Journal of Postgraduate Medicine Medknow Publications and Staff Society of Seth GS Medical College and KEM Hospital, Mumbai, India ISSN: 0022-3859 EISSN: 0972-2823 Vol. 56, Num. 3, 2010, pp. 192-195

Journal of Postgraduate Medicine, Vol. 56, No. 3, July-September, 2010, pp. 192-195

Original Article

Maternal indicators and obstetric outcome in the north Indian population: A hospital-based study

Kumar A, Chaudhary K, Prasad S

Department of Obstetrics and Gynecology, Maulana Azad Medical College and Lok Nayak Hospital, New Delhi - 110 002, India

Correspondence Address: Dr. Ashok Kumar, Department of Obstetrics and Gynecology, Maulana Azad Medical College and Lok Nayak Hospital, New Delhi - 110 002, India, ash64kr@yahoo.com

Date of Submission: 27-Mar-2009
Date of Decision: 29-May-2010
Date of Acceptance: 01-Jun-2010

Code Number: jp10053

PMID: 20739764

DOI: 10.4103/0022-3859.68647

Abstract

Keywords: Body mass index, maternal indicators, obstetric outcome

Introduction

Maternal nutritional state is an important predictor of perinatal results. This concept has gained more importance in the recent years as there is now growing acceptance of the 'fetal origin of adult disease' hypothesis. A low prepregnancy body mass index (BMI) is one of the strongest predictors of adverse perinatal results. Low birth weight (LBW) (<2500 g) and preterm birth (<37 completed weeks) are associated with infant and childhood morbidity including asthma ^[1] and neuro-developmental delays ^[2],[3] and with adverse health in adulthood ^[4] including insulin resistance, ^[5] hypertension ^[6] and coronary artery disease. ^[7] The potentially serious health consequences of these birth outcomes underscore the public health importance of preventing LBW and preterm by identifying and correcting modifiable risk factors. This study aims to identify the association of maternal parameters such as prepregnancy weight, height, BMI, hemoglobin (Hb) and parity with the outcome of pregnancy.

Materials and Methods

This was a prospective hospital-based study conducted from July 2005 to July 2006. During this period, a total of 2027 pregnant women were registered in the antenatal clinic of the principal investigator before eight weeks gestation and delivered in the hospital. All pregnant women were sure of their dates. The body weight (in kilograms) of all women was measured at the first visit by a calibrated scale accurate to 0.5 kg. Height was measured in meters. Height and weight measurements were used to calculate the body mass index [BMI = weight / (height) ² ]. The age, parity and hemoglobin of all subjects were also recorded.

All subjects were followed up in the antenatal clinic till their deliveries. The following pregnancy outcome variables were studied: birth weight, period of gestation at the time of delivery and the mode of delivery. The birth weight of the newborn was recorded in the first two hours of life in grams by a calibrated scale having minimal calibration of 1 g.

All women with multiple pregnancies, any cardiovascular, renal, respiratory, autoimmune or metabolic disorder, or any complication that developed during their pregnancies such as preeclampsia, gestational diabetes, ante partum hemorrhage were excluded from the study.

The women were divided according to

• Weight ^[8] as underweight: less than 40 kg, average weight: 40-60 kg and overweight: more than 60 kg.
• BMI ^[8] as very low BMI: less than 18.5 kg/m ² , low BMI:18.5-19.8 kg/m ² , average BMI: 19.8-26 kg/m ² and high BMI: more than 26 kg/m ² .
• Height as short stature: less than 140 cm and of average height: 140-165 cm.
• Hemoglobin ^[9] as severe anemia: less than 7 g%, mild to moderate anemia: 7-10 g% and normal: more than 10 g%.

The birth weight of the newborn was divided as very low birth weight (VLBW): less than 2000 g, low birth weight (LBW): 2000 to 2500 g and normal weight: 2500 to 4000 g. The period of gestation at delivery was classified as preterm (< 37 weeks) and term (37 weeks to 41 weeks).

