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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 16  |  Issue : 1  |  Page : 18-24

Associations between birthweight, birth order, and age at menarche of schoolgirls in Niger Republic


1 Department of Anatomy, Faculty of Basic Health Sciences, Federal University, Lafia, Nigeria
2 Department of Anatomy, Faculty of Medical Sciences, Ahmadu Bello University, Zaria, Nigeria

Date of Web Publication9-Aug-2017

Correspondence Address:
Monday Nwankwo
Department of Anatomy, Faculty of Medical Sciences, Federal University, Lafia
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jeca.jeca_27_16

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  Abstract 

Background: Few data are available on the association between birthweight, birth order (BO), and age at menarche.
Previous studies have indicated a significant association between birthweight, BO, and age at menarche.
Aim: this cross-sectional study examines the association between birthweight, BO, and age at menarche of Nigerien schoolgirls.
Materials and Methods: Sociodemographic and anthropometric data were collected with questionnaires from a total of 487 adolescent schoolgirls aged 12–27 years.
Results: Schoolgirls with low birthweight reach menarche earlier than those with normal birthweight (13.59 years vs. 13.94 years, P= 0.004). BO showed statistically significant impact on age at menarche with the first-born girls reaching menarche earlier than the later-born girls (F = 5.17,P< 0.001). Age at menarche was positively related to all the measured anthropometrics at P< 0.01. Multiple regression analyses revealed that only BO is a significant predictor of age at menarche (P < 0.000).
Conclusion: Our results suggest an association between birthweight, BO, and age at menarche.

Keywords: Age at menarche, anthropometrics, birth order, birthweight, Niger Republic


How to cite this article:
Katiella AK, Nwankwo M, Danborno B. Associations between birthweight, birth order, and age at menarche of schoolgirls in Niger Republic. J Exp Clin Anat 2017;16:18-24

How to cite this URL:
Katiella AK, Nwankwo M, Danborno B. Associations between birthweight, birth order, and age at menarche of schoolgirls in Niger Republic. J Exp Clin Anat [serial online] 2017 [cited 2017 Aug 18];16:18-24. Available from: http://www.jecajournal.org/text.asp?2017/16/1/18/212637




  Introduction Top


Menarche, the first menstrual period, is an indicator of a woman's pubertal status and a marker of reproductive viability. There is growing evidence indicating that age at menarche is associated with birthweight and birth order (BO) (Cameron and Nadgdee, 1996; Ibáňez and de Zegher, 2000; Lazar et al., 2003; Romundstad et al., 2003). Menarche is a late event in puberty and varies based on genetic make-up, environmental, and sociodemographic factors. Previous studies reported that most children born small for gestational age (SGA) show significant catch-up growth in their first 6–12 months of life while about 10%–17% do not exhibit catch-up growth (Lazar et al., 2003). Children born SGA grow below normal percentile value for their age throughout childhood with no marked improvement at pubertal stage, thereby attaining a stature below their genetic target height (Fitzhardinge and Inwood, 1989; Albertsson-Wikland and Karlberg, 1994; Karlberg and Albertsson-Wikland, 1995; Karlberg and Lou, 2000; Lazar et al., 2003). Birthweight is a reliable marker of fetal growth in utero (Wilcox, 2001). Previous studies have shown that high birthweight is related to higher age at menarche (Cooper et al., 1996; Persson et al., 1999; Adair, 2001).

The paucity in the availability of convincing studies makes it rather unclear which factor plays more role in triggering menarche. For instance, it has been widely believed for long that genetic and environmental factors modulate the onset of age at menarche (Towne et al., 2005). Body mass index (BMI) (Moisan et al., 1990; Freedman et al., 2002) and height (Moisan et al., 1990; dos Santos et al., 2002) and level of exercise (Frisch, 1987) were positively associated with menarche. Early menarche has been hypothesized to be associated with high BMI, taller girls and those who do not exercise often. The impact of body size and composition at birth and other prenatal factors is equally superimportant, yet this impact remains vague. For example, there are conflicting results on the effect of birthweight and breastfeeding on the timing of menarche (Adair, 2001; Windham et al., 2004; Blell et al., 2008). However, Opdahl et al. (2008) reported delay in the onset of menarche among girls born with higher birthweight while Ong et al. (2009) also reported delay in the onset of menarche among well-breastfed infants.

