Exploring the association of parity and its interaction with history of preterm delivery on gestational duration.

• Preterm delivery is a major cause of child mortality. While the relationship between parity and preterm delivery is known, its association with gestational duration and variability remains underexplored. Differences in variance may suggest interaction with other well-established risk factors.With 1.1 million spontaneous deliveries (1990-2012) from the Swedish Medical Birth Register, we assessed while accounting for potential confounders the effects of parity on the mean and variance of gestational duration, and its possible interactions with history of preterm delivery. Pedigrees allowed to account for nonobserved, shared confounders using linear mixed models.Parity has a modest association with mean gestational duration, but a large effect on its variance. For example, the first pregnancy had the shortest mean gestational duration, 0.29days shorter (95% CI: -0.33, -0.25) than the second, and the largest variance (σ2 =135days2). Accounting for shared unobserved confounders highlighted a group effect bias, likely linked to the mothers' total number of offspring. Parity interacts with other risk factors, including previous preterm delivery where the magnitude of its effect increases with parity (up to 4.6days effect difference).Nonshared factors across a mother's pregnancies highlight parity's importance to gain insight into the mechanisms governing the timing of delivery.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Reproduktionsmedicin och gynekologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Obstetrics, Gynaecology and Reproductive Medicine (hsv//eng)

Nyckelord

Pregnancy

Infant

Newborn

Female

Child

Humans

Premature Birth

epidemiology

Gestational Age

Risk Factors

Mothers

Sweden

epidemiology

Parity

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)