In a population‐based retrospective cohort study, infants whose fathers were 40 or older—or 24 or younger—had a higher risk of various adverse outcomes than those whose fathers were aged 25–29.1 Infants of fathers aged 40–45 had an increased risk of being stillborn (odds ratio, 1.2), while infants of fathers older than 45 had an elevated risk of being low‐birth‐weight, preterm or very preterm, or stillborn (1.1–1.5). Furthermore, infants whose fathers were 24 or younger had an increased likelihood of being low‐birth‐weight, preterm or small for gestational age (1.1–1.2), whereas those whose fathers were aged 30–39 had a decreased likelihood of these outcomes (0.90–0.96).
Numerous studies have found associations between young or advanced maternal age and an elevated risk of negative birth outcomes. However, few have examined paternal age and such outcomes, and the findings have been mixed. This study examined 755,000 singleton births at 20–44 weeks’ gestation, using data from Missouri maternally linked vital statistics records for 1989–2005. Chi‐square tests and analysis of variance were used to assess differences in mothers’ characteristics and obstetric complications by paternal age, and multivariate logistic regression analysis was used to identify associations between paternal age and birth outcomes. General estimating equations were employed to avoid possible bias resulting from the inclusion of siblings.
The majority of infants had fathers aged 25–29 or 30–34. Most of the rest had fathers in their early 20s or late 30s; about one in 10 infants had fathers who were teenagers or were 40 or older. Maternal characteristics differed by male partner's age. For example, infants whose fathers were younger than 20 had the greatest likelihood of having a mother who was black or single, had not graduated from high school or had smoked during the prenatal period, but their mothers were more likely than others to have received adequate prenatal care. Infants whose fathers were 40 or older were the most likely to have mothers who were at least 35 years old or had used alcohol in the prenatal period. For the cohort overall, the mean gestational age was 39 weeks, and the mean birth weight was 3,400 g; infants of fathers 40 or older had the lowest gestational ages, whereas those whose fathers were 24 or younger had the lowest birth weights.
The frequencies of obstetric complications likewise differed across paternal subgroups. Females whose partners were 40 or older were the most likely to experience hypertension during pregnancy, placental abruption or placental previa, whereas those with teenage partners had the highest risks of anemia, preeclampsia and eclampsia.
Birth outcomes also varied significantly across age‐groups. The highest rates of preterm birth (delivery at less than 37 weeks’ gestation) and stillbirth (fetal death at 20 or more weeks) occurred among infants whose fathers were older than 45, and infants with fathers aged 20–24 were the most likely to be low‐birth‐weight (less than 2,500 g) or small for gestational age (less than the 10th percentile of weight for gestational age).
In multivariate analysis that controlled for maternal characteristics, prenatal risk behaviors and obstetric complications, the odds of low birth weight, preterm birth, very preterm birth (delivery at fewer than 33 weeks), stillbirth and late stillbirth (at more than 28 weeks) were higher among infants whose fathers were older than 45 than among those whose fathers were aged 25–29 (odds ratios, 1.1–1.5). Infants whose fathers were 40–45 years old had an increased risk of being stillborn (1.2) and a decreased risk of being small for gestational age (0.95). In addition, infants whose fathers were aged 30–39 had a reduced likelihood of being low‐birth‐weight, preterm or small for gestational age (0.90–0.96). In contrast, infants with fathers who were 24 or younger had an elevated risk of these outcomes (1.1–1.2), as well as of preterm birth (1.3). Finally, the odds of early stillbirth (at 28 or fewer weeks) were increased for infants whose fathers were aged 20–24 (1.2), while the odds of late stillbirth were reduced for infants whose fathers were teenagers (0.6).
The researchers note a number of study limitations: a wide time range, over which obstetric practices varied, and the lack of data on economic status, as well as on paternal social and demographic characteristics. However, they also point out the study's strengths, including the large sample size, use of a population‐based data set to enhance generalizability and the assessment of numerous birth outcomes. The investigators believe their findings raise the questions of the degree to which prenatal care is directly related to birth outcomes and the role that paternal attributes may play in these outcomes. Overall, the findings suggest that fathers should be included in "the current framework of prenatal care and … counseling during the preconception period."—J. Thomas