Second, our haplotype-based genetic score analysis showed that both maternal transmitted genetic score and paternal transmitted genetic score were highly significantly associated with birth length and birth weight, but the nontransmitted score was not (particularly for birth weight), which again indicated that maternal height has relatively minimal effect on birth length or birth weight if not transmitted genetically. Again, this conclusion was supported by multiple lines of evidence: (i) gestational age was (marginally) associated with maternal height genetic score but not with fetal height genetic score, and after adjustment for fetal genetics, the association between gestational age and maternal height genetic score were still significant; (ii) gestational age was associated with maternal nontransmitted haplotype genetic score, which indicated the effect of maternal height on gestational age was transmitted through phenotypic causal mechanism rather than genetic inheritance (i.e., transmission of alleles); (iii) the estimated causal effect of 0.4 d/cm of maternal height on gestational age was similar to the size from observational association; and (iv) single-marker analysis indicated that those adult height SNPs were excessively associated with gestational age, and the estimated effect sizes of these SNPs (in mothers) on gestational age, although relatively low, were correlated with their effect on maternal height, which suggested the effect of these SNPs is projected through a common intermediate (i.e., maternal height) rather than through SNP-specific pathways (biological pleiotropy). We also performed analysis using preterm status as a dichotomous outcome, and the results (S9 Table) indicated that shorter maternal height is a risk factor for preterm birth (observational association p = 3.77 × 10−6, with an estimated 3% increase in risk if the mothers are 1 cm shorter). Genetic score analysis also showed significant association between preterm birth risk and the nontransmitted haplotype score (p = 0.0456), which suggests that maternal height causally influences preterm birth risk.
– The height and weight of a newborn baby is largely governed by his or her own genes, but it's the height of the mother that's giving researchers a telltale sign, reports the Telegraph. Specifically, shorter women have shorter pregnancies and thus more premature babies, report investigators at the March of Dimes Prematurity Research Center Ohio Collaborative in the journal PLOS Medicine. The team analyzed 3,485 Nordic women and their babies, and found that a woman's height actually shapes the fetal environment, thereby influencing the length of her pregnancy. This has broad health implications around the world, where 15 million babies are born prematurely every year and more than 1 million of them die due to complications of early birth—which include breathing problems, vision loss, and intellectual delays, report researchers in a press release. "That a woman's height influences gestational length, independent of the genes she passes on that determine fetal size, is a major finding by our research networks, and the first of what we expect to be many genetic contributions," one researcher says. (Premature birth is now the world's top killer of children under 5.)