The present study aimed at determining nutritional factors influencing birth outcomes among pregnant adolescents in rural and urban communities in Ghana. The major findings are that the prevalence of low birth weight, preterm birth, stillbirth, neonatal mortality, haemorrhage, and postpartum hypertension were 15.9%, 12.5%, 2.2%, 3.1%, 11.5%, and 2.2%. Among the nutritional factors assessed, only MUAC status during pregnancy was associated with birth weight, while, fiber intake was associated with the gestational age of the mothers. Combined analyses of study variables showed that both the MUAC and gestational age of participants was effectual in determining birth weight. Gestational age and MUAC status during pregnancy were the significant predictors of birth weight.
The prevalence of low birth weight and preterm birth in our study is higher than that reported in other regions of Ghana [42, 43], the current 2017 Ghana Maternal Health Survey [44], in Brazil [8, 22], and Ethiopia [45]. Low birth weight is a significant underlying cause of neonatal and infant mortality in low-and-middle-income countries such as Ghana [44], which implies that participants with low birth weight are at increased risk of neonatal and infant mortality. A multiple regression analysis showed that maternal anthropometry and gestation age were co-effective in determining birth weight. The result indicated that MUAC (β = 0.283, p = 0.002), BMI (β = 0.221, p = 0.015), gestation age (β = 0.285, p < 0.001), and ZPP (β = 0.131, p = 0.057) were significantly associated with birth weight. The association from the standardized beta coefficient was positive which implies that a point increase in MUAC, BMI, gestation age, and ZPP values would likely result in an increase in the birth weight of babies, and vice versa. The results suggest that pregnancy anthropometrics and ZPP were the nutritional factors that co-effectively determined birth weight. Also, gestational age attained can predict birth weight in adolescent pregnancy. Studies have predicted that maternal gestational age and weight status are associated with birth weight [46–49].
The study found that the adolescent girls had inadequate intake of macronutrients; energy, protein, fiber, and micronutrients; thiamin, riboflavin, folate, vitamins A and E, iron, calcium during pregnancy and their mean intakes for the participants were far lower than RDA/EER/AI. Poor dietary intakes owing to their poor income status at that stage of life might have contributed to nutrients deficiencies in these populations. Another school of thought is that pregnancy comes along eating disorders including anorexia, food aversion, hyperemesis, and other conditions that might limit food intake [50, 51]. A study by Baker et al. [52] also found micronutrient deficiencies among pregnant adolescents in the United Kingdom. In our case, most of these teenagers were having their first pregnancy, and are less likely to adapt to these pregnancy symptoms, which can reduce their appetite for food, and consequently lead to nutrients deficiencies. However, there was no direct effect of nutrients intake on the infant’s birth weight, which suggests dietary intake might be indirectly linked with birth weight, and influence by maternal weight. The same association was found between adolescent mothers with preterm and term birth, except for inadequate fiber intake, in which, preterm birth participants were more likely to have inadequate fiber intake. On the contrary, some studies had reported a relationship between maternal dietary intake and weight gain [53, 54], and weight gain and birth weight [49, 55, 56], low iron and folate intake and small-for-gestational-age babies [52] which suggest that fetal development may rely on nutrients stores during pregnancy. Notwithstanding to exception that, when maternal nutrients stores are depleted under certain circumstances such as severe hunger, there might also be an association between maternal diet and birth outcomes such as birth weight and gestation age [57, 58].
