Rate and risk factors of diastasis recti abdominis developed during the postpartum period: a cross-sectional study

Abstract

Background

To identify risk factors affecting the occurrence of diastasis recti abdominis.

Methods

The retrospective study included 594 women who gave birth with a diagnosis of diastasis recti abdominis between February 2023 to February 2024. Based on the maximum separation width, the diastasis recti abdominis participants were divided into three groups (mild, moderate, and severe). Additionally, 205 postpartum women without concomitant diastasis recti abdominis during the same period were selected as control group. Data included maternal demographic and pregnancy parameters were analyzed.

Results

The overall prevalence of the diastatis recti abdminis in our population was 56.6% (594/1050). Based on the results of this study, we identified that the more severe the diastasis recti abdominis, the higher incidence of the maximum separation width occurred at the umbilical level; Multivariate logistic regression analysis found that the parity and cesarean section had a positive relation with the occurrence of diastasis recti abdominis; Interaction analysis demonstrated that only cesarean section had a positive and strong correlation with the development of diastasis recti abdominis, whereas no increase in the likelihood of diastasis recti abdominis was found among women exposed to vaginal delivery.

Conclusions

Cesarean section is the independently contributing factors to develop the diastasis recti abdominis besides other socio-demographic and obstetric variables, suggesting that controlling cesarean section has a unique advantage in this regard. The widest separation distance occurs most frequently at the level of the umbilicus, and the percentage of which increases with increasing diastasis recti abdominis severity.

Introduction

The abdominal wall is an ensemble of muscles that has essential roles in supporting postural trunk, pelvic stability and stabilize the spine. During a woman’s life, many factors can affect abdominal muscles function. Pregnancy is marked by drastic anatomical and hormonal changes that enable the woman to accommodate and nourish the growing fetus. One of the most prominent changes during gestation affects the abdominal muscles, that is rectus abdominis. With the progression of pregnancy, hormonal influences and mechanical stretching of the abdominal wall result in separation of the two rectus abdominis muscles along the linea alba (LA), a condition known as diastasis recti abdominis (DRA) [1].

Historically, DRA has long been regarded as an exclusively aesthetic problem [2]. Women with DRA usually lack awareness of the medical issue [3]. For this reason, many affected women are more likely to seek help through social media [4], and frequently referred to private clinics for surgical intervention [5]. Of note is that, numerous studies have found that DRA is commonly associated with weaker abdominal muscles [6], low back pain, and severe pelvic girdle pain [7], which in turn cause distress as well as reduced activity [8], consequently has a negative impact on patients’ quality of life [9]. Additionally, several studies have also reported that DRA increases the risk of hernias [10].

Studies have found that DRA occurs most frequently during pregnancy and the postpartum period [9], with prevalence rates as high as 100% in the third trimester [11], 83% immediately after childbirth [12], and 82.6% at 12 months postpartum [1]. Moreover, it may remain separated in 35–70% of post-pregnancy women without treatment or exercise [13]. Unfortunately, even though an alarming number of women are affected, there is no international consensus on its definition, classification, symptoms, outcomes, and treatment [14]. Most importantly, existing literature focuses on the examination and management of DRA, but with low methodological quality and small sample sizes. From clinical practice, recognizing specific risk factors for DRA is the first step in preventing and predicting its development [15]. Published data on potential risk factors of DRA are sparse and conflicting. Hence, there is an imperative need to further elucidate the risk factors of DRA during pregnancy and the postpartum period. Therefore, the objective of this study is to analyze postpartum women with DRA to explore potential risk factors in greater depth.

Materials and methods

Study design

Study design: A cross-sectional study.

Study site: This study was performed at seven obstetrics departments affiliated to the Hefei Maternal and Child health care Hospital, Hefei, China.

Study timeline: between February 2023 and February 2024.

Study setting: The most commonly used measurement method to assess inter-rectus distance (IRD) was palpation before 2023. Although palpation technique is reliable tool but not valid substitutes to ultrasound imaging for the clinical measurement of DRA [16], since then, ultrasound was accepted as a more reliable and objective method. As a result, this study only collected data after 2023. Because of the retrospective design, informed consent was waived. This retrospective research was approved by the institutional ethics committee of Hefei Maternal and Child health care Hospital, and was conducted in accordance with the Declaration of Helsinki.

Study population: women who delivered at the Maternal Fetal Medical Center of our hospital received the ultrasound examination at the postpartum rehabilitation clinic six weeks postpartum.

