A key issue concerning the sleeping arrangements of twins is the question of co-bedding. Little research has addressed the potential benefits and risks of this practice. Past research has tended to focus on twins with special health needs, rather than home sleeping arrangements for healthy, term twins. Nevertheless the practice of co-bedding twin infants is common:
A study carried out in New Zealand, based on postal surveys, investigated the prevalence of co-bedding and SIDS-related child care practices in twins (Hutchinson et al 2010). The researchers stated that despite a lack of evidence of the risks or benefits of co-bedding this practice was very popular, especially among younger twins (52% of 109 twin pairs co-bedded at 6 weeks of age, 31% at 4 months, and 10% at 8 months of age). The authors neither advocate nor warn against the practice of co-bedding due to the lack of sufficient data, and conclude that more research is needed.
Damato et al (2012) based their research on home interviews with parents of 104 pairs of twins in the US. Their study found that more than 65% of twins were co-bedded at 4 weeks of age while 42% of twins were co-bedded by 13 weeks of age. Room sharing was practiced among 64% of families at 4 weeks of age and by 40% by 13 weeks of age.
Ball’s studies (2006, 2007) investigated UK parents’ perspectives and concerns about co-bedding, and also employed video data to assess potential risks and benefits of co-bedding compared to separate sleeping. In this study, parents of twins were asked to keep sleep logs and were interviewed through mail. At this point parents’ reasons for sleeping their twins together or apart were given. Subsequently, the actual sleeping arrangements were recorded and observed. To collect data in the first phase of the research, cameras were installed in participants’ homes for two nights. In the second phase, families visited the Sleep Lab for three nights. During both phases parents were asked to behave normally and to put children to bed as they usually do. The study found that:
- Co-bedding facilitates rooming-in and thus can influence the reduction of SIDS risk
- Make-shift barriers separating co-bedded infants are unnecessary and can result in harm
- Hospital practices can influence parents’ behaviour – co-bedding was more popular among parents who observed such sleeping arrangements while in hospital
- Parents may find that co-bedding makes night-time care easier due to sleep synchronisation of twins
No evidence was found to support parents’ concerns about co-bedding (i.e. concerns which led to parents deciding to sleep twins separately - twins disturbing each other, risk of overheating and suffocating). Parents’ reasons for sleeping infants together were supported by the observation that co-bedded twins had synchronous sleep patterns and were subjectively easier to care for; this in turn might be connected with co-bedded infants remaining in the parents’ room for longer. Neither co-bedding nor separate sleeping resulted in parents obtaining more sleep.
The US National Association of Neonatal Nurses’ statement concerning co-bedding of twins and higher order multiples (2011) is non-prescriptive, with the organisation emphasising the lack of sufficient body of knowledge. At the same time the American Academy of Pediatrics (AAP) (Moon et al 2011) recommends against co-bedding twins, justifying this advice with exactly the same argument - the lack of data on the benefits of this practice. However, the AAP does not focus on healthy infants and does not mention the research conducted by Ball (2007). NHS Choices (UK), on the other hand, advises that "You may put your twins to sleep in a single cot while they're small enough, either because they slept together in hospital or because space is tight. This is called co-bedding and is perfectly safe. In fact, putting twins in the same cot can help them regulate their body temperatures and sleep cycles, and can soothe them and their twin." (2012)
While most twins are initially co-bedded in a side-by-side position, a great variety of co-bedding configurations are used by parents. These are not all equally safe, and a general rule is that babies cobedded babied should be positioned with their feet to the foot of the cot as for singletons. Diagonal positioning is undafe if used with blankets as these are difficult to secure in this position, but with the use fo sleeping bags is less hazardous. Parents should avoid cobedding twins in a moses basket or small bassinette due to lack of space.
It is important that parents are aware that it is the presence of an adult carer that is associated with reduced SIDS risk, rather than the presence of another infant, and that general infant sleep safety recommendations apply just as with singletons.
Co-regulation and the stress response
Prior to birth the twin fetuses are in constant contact in utero, giving rise to a synchrony in movement and co-regulation in biological measures (Gallagher et al., 1992; Klaus & Klaus, 2000; Nyquist & Lutes, 1998; Touch et al., 2002; Sherer et al., 1990). Once birthed, they are uniquely adapted to develop alongside their twin counterpart. It is therefore thought that close contact is beneficial to their wellbeing in the extrauterine environment (Hayward et al., 2015; Nyquist & Lutes, 1998).
The benefits of twin co-bedding are still being investigated. Hayward et al (2015) found co-bedding preterm twins had fewer adverse health issues and longer durations of quiet sleep than non-co-bedding preterm twins. Co-regulation of infant heartbeats means that co-bedding infants have significantly lower heart rates and thus have a lower stress levels overall (Hayward et al., 2015; Byers et al., 2003; Stainton et al., 2005).
Co-bedding and co-regulation can be important in medical situations. Twins and higher order multiples are more likely to be born preterm and require some medical intervention. However it has been shown that co-bedding twins provides comfort to infants undergoing stressing procedures, comparable to the presence of a mother (Campbell-Yeo et al, 2009).