To our knowledge, no previous study in Niger Republic has investigated the association between birthweight, BO, and age at menarche.

The aims of the present study were 2 fold: to relate birthweight, BO, and age at menarche among contemporary schoolgirls in Niger Republic. We also investigated the association between body anthropometrics and age at menarche.


  Materials and Methods Top


The 487 girls who participated in the present cross-sectional study were Nigerien secondary schoolgirls. The data were gathered in 2011 from schoolgirls aged 12–27 years with the primary purpose to investigate the impact of birthweight, BO, and anthropometrics on menarcheal age (MA). The sample consists of girls predominantly Kanouri, others are Hausa, Peulh, Arabe, Touareg, Toubou, Tribu, and Zarma ethnic descents residing in Diffa region, Niger Republic. The cultural and genetic characteristics of the participants in whom the study was conducted were dissimilar. The social class of the participants could be stated as predominantly urban lower class. Our sample participants were selected randomly among postmenarcheal students who volunteered to participate in the study. Information on MA, birthweight, and family background was obtained through structured questionnaire. Where necessary, the term “menarche” was explained. Low birthweight (LBW) was defined as LBW <2500 g and normal birthweight (NBW) >2500 g according to the recommendations of the WHO (1980). Menarche was categorized as dichotomous variable: Early if it occurs before 12 years, which is approximately one unit of standard deviation (SD) below the mean MA of the overall population and ≥12 years as normal. In our study, any participant with physical or known health challenges that might affect her onset of menarche was excluded from the study. The study protocols were reviewed and approved by Health Research Ethic Committee of the Ahmadu Bello University, Zaria. Further permission was obtained from authorities of participating schools and parents/guardians. Only participants whose parents/guardians assented to the consent form participated in the study.

Anthropometrics

After filling the questionnaires, they are cross-checked for errors, after which anthropometric measurements of participants were taken. Birthweights (BWs) were abstracted from birth certificate of participants. Weight was measured to the nearest 0.1 kg using a weighing scale (Tanita BF680W, Tanita Corp., Tokyo, Japan) and height was measured to the nearest 0.1 cm with a stadiometer. Height was measured with the participant standing bare foot and head positioned in the Frankfort plane with arms straight and relaxed. Measurement of circumferences was made by inextensible tape in duplicate to the nearest 0.1 cm after which their mean values were used for the analyses. Chest circumference was measured with participants in standing position while shoulders and arms were relaxed. Waist circumference was measured at the point between the mid-point of the lowest rib, at the top of iliac crest during quiet expiration as the method proposed by Jellife et al. (1989). Hip circumference was measured with the tape wrapped round the largest part of the gluteal region. Thigh circumference (TC) was measured at the lateral region of the mid-point of the thigh, mid-way between trochanterion and the tibia. Mid-upper arm circumference (MUAC) was measured at the mid-point of the upper half of the left arm. BMI = body mass/height 2 in kg/m 2. All measurements were taken by a trained female investigator to eliminate the problems of interobserver errors following Lohman et al. (1988) methodologies. We have described these procedures succinctly in our previous work (Nwankwo et al., 2015).

Statistical analyses

The collected data were analyzed by means of STATISTICA 7 PL (StatSoft, Tulsa, OK). P < 0.05 (two sided) was deemed statistically significant. Descriptive statistics were first calculated and expressed as mean ± SDs. Independent-samples t- tests with unequal sample size were used to compare schoolgirls' MA and anthropometrics between LBW and NBW participants. Group differences were tested for statistical significance using ANOVA and Tukey's post hoc tests for multiple comparisons. The significance of Pearson's correlation coefficients was computed for continuous data while significance of Spearman's rank correlation coefficients was computed for categorical variables (BO; coded 1 = first born, 2 = second born, 3 = third born, and 4 = fourth or later born). Multiple regression analyses were computed to gauge the impact of BW, BO, and other anthropometrics on MA. MA was always set as a continuous variable. Binary logistic regression was computed to investigate the association of MA, anthropometrics, and with LBW.