Sample size calculation: For retrospective cross-sectional survey study: The sample size was calculated using the formula ; Confidence level 95% (two-sided), corresponding to µ = 1.96; Probability p: The general incidence rate of DRA is 28.4% [17], relative error r = 15%, d = 15% * 28.4%; Based on the above values, the minimum sample size was calculated to be 512 people. If a 10% rejection rate was considered, the final sample size was 564 people. Ultimately, we recruited 594 postpartum women, a sample size that was more representative and persuasive.

Inclusion criteria: Women without a history of abdominal surgery (except for cesarean section and open abdominal myomectomy) who visited the maternity clinic for DRA assessment 6–8 weeks postpartum.

Exclusion criteria: Women with congenital abdominal wall, neuromuscular and connective tissue dysplasia, severe spinal injury or abnormality, previous pelvic or abdominal surgery, and missing records.

Pregnancy age was determined by fetal crown–rump length measured during the first trimester ultrasound.

Study procedure: All postpartum women underwent IRD measurement trans-abdominally lying in a relaxed supine position with the abdomen exposed (Nuewa R9 using a linear array transducer 5–14;MHz). The IRD was measured at four sites, including the xiphoid, 3;cm above the umbilicus, the umbilicus, and 3;cm below the umbilicus. Three measurements were carried out for each evaluation, and the mean value of the measurements was taken as the reference value.

Operational definition: IRD was defined as the distance between the medial edges of the two rectus abdominis muscles measured by ultrasound.

Data management: Information on maternal and pregnancy characteristics was recorded, regarding maternal age; body mass index (BMI); gravidity; parity; mode of delivery (vaginal or caesarean section); weight gain during pregnancy; gestational week at delivery; pregnancy induced hypertension or diabetes (pre-pregnancy diabetes or gestational diabetes mellitus); dietary control of blood sugar or administration of insulin; presence of scarred uterus (history of cesarean section or myomectomy), twin births or macrosomia; two or three full-term deliveries; twin births or macrosomia of last delivery; neonatal weight; the maximum separation width; location of the maximum separation width (at the xiphoid, 3;cm above the umbilicus, the umbilicus, or 3;cm below the umbilicus).

All data were collected from electronic medical records.

Definition

Pregnancy-induced hypertension is defined as blood pressure ≥ 140/90 mmHg, measured twice at least four hours apart after 20 weeks of gestation, without proteinuria.

Gestational diabetes mellitus refers to glucose intolerance that first emerges or is first recognized during pregnancy. The diagnostic criteria of gestational diabetes mellitus used in China are a two hours 75;g oral glucose tolerance test (OGTT) performed during the 24th-28th gestational weeks in all pregnant women without overt diabetes. The gestational diabetes mellitus could be diagnosed if one or more of the OGTT plasma glucose values meets or exceeds the following cutoff values: 5.1mmol/L at fasting; 10.0mmol/L at 1;h; and 8.5mmol/L at 2;h.

Macrosomia is defined as newborns weighing over 4000;g.

DRA was diagnosed if the IRD exceeded 2;cm at any of the measurement sites.

DRA classification followed the recommendations of the German Hernia Society (DHG) and the International Endohernia Society (IEHS) [18]. It could be classified into three categories according to the width of IRD: mild (2–3 cm), moderate (3–5 cm), and severe (more than 5 cm).

Statistical analysis

The statistical analyses were performed by SPSS 13.0 statistical packages (SPSS Inc., Chicago, USA.). Counting variables were expressed by percentage. Continuous variables were expressed by mean and standard deviation (SD). Comparisons between two groups were analyzed using analysis of variance for continuous variables and the Chi-square test for categorical variables, as appropriate. A multivariate analysis was performed using a logistic regression model to identify the association between DRA and various parameters, and the odds ratio (OR) as well as its 95% confidence interval (CI) were utilized to quantify this association. Interaction analysis was conducted to assess the effect of parity and cesarean section on DRA, and the adjusted odds ratio (AOR) as well as its 95% CI were utilized to quantify the degree of influence. A P-value of < 0.05 was considered statistically significant.

Results

During the study period, a total of 1650 women received abdominal ultrasound examination, among which, including 1050 postpartum women and the remaining were from the general population. Within these postpartum women, 594 cases met the inclusion criteria and were diagnosed with DRA. The participants were divided into three groups according to the maximum separation width, group 1 (mild, 249 cases), group 2 (moderate, 247 cases), and group 3 (severe, 98 cases). Additionally, 205 postpartum women over the same period with an IRD of < 2cm at all four measurement sites were included as the control group. Consequently, the incidence of DRA in females 6–8 weeks postpartum was 56.6% (594/1050).

