Exactly how that process works is being explored by University of Otago scientists Dr Sharon Ladyman and Dr Rosemary Brown.
Each are recipients of grants of close to $1million from the Marsden Fund to research aspects of the hormone prolactin.
University of Otago department of anatomy senior research fellow Dr Ladyman has been granted $939,000 to study how neurons keep mothers cool during pregnancy.
The hormone prolactin was named after its main role in milk production and is at high levels in the body when women are pregnant and lactating.
Women were encouraged to exercise often during pregnancy, but a lot of struggled to meet that level, Dr Ladyman said.
She wanted to understand if there was a biological reason for that, if women did not want to harm their baby, or were too tired to do physical exercise.
Dr Ladyman and Dr Brown had previously found data showing prolactin was able to influence neurons in the preoptic area of the brain involved in reducing body temperature.
"Those cells could rapidly change body temperature."
Prolactin was driving the suppression of physical activity but how and why it did that was the question Dr Ladyman was seeking to answer with this research grant.
"So how does prolactin regulate body temperature during pregnancy and does that contribute to lowered physical activity."
Metabolic heat was generated during pregnancy, however, a higher body temperature was not good for a developing foetus.
"So you can image then mum exercising, you are increasing your body temperature, and then there is this biological system saying ‘the body temperature is too high, we need to limit that — how can we do that? — by decreasing exercise’."
Department of physiology lecturer Dr Brown has been granted $960,000 to study how hormones reward mothers to support maternal-infant interactions.
"So understanding the changes that are taking place in the brain of a mother when she is pregnant, and then once she has had her child that will help her look after her offspring."
A mother’s motivation to display nurturing behaviour is critical for the survival of a species.
Increased motivation to interact with young after pregnancy had been observed across many species, Dr Brown said.
Her research would explore the "rewarding aspect" of this behaviour.
The brain’ s reward system involves the release of dopamine which generates good feelings and encourages repeat behaviour.
"So dopamine is released when you are doing a particular activity and it makes you want to do it again."
Her research was aimed at uncovering how prolactin was interacting with the reward system in mothers.
"Is it driving these changes in reward behaviour that you see?"
Previous research in mice had indicated if prolactin signalling was blocked, then mothers would abandon their young within the first 24 hours of giving birth.
"So it is absolutely essential but we don’t understand how it is doing that."
