interestingly, the disparity by marital status was wider among whites than among blacks. Indeed, whereas the disparity persisted for early neonatal mortality among whites, it vanished among blacks. These observations may imply that within the considered racial groupings, the adverse effects of single motherhood are more pronounced among whites than blacks. Previous studies have proposed that marital status has a stronger linkage to adverse neonatal outcomes among low-risk groups. Because whites are considered a low risk group in comparison to blacks, it stands to reason that disparity by marital status is more marked in whites. The underlying explanation is that, generally, black mothers are exposed to other characteristics that are related to single motherhood and in themselves lead to poor pregnancy outcomes. For example, black males have very high unemployment rates as compared to their white counterparts, so that a married black gravida may not enjoy an appreciable level of socioeconomic advantage by being married in contrast to her white counterpart. A probable limitation in the data set used for this study is the variation across states in the method used in obtaining information on marital status. Before 1997, the overwhelming majority of the states (45 in all) used the direct questioning approach in determining whether a mother was married or not. The remaining five states (Connecticut, Michigan, Nevada, New York and California) used the inferential method (e.g. receipt of paternal acknowledgement, missing information on the father or different surnames for parents) to determine marital status. However, as from 1997, California changed to the direct questioning method leaving Connecticut, Michigan, Nevada, and New York as the only states that still subscribed to the inferential procedure. This heterogeneity in methodology could affect the classification of marital status. The extent to which this could have affected our results is difficult to determine, since it remains inconclusive as to which of the aforementioned procedures represents the best approach in terms of minimizing classification errors of marital status.
Another limitation in this study is the lack of information on the use of assisted reproduction technology (ART). Since only about 10-11% of twins are iatrogenic, it is unlikely that differentials in ART use by marital status could have influenced our findings. Further, assuming it did then one would have expected ART use to be more frequent among married rather than unmarried women. This would have resulted in poorer birth outcomes among married gravidas because offspring resulting from assisted conceptions have higher levels of morbidity and mortality. cialis soft tablets
The gestational ages of infants were mostly calculated from the date of the LMP as recalled by mothers. It is likely that errors in recall might have influenced the derived intrauterine ages of neonates at birth, with over- and underestimates occurring most likely at random. Although this could have affected gestational age-specific mortality rates, it is hardly unlikely that occurrence of neonatal death could have been induced or averted by any errors in gestational-age computations based on maternal recall of dates of the LMP.
A strength of the study is that it is population-based and, therefore, unlikely to have been impacted by biases attributable to selection or referral of patients. The large sample size enabled us to control for many potentially confounding characteristics, yielding minimally biased estimates, so that the inferences deduced from the results of the study are valid and generalizable. Another strength of the study is the appropriate statistical procedure to adjust for correlations among twin siblings. The procedure involves taking into account both intra- and intercluster sources of variation. Consequently, the results being reported in this study are more conservative than one would expect using the traditional methods of analysis. eriacta 100 mg
In summary, we found neonatal mortality of twins to be greater among single than married mothers, an association that is explained by the preponderance of preterm births among twins of unmarried gravidas. Our findings reinforce the importance of future research to develop and test interventions that will decrease the incidence of preterm delivery in both singleton and multiple births.