The American Congress of Obstetricians and Gynecologists recommends regular exercise for women during pregnancy, including running. Some pregnant women have even been known to run marathons while in their third semester. However because the strain that extreme exercise places on the mother and her unborn child, some OB/GYNs recommend swimming rather than running as a way for pregnant women to stay in shape. Regardless of whether a human female chooses to run or swim, at least she never has to face what her Bottlenose Dolphin counterpart does, where extreme exertion can literally mean the difference between life and death.
According to a recent study published in the Journal of Experimental Biology, and reported by Victoria Gill, a science reporter for BBC Nature, pregnant Bottlenose Dolphins have their top swimming speed cut nearly in half. The research states that while a non-pregnant dolphin can swim at more than 14mph, late in their twelve month pregnancy this is reduced to 8mph.
It should be noted that according to other expert sources, the top speed of Bottlenose Dolphins is estimated to be 20mph; however, the reduction in swimming speed cited in the JEB study likely holds true. And the brutal significance of this fact is starkly evident when you consider that the three main predators of Bottlenose Dolphins, namely, Transient Orcas, Great White Sharks, and Tiger Sharks, can swim at least as fast as a non-pregnant dolphin, and in the case of Orcas, much, much faster (32mph).
Thus, while it is generally considered a good thing for a human female who runs regularly to slow her pace during pregnancy, just the opposite is true for her dolphin counterpart. So to all Bottlenose Dolphin mothers-to-be, we say swim, lady swim...for your life!