The demographic variables and pregnancy characteristics of the study population are presented in Table 1. Clinically significant differences were observed between the four groups regarding maternal age, BMI, gravidity, and parity (P < 0.05). Gestational weeks, weight gain during pregnancy, and percentage of pregnancy induced hypertension were similar between-groups (P > 0.05). The proportion of diabetes and dietary control for blood sugar were significantly different between the groups (P < 0.05), and the rate increased progressively with increasing DRA severity. No significant differences were found between the four groups in the prevalence of scarred uterus and insulin use (P > 0.05). The proportion of vaginal delivery, cesarean section, twin births, macrosomia, and two or three full-term childbirths showed significant differences in each groups (P < 0.05). As DRA severity progressed, there was a corresponding increase in the percentage of cesarean sections. Furthermore, the rate of twin births of last delivery was significantly different in the four groups (P < 0.05), whereas the frequency of macrosomia in the last delivery did not differ significantly between the four groups (P > 0.05). The distribution of birth weight was significantly different among the four groups (P < 0.05). With increasing DRA severity, the maximum separation was most likely to occur at the umbilical area (P < 0.05), while the proportion occurring 3cm above the umbilicus gradually decreased (P < 0.05). Additionally, the distribution of the maximum separation distance at the xiphoid or 3cm below the navel did not differ significantly between the four groups (P > 0.05). All the participants were Han Chinese and denied a history of tobacco and alcohol use.

Table 1.

Comparison of baseline demographics and pregnancy characteristics of the study population between four groups

Variables	Non-DRA (205 cases)	DRA			F/χ2	P value
		Mild (249 cases)	Moderate (247 cases)	Severe (98 cases)
Maternal age (years)	29.3 ± 4.1	29.4 ± 3.1	30 ± 3.8	31.5 ± 3.7	22.870	< 0.001
BMI (kg/m2)	21.2 ± 2.8	21.2 ± 2.8	21.9 ± 3.2	22.9 ± 3.6	23.300	< 0.001
Gravidity (n, %)					21.809	< 0.001
1	124(60.5)	141(56.6)	106(42.9)	27(27.6)
2	44(21.5)	58(23.3)	77(31.2)	48(49.0)
≥ 3	37(18.0)	50(20.1)	64(25.9)	23(23.5)
Parity (n, %)	46(22.4)	62(24.9)	99(40.1)	56(57.1)	43.936	< 0.001
Gestational age at delivery (weeks)	39.2 ± 1.3	39.2 ± 1.2	39.2 ± 1.1	39.0 ± 1.0	1.130	0.288
Weight gain during pregnancy (kg)	14.6 ± 4.8	15.1 ± 4.9	15.5 ± 4.8	15.0 ± 4.9	1.730	0.188
PIH (n, %)	23(11.2)	18(7.2)	25(10.1)	8(8.2)	0.251	0.616
Diabetes (n, %)	41(20.0)	53(21.3)	54(21.9)	34(34.7)	5.270	0.022
Dietary control (n, %)	40(19.5)	52(20.9)	52(21.1)	32(32.7)	4.180	0.041
Insulin use (n, %)	1(0.5)	1(0.4)	2(0.8)	3(3.1)	3.594	0.058
Vaginal delivery (n, %)	159(77.6)	174(69.9)	142(57.5)	39(39.8)	47.762	< 0.001
Caesarean section(n, %)	46(22.4)	75(30.1)	105(42.5)	59(60.2)	47.762	< 0.001
Scarred uterus (n, %)	14(6.8)	22(8.8)	43(17.4)	32(32.7)	38.795	< 0.001
Two full-term deliveries (n, %)	42(20.5)	53(21.3)	79(32.0)	50(51.0)	31.624	< 0.001
Three full-term deliveries (n, %)	2(1.0)	4(1.6)	16(6.5)	2(2.0)	5.221	< 0.001
Twin births (n, %)	2(1.0)	2(0.8)	1(0.4)	6(6.1)	5.676	< 0.001
Macrosomia (n, %)	8(3.9)	12(4.8)	21(8.5)	13(13.3)	10.765	< 0.001
Twin births of last delivery (n, %)	3(1.5)	7(2.8)	11(4.5)	9(9.2)	10.409	< 0.001
Macrosomia of last delivery (n, %)	0(0)	1(0.4)	1(0.4)	1(1.0)	1.532	0.216
Neonatal weight (kg)	3.3 ± 0.4	3.3 ± 0.4	3.4 ± 0.5	3.6 ± 0.7	33.150	< 0.001
The maximum separation width (cm)	1.6 ± 0.3	2.5 ± 0.3	3.6 ± 0.4	5.5 ± 0.6	5122.190	< 0.001
Location of the maximum separation width
The xiphoid (n, %)	0(0)	0(0)	1(0.4)	0(0)	0.510	0.475
3cm above the umbilicus (n, %)	39(19.0)	33(13.3)	27(10.9)	9(9.2)	7.569	0.006
The umbilicus (n, %)	165(80.5)	216(86.7)	218(88.3)	88(89.8)	6.361	0.012
3cm below the umbilicus (n, %)	1(0.5)	0(0)	1(0.4)	1(1.0)	0.423	0.516

