Intergenerational Cohort Study of Preterm and Small-for-Gestational-Age Birth in Twins and Singletons

Abstract

To date, several studies have investigated the intergenerational effect of preterm and small-for-gestationalage (SGA) births. However, most studies excluded both twin mothers and twin offspring from the analyses. Thus, the objective of this study was to investigate the intergenerational effect of preterm birth and SGA births among twins and singletons. A prospective population-based register study of mother-firstborn offspring pairs recorded in the Swedish Medical Birth Register was performed. The study included 4,073 twins and 264,794 singletons born from 1973-1983 and their firstborns born from 1986-2009. Preterm birth was defined as birth at <37 weeks of gestation, and SGA as birth weight <2 standard deviations of the Swedish standard. Logistic regressions were performed to estimate the intergenerational effect of each birth characteristic. Adjustments were made for maternal grandmothers' and mothers' socio-demographic factors, in addition to maternal birth characteristics. Among mothers born as singletons, being born preterm was associated with an increased risk of delivering a preterm child (adjusted odds ratio (OR) 1.39, 95% Confidence Interval (CI) = 1.29-1.50), while being born SGA increased the likelihood of having an SGA child (adjusted OR 3.04, 95% CI = 2.80-3.30) as well as a preterm child (adjusted OR 1.30, 95% CI = 1.20-1.40). In twin mothers, the corresponding ORs tended to be lower, and the only statistically significant association was between an SGA mother and an SGA child (adjusted OR 2.15, 95% CI = 1.40-3.31). A statistically significant interaction between twinning and mother's size for gestational age was identified in a multivariate linear regression analysis, indicating that singleton mothers born SGA were associated with a lower birth weight compared with mothers not born SGA. Preterm birth and SGA appear to be transferred from one generation to the next, although not always reaching statistical significance. These effects seem to be less evident in mothers born as twins compared with those born as singletons.

Importance of the environment for gestational duration variability and correlation between relatives – results from the Medical Swedish Birth Registry, 1973-2012

“…In addition, the suggestion that heritable factors for preterm delivery work through the mother is supported by our findings of a larger risk ratio on the maternal side. Other studies based on the Swedish MBR provide similar conclusions [17,18].…”

“…While there seems to be considerable interest in understanding the composition of observed parent-offspring associations, there is, to our knowledge, no previous study analyzing these associations with regard to birth years of relatives. Some [ 4 , 8 , 18 – 22 ], but not all [ 17 , 23 – 27 ]; studies on intergenerational associations address, to varying extents, the problem related to intergenerational effect factors. However, when exploring biologically determined phenotypic similarity between relatives, time-related environmental factors might be considered methodologically for another reason than that of managing the effect of the artificially diminished degrees of similarity attributed to those factors, as in some studies [ 4 , 20 ].…”

Effect of maternal stress during pregnancy on the risk for preterm birth

“…Nicotine and carbon monoxide are potent vasoconstrictors that are thought to cause placental damage and decreased uteroplacental blood flow [ 4 ]. Previous preterm delivery is also associated with an increased risk (OR 1.39, 95 % CI =1.29–1.50) for preterm birth in the next pregnancy [ 6 ]. These are all risk factors and probably indifferent of the presence of maternal stress.…”

Epidemiology and Risk Factors for Premature Birth

“…От съществено значение за предтерминното раждане са и медико-биологичните етиологични фактори. Един от тях се явява преразтягането на матката, като основна причина за това може да бъде наличието на: многоплодна бременност, случила се по естествен начин или след използване на асистирани репродуктивни технологии [52,53,54,55,56] или на полихидрамнион (повишено количество околоплодна течност) [51,57]. Други рискови фактори се явяват: плацента превия [58,59], неправилно предлежание на плода, наличие на миоми, малформации на шийката на матката (включително истмико-цервикална недостатъчност) [51,60], прееклампсия [61], маточни контракции, остри инфекции по време на бременността (вагинални -хламидии, трихомоназа, микоплазма, токсоплазмоза, бактериална вагиноза; хронични заболявания (хипертония, сърдечно-съдови заболявания, заболявания на белите дробове, черния дроб или бъбреците анемия и др.)…”