Ginekologia i Poloznictwo
ISSN 1896-3315 e-ISSN 1898-0759

Effect of body mass index (BMI) on mode of delivery and maternal and neonatal complications in nulliparous women

Mohamed Mahmoud Salman^*, Reda Mokhtar Kamal Ghanem, Arsany Nabil Foad Wasef and Mohamed Mahmoud Abd El Aleem ^*Correspondence: Mohamed Mahmoud Salman, Departments of obstetrics and Gynecology, Faculty of Medicine, Ain Shams University, Egypt, Email:

Received: 04-Sep-2022, Manuscript No. gpmp-22-73673; Editor assigned: 05-Sep-2022, Pre QC No. P-73673; Reviewed: 09-Sep-2022, QC No. Q-73673; Revised: 15-Sep-2022, Manuscript No. R-73673; Published: 29-Sep-2022

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Introduction

The BMI is a simple index of the weight-for-height and it is calculated by dividing a person’s weight in kilograms by the square of their height in meters (kg/m²) [1-3].

Underweight (a BMI of < 19.9 kg/m²) has been shown to be associated with an increased risk of preterm deliveries, low birth weight and anemia, and a decreased risk of pre-eclampsia, gestational diabetes, obstetric intervention and post-partum hemorrhage [4].

In a study from 2006, Barau et al. [5] found a linear association between maternal pre-pregnancy body mass index (BMI) and risk of cesarean section in term deliveries [5].

In addition to an increasing rate of cesarean sections in obese women, some studies have revealed a decrease in use of forceps and vacuum extraction, with increasing BMI [6].

However, a slightly increased risk for instrumental vaginal delivery was reported in a Norwegian study [7] and no significant difference in prevalence of vaginal instrumental delivery is reported in some studies [2]. The aim of the study is to assess the effect of BMI on mode of delivery and maternal and neonatal complications in nulliparous women.

Patients and Methods

After ethical committee approval and written consents from the patients, this comparative cross sectional observational study was conducted at tertiary care hospital at Ain Shams University hospitals and performed on total of 330 nulliparous pregnant women who attended the pre-labor unit starting from June 2021 till January 2022.

Study population: Nulliparous pregnant women that categorized into six different BMI (kg/m²) groups (55 in each group) with the following inclusion criteria:

Inclusion criteria: Age (18-35 years old), Know pre-pregnancy BMI, Nullipara, A living singleton pregnancy, Gestational age (37-40 weeks), Cephalic presentation and No fetal or umbilical cord anomaly.

Exclusion criteria: Deliveries where maternal height or pregestational weight were not recorded, Presence of congenital fetal malformation, Antepartum hemorrhage (placenta previa or accidental hemorrhage) and Any factors that can independently cause adverse perinatal and neonatal outcome and can act as confounding factors like smoking or drugs).

Study Procedures:

• After explaining the procedures of the study, written informed consent was obtained from patients and their basic demographic information such as age, height, weight, gestational age, and cervical dilation were recorded at Ain Shams University Maternity Hospital prelabour ward using ultrasound machine (Sono ACER 5).

• Maternal BMI was calculated from the pre-pregnancy weight recorded in the woman’s personal pregnancy health card and at time of delivery.

• A total of 330 term pregnant women were categorized into six different BMI (kg/m2) classes, determined by their pre-pregnancy and at time of delivery BMI:

1. Underweight: (BMI <18.50)

2. Normal weight: (BMI 18.50 – 24.99; reference group) Controlled one

3. Overweight: (BMI 25.00–29.99)

4. Obese: (BMI 30.00 – 35.00)

5. Severe obesity: (BMI 35.00 – 40.00)

6. Morbid obesity: (BMI > 40.00)

• Data of the study participants was collected through a full history taking (medical, obstetrical and gynecological), clinical and ultra-sonographic findings by using a pre-constructed case record sheet.

• The participants were investigated for routine laboratory tests including: (complete blood count, urine analysis and random blood sugar) & (full liver, kidney profile, PT and PTT in medical disorder).

• Abdominal examination (Leopold maneuver’s) to detect both uterine contractions (frequency, intensity and duration) and fetus (lie, presentation, position, engagement of presenting part and fetal heart sound).

