Every year, an estimated 15 million babies are born preterm worldwide (<37 gestational weeks) and this number is rising. In Portugal, where this study was conducted, approximately 7.7% of children were born prior to term in 2014, while in 2001 it was about 5.6%.1 Such significant increase constitutes an important public health issue. Indeed, younger and more fragile infants are surviving their neonatal intensive care unit (NICU) stays, with many of them exhibiting high rates of special needs as they grow older.2 Several mental health problems have also been reported for parents. Evidence has revealed that mothers of preterm infants often show elevated stress levels and psychological difficulties, which, in turn, seem to compromise their parenting abilities and, consequently, child development.3 Therefore, more research focused on the impact of medical and social risk factors on parental adjustment is crucial in the field of prematurity.

Research conducted during the last decades has provided a growing body of evidence on the adverse effects of child health risks for parents’ psychological functioning.4 Recently, researchers have been particularly interested in the putative aggravating role of being a mother of multiples. Adding to the stresses of being a parent of a preterm (more fragile) infant, families of preterm multiples are often exposed to additional health and emotional demands, including prolonged hospitalization, child cerebral palsy, hemorrhage, and developmental delays.5,6 Moreover, mothers with multiple gestation pregnancies and their partners have to care for and relate to more than one baby, to whom they may have been separated during their first days after delivery. Such parents often experience more financial pressures, fatigue, social isolation, and practical difficulties that emerge from the need of looking after for more than one infant at once.7 Not surprisingly, researchers have recently revealed that mothers of preterm multiples are more likely to be depressed, to present elevated anxiety, and to experience more parenting stress.8–11

Despite the importance of the findings described above, the research in this field is still characterized by a lack of studies focused on the identification of environmental factors that may buffer the negative effects of multiple births on the psychological well-being of mothers of preterm infants. This gap in the literature is notable, given years of research highlighting the negative impact of family psychosocial adversities on women's psychological functioning. For instance, Goyal et al.12 showed that first time mothers exposed to low socioeconomic status were 11 times more likely than mothers with no socioeconomic risk factors to have clinically elevated depression scores. Although not focused on the role of multiple births, also of note is the work of Wormald et al.13 These investigators analyzed the levels of stress of parents of very low birth weight (VLBW) infants, finding that the mothers of VLBW infants who exhibited significantly higher stress levels were the ones who were exposed, not only to medical complications, but also to more socioeconomic adversities (e.g., lower education, unemployment).

Sample characteristics are presented in Tables 1 and 2. At time of assessment, mothers were aged 19–48 years (34.01±5.20). Seventy-two were primiparous and 17 were mothers of multiples (all twins, except one mother of triplets). In the majority of cases, the pregnancy was planned (82.1%), medically monitored (96.8%), and infants were delivered vaginally (50.5%). The majority of mothers were married (91.6%). The remaining were single (6.3%) or divorced (2.1%). Regarding maternal education, three mothers had four years of formal education, 25 had five to nine years, 30 had ten to 12 years, and the remaining had a college degree. Seventy-three mothers had a job, 21 were unemployed, and one mother was retired. Moreover, 31 (32.6%) families were living with incomes below the national poverty line.

For the total sample, mothers’ mean perceived stress was 32.44±21.12, while the mean of psychological symptoms was 1.42±.37 (Table 3). Analyses showed that mothers of preterm multiples and mothers of preterm singletons were not significantly different in any of the following demographic and study variables: maternal age, t(93)=−1.18, p=0.24; child medical risks, t(93)=−0.45, p=0.66; or family socioeconomic disadvantage, χ2=3.91, p=0.06. Likewise, mothers exposed and mothers not exposed to socioeconomic disadvantage did not differ in terms of child medical risks, t(93)=0.90, p=0.37; however, mothers living in a context of socioeconomic disadvantage were significantly older, t(93)=2.35, p=0.02.

