A recent study published in the journal Science on May 16, 2024, has revealed that human pregnancy demands almost 50,000 dietary calories over nine months. This energy expenditure is much higher than previously estimated and is equivalent to about 50 pints of ice cream.
The study was conducted by an Australian team led by Dustin Marshall, an evolutionary biologist at Monash University. Marshall and his students discovered that only about 4% of this energy is transferred to the baby’s tissues, with the remaining 96% being used by the mother’s body.
This research is part of Dr. Marshall’s broader investigation into the metabolic demands of various species. The team compiled data from 81 species, ranging from insects to mammals, to estimate reproductive energy costs. They found that the energy demands vary significantly, with species size and metabolic rate being key factors.
The findings indicate that the indirect costs of pregnancy often surpass the direct energy used by the offspring. In mammals, only 10% of the total energy during pregnancy is invested in the offspring, with the rest being an additional metabolic burden on the mother. This high indirect energy cost is particularly pronounced in live-bearing species compared to egg-laying ones.
The study's insights could help explain why female mammals, including humans, invest heavily in post-birth care due to the substantial energy expended during pregnancy.