• Vaginal examination: for detecting capacity of the pelvis confirming fetal presenting part, position, station, degree of flexion and cervical scoring using (Bishop score) to detect cervical dilatation, effacement, station, consistency and position.

• Routine obstetric ultrasound to detect fetal status, liquor, umbilical cord and placental condition.

• Fetal distress was regarded when fetal bradycardia, variable deceleration or late deceleration is found using partogram and cardiotocography during labor.

• 1^st stage of labor (time from the onset of labor until complete cervical dilatation) and prolonged 1st stage < 1.2 cm/hour for nulliparous patients.

• 2^nd stage labor (time from complete cervical dilatation to expulsion of the fetus) and prolonged 2nd stage > 2 hours in nulliparous patients.

• Arrest disorder of first stage: no cervical change for ≥ 4 hours despite adequate contractions or ≥ 6 hours with inadequate contractions.

• Arrest disorder of second stage: in nulliparous women no progress after ≥ 4 hours with epidural anesthesia or ≥ 3 hours without epidural anesthesia [8]

• The fetal outcome was assessed by pediatrician regarding the Apgar score and need for NICU admission.

The delivery methods were done by supervisors and expert who categorized into spontaneous vaginal delivery, instrumental vaginal delivery (including vacuum extraction and forceps), planned cesarean section and emergency cesarean section.

Sample Size: Using STATA program, assuming a prevalence rate of maternofetal complication of 90% ranging between 10 and 30%, a sample size of 55 pregnant females in each of the study groups (330 totals) will be enough at 0.05 alpha errors and 0.80 power of the test [3].

Outcome measures

Primary outcome: The mode of the delivery (vaginal and C.S).

Secondary outcome:

• Duration of labour (1^st stage & 2^nd stage).

Maternal complication:

• Post-partum hemorrhage (traumatic and atonic)

Neonatal complication:

• Birth weight.

• The Apgar score at one and five minutes.

• Perinatal death.

• Admission to the neonatal intensive care unit.

• Neonatal birth injures.

Ethical Considerations: The patient data were anonymous. Data presentation was not being by the patient’s name but by diagnosis and patient confidentiality was protected. An informed consent was taken from all participants, it was in Arabic language and confirmed by date and time. Confidentiality was preserved by assigning a number to patient’s initials and only the investigator knew it

Conflict of interest: the candidate declared that there is no conflict of interest and the cost of the study was paid by the candidate.

Statistical analysis: Analysis is to be performed using SPSS for windows v20.0, Data to be presented in terms of range, mean and standard deviation (for numeric parametric variables); range, median and inter-quartile range (for numeric non-parametric variables); or number and percentage (for categorical variables). Difference between two independent groups is to be analyzed using independent student’s t-test as well as the mean difference and its 95% CI (for numeric parametric variables); or chi-squared test as well as the risk ratio and its 95% CI (for categorical variables). Binary logistic regression analysis is to be performed for estimating the association between good/poor response and the measured variables ROC curves are to be constructed for estimating the validity of measured variables as predictors of good or poor response validity is to be presented in terms of sensitivity, specificity, positive and negative predictive values and their corresponding 95% CIs significance level is set at 0.05.

Results

During this study, 370 patients were assessed for eligibility and 330 nulliparous pregnant women were included in the study and categorized into six different BMI (kg/m²) groups (55 in each group). Of all eligible patients, 22 patients were excluded from the study based on the inclusion criteria and 18 patients refused to participate in the study.

Ultimately, the analysis was based on the data of 330 nulliparous pregnant women that categorized into six different BMI (kg/m²) groups (55 in each group). Table (1) shows that no statistically significant differences between the studied groups regarding maternal age. Table (2) shows that Maternal BMI among the studied groups. Table (3) shows that no statistically significant differences between the studied groups regarding neonatal gestational age.

Tab. 1. Maternal age (years) among the studied groups.

Tab. 2. Maternal BMI (kg/m2) among the studied groups.

Tab. 3. Neonatal gestational age (weeks) among the studied groups.

Table (4) shows that Cesarean delivery frequency was least frequent in underweight group then increases progressively to be most frequent in morbid obese group, the difference statistically was significant. Table (5) shows that Duration of 1^st stage of labor was shortest in underweight group then increases progressively to be longest in morbid obese group, the difference statistically was significant. Table (6) shows that Duration of 2^nd stage of labor was shortest in underweight group then increases progressively to be longest in morbid obese group, the difference statistically was significant.

