Maternal contributions to preterm delivery

Abstract

Preterm delivery (PTD) is a complex trait with a significant familial component. However, no specific inheritance patterns have been established. The authors examined the contribution of PTDs in both the woman's family and her partner's family to her risk of PTD. The authors linked birth information from Danish national registers with pedigree information from the Danish Family Relations Database for 1,107,124 live singleton deliveries occurring from 1978 to 2004. Risk ratios were estimated comparing women with and without various PTD histories. Women with previous PTDs were at greatly increased risk of recurrent PTD (risk ratio = 5.6, 95% confidence interval: 5.5, 5.8); however, their PTD risk was unaffected by a partner's history of preterm children with other women. PTDs to a woman's mother, full sisters, or maternal half-sisters also increased her PTD risk (risk ratio = 1.6, 95% confidence interval: 1.5, 1.6), whereas PTDs in her paternal half-sisters, the female partners of her male relatives, or members of her partner's family did not affect her PTD risk. Inheritance patterns were similar for all gestational ages from very early through late PTD. The substantial portion of PTD risk explained by effects passed through the female line suggests a role for either imprinting or mitochondrial inheritance.

Figure 1.

A woman's risk of preterm delivery (PTD), by history of PTD in her own family and in her male partner's family, Denmark, 1978–2004. Female members of the woman's family and her male partner's family who delivered live children before the woman herself in the period 1978–2004 after gestations of known length were included in the analyses. A history of PTD was defined as having 1 or more female family members in the category in question with children born at or before 36 completed weeks’ gestation and before the birth of the woman's child. The risk ratios compare the risk of PTD in women with a history of PTD (≥1 PTD) in the specified female family members with the risk in women with no such family history. The open circles identify risk ratios related to a history of PTD in female relatives on the woman's maternal side. CI, confidence interval.