Data are expressed as mean ± SD or n (%)

DRA diastasis recti abdominis, BMI body mass index, PIH pregnancy induced hypertension

P < 0.05, considered statistically significant

Table 2 presents the results of the multivariate logistic analysis of the correlation among the DRA and various parameters. After adjusting all the listed variables, we found that parity and cesarean section were positively associated with the occurrence of DRA (OR = 1.726, 95% CI 1.183–2.518, P < 0.05; OR = 2.075, 95% CI 1.428 ~ 3.015, P < 0.05; respectively).

Table 2.

Multivariate logistic regression analysis of the association between DRA and various parameters

	β	SE	Wald χ2	OR(95%CI)	P
P (Yes vs. No)	0.546	0.193	8.026	1.726(1.183 ~ 2.518)	0.005
CS (Yes vs. No)	0.730	0.191	14.666	2.075(1.428 ~ 3.015)	< 0.001

DRA; diastasis recti abdominis, P; parity, CS; caesarean section, S_E;standard error, OR; odds ratio, CI; confidence interval

P < 0.05, were considered statistically significant

;Stepwise logistic regression (sle = 0.10 sls = 0.10)

Table 3 describes the results of the interaction analysis regarding the effect of parity and cesarean section on DRA. Remarkably, compared to the women without cesarean section, the risk of DRA was approximately 2.0 times higher in those with cesarean section (AOR = 1.948, 95% CI 1.228 ~ 3.09, P < 0.05). Conversely, the incidence of DRA was not significantly affected by vaginal delivery (AOR = 1.857, 95% CI 0.589 ~ 5.859, P > 0.05). Interestingly, multiparous women who underwent cesarean section had a 10.6-fold higher risk of developing DRA than those who was primipara without cesarean section (AOR = 10.573, 95% CI 1.563 ~ 71.503, P < 0.05). These analyses suggest that cesarean section is an important determinant in the development of DRA.

Table 3.

Interaction analysis of impact of parity and caesarean section on DRA

	OR(95%CI)	P	AOR(95%CI)	P
P_cs (01 vs. 00)	2.057(1.328 ~ 3.187)	0.001	1.948(1.228 ~ 3.09)	0.005
P_cs (10 vs. 00)	1.714(1.099 ~ 2.674)	0.017	1.857(0.589 ~ 5.859)	0.291
P_cs (11 vs. 00)	4.232(2.289 ~ 7.823)	< 0.001	10.573(1.563 ~ 71.503)	0.016

DRA diastasis recti abdominis, P parity, CS caesarean section, OR odds ratio, AOR adjusted odds ratio, CI confidence interval

1 = yes, 0 = no; P_cs 01 vs. 00, P = no and CS = yes vs. P = no and CS = no; P_cs 10, P = yes and CS = no; P_cs 11, P = yes and CS = yes

P < 0.05, was considered statistically significant

Discussion

The study provided novel findings showing that the maximum separation distance was most frequently located at the umbilical area, and the greater the separation, the higher the likelihood of it occurring at that level. Another key finding was the positive association between parity, cesarean section and the development of DRA. Additionally, by interaction analysis we confirmed that for primiparous women undergoing cesarean section, the risk of DRA was approximately twice as high as for those without cesarean section, whereas women who delivered vaginally only had no clinically meaningful effect on the DRA occurrence. Furthermore, multiparous women who underwent cesarean section had a 10.6-fold higher risk of developing DRA in comparison with women who was primipara without cesarean section.

LA plays a crucial role in stabilizing the abdominal wall. Under normal conditions, the paired rectus abdominis are connected at the LA with no more than 1 to 2 cm separation [18]. In the case of increased intra-abdominal pressure, the LA is prone to stretching and laxity, which result in the enlargement of IRD, ultimately causing a DRA [2]. Indeed, the IRD exhibits a negative correlation with the elasticity of LA [19]. DRA can develop at any point along the length of the LA [12]. Based on a recently published study on 3D anatomical analysis of the LA on general population, it was noted that the maximum width was most frequently located at the umbilical level [20]. This finding was in agreement with research studies targeted at postpartum DRA women and gravidas during different gestational periods respectively, showing that the maximum separation sites were most frequently located at the umbilicus [21, 22]. The results of the present investigation support the above-mentioned findings, and extends our understanding that DRA severity is a major determinant of the location of maximum separation. Therefore, our findings provide valuable information that may inform individualized exercise interventions to reduce IRD in postpartum women with DRA.