Tab. 4. Mode of delivery among the studied groups.

Tab. 5. Duration of 1st stage of labour (hours) among the studied groups.

Tab. 6. Duration of 2nd stage of labor (hours) among the studied groups.

Table (7) shows that Neonatal weight was lowest in underweight group then increases gradually to be highest in morbid obese group, the difference statistically was significant. Table (8) shows that APGAR-1 score was highest in underweight group then increases gradually to be lowest in morbid obese group, the difference statistically was not significant. Table (9) shows that APGAR-5 score was highest in underweight group then increases gradually to be lowest in morbid obese group, the difference statistically were not significant. Table (10) shows that NICU admission frequency was least frequent in underweight group then increases gradually to be most frequent in morbid obese group, the difference statistically was not significant. Table (11) shows that Neonatal birth injuries not recorded in the studied groups.

Tab. 7. Neonatal weight (kg) among the studied groups.

Tab. 8. APGAR-1 score among the studied groups.

Tab. 9.APGAR-5 score among the studied groups.

Tab. 10. NICU admission among the studied groups.

Tab. 11. Neonatal birth injuries among the studied groups.

Discussion

Since high maternal body mass index (BMI) during pregnancy represents major conflict and often associated with short- and long-term unfavorable health outcomes both for child and mother during pregnancy and delivery, evaluating the effect of maternal body mass index on fetal and maternal outcome during pregnancy was highlighted as a main point of interest [9-11].

In this study, we aimed to assess the effect of BMI on mode of delivery and maternal and neonatal complications in nulliparous women.

This comparative cross sectional observational study was conducted at tertiary care hospital at Ain Shams University hospitals from June 2021 till January 2022 and performed on total of 330 nulliparous pregnant women who attended the pre-labor unit.

During this study, 370 patients were assessed for eligibility and 330 nulliparous pregnant women were included in the study and categorized into six different BMI (kg/m2) groups (55 in each group). Of all eligible patients, 22 patients were excluded from the study based on the inclusion criteria and 18 patients refused to participate in the study.

Ultimately, the analysis was based on the data of 330 nulliparous pregnant women that categorized into six different BMI (kg/m2) groups (55 in each group).

• Underweight: (BMI <18.50)

• Normal weight: (BMI 18.50–24.99) which is a reference group (controlled one)

• Overweight: (BMI 25.00–29.99)

• Obese: (BMI 30.00 – 35.00)

• Severe obesity: (BMI 35.00 – 40.00)

• Morbid obesity: (BMI > 40.00)

Different studies were done evaluating the association between pre-pregnancy BMI and obstetric and neonatal outcomes in obese women, some of them agree and others differ from our results.

The current study revealed that there were no statistically significant differences between the studied groups regarding maternal age (18-35 years) and neonatal gestational age (37-40 weeks).

Regarding mode of delivery, our study results revealed that Cesarean delivery frequency was least frequent in underweight group then increases progressively to be most frequent in morbid obese group, the differences statistically were significant (p<0.001).

Regarding progression of normal labor, our results revealed that Duration of 1st stage and 2nd stage of labor were shortest in underweight group then increases progressively to be longest in morbid obese group, the differences statistically were significant (p value=0.004, 0.009) respectively.

Pettersen-Dahl et al., [3] conducted a retrospective register study that enrolled 4605 were primiparous singleton deliveries to assess the association between maternal BMI and delivery method in non-breech, singleton deliveries, after 36 weeks of gestation.

In concordance with our results, Pettersen-Dahl et al., [3] revealed that the risk of emergency cesarean delivery increased significantly by 77% with increasing maternal BMI, and increased by more than a twofold in the obese group (BMI ≥30) compared with women with underweight or normal weight (p<0.001).

Also, in line with our study, Pettersen-Dahl et al., [3] revealed that Prolonged first stage of labor (34%) and fetal asphyxia (33%) were significantly found in obese women (BMI ≥30) and were the most frequent reasons for emergency cesarean deliveries. Prolonged second stage was the indication in 9.4% of the emergency cesareans.

