Effect of prepregnancy body mass index and gestational weight gain on obstetric and neonatal outcomes – A pilot study

Objectives: The study was undertaken to explore the effects of prepregnancy body mass index (BMI) and excess weight gain on maternal and neonatal outcomes different maternal and neonatal outcomes. Methods: Obstetrics records of 496 singleton pregnant women delivered between 2007 and 2009 in IBN SINA Medical College Hospital were reviewed. On the basis of BMI on their first visit the patients were divided into 3 groups; Mat BMI Gr 1, normal (BMI 20–24.9 Kg/m, n=366), Mat BMI Gr 2, overweight (BMI 25-29.9 Kg/m, n=102), Mat BMI Gr 3, obese (BMI >30 Kg/m, n=28). On the basis of gestational weight gain, the subject divided into 2 categories, Gets WtGain Gr A, gestational weight gain 8–15.9 Kg (n=315), Gest WtGain Gr B, gestational weight gain >16 Kg weight gain (n=181). Data were expressed as number (percentage). Proportion test was performed for comparison between two groups. P value <0.05 was taken as level of significance. Results: of the total 496 pregnant women 74.59% were between 19-34 years of age. Among all the women 64.11% had high school education of different grade. Of all the pregnancies 23.18% were nulliparous. Of the total 496 women 366 (79.79%) were normal weight, 102 (20.56%) overweight and 28 (5.64%) obese. Obese women group had significantly higher proportion of hypertensive cases compared to the normal weight (p<0.001) and overweight (p<0.01) group. Relatively higher proportion of macrosomia, birth trauma, shoulder dystocia and NICU admission among babies of obese women (p=ns). One hundred and eighty one (36.49%) of study subjects had gestational weight gain above the cut-off (>16 kg) value (p<0.001). Women with weight gain bout the cut-off level had relatively higher proportion of macrosomic babies (p=ns). Conclusions: The data reconfirmed that obesity is associated with hypertension. Significant proportion of women had weight gain more than cut-off value which needs to be addressed to ensure sound maternal and fetal wellbeing. However, a multicentre large scale study is warranted which may help the researchers to conclusively comment on the issue and thus plan future strategies for health care during pregnancy.


Introduction
Maternal nutritional status is important for health and quality of life in women and growing fetus.Maternal weight gain in pregnancy can offer a good means of assessing the wellbeing of the pregnant mother and by influence of her baby 1 .Inadequate prenatal weight gain is a significant risk factor for intrauterine growth restriction, preterm delivery and low birth weight in infants [2][3][4][5] .Obesity and excessive weight gain on the other hand can lead to adverse maternal and fetal outcomes 6,7 .Various recommendations have been made about weight gain during pregnancy.The Institute of Medicine (IOM) published recommended weight gains by prepregnancy BMI which have been the standard for subsequent research 8 .These recommendations are for BMI <19.8 Kg/m 2, total weight gain between 12.5 to 18 kg; BMI=19.8 to 26.0 Kg/m 2 , total weight gain between 11.5 to 16 Kg ; BMI >26.0 to 29.0 kg/m 2 , total weight gain between 7.0 to 11.5 Kg and for BMI >29.0 Kg/m 2 , total body weight gain of 7.0 kg.This study was done to find out the effects of pregnancy weight gain in different BMI groups on maternal and neonatal outcomes in women delivering singleton babies at term.

Subjects
Medial records of all 496 women started their antenatal care in the first trimester, attended for antenatal care at least four occasions and delivered in department of Obstetrics and Gynaecology, IBN SINA Medical College Hospital during the period of 2007 and 2009 were reviewed.Women carrying singleton pregnancies and delivered between 37 and 42 completed weeks were included in the study.
The research protocol was approved by the institutional 'Research and Ethics Committee'.