From a prevention standpoint, recognizing women who are most susceptible to DRA allows physicians to practice targeted prevention in an attempt to avoid further damage. Our data showed that cesarean section was an independent and statistically significant risk factor for DRA. Notably, the association between the occurrence of DRA and cesarean section has been widely researched. In three recently published cohort studies, two of which proposed that caesarean delivery was an independent risk factor for postpartum DRA [23, 24], another study confirmed that women who had a history of caesarean delivery experienced a 4.5 times greater risk of DRA than those who delivered vaginally [7]. However, a direct comparison with the present results was challenging due to differences in research design. Throughout the three above-mentioned studies, comparison was made between women with and without DRA, whereas the DRA participants in our study were classified into three categories based on the largest IRD. Currently, only one study has reported cesarean section as a factor associated with persistent diastasis [12], however, the study was restricted by the small sample size (n = 253). Therefore, the present study with relatively large data of 594 DRA cases gave a more reliable and more objective view about the pronounced effect of cesarean delivery on DRA. This has important implications for clinical management, by clarifying the predisposing factors, we can recognize the high-risk population and ideally find measures to prevent the occurrence of DRA, which may be extremely beneficial for both the clinicians and patient.

Up to now, there is substantial evidence demonstrating a positive effect of parity on the occurrence of DRA [1, 23, 25]. However, published data on the magnitude of the effect of mode of delivery on DRA are limited, and results were conflicting due to confounding in data among other factors. To our knowledge, this is the first study to assess the effect of two modes of delivery on DRA based on DRA severity. The current body of research collected detailed characteristics that may be potentially associated with the development of DRA, and performed a multivariate logistic regression analysis in collaboration with interaction analysis. According to the results, we found a great impact of cesarean section on DRA, while women exposed to vagina delivery were least likely to suffer from the condition. Overall, given the evidence highlighted above, our work was sufficiently compelling to support the notion that the increased likelihood of DRA can be attributed solely to cesarean section.

The retrospective nature of the study may limit the generalizability of our findings to all women with postpartum DRA. However, this study also included a number of strengths. A main strength was the relatively large number of participants, this robust dataset was sufficiently powered to support firm conclusions; Furthermore, the study was done with a proper control group of women without DRA, which allowed us to balance confounding factors; Moreover, it was observed that most of studies have included women with mild and moderate DRA only, while severe post-pregnancy diastasis was rare [26]. Our research included a relatively large sample of severe DRA cases, which provided us with the opportunity to better explore the clinically relevant risk factors for postpartum DRA. Finally, ultrasound is widely recognized as the gold standard for IRD measurement [14], and we made use the imaging technique to diagnose as well as quantitatively assess of DRA, which is more reliable and accurate.

In conclusion, DRA poses both psychological and physiological challenges for postpartum women. Until now, there is however, sparse scientific evidence in the literature for risk factors of the condition. To fill the gap in knowledge, our study comprehensively evaluated individual risk factors for DRA. The findings support that cesarean section is the key factor leading to the development of DRA, and the widest inter-rectus distance occurs most frequently at the umbilical level, the percentage of which increases significantly along with the severity of DRA. These findings provide important insights for the identification, prevention, and management of DRA.

Abbreviations

DRA

Diastasis recti abdominis

LA

Linea

IRD

Inter-rectus distance

BMI

Body mass index

OGTT

Oral glucose tolerance test

SD

Standard deviation

OR

Odds ratio

CI

Confidence interval

AOR

Adjusted odds ratio

Authors’ contributions

J Yi produced the initial full write-up of the manuscript; J Yi, ZG Tang, LL Wang, B Zhang, XX Chen, SP Gao and ZX Chen contributed to data collection and analysis; and J Yi and ZG Tang revised the final manuscript carefully. All authors have read and approved the final manuscript.

Funding

Not applicable.

Data availability

The datasets analyzed in this study are available from the corresponding author upon request.

Declarations

Ethics approval and consent to participate

This retrospective research was approved by Hefei Maternal and Child health care Hospital. Informed consent was waived by the Institutional Review Board because of the retrospective nature of our study.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.