when do babies lose the ability to swim
Infant swimming Most human babies demonstrate an innate swimming or diving reflex from birth until the age of approximately six months. However, babies this young cannot actually swim, due to their lack of body features and strength. Other mammals also demonstrate this phenomenon (see mammalian diving reflex). This reflex involves apnea (loss of drive to breathe), slowed heart rate (reflex bradycardia), and reduced blood circulation to the extremities such as fingers and toes (peripheral vasoconstriction).[1] During the diving reflex, the infant's heart rate decreases by an average of 20%.[1] The glottis is spontaneously sealed off and the water entering the upper respiratory tract is diverted down the esophagus into the stomach.[4] The diving response has been shown to have an oxygen-conserving effect, both during movement and at rest. Oxygen is saved for the heart and the lungs, slowing the onset of serious hypoxic damage. The diving response can therefore be regarded as an important defence mechanism for the body.[5]
Obligate nasal breathing Human infants are commonly described as obligate nasal breathers as they prefer breathing through their nose rather than mouth.[3] Most infants, however, are able to breathe through their mouth if their nose is blocked.[3] There are however certain infants with conditions such as choanal atresia in which deaths have resulted from nasal obstruction.[3] In these cases there are cyclical periods of cyanosis. The infant initially attempts to breathe through the nose, and is unable to; hypercapnia occurs, and many babies instinctively begin to cry. While crying, oral ventilation occurs and cyanosis subsides. There is variation in the length of time until a baby begins oral breathing, and some will never cease attempts at nasal breathing. It has also been suggested that infants may not be able to sustain oral breathing for significant lengths of time, because of the weakness of the muscles required to seal the nasal airway and open the oral airway.[3]