Depression in women during pregnancy is known to be associated with low birth weight and increased risk of premature birth. Maternal stress, such as the death of a loved one, lack of social support, or a difficult or abusive relationship, has also been shown to increase the risk of premature birth. However, little research has examined the impact of paternal depression on the health of the mother or the unborn child.
In this study, more than 350,000 births in Sweden between 2007 and 2012 were investigated for parental depression and incidence of either very preterm birth (between 22 and 31 weeks) or moderately preterm birth (32-36 weeks).
For both men and women, depression was defined as having had a prescription of antidepressant medication, or receiving outpatient/inpatient hospital care, from 12 months before conception to the end of the second trimester of pregnancy. People with depression were classed as 'new' cases if they had had no depression in the 12 months prior to diagnosis, all other cases were defined as 'recurrent' depression.
While both new and recurrent depression in the mothers was associated with an increased risk of moderately preterm birth of around 30% to 40%, new depression in the fathers was associated with a 38% increased risk of very preterm birth. Recurrent depression in the fathers was not associated with preterm birth at all.
Professor Anders Hjern, from the Centre for Health Equity Studies in Stockholm (CHESS), said: "Depression of a partner can be considered to be a substantial source of stress for an expectant mother, and this may result in the increased risk of very preterm birth seen in our study. Paternal depression is also known to affect sperm quality, have epigenetic effects on the DNA of the baby, and can also affect placenta function. However, this risk seems to be reduced for recurrent paternal depression, indicating that perhaps treatment for the depression reduces the risk of preterm birth.
"For the mothers, depression increased the risk of preterm birth, regardless of whether the depression was new or recurrent.
"Our results suggest that both maternal and paternal depression should be considered in preterm birth prevention strategies and both parents should be screened for mental health problems. Since men are less likely to seek professional help for any mental health problems, a proactive approach towards targeting the wellbeing of expectant fathers may be beneficial."
John Thorp, BJOG Deputy Editor-in-chief, added: "This study highlights the importance of treating depression for both men and women, and the impact untreated depression can have on the health of offspring.
"Further progress is needed into the understanding of how depression of either parent affects pregnancy in order to help prevent preterm birth."
Dr Patrick O'Brien, an obstetrician and spokesperson for the Royal College of Obstetricians and Gynaecologists (RCOG), said: "Depression in pregnancy can be very serious for a woman and can also impact on the health of her baby. We know that between 12% and 20% of women experience anxiety and/or depression during pregnancy and the first year after childbirth.
"This research is interesting as it finds that paternal mental health can also have an effect on the health of the baby. However, more research is needed to establish the mechanism behind this effect.
"We encourage anyone, and particularly those planning a family or who are pregnant, and are experiencing a change in mood, irritability or anxiety to seek advice. No one should suffer in silence -- there is help and support available."