  Results Top


In the first step of analysis, participants were ethnically grouped into four. MA did not differ significantly (P > 0.05) between the four groups. However, age and other anthropometric variables differed significantly between the four groups. The mean age and MA for the combined population were, respectively, 16.52 ± 2.24 and 13.84 ± 1.25 years. Schoolgirls from Peulh ethnicity have significantly lower mean birthweight, while schoolgirls from Hausa ethnic group showed significantly the highest mean birthweight. Weight and BMI were significantly higher among participants from other ethnic groups. Others are chest, hip, and MUACs. On the flip side, height and TC were significantly higher among participants from Hausa and Kanouri ethnicities [Table 1].
Table 1: Age and anthropometric characteristics of respondents according to ethnicity

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The two birthweight categories differed significantly regarding MA. MA of participants with LBW was significantly lower than that of participants with NBW (t = 2.86, P = 0.004). Participants under LBW group reached menarche 4 months earlier than those in the NBW group. Regarding other anthropometrics, participants with NBW have significantly higher values than their counterparts with LBW [Table 2].
Table 2: Description of sample according to menarcheal age and anthropometric variables stratified by birthweight

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In the next step of analysis, BO was used as categorical variable to investigate its impact on MA, birthweight, and other anthropometric variables. As shown in [Table 3], with increasing BO, MA, birthweight, weight, height, chest, waist, hip, and MUACs increased statistically significantly (P< 0.05).
Table 3: Menarcheal age and anthropometric characteristics of respondents according to birth order

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In this step of the analysis, correlations between MA, birthweight, and BO indicate that they are significantly correlated positively at P < 0.01. MA also correlated with other anthropometric variables at P < 0.01 except BMI [Table 4]. Most other variables also correlated with each other; for this reason, we used multiple regression analysis to show which variables had the strongest impact on MA. Since BMI did not indicate a significant correlation with MA, we excluded it from the multiple regression analysis. MA correlated significantly with the nine variables which were included in the regression analysis. Of these nine variables, only one was significantly correlated with MA: BO [Table 5]. The result also shows that the nine independent variables have a coefficient of multiple regression (R2) of 0.692, accounting for 69.2% of the variance in MA among the schoolgirls in Niger Republic.
Table 4: Pearson's and Spearman's rank correlation coefficients of menarcheal age, birth order, and anthropometrics of respondents

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Table 5: Multiple regression analyses

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With respect to the impact of birthweight and adolescent anthropometrics, early onset of menarche was significantly associated with birthweight and body circumferences but not significantly associated with weight, height, and BMI [Table 6].
Table 6: Binary logistic regression analyses

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  Discussion Top


Birthweight is generally an important predictor of infant's well-being and an indirect indicator of maternal nutritional status and intrauterine environment. Menarche marks are the hallmark of puberty and the highest indicator of reproductive potential in females. This study describes the relationship between birthweight, BO, and MA among contemporary schoolgirls from Niger Republic. Results from the study demonstrated that birthweight and BO significantly influence age at menarche. Age at menarche decreases with decrease in birthweight, it was also lower among early born than later born schoolgirls. Relationship between the anthropometric measurements with MA was also investigated. Exclusive information about the contribution made by birthweight, BO, and anthropometric variables was also provided. We studied only postmenarcheal public schoolgirls from urban setting, mainly from low-income families.

Results from the present study revealed that there was no significant difference in MA based on ethnicity. The results may not be generalizable to age at menarche among various girls from the various ethnic groups. We did not separately address the influence of sample size and each ethnic group (we reduced eight ethnic groups to four). Our result is not in keeping with the work of Talma et al. (2013) among girls of Dutch, Moroccan, and Turkish descents in the Netherlands. Their anthropometric variables, however, did indicate a significant difference across the various ethnic groups. The same reasoning should be considered to be able to make a more insightful conclusion about the possible confounding influence of the sample size on anthropometrics. Therefore, future studies are needed to address the impact of sample size while comparing MA and anthropometrics among schoolgirls from various ethnic groups in Niger Republic.

