Wednesday December 17 2014
Could your partner’s pregnancy be making you broody?
“Men suffer pregnancy symptoms too: Fluctuating hormones make fathers-to-be … more caring,” the Mail Online reports. A small US study found evidence of changes in hormonal levels that may make fathers-to-be more able to cope with the demands of fatherhood.
The story comes from a study that looked at whether expectant fathers and their partners experience any changes in their hormone levels during pregnancy. It found that, as expected, women experienced a large increase in four hormones associated with pregnancy. Their male partners also experienced small changes in the hormones testosterone and oestradiol.
The researchers, as well as the media, speculate that these small changes in hormone levels could lead to men becoming less aggressive, less interested in sex, and more caring. Though whether such changes are linked to subsequent changes in their behaviour is unproven.
Where did the story come from?
The study was carried out by researchers from the University of Michigan. There is no information about external funding.
The study was published in the peer-reviewed American Journal of Human Biology.
The Mail Online overstated the results of the study, claiming that “men’s hormones go into a spin in the months before becoming a parent” and that this helps them prepare to bond with their babies – and stops them from straying. This is all speculation. The study did not look at men’s behaviour in the months before birth, only at their hormone levels. It is also misleading in that it claims that the men experienced “pregnancy symptoms”, when none were reported in the study.
What kind of research was this?
This study measured changes in levels of certain hormones in 29 first-time expectant couples at four points throughout the prenatal period. The authors point out that expectant mothers experience large increases in hormones such as testosterone, cortisol, oestradiol and progesterone. They say that these hormones are implicated in the neuroendocrine pathways (a complex connection of nerves that both respond to and also produce hormones) that affect maternal behaviour and may have long-term implications for women and their families.
They say that far less is known about changes in the hormone levels of expectant fathers, even though their behaviour may be influenced by the same neuroendocrine pathway. In addition, it is not known if there is any correlation between couples in changes in hormone levels.
The researchers focused on four hormones, which have large prenatal changes in women and which they say have important implications for parental behaviour. These are:
- Testosterone – higher levels are associated with aggression and lower levels with parental care. Women’s testosterone levels increase during pregnancy and decline after birth.
- Cortisol – associated with stress and challenges. In women, cortisol increases through pregnancy and declines after birth.
- Oestradiol – associated with caregiving and bonding and thought to be important for maternal attachment. In women it increases during pregnancy and drops after birth.
- Progesterone – associated with social closeness and maternal behaviour. In pregnant women it increases during pregnancy and drops after birth.
What did the research involve?
The researchers measured changes in all four hormones in 29 expectant couples. The couples, who were recruited online and in print, were paid $50 per session for participating. They had to be between 18 and 45, living together, expecting their first child and within the first two trimesters of pregnancy. Smokers, those with medical conditions that could influence hormone levels, and those taking hormone altering medications were excluded.
The couples’ hormone levels were assessed up to four times throughout the prenatal period, at approximately weeks 12, 20, 28 and 36 of pregnancy. Each couple came to the laboratory together and had their hormone levels measured at the same time and on the same day of the week. They provided two saliva samples on each visit. These were frozen until being tested for levels of testosterone, cortisol, oestradiol and progesterone, using commercially available kits.
The researchers analysed the results using standard statistical methods.
What were the basic results?
- As expected, women showed large prenatal increases in all four hormones.
- Men showed significant but small prenatal declines in testosterone and oestradiol, but there were no detectable changes in men’s cortisol or progesterone.
How did the researchers interpret the results?
The researchers say their study is the first to demonstrate prenatal testosterone changes in expectant fathers.
They say the findings on testosterone and oestradiol support the idea that the same hormones may be involved in maternal and paternal care.
They say their findings provide some support for the theory that similar neuroendocrine pathways support both maternal and paternal behaviour.
This is an interesting study, but it was very small and, as the authors point out, found only limited evidence of small hormone changes among expectant fathers, so it is difficult to draw any conclusions from it.
One important limitation was the lack of a comparison group of non-expectant couples. This means the authors cannot say whether any hormone changes among the men occurred as a result of expectant fatherhood or other causes.
Nor did the researchers assess the men’s hormones before conception or postnatally, so they could not determine how men’s hormone levels change during the entire transition to parenthood.
In women, changes in hormone levels are vital to maintain the pregnancy and are also thought to affect maternal feelings and behaviour. This study does not provide conclusive results on the changes in hormone levels that occur in expectant fathers or whether these might be linked to changes in behaviour.
Becoming a dad for the first time can be an overwhelming and somewhat frightening experience, though most men quickly learn and adapt. The human race wouldn’t be here if that wasn’t the case.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.