The aim of our study was to evaluate the GWG and compare it according to the IOM recommendation . In addition, the results on maternal and neonatal outcomes were evaluated by classifying GWG as insufficient, appropriate and excess according to IOM.
GWG after BS can vary widely in studies [16, 19, 20]. The average GWG was 12.59 kg in our study, with 3 patients losing weight during pregnancy.
Our findings are line with those of Hammeken et al.  showed that GWG in the RYGB group was 11.5 ± 9.9 kg and Ceulemans et al.  showed that the average GWG in the malabsorptive and restrictive group was 12.5 kg. Whereas Chagas et al.  found a mean GWG of 7.68 kg in pregnant patients who had undergone gastric bypass.
In our study GWG was insufficient for 22%, appropriate for 23% and excessive for 55% of the pregnancies. Our insufficient GWG rate was similar the general population’s. The IOM  described a 25.5% rate of insufficient GWG in obese and normal BMI populations and 14% rate of insufficient GWG in overweight patients. Lindberg et al.  showed that insufficient GWG was between 12.2%-25.5% in overweight and grade II obesity.
Obese patients tend to gain excessive weight gain during pregnancy. However, a higher percentage of patients in the studies presented with obesity, the pregnant women lost weight during gestation despite being overweight and obese.
This can be explained by the fact that a relatively larger proportion of the pregnant women having a surgery-to-conception interval of less than 18 months and there are in the catabolic phase and therefore cannot gain sufficient weight. As the greatest weight loss occurs during the first 6–18 months post-surgery, this period may be physiologically catabolic because of lower food intake or less absorption of nutrients. During the second year after surgery, the rate of weight loss decreases and weight stabilizes .
In our study, average prepregnancy BMI was 30.91 ± 6.18 kg/m2 and there is no statistically significant difference in mean BMI at conception between the groups. 26.9% of the patients were overweight and 53.6% were obese. The mean time from operation till conception was 27.74 months. The time from operation till conception of excessive group is significantly longer than insufficient and appropriate group. These findings are in line with those of Stentebjerg et al.  after RYGB. They found that 62% of the women with BS who became pregnant were still obese at conception and there was no statistically significant difference in mean BMI at conception between the groups. But 43% of their patients had insufficient GWG, which was 22% in our study. Despite being a higher percentage of patients presented with obesity in the study of Stentebjerg et al.  the time from operation till conception was shorter than our study. The median time from operation till conception was 14 months which was 27.74 months in our study.
Grandfils et al.  found that the women with BS who became pregnant were still obese at conception and women with insufficient GWG had higher pre-pregnancy BMIs when compared to women with normal or excessive GWG. There was no statistically significant difference in mean the median time from operation till conception between the groups. Grandfils et al.  showed that GWG was insufficient for 35%, was appropriate 27% and was excessive for 38% of the pregnancies and the mean time from operation till conception of insufficient group was shorter than adapted and excessive groups.
Chagas et al.  showed that average prepregnancy BMI was 27.36 ± 3.26 kg/m2. 53.3% of the patients were overweight and 23.3% were class I obese. Additionally, they showed that 51.7% of the women presenting insufficient, 34.5% of appropriate, 13.8% of excessive weight gain . The mean time from operation till conception was 17.70 months. This situation can be explained by the lower BMI at conception and the shorter time from operation till conception than our results due to the fact that they gained insufficient weight.
Finally, in a retrospective analysis of 127 pregnancies after malabsorptive and restrictive surgery,
Ceulemans et al.  reported that 24% of patients gained insufficient, 20% patients gained appropriate and 56% of patients gained excessive weight. These results are in line with our findings: In our study GWG was insufficient for 22%, appropriate for 23% and excessive for 55% of the pregnancies. Ceulemans et al.  found that the women with BS who became pregnant were still obese at conception (37% overweight, 32% obese). Although there was no difference between the groups in terms of BMI and the time from operation till conception, 56% of patients gained excessive weight (80% of these pregnancies occured 18 months after surgery). And the LRYGB patients with BMI above 32.5 kg m2 gained the largest amount of weight during pregnancy .
In our study, there was no significant difference in the mean birthweight, LGA and SGA births, low birthweight between the groups. Considering the literature studies according to IOM, there are different results in terms of SGA risk. When et al.  found that SGA rate was higher in normal weight women who gained insufficient weight during pregnancy.
Catalano et al.  showed that an increase in the incidence of SGA was found in the obese or overweight patient group with a weight gain of less than 5 kg during pregnancy.
In the study that 74% of their patients had RYGB, Ceulemans et al.  found that a significant difference in the prevalence of SGA infants with 47% in patients with insufficient group versus 15% and 13% in those with appropriate and excessive group, respectively. Similar to findings, Grandfils et al.  suggest that the large proportion of women with insufficient GWG may account for increased rates of SGA after restrictive and malabsorptive surgery (34% in the insufficient group versus 27% in the appropriate and 19% in the excessive group). Stentebjerg et al.  showed reductions in birth weight when GWG was insufficient, but no statistical significance was found after RYGB. Berglind et al.  showed that birthweight increased with GWG. Ducarme et al.  showed a significant reduction in low birthweight and macrosomia after BS despite lower mean GWG compared with controls with obesity.
Because one of the reasons for SGA with BS is insufficient GWG, especially among women with short interval to pregnancy after BS. The pregnant women lost weight during gestation.
In our study, there was no significant difference in the mean gestational age at delivery between the groups. These results are in line with Stentebjerg et al. . Ceulemans et al.  showed that the gestational age at delivery was comparable between the 3 GWG groups but more patients with insufficient GWG delivered before 37 weeks. In contrast, Grandfils et al.  showed that gestational age was significantly different between groups and it occurred when the GWG was insufficient.
In the general population, preterm delivery has been associated with insufficient GWG, regardless of BMI at conception . In our study, there was no significant difference in the mean preterm delivery between the groups. Stentebjerg et al.  found no difference in the prevalence of preterm deliveries between groups. Grandfils et al.  found patients with insufficient GWG to be at an increased risk for preterm labor, especially compared with those patients with excessive GWG. These results are in line with Ceulemans et al. .
Anemia is frequent in fertile women; and during pregnancy, Hbg and hematocrit (Hct) levels decrease physiologically due to hemodilution caused by physiological plasma volume expansion . Patients who undergo both malabsorptive and restrictive procedures are at risk for iron deficiency .
Several studies have established a relationship between anemia and SGA and birth low birth weight [30, 31]. There was no difference between mean hemoglobin, anemia, low ferritin level and ferritin level at early pregnancy and predelivery between groups (p < 0.05). There was no significant difference between the groups in terms of receiving iron supplement. These results are consisting with Stentebjerg et al. .
There was a significant difference in mode of delivery or type of labor between the groups (p < 0.05). Vaginal delivery in sufficient group (50%) is significantly higher than appropriate (15.8%) and excessive group (24.4%) whereas CD rate was found to be significantly lower in the groups with insufficient weight gain than the other groups, while the groups were similar in terms of indications for CD. The CD rate in all deliveries in Turkey is high, around 53% . The frequency of cesarean section in pregnant women after BS ranges from 15.4%-61.5% . In our study, the rate of CD was 72% and 44% of it was former CD. Grandfils et al.  found that, no significant difference was found between the cesarean rates between the groups that were insufficient, appropriate and excessive weight gain. Stentebjerg et al.  showed that, CD with excess weight gain was found to be higher than in other groups, and its detection in the excessive group was explained by the maternal age. And the lowest rate was in the group with appropriate weight gain.