We found significant difference between MA of girls with LBW and participants with NBW. Differences between anthropometric characteristics were also found to be significantly different among participants based on their BW categories. Participants with LBW have significantly (P = 0.004) lower mean MA while participants with NBW have significantly higher anthropometric characteristics. Our finding is in keeping with the works of Cooper et al., 1996; Persson et al., 1999; Ibáñez et al., 2000; Adair, 2001; and dos Santos, 2002. Ghirri et al. (2001) reported that SGA girls had slightly lower age at menarche than appropriate for gestational age girls. Ibáñez et al. (2006) reported similar findings among Spanish girls. LBW girls reach menarche 8–10 months earlier than NBW group. In an earlier study by Ibáñez et al. (2000) on Catalonian girls, they reported that menarche occurred 19.2 months earlier among girls with LBW. A prospective study performed on a group of cohort of Australian girls demonstrated that early age at menarche was seen among girls with LBW (Sloboda et al., 2007). Contrary to the preceding findings, there are few other studies that have not been able to link early age at menarche to LBW (Albertsson-Wikland and Karlberg, 1994; Jaquet et al., 1999; and Veening et al., 2004). Earlier studies have proposed that infants born with LBW might have been predisposed to high level of insulin due to the occurrence of insulin resistance in utero. Elevated insulin level could stimulate early release of luteinizing hormone later in life, resulting in early puberty (Gluckman et al., 1996; Cara and Rosenfield, 1988; and Chiarelli et al., 1999). Other studies have also reported that uterine environment might play a significant role in the onset of puberty (Grumbach and Styne, 1998; Palmert and Boepple, 2001). Therefore, in our study, the fact that there exists a significant difference in MA of participants based on BW and the impacts of high level of insulin and uterine environment might explain the difference observed. However, there is a role of catch-up growth later in life due to prenatal growth restriction. However, we recommend that future studies in this area should account for the confounding impact of pregnancy factors that might affect fetal size such as gestational diabetes, preeclampsia, twinship, and preterm birth.

BO has the strongest influence on age at menarche in our study. The result showed that an earlier age at menarche was associated with early-born schoolgirls. First-born girls reached menarche (11.65 ± 0.85 years) earlier than fourth birth girls (14.65 ± 0.70 years). Our findings were in keeping with previous studies (Laska-Mierezejewska, 1995; Cameron and Nadgdee, 1996; and Apraiz, 1999). Low birth spacing has been hypothesized as the possible biological explanation (Malina et al., 1997; Apraiz, 1999).

All adolescent anthropometrics indicate strong significant positive associations with BW. Certain growth factors might help explain the associations between birthweight and adolescent anthropometrics. Insulin-like growth factor-I (IGF-I) and leptin level in the umbilical cord have been suggested to contribute to BW independently (Vatten et al., 2002). These endocrine factors (IGF-I and leptin) have been reported to play roles both in the timing of puberty and anthropometric development later in life (Smith et al., 1989).

According to the results from regression analyses, age at menarche increased significantly (P< 0.001) with increase in BO in the sibship. BO is a very important indicator of age at menarche and predictor of MA. Age at menarche also increases nonsignificantly (P = 0.546) with increase in BW.

Our findings on the influence of BW, anthropometrics, and occurrence of early or normal age at menarche revealed that BW is positively associated with menarche. Girls with LBW experience early age at menarche. We also found that in addition to weight at birth, other adolescent body anthropometrics are also significantly associated with age at menarche. The adolescent anthropometrics are indicators of body fat distributions. However, weight, stature, and BMI at adolescent are not significantly associated with the onset of menarche. Therefore, birthweight and certain body fat distribution indicators are important predictors of the onset of menarche.

These data have shown that Nigerien schoolgirls' birthweight and BO are significantly associated with age at onset of menarche. Many studies suggest that infants born with LBW might have been predisposed to high insulin level due to insulin resistance in utero. High insulin level might stimulate early release of luteinizing hormone at adolescent leading to early puberty. Low birth spacing has been proposed as the possible biological explanation for the association between BO and age at menarche.


  Conclusion Top


The results in this article revealed that birthweight and birth order are associated with age at onset of menarche. Adolescents with low birthweight reach menarche earlier, age at menarche increases with increase in birth order, and adolescents under normal birthweight category have significantly higher body dimensions than their counterparts under low birthweight category.

Acknowledgment

The authors are indebted to the participants, their parents, authorities of participating schools, and our research assistant for making this study possible.[41]

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

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