Striae distensae in pregnancy: risk factors in primiparous women

Abstracts

FUNDAMENTOS: Estrias ocorrem em mais de 70% das gestantes. Elas tendem a se desenvolver a partir da 25ª semana gestacional. Apesar de sua etiologia não ser bem compreendida, aceita-se que a combinação de fatores genéticos com alterações endócrinas e estiramento mecânico da pele tem papel significante. Em função dos diferentes resultados encontrados na literatura, os autores avaliaram os fatores de risco comumente citados com o objetivo de determinar se estão associados com a ocorrência de estrias na gestação. OBJETIVO: Avaliar em primíparas os supostos fatores de risco para o aparecimento de estrias. MÉTODOS: Estudo observacional transversal não controlado e descritivo em primíparas. O período avaliado foi de quatro meses (janeiro a maio de 2008), em uma maternidade pública. Foram incluídas 164 primíparas de feto único após 48 horas do parto. Um total de 14 variáveis foi registrado em cada paciente. RESULTADOS: Das 164 mulheres em estudo, 59,8% desenvolveram estrias durante a gestação. Foi estatisticamente significante a associação entre a faixa etária materna (p < 0,01), o peso materno adquirido durante a gestação (p < 0,01) e o peso de recém-nascido (p = 0,01) com o aparecimento de estrias na gestação. O teste de associação utilizado foi o qui-quadrado. CONCLUSÃO: As estrias foram mais frequentes em pacientes mais jovens, nas que adquiriram maior peso na gestação e/ou nas que deram à luz bebês mais pesados. Este estudo sugere que a idade materna mais avançada poderia ser um fator protetor contra a presença de estrias na gestação.

Derme; Estrias angióides; Fatores de risco; Gravidez; Primíparas

INVESTIGATION

Striae distensae in pregnancy: risk factors in primiparous women^*

Marcus Maia^I; Carolina Reato Marçon^II; Sarita Bartholomei Rodrigues^III; Tsutomu Aoki^IV

^IJoint Professor, Dermatology Clinic, Santa Casa de Misericórdia de São Paulo – São Paulo (SP), Brazil

^IIThird year resident physician, Dermatology Clinic, Santa Casa de Misericórdia de São Paulo – São Paulo (SP), Brazil

^IIIAssistant physician, Clinical Practice, Santa Casa de Misericórdia de São Paulo – São Paulo (SP), Brazil

Mailing Address

ABSTRACT

BACKGROUND: Striae occur in over 70% of pregnant women and tend to develop after 25 weeks of gestation. Despite the fact that their etiology has not yet been fully understood, it is accepted that a combination of genetic factors, endocrine alterations and mechanical stretching of skin play a significant role. Due to different results reported in the literature, the authors assessed commonly cited risk factors to determine whether they are associated with the development of striae in pregnancy.

OBJECTIVE: To assess hypothetical risk factors for the development of striae in primiparous women.

METHODS: This was a cross-sectional, observational, non-controlled, descriptive study with primiparous women. the study was conducted in a public maternity unit and Lasted for four months (from January to May 2008). 164 Primiparous women who had had a single fetus pregnancy took part in the study 48 hours after delivery. Fourteen Variables were recorded for each patient.

RESULTS: From the total sample, 59.8% developed striae during pregnancy. The association of maternal age range (p < 0,01), maternal weight gain during pregnancy (p < 0,01) and birth weight of newborn infants (p = 0,01) with the development of striae during pregnancy was statistically significant. The chisquared test of association was used.

CONCLUSIONS: Striae were more frequently observed in younger women, in those who gained more weight during pregnancy and/or those who had babies with higher birth weight. This study suggests that increased maternal age could be a protecting factor against striae during pregnancy.

Keywords: dermis; angioid streaks; risks factors; pregnancy; primiparous

INTRODUCTION

Striae distensae are linear atrophic skin lesions, well defined and secondary to connective tissue abnormalities ¹. In light of morphological observations and molecular data, striae suggest correlation between loss of fibroblast synthesis capability and abnormalities to connective tissue, in addition to significantly decreased collagen, elastin and fibrilin fibers when compared to normal skin ². They are associated with many disease states and physiological situations, including pregnancy ³. In pregnant women, striae occur in more than 70% of the patients ⁴ and they are commonly found in the abdomen, hips, buttocks and breasts ⁵. They tend to develop after week 25 of gestation ^5,6 with erythematous color, and then are reduced during puerperium and remain as silver scars. The resulting cosmetic aspect is a source of concern for most women ⁴.