Although, maternal weight gain, nutritional status, and anaemia has a strong association with birth outcomes such as birth weight and gestational age [46–48, 54, 59]. Only a few prior studies have examined these risk associations among pregnant adolescents in a developing country like Ghana. In the current study, we found that 27.8% of the participants were either overweight or obese during pregnancy while, few of them were underweight. Based on the MUAC assessment, 28.8% of the participants were wasted. We found a significant relationship between birth weight and MUAC status during pregnancy, which was consistent with a study by Assefa et al. [12]. Low birth weight adolescent mothers were more likely to be severely wasted during pregnancy. Additionally, we found a high prevalence of maternal anaemia, low serum levels of prealbumin (97.2%), and vitamin A (86.4%). High maternal anaemia prevalence among teenagers has been reported in the study area [60], another region in Ghana [61], and Malaysia [62]. This may be due to poor nutrition at adolescent age, since there is a competition of nutrients for their tissue growth, before that of the developing foetus [2, 60]. Anaemia prevalence was not significantly associated with birth outcome, but anaemic mothers had higher low birth weight. In contrast to our findings, studies done in Ghana, China and India have reported that iron deficiency anemia was significantly associated with low birth weight and preterm birth among pregnant adults [43, 63, 64]. Maternal low serum levels of prealbumin, ferritin, and vitamin A were found non-significantly higher among low birth weight participants than normal birth weight participants. In this study, adolescent mothers who had preterm birth were also non-significantly more likely to have anaemia, low serum levels of prealbumin, and vitamin A during pregnancy than those who had term birth. The study found that zinc protoporphyrin (ZPP) levels were associated with an infant’s birth weight (β = 0.131, p = 0.057). ZPP as a biomarker is used to indicate an adequate supply of body iron to red blood cells (RBC) in the bone marrow [20]. ZPP is usually elevated when there is iron deficiency during erythropoiesis, which can be measured and used as a screening marker in pregnant women [20]. A study by Harthoorn-Lasthuizen et al. [65] reported that pregnant women who were anaemic throughout pregnancy had an elevated ZPP, indicating iron deficiency anaemia during RBC formation. Another study Schiman et al. [66] reported that an elevated ZPP level in the first trimester can predict 56% for third-trimester anaemia. In contrast to Schiman et al. findings, a study by Tchai et al. [67] reported that using only ZPP as a marker shows lower efficiency in predicting iron deficiency anaemia in pregnancy when compared to serum ferritin and ZPP/heme ratio. The current study did not report the prevalence of elevated ZPP in the participants, however, the majority of the study participants reported low haemoglobin levels (anaemia). It is unclear whether the anaemia prevalence in the participants affected the ZPP levels and/or, can result in elevated ZPP levels, which resulted in a significant association with birth weight. Therefore, using reports from previous studies of ZPP and iron deficiency anaemia in pregnancy, the current study suggests that monitoring of ZPP throughout pregnancy in the clinical setting can a good marker in deciding which maternal women will need iron supplementation. Maternal biochemical parameters such as total antioxidant capacity, c reactive protein did not show any significant association with birth outcomes, because some of these parameters are related in advanced maternal age births [19]. For adolescents, it is less likely to observe oxidative stress and other inflammatory conditions that would influence birth outcomes.
The implication of these results for clinical practice is that pre-pregnancy and pregnancy nutritional status of high-risk teenagers may need monitoring and intervention. Additionally, early intervention to modify the weight status of pregnant adolescents by improving the quantity and quality of maternal diet may influence the infant's birth weight and consequently lead to a reduction in other adverse birth outcomes such as preterm birth, stillbirth, neonatal, and infant mortality. In developing countries like Ghana, intervention programs and policies on women's health, especially pregnancy, have largely focused on the adults, with less attention to the vulnerable teenagers. This is because the ethical conduct of the society frowns at teenage pregnancy. Let not forget that, some of these nutritional factors such as maternal poor diet and low pregnancy anthropometry can alter fetal growth and development which would consequently harm their adult life [68]. We advocate that health intervention programs and nutrition education on improving nutritional status, and early recognition of pregnancy complications should be made inclusive, to incorporate the adolescents, to prevent poor nutritional status leading to adverse pregnancy outcomes among these populations.
Although the study reports interesting results among these cohorts in Ghana, some limitations may affect the interpretation of the results. To begin with, the small sample size for the birth outcome data might not have influenced some statistical associations and analyses. Secondly, we could not follow up on participants throughout pregnancy to collect nutritional factors, therefore the trends in changes in nutritional parameters that could affect birth outcomes were not observed. Lastly, this was a cross-sectional study, hence, future longitudinal cohorts/interventional studies would properly enlighten our understanding of nutritional factors underpinning adverse birth outcomes among teenagers.