Statistical analysis

Most of the variables used were continuous in nature and normally distributed except for the mode of delivery, which was expressed as a categorical variable. To measure the relationship between different maternal variables and obstetric outcome in the entire study group, the Pearson's correlation coefficient along with significance was used. Further, variables were logically categorized and the distribution of subjects in various categories was studied. The significant correlation between these groups was then determined by the Chi-square test or the Fisher's exact test. The correlation between mode of delivery and maternal parameters was studied using student t-test or mann whitney non-parametric test. The association of LBW with maternal indicators was performed using univariate and multivariate logistic regression model. P values < 0.05 were considered to be significant.

Results

The mean age, parity and hemoglobin of the study group was 24.6 ± 3.82 years (range 23 years; 17-40 years), 1.00 ± 0.94 (range 5; 0-5) and 10.41 ± 1.14 g% (range 8.5 g%; 6-14.0 g%) respectively. The mean height, weight and BMI were found to be 151.8 ± 4.18 cm (range 35 cm; 125-160cm), 54.31 ± 10.03 kg (range 50 kg; 30-80kg) and 23.76 ± 4.34 kg/m ² (range 30.27 kg/m ² ; 12.98-43.25 kg/m ² ) respectively. Approximately 2.6% (n=53/2027) of women were underweight, 74.7% (n=1514/2027) were of average weight and 22.7% (n=460/2027) were overweight; 7.2% (n=147/2027), 9.7% (n=196/2027), 57.3% (n=1161/2027) and 25.8% (n=523/2027) of subjects had very low, low, average and high BMI respectively; 3.5% (n=70/2027) of women had short stature and 96.5% (n=1957/2027) were of average height; 0.7% (n=14/2027) and 41.8% (n=848/2027) had severe anemia and mild to moderate anemia respectively and 57.5% (n=1165/2027) of the women had normal hemoglobin levels.

The mean gestational age at delivery was 38.13 ± 1.89 weeks (range 13 weeks; 29-40 weeks) and the mean birth weight of the infants was 2725.40 ± 424.64 g (range 3100g; 900-4000 g). Approximately 5% (n=106/2027), 19.8% (n=400/2027) and 75% (n=1521/2027; 75%) of the babies were VLBW, LBW and of normal weight respectively. Similarly, 76.8% (n=1557/2027) of the babies were of term gestation and the rest were preterm (< 34 weeks; n=111/2027; 5.5%); (34-37 weeks; n=359/2027; 17.7%). The sex ratio was found to be 804 female infants per 1000 male infants. The cesarean rate was 15.3% (n=311/2027).

The correlation between different maternal variables and obstetric outcome has been described in [Table - 1]. The correlation among various maternal variables has been shown in [Table - 2]. Maternal height, prepregnancy weight, BMI and parity were found to be significantly correlated to the birth weight of the babies. Incidentally it was also found that taller women had a significantly high number of preterm deliveries (r = -0.056, P=0.012).

Women with low BMI were found to have a higher probability of delivering a LBW baby. It was found that 35.4% (n=52/147) of very low BMI and 33.7% (n=66/196) of low BMI group delivered LBW babies as compared to 24% (n=280/1161) women in normal BMI group (r=28.1, P= 0.001). The risk of having LBW babies in the low BMI group was found to be 1.9 times that of normal BMI (OR 1.950, 95% CI 1.108 - 3.431). It was found that 37.7% (n=20/53) of the underweight females delivered LBW babies as compared to 26.5% (n=402/1514) of normal weight females (r=25.4, P<0.05).

It was found that the rate of preterm delivery was significantly higher in two groups i.e. women with Hb <7 g% and women with parity >3. Approximately 43% (n=6/14) of severely anemic women had preterm deliveries as compared to 23% (n=464/2013) in the group with higher Hb (r =14.5, P<0.001). It was also found that women with a parity of >3 had a preterm delivery rate of 36.9% (n=41/111) as compared 22.4% (n=429/1916) in the group with lower parity. The likelihood of vaginal delivery was found to be almost double in women with a higher order parity (>3), (OR 1.8, 95% CI 0.96-3.45). The chances of caesarian delivery increased as the height, weight and BMI increased (P value <0.05).