Despite its not well understood etiology, it is accepted that the combination between mechanical stretching of the skin, genetic factors, endocrine abnormalities and sometimes secretion of relaxin during pregnancy ⁷, in isolation or associated, play a key role ^5,8 in pregnant women. The clinical and demographic risk variables reported in the literature such as independent or associated factors and the conclusions are frequently controversial ⁶. Maternal age, type of skin, and newborn weight are some of the variables considered to be significant. However, other factors have been implied, such as weight gain in pregnancy, family tendency, socioeconomic class, hair color, glucose impaired tolerance and nutrition ⁴.

As a result of the studies found in the literature and owing to the fact that they had included pregnant patients in general, ^5,9, the authors have assessed risk factors to determine whether they are associated with the occurrence of striae in pregnancy in primiparous women. The inclusion of primiparous women in the study enabled the analysis of a standardized situation, based on the fact that the parameters had not influenced any previous pregnancy.

MATERIAL AND METHOD

Cross-section descriptive non-controlled observational study about risk factors for the development of striae distensae in primiparous women.

The studied population comprised primiparous women, defined as women who gave birth after 28 weeks of gestational age and had no previous pregnancy for over 12 weeks (abortion). The assessed period was 4 months, between January and May 2008, in a public maternity.

Data were collected after the approval of the hospital ethics committee and it comprised interview, physical examination, completion of a protocol (attached) and free informed consent term.

One hundred sixty-four primiparous women of single fetus were interviewed and examined 48 hours after delivery. A total of 14 variables were documented for each patient: 1) maternal age at delivery; 2) maternal weight acquired during pregnancy, divided into less than 15Kg and more than 15Kg; 3) level of education, divided into illiterate, elementary school, high school education and college level education; 4) skin color, divided as white, light dark, dark and yellow; 5) previous history of striae developed before the pregnancy; 6) family history of striae developed during pregnancy in 1st grade relatives - mother and/or sisters; 7) gestational age at onset of striae; 8) history of skin disease before pregnancy; 9) smoking before and/or during pregnancy; 10) use of corticoid by topical, oral, inhalation or intravenous administration during pregnancy; 11) use of oil or lotions during pregnancy; 12) gestational age at delivery; 13) type of delivery, and 14) newborn weight.

In addition to presence of striae, they were classified according to severity, using Atwal et al., ⁴ method, which comprises a numeric system that ranges according to number and level of erythema. The examined sites included the 4 most common striae areas: abdomen, breasts, thighs and gluteus/ hip. In each site, the score can reach maximum 6 points: 0-3 for number of striae present and 0-3 for erythema level. The score for number of striae was zero = no striae; fewer than 5 striae = 1 point; between 5 and 10 striae = 2 points, and more than 10 striae = 3 points. The level of erythema was classified as follows: zero = no erythema; mild erythema (light red or pink) = 1 point; marked erythema (dark red) = 2 points, and purple erythema = 3 points. The score may total a maximum of 24 points. Based on final score, women were divided into 4 groups: scores 0-3, as not having significant striae; 4-9, as mild; 10-15 as moderate, and more than 16 points, as significant striae. White silver striae were considered to be old and were not included in the analysis. Some questions in the questionnaire depended on the patient memories and we included the option: "I cannot recall it."

Statistical Analysis

Data were compiled and analyzed using software Stata version 9.0.

Univariate analysis was performed to assess the association between the studied variables and the outcomes (onset of striae during pregnancy), using the chi-square test. To check the correlation between variables significantly associated with the risk of developing striae we used the logistic regression that controlled the factors that can potentially cause confusion when analyzing dichotomic data (yes/ no).

RESULTS

Among the 164 studied women, 59.8% (98 out of 164) developed striae during pregnancy.

In the univariate analysis (Table 1), the outcome "development of striae during pregnancy" showed statistically significant association with maternal age range (p value < 0.001), and newborn weight (p value = 0.011).

Development of striae during gestation occurred in 79.6% of the 54 women who were aged less than 19 years and in 62.5% of the 72 women aged between 20 and 25 years. This proportion decreased as the age range increased, but there was an increase in number of women aged over 35 years.

Striae also occurred in 50% of the women who acquired up to 15 kg during pregnancy and in 75% of the women who acquired 15 Kg or more during pregnancy. Among the total, 80% of the mothers who had a baby heavier than 3.5 Kg developed striae gravidarum.

There was no statistically significant association between onset of striae during pregnancy and the other studied variables.

As to classification of striae according to severity, out of 98 women who developed striae gravidarum, 23.5% had insignificant striae (0-3 points), 58.2% had mild striae (4-9 points), 15.3% had moderate striae (10-15 points), and only 3% had marked striae (16-24 points).