Methods
Body mass index (BMI) on the first visit was taken as prepregnancy BMI.Subjects were subgrouped on the basis of their prepregnancy BMI.Mat BMI Gr 1 (normal), maternal BMI 20-24.9Kg/m 2 , n=366); Mat BMI Gr 2 (overweight), maternal BMI 25-29.9Kg/m 2 , n=102); Mat BMI Gr 3 (Obese), maternal BMI >30 kg/m2) (n=28) 9 .Gestational weight gain was defined as the difference between the maternal weights measured within one week prior to delivery from that of the first visit in the hospital.According to gestational weight gain they wee subdivided into Gest WtGain Gr A, mater gestational weight gain 8-15.9Kg (n=315) and Gest WtGain Gr B, maternal gestational weight gain >16 Kg (n=181) 10 .

Statistical methods
Data were expressed as number (percentage).Proportion test was performed for comparison between two groups.P value <0.05 was taken as level of significance.

Results
Age (yrs, mean±SD) of all the women was 26.3±5.7.Of all the women 10.48% were below 18 years of age.Among the rest 74.59% were between 19-34 years and 14.91% over 34 years.Of all the pregnant women 76.81% were multiparous and remaining (23.18%) nuliparous.Regarding educational showed that 12.9% were illiterate, 64.11% had high school level education and 22.9% were graduate and/ or higher education (Table 1).Women with hypertension in maternal BMI group 3 was 53.5% which was significantly higher compared to the maternal BMI group 1 (p<001) and group 2 (p<0.01)(Table 2).Induction of labour mostly (61.2%) found in maternal BMI group 1.
Frequency of neonate related variables maconium stained fluid, macrosomia, birth trauma, shoulder dystocia and NICU admission did not show statistical difference in the three groups (Table 2).3).

Discussion
Obesity is increasing especially among females.Maternal obesity has been correlated with an increased risk of chronic hypertension and diabetes prior to pregnancy and adverse pregnancy outcomes including Pre-eclampsia, gestational diabetes, fetal macrosomia and caesarian deliveries 11,12 .The perinatal problems that have been identified with maternal obesity and pregnancy include an increased risk of birth asphyxia, birth trauma and neonatal hypoglycaemia 13 .
Definitions of overweight, obesity and underweight vary in different reports.But recently BMI is widely accepted as a better measure of over or underweight 14 .In our study we searched the effects of prepregnancy body mass index and gestational weight gain on perinatal outcomes.Some results were similar but few differences were observed.Birthweight was significantly affected by excessive gestational weight gain.Cedergen 15  The current guidelines provide gestational weight gain ranges based on prepregnancy BMI and were recommended by the Institute of Medicine (IOM) to limit the adverse pregnancy outcomes.However, the current IOM guidelines for obese women (Prepregnancy BMI greater than or equal to 30 Kg/m 2 ) do not provide an upper limit on gestational weight gain, only advising women to gain at least 15 Ibs (6.75kg) and don't distinguished between the different levels of obesity as defined by the National Institute of Health (NIH) 16 .
The effects of maternal underweight on obstetrics performance are less clear.Some researchers 17,18 have found increased incidences of preterm delivery, low birth weight, and increased perinatal loss in these women, others 19 have reported a protective effects of maternal underweight on certain pregnancy complications and interventions.
In our retrospective analysis, these were not sufficient number of underweight women or women low gestational weight gain.Therefore the subjects were divided into 02 groups based on gestational weight gain and 3 groups based on BMI.

Conclusions
This study has shown that high prepregnancy BMI had adverse obstetric outcomes such as increased risk of gestational diabetes, gestational hypertension, preeclampsia, macrosomia and cesarean delivery and increased frequency to admission in neonatal internsive care.It appears that higher prepregnancy BMI had more adverse effects on obstetrics outcomes in our study.We should consider both prepregnancy BMI and gestational weight gain during follow up in pregnancy and before pregnancy.Women with high BMI should be advised to lose weight and not to gain much weight during pregnancy.
Further prospective studies with large populations are needed for ideal weight gain in pregnancy due to different prepregnancy BMI classes.

Table 1 :
Age distribution, educational status of the pregnant women 2).Frequency of gestational diabetes mellitus, hypertension, preeclamsia and Caesarian delivery did not show significant difference in the three groups.

Table 2 :
Pregnancy and neonatal outcome according to body mass index

Table 3 :
Pregnancy and neonatal outcomes according to gestational weight gain