Baby hammocks or "sarong cradles" offer a form of cosleeping that is traditional in many cultures, particularly South-East Asia.
After two cases of infants being found dead in hammocks concern was raised as to their relative safety. The danger lies in the potential for infants to roll into such a position where their upper airways are compromised. Chiu et al. (2014) found that there is no difference in safety between those using hammocks correctly and non-hammock using babies. However once the baby can roll, as when swaddling, this method of sleep aid should not be used.
It is worth noting that Chiu et al. (2014) also found that infants sleep less in hammocks, but sleep intensity was greater.
Studies (Ng et al. 1997; Ramdzan et al., 2014) consistently find that traditional hammock users in South-East Asia are more likely to be subject to serious head injuries and recommend banning their use on this basis.
Western 'Baby Hammocks' are now available that stretch over the top of a conventional cot or crib. As with many other infant sleep products advertising claims that this hammock 'helps reduce risk of SIDS' and reduce the risk of 'flat head syndrome'. There is no research evidence to support either of these claims. We are concerned that when used with small babies these devices cause the infant's neck to flex chin to chest which can be dangerous in causing obstructions of an infant's airway.
Several types of baby swings are marketed as sleep spaces -- and even if not intended for sleep babies sometimes fall asleep in swing seats. However it is not safe for babies to sleep in swing seats (or baby bouncers) of any kind, nor to be left in them unattended. Should a baby fall asleep in a swing they should be moved to flat sleep surface and place in the supine position (i.e. on back).
Small babies in swings can find it difficult to hold up their heads and keep their airways clear. They can also slip from the restraints into a position where the harness compresses their airway.
Although there are anecdotal data about infant deaths in baby swings they remain a rare location for infant death because they are an unusual and rare location for infant sleep. Guidance about swings is generally derived from studies of other sitting devices such as car seats (Cote 2008, Batra et al 2015).