Our findings are in line with the reported data ofMelchor et al., [9]in whicha retrospective cohort study was conducted and performed on 16,609 women to examine the association between pre-pregnancy BMI and obstetric and neonatal outcomes and revealed that a higher BMI was associated with a greater risk of induction of labor (delayed spontaneous onset of labor) and increasing BMI correlates linearly with cesarean delivery rates as cesarean sections are almost 3 times more common among obese pregnant women(p<0.001).

Also,Verma et al., [12] conducted a prospective study that enrolled 784 women with singleton pregnancies to evaluate the impact of the maternal body mass index on the pregnancy outcome and revealed that the caesarean section rate was found to be increased with a higher maternal BMI with higher rate of spontaneous normal delivery in the underweight group (BMI > 19 .9kg\m²) (p<0.001).

Our results are in agreement with results of previous studies done by Kalk et al., [13], Yang et al., [10]who reported that women with body mass index >30 kg/m² were at increased risk for cesarean section.

The reasons why an increase in BMI is associated with decrease in spontaneous deliveries and increased risk of cesarean sections have been assumed that fetal hyperglycemia and hyperinsulinemia causes increased fetal growth and higher risk of macrosomia [14,15]. Macrosomia may lead to an obstructed labor and more frequent need for cesarean delivery. Increased amounts of soft tissue deposits in women with increased BMI may also cause a relative narrowing of the pelvis and genital tract. Increased amounts of soft tissue may also lead to weaker contractions due to the dilution effect, and can lead to labor arrest [3].

Regarding fetal outcomes, our results revealed that Neonatal weight was significantly lowest in underweight group then increases gradually to be significantly highest in morbid obese group (p<0.001) with no statistically significant differences as regard APGAR score at 1-min and 5-min between the studied groups with no recorded fetal injuries or fetal mortalities.

Consequently, there were no statistically significant differences as regard NICU admission frequency between the studied groups (p value=0.803).

In agreement with our results,Melchor et al., [9]revealed that a higher BMI was associated with a greater rate of macrosomia ≥4000g. In contrast to our results, the infants of obese women were more likely to be admitted to the NICU which may explained by presence of associated gestational diabetes in the obese women in the study.

In agreement with our results,Verma et al., [12] revealed that growth retardation (17.2%) was more in the underweight group (BMI > 19 .9kg\m) as compared to those in the normal and the higher BMI groups with a strong association between IUGR and the underweight group (17.2%, as compared to 6-7.5% in the other groups, p<0.001).

These results are in agreement with results of previous studies done by Heude et al., [15], Yang et al., [10] who reported that small for gestational age (SGA) was significantly highest in underweight women and large for gestational age (LGA) was significantly highest in obese women which is associated with direct effect of gestational weight gain.

Regarding postpartum hemorrhage, postpartum hemorrhage frequency was least frequent in underweight group then increases gradually to be most frequent in morbid obese group; the difference statistically was not significant.

In agreement with our results, D'Souza et al., [16] conducted a systematic review including 10,258 studies that reported on pregnancy outcomes in women with body mass index ≥30 kg/m² and revealed that women with body mass index >30 kg/m² were at increased risk for cesarean section and there was no increase in the incidence of postpartum hemorrhage with increasing BMI category.

The strength points of this study

The strength points of this study are that it is comparative cross sectional observational study design and having no patients lost to follow-up during the study. It is the first study in Ain shams university maternity hospital to assess the strength of the association between the independent risk factor of obesity and the outcome of mode of delivery in absence of other overlapping risk factors e.g DM and Hypertensive disorders.

The limitations of the study

The limitations of the study are worthy of mention including relatively smaller sample size relative to the previous studies, not being a multicentric study and this represents a significant risk of publication bias. Another limitation is the presence of Covid-19 pandemic which limited the available participants.

Conclusion

As evident from the current study, an increased maternal pre-pregnancy BMI is an important and independent risk factor for delivery by cesarean section. A significant difference was observed in risk of cesarean between women with BMI ≥30 and women with normal weight in all subgroups of women with significant prolongation in 1^st stage and 2^nd stage of labor.

Neonatal weight was significantly lowest in underweight group then increases gradually to be significantly highest in morbid obese group.

Maternal overweight and obesity in pregnancy are important contributors to obstetric complications and adverse outcomes, with an associated significant impact on healthcare burden.