Striae severity was not associated with maternal age range, weight gain during pregnancy or newborn weight.

In the multivariate analysis (Table 2), with logistic regression, we used the variables that were associated with the outcome with p value below or equal to 0.25 as possible confounding factors. In the model, the outcome variable "development of striae during pregnancy" and the associated risk factors were age range, maternal weight range acquired during pregnancy, newborn weight, level of education and smoking.

Variables with statistical significance in the final model were age range (OR = 0.41; CI95%: 0.28 - 0.61), mother's weight acquired during pregnancy (OR = 3.60; CI95%: 1.58 - 8.19), and newborn weight (OR = 2.54; CI95%: 1.44 - 4.50).

DISCUSSION

The present study assessed risk factors for the occurrence of striae distensae during pregnancy in primiparous women. The studied risk factors have been frequently reported in the literature so as to associate them with the occurrence of striae in pregnancy.

At first, we should bear in mind that the selected sample comes from a public maternity, which characterizes a specific social group, not representing the whole population. As a consequence, the results and their interpretation should take that into account.

The presence of striae in pregnancy in the studied group was high (59.8%) and in agreement with the results (52%) of the only existing similar study, from the United Kingdom ⁴. Other studies ^5,9 have considered pregnant subjects in general, and the mean frequency was 77% ^10,11. The assessment restricted to primiparous women provided better analysis of the occurrence of striae during pregnancy, without the interference of previous gestations. Therefore, the comparative discussion will be made only with the study reported before ⁴.

Age distribution showed higher percentage of young patients (< 25 years), which could have been different if the study had been carried out in a private maternity. Therefore, striae gravidarum proved to be significant in young people, decreasing as a result of age range (Chart 1). The observation of higher incidence of striae in women over 35 years was not considered, because the patient sample in this age range was very small (9 patients).

Among the patients that had striae gravidarum (59. 8%), the youngest presented them in higher amount and intensity. The results found in the United Kingdom study were in agreement with our results ⁴.

The pathophysiological mechanism of striae is still uncertain, but it may be related with skin stretching caused by microfibrils' damage to fibrilins, which in younger women may be more fragile, and thus, more susceptible to rupture ⁴. However, future investigations are necessary to evidence whether younger skin has fewer fibrilins or a less resistant form with consequent predisposition to formation of striae in their stretching ⁴, suggesting that increased age range may be a protective factor.

Maternal weight acquired in pregnancy was a statistically significant variable (Chart 2), corresponding to greater skin stretching. Likewise, this would be the explanation for women who had high weight newborns (Chart 3). As the highest frequency of striae was detected in younger subjects (< 25 years old), we considered the possibility of having the patients who acquired the most weight during pregnancy and those with heavier newborn babies to belong to the younger group, which would lead to a bias in the interpretation of these significant findings. However, it did not occur and these variables could be considered as risk factors of independent significance.

Data analysis supports the statement that if there had been no maternal weight increase during pregnancy and high weight newborns, the prevalence of striae onset could be reduced by about 50%.

There was no significant association between presence of striae in gestation and skin color, smoking and/or use of oil and lotion. Concerning the use of lotions, in the literature there is only one publication that used a placebo control model, containing the components Asia centella extract, alpha tocopherol, collagen-elastin hydrolysate and menthol, which suggested the prevention of striae gravidarum in some women ¹². Previous history of striae, previous skin diseases, use of corticoid during pregnancy, type of delivery and family history had no significant association with the occurrence of striae. Family history of striae has been reported as an associated factor ^13,14, which could indicate genetic characteristic. However, it has not been confirmed in this study, similar to the variable of previous striae. It might be so that maturity of fibers obtained with increased maternal age could be more important than these variables.

Concerning level of education, even though it has not shown statistical significance, we could detect a trend to higher frequency of striae in less educated women. This situation could be explained by the fact that women in this group got pregnant at very young age when compared to those with higher level of education. Atwal et al ⁴ agreed with this interpretation, but have not found any significance association either.

The limitations of the present study are: number of women with older age which would be higher if the study had been carried out in a private maternity; difficulty to correlate literature data and ours, owing to the fact that they were studies carried out with different population groups and pregnant women in general. A broad population study would probably lead to more reliable conclusions.

CONCLUSION

Striae gravidarum were more frequent in younger patients, in those who gained more weight during pregnancy and in high-weight babies.

The present study suggests that excessive skin stretching is a risk factor and increased maternal age is a protective factor against the onset of striae gravidarum.

REFERENCES

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Publication Dates

• Publication in this collection
  25 Feb 2010
• Date of issue
  Dec 2009

History

• Accepted
  21 Sept 2009
• Received
  22 Aug 2008