Effects of multiple births and socioeconomic disadvantage

Then, two-way MANOVA was performed. Multiple births and family socioeconomic disadvantage were included in the analysis as factors, while child medical risk was entered as a covariate. Data entered into the MANOVA satisfied the requirements for homogeneity of covariance matrices (Box's test, p=0.12) and equality of variances for each dependent variable (Levene's tests: for perceived stress, p=0.11; for psychological problems, p=0.93). The main results revealed a statistically significant principle effect of multiple births on the combined dependent variable, F(1,95)=5.25, p=0.007, Wilks’ Λ=0.89. Further examination of this result indicated that mothers of preterm multiples reported higher levels of stress than mothers of preterm singletons, F(1,95)=10.70, p=0.002, Eta2=0.11. No significant differences were observed between mothers exposed and unexposed to socioeconomic disadvantage (Table 3). However, there was a marginally significant multiple births vs. socioeconomic status effect on the combined dependent variables, F(1,95)=2.75, p=0.06, Wilks’ Λ=0.94. Given this tendency, between-subjects effects were then examined. Results indicated that the impact of multiple births on maternal psychological problems (but not levels of stress) differ whether mothers were exposed (vs. unexposed) to socioeconomic adversities, F(1,95)=5.25, p=0.02, Eta2=0.055. More specifically, simple effects analysis revealed that, in the context of socioeconomic disadvantage, mothers of preterm multiples significantly reported more psychological symptoms (1.77±0.33) than mothers of preterm singletons (1.37±0.34). However, in the absence of socioeconomic adversities, mothers of preterm multiples (1.39±0.33) and mothers of singletons (1.45±0.42) reported similar levels of psychological problems (Fig. 1).

Figure 1.

Maternal perceived stress and psychological problems: means±standard deviations for the multiple births vs. socioeconomic disadvantage.

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The present study aimed to examine the differences between mothers of preterm multiples and mothers of preterm singletons with respect to perceived stress and maternal psychological symptoms, while controlling for the effect of child medical risks. As expected, the results revealed that mothers of preterm multiples experienced significantly higher stress levels than mothers of preterm singletons months after delivery, when their children were 12 months of corrected age. It is important to highlight that this result is in line with previous studies, which have also shown, consistently, that mothers of multiples are significantly more likely than mothers of singletons to report severe parenting stress, not only days after delivery, but also months after giving birth.11,18

Surprisingly, no significant differences emerged between groups with respect to maternal psychological symptoms in the present study. This data is consistent with other studies that have also failed to document differences between mothers of multiples and mothers of singletons in psychological functioning. For instance, Glazebrook et al.19 found that mothers of multiples did not have poorer mental health than mothers of singletons, one year postpartum. Nevertheless, the present results differ from other research that, on the contrary, indicated the presence of elevated psychological difficulties among mothers of preterm multiples.9,10 Such divergent results across studies may be attributable to methodological issues. More precisely, in the present investigation, as well as in the work of Glazebrook et al.,19 maternal mental health was assessed using global reports of psychological functioning, while in other studies researchers have relied on measures aimed to specifically assess maternal levels of anxiety or depression.20 In addition to this possibility, it may also be the case that maternal psychological difficulties may be more salient in the very first days or months after giving birth, during a period when the mother is still adapting to the role of being a parent of two or more fragile children. Accordingly, Van den Akker et al.,21 in a meta-analysis, concluded that maternal depression was more common before the end of one year postpartum. On the contrary, in the present study assessments occurred one year after delivery. However, it is unclear whether any of these explanations is responsible for the results reported herein. Future studies, longitudinal in design, are clearly needed.

Adding to the above research aims, this report also sought to innovate and extend the current literature by exploring the putative amplifying adverse effect of socioeconomic disadvantage on the relation between multiple preterm births and maternal adjustment. Data showed that mothers of preterm multiples significantly reported more psychological symptoms than mothers of singletons, but only when exposed to socioeconomic adversities. This result clearly points to the relevance of parental socioeconomic background for women's adjustment, as previously suggested by other studies.12,13 However, and most importantly, these results may help to clarify the inconsistencies found in the literature about the emergence of psychological symptoms among mothers of preterm multiples, as discussed in the preceding paragraph. More precisely, this study expands previous literature by suggesting that the birth of multiples does not necessary adversely impacts women's mental health. Instead, it may be the case that the negative impact of multiple births on the psychological functioning of women occurs when mothers are, simultaneously, exposed to a context of social disadvantage. Such adversity will prevent families from obtaining the resources and support needed to adequately care for and relate to more than one small, fragile infant at once.

Importantly, these findings also revealed that the elevated susceptibility of mothers of preterm multiples to show adjustment problems, more than one year postpartum, seems to occur even after controlling for the putative effect of child medical risks. In fact, it is worth bearing in mind that no significant associations emerged, in the current report, between child risks at birth and maternal perceived stress and psychological problems. This lack of a significant effect is not in line with other studies.4 However, this does not necessarily mean that child medical adversities have no implications on the well-being and maternal psychological functioning. Perhaps other child factors may be more prominent one year postpartum, such as the presence of neurological dysfunctions, as already evidenced by Walter et al.22 On this subject, more studies are needed.

Fundação para a Ciência e a Tecnologia (SFRH/BPD/100994/2014, SFRH/BD/86075/2012).

The authors declare no conflicts of interest.