The association of the maternal indicators with birth weight was performed by univariate and multivariate logistic regression [Table - 3] and [Table - 4].

Discussion

In this prospective cohort of young pregnant women, infant birth weight increased with increasing maternal BMI, maternal prepregnancy weight and maternal height. Infants born to more than one-third of women who were in the lowest end of the BMI distribution before pregnancy (BMI ≤ 18.5 kg/m ² ) were at increased risk for fetal growth deficits. Maternal BMI has been used as an epidemiological factor predictive of fetal growth since a long time. ^{[10],[11],[12]} A low BMI status, indicative of chronic energy depletion, is a particularly important aspect of the nutritional risk of women in a community during the reproductive years. The nutritional status of a woman before conception is related to the birth weight of her child. Energy, fatty acids, and micronutrient deficiencies in women either before conception or very early in pregnancy have all been implicated in causing low birth weight in infants. Infant birth weight is not only associated with measures of infant health and neonatal morbidity, but it has also been linked to increased risk of numerous adult disorders. If LBW babies survive, they have greater rates of morbidity and poorer neurological development (poor vision, decreased educational attainment, and more cerebral palsy, deafness and autism).

It was found that 37.7% of the underweight females delivered LBW babies, which was significantly higher than that of normal weight women (26.5%). The height, weight and period of gestation were found to be significant maternal indicators for low birth weight on multivariate logistic regression. Tripathi et al.,^[13] have found that using a prepregnancy weight of less than 40 kg is a useful cutoff to predict women who will deliver LBW babies. A positive correlation of birth weight with prepregnancy weight (r=0.42), height (r=0.23) and BMI (r=0.43) was found in an Indian study conducted at Ludhiana and surrounding villages. ^[14]

Premature delivery is another leading cause of perinatal morbidity and mortality. The rate of preterm delivery was much higher in anemic and multiparous women (parity >3). Anemia has been found as an independent marker of fetal low birth weight and preterm deliveries. ^[15] The risk of operative delivery increases as the BMI of women increases, the possible reason being increase in the fetal weight. ^[16],[17] The strength of the associations, the steady increase in the risk of adverse fetal growth outcomes with the increasing degree of underweight, the demonstration of a temporal sequence (with low BMI preceding conception) and the consistency of the results for multiple measures of fetal growth suggest a possible causal relation between severe low prepregnancy, BMI and fetal growth deficits.

Thus the objective of any intervention should be to ensure that women have a prepregnancy weight of more than 40 kg, a BMI of more than 19.8 and hemoglobin of at least 7 g% or more.

An important limitation of the current study is the lack of data on maternal weight gain during pregnancy, which could modify the relation between prepregnancy BMI and pregnancy outcomes. It is possible, for instance, that some of the women who were very thin before conception, gained adequate weight during pregnancy to produce a normal-weight or near-normal-weight infant. The greater weight gain during pregnancy compensates for the adverse effects on fetal growth associated with low maternal BMI during early gestation. However, it has been observed that women with low prepregnancy BMI are still more likely to have smaller infants than heavier women, even when their gestational weight gain is the same. ^[8]

The present study is probably the largest hospital-based study conducted in the northern region of the Indian subcontinent to provide a scientific basis for the reduction of a large amount of perinatal morbidity by taking simple and timely measures to improve maternal nutrition.

Understanding the effect of maternal adiposity on obstetric outcome has public health importance. The maternal nutritional parameters are associated not only with infant health and survival but also may influence development and health in later life. Moreover, these are modifiable risk factors implicating that a large amount of morbidity (fetal and maternal) can be reduced by taking timely measures.

References

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