Co-bedding of preterm twins to optimize growth and brain development

Review question

We reviewed evidence on the benefits and harms of co-bedding stable preterm twins and found six relevant studies.


Preterm twins are at high risk for problems in growth and development. Co-bedding (placement of twins in the same cot or incubator) has been proposed to benefit twins because it simulates the environment that they shared before birth, in which twins have been seen to support each other through a series of observed activities, termed "co-regulation." These activities have been proposed to promote growth and brain development when they are allowed to continue after birth. Risks of placing twins in the same incubator or cot include caregiver error and infection.

Study characteristics

This review found six mostly small studies with some limitations in their methods. All six studies were conducted in the neonatal nursery of a major tertiary hospital. In all studies, researchers enrolled preterm infants of average postmenstrual age of 29 weeks (nearly two and a half months preterm). Some studies enrolled twins only; others enrolled twins and triplets and quadruplets and chose to co-bed two of the higher-order multiples considered most stable at the time of enrollment.

Key results

Overall, researchers reported no differences between the co-bedded group and the group receiving care separately in terms of weight gain, episodes of major disturbances in their breathing, heart rate or oxygenation level (apnea, bradycardia, or desaturation episodes), length of hospital stay, and occurrence of infection. Conflicting results were noted in the two included studies that assessed infants' pain response after heel prick.

Quality of evidence

Overall quality of evidence was low because of limitations in study methods, small sample sizes giving rise to imprecise results, and inconsistency in study results. We can make no recommendations for or against co-bedding for stable preterm twins in the neonatal nursery on the basis of evidence gathered in this review. Further research on this topic is needed.

Authors' conclusions: 

Evidence on the benefits and harms of co-bedding for stable preterm twins was insufficient to permit recommendations for practice. Future studies must be adequately powered to detect clinically important differences in growth and neurodevelopment. Researchers should assess harms such as infection, along with medication errors and caregiver satisfaction.

Read the full abstract...

The increased birth rate of twins during recent decades and the improved prognosis of preterm infants have resulted in the need to explore measures that could optimize their growth and neurodevelopmental outcomes. It has been postulated that co-bedding simulates twins' intrauterine experiences in which co-regulatory behaviors between them are observed. These behaviors are proposed to benefit twins by reducing their stress, which may promote growth and development. However, in practice, uncertainty surrounds the benefit-risk profile of co-bedding.


We aimed to assess the effectiveness of co-bedding compared with separate (individual) care for stable preterm twins in the neonatal nursery in promoting growth and neurodevelopment and reducing short- and long-term morbidities, and to determine whether co-bedding is associated with significant adverse effects.

As secondary objectives, we sought to evaluate effects of co-bedding via the following subgroup analyses: twin pairs with different weight ranges (very low birth weight [VLBW] < 1500 grams vs non-VLBW), twins with versus without significant growth discordance at birth, preterm versus borderline preterm twins, twins co-bedded in incubator versus cot at study entry, and twins randomized by twin pair versus neonatal unit.

Search strategy: 

We used the standard search strategy of the Cochrane Neonatal Review Group (CNRG). We used keywords and medical subject headings (MeSH) to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 2), MEDLINE (via PubMed), EMBASE (hosted by EBSCOHOST), the Cumulative Index to Nursing and Allied Health Literature (CINAHL), and references cited in our short-listed articles, up to February 29, 2016.

Selection criteria: 

We included randomized controlled trials with randomization by twin pair and/or by neonatal unit. We excluded cross-over studies.

Data collection and analysis: 

We extracted data using standard methods of the CNRG. Two review authors independently assessed the relevance and risk of bias of retrieved records. We contacted the authors of included studies to request important information missing from their published papers. We expressed our results using risk ratios (RRs) and mean differences (MDs) when appropriate, along with 95% confidence intervals (95% CIs). We adjusted the unit of analysis from individual infants to twin pairs by averaging measurements for each twin pair (continuous outcomes) or by counting outcomes as positive if developed by either twin (dichotomous outcomes).

Main results: 

Six studies met the inclusion criteria; however, only five studies provided data for analysis. Four of the six included studies were small and had significant limitations in design. As each study reported outcomes differently, data for most outcomes were effectively contributed by a single study. Study authors reported no differences between co-bedded twins and twins receiving separate care in terms of rate of weight gain (MD 0.20 grams/kg/d, 95% CI -1.60 to 2.00; one study; 18 pairs of twins; evidence of low quality); apnea, bradycardia, and desaturation (A/B/D) episodes (RR 0.85, 95% CI 0.18 to 4.05; one study; 62 pairs of twins; evidence of low quality); episodes in co-regulated states (MD 0.96, 95% CI -3.44 to 5.36; one study; three pairs of twins; evidence of very low quality); suspected or proven infection (RR 0.84, 95% CI 0.30 to 2.31; three studies; 65 pairs of twins; evidence of very low quality); length of hospital stay (MD -4.90 days, 95% CI -35.23 to 25.43; one study; three pairs of twins; evidence of very low quality); and parental satisfaction measured on a scale of 0 to 55 (MD -0.38, 95% CI -4.49 to 3.73; one study; nine pairs of twins; evidence of moderate quality). Although co-bedded twins appeared to have lower pain scores 30 seconds after heel lance on a scale of 0 to 21 (MD -0.96, 95% CI -1.68 to -0.23; two studies; 117 pairs of twins; I2 = 75%; evidence of low quality), they had higher pain scores 90 seconds after the procedure (MD 1.00, 95% CI 0.14 to 1.86; one study; 62 pairs of twins). Substantial heterogeneity in the outcome of infant pain response after heel prick at 30 seconds post procedure and conflicting results at 30 and 90 seconds post procedure precluded clear conclusions.