Effective interventions to reduce the prevalence of overweight and obesity in pregnant women could have significant beneficial effects on pregnancy outcomes. Public health efforts are urgently required to promote weight management among women of reproductive age before conception and during pregnancy.

Authors Contribution

(A) Study Design · (B) Data Collection . (C) Statistical Analysis · (D) Data Interpretation · (E) Manuscript Preparation · (F) Literature Search · (G) No Fund Collection

References

1. WHO (2013): Nutrition, physical activity and obesity Norway.
2. Usha Kiran TS, Hemmadi S, Bethel J, et al. Outcome of pregnancy in a woman with an increased body mass index. BJOG. 2005;112(6):768-772.

Google Scholar, Crossref, Indexed at

3. Pettersen‐Dahl A, Murzakanova G, Sandvik L, et al. Maternal body mass index as a predictor for delivery method. Acta Obstet Gynecol Scand. 2018;97(2):212-218.

Google Scholar, Crossref, Indexed at

4. Ehrenberg HM, Dierker L, Milluzzi C, et al. Low maternal weight, failure to thrive in pregnancy, and adverse pregnancy outcomes. Am J Obstet Gynecol. 2003;189(6):1726-1730.

Google Scholar, Crossref, Indexed at

5. Barau G, Robillard PY, Hulsey TC, et al. Linear association between maternal pre‐pregnancy body mass index and risk of caesarean section in term deliveries. BJOG. 2006;113(10):1173-1177.

Google Scholar, Crossref, Indexed at

6. Scott‐Pillai RA, Spence D, Cardwell CR, et al. The impact of body mass index on maternal and neonatal outcomes: a retrospective study in a UK obstetric population, 2004–2011. BJOG. 2013;120(8):932-939.

Google Scholar, Crossref, Indexed at

7. Morken NH, Klungsøyr K, Magnus P, et al. Pre‐pregnant body mass index, gestational weight gain and the risk of operative delivery. Acta Obstet Gynecol Scand. 2013;92(7):809-15.

Google Scholar, Crossref, Indexed at

8. Abalos E, Oladapo OT, Chamillard M, et al. Duration of spontaneous labour in ‘low-risk’women with ‘normal’perinatal outcomes: A systematic review. Eur J Obstet Gynecol Reprod Biol. 2018;223:123-132.

Google Scholar, Crossref, Indexed at

9. Melchor I, Burgos J, Del Campo A, et al. Effect of maternal obesity on pregnancy outcomes in women delivering singleton babies: a historical cohort study. J Perinat Med. 2019;47(6):625-630.

Google Scholar, Crossref, Indexed at

10. Yang Z, Phung H, Freebairn L, et al. Contribution of maternal overweight and obesity to the occurrence of adverse pregnancy outcomes. Aust N Z J Obstet Gynaecol. 2019;59(3):367-374.

Google Scholar, Crossref, Indexed at

11. Lima RJ, Batista RF, Ribeiro MR, et al. Prepregnancy body mass index, gestational weight gain, and birth weight in the BRISA cohort. Revista de saude publica. 2018;52.

Google Scholar, Crossref, Indexed at

12. Verma A, Shrimali L. Maternal body mass index and pregnancy outcome. J Clin Diagn Res: JCDR. 2012;6(9):1531.

Google Scholar, Crossref, Indexed at

13. Kalk P, Guthmann F, Krause K, et al. Impact of maternal body mass index on neonatal outcome. Eur J Med Res. 2009;14(5):216-222.

Google Scholar, Crossref, Indexed at

14. Dempsey JC, Ashiny Z, Qiu CF, et al. Maternal pre-pregnancy overweight status and obesity as risk factors for cesarean delivery. J Matern Fetal Neonatal Med. 2005;17(3):179-185.

Google Scholar, Crossref, Indexed at

15. Heude B, Thiébaugeorges O, Goua V, et al. Pre-pregnancy body mass index and weight gain during pregnancy: relations with gestational diabetes and hypertension, and birth outcomes. Matern Child Health J. 2012;16(2):355-363.

Google Scholar, Crossref, Indexed at

16. D'Souza R, Horyn I, Pavalagantharajah S, et al. Maternal body mass index and pregnancy outcomes: a systematic review and metaanalysis. Am J Obstet Gynecol MFM. 2019;1(4):100041.

Google Scholar, Crossref, Indexed at