To evaluate the effect of excessive body mass index gain (BMIG) on labor progress and its ma- ternal outcome. Patients & Methods: The study includ- ed 554 pregnant women fulfilling the inclusion criteria. At time of booking, body height and weight were deter- mined and body mass index (BMI) was calculated. At expected date for delivery, BMI was determined and the percentage of excess BMI gain (% EBMIG) was calculated. Maternal outcomes included the frequency of postdated (PD) labor, defined as preg- nancy prolonged beyond 294 days, frequency of women required induc- tion of labor, labor augmentation, in- strumental labor and/or cesarean sec- tion (CS). The relation between % EBMIG and maternal outcomes was determined and the probable cutoff points of %EBMIG for prediction of labor-associated outcomes were deter- mined. Results: Distribution of enrolled wom- en among BMI grades significantly changed at expected time of delivery with significantly higher BMI com- pared to booking time. At expected time of delivery, all women got higher BMI with a mean %EBMIG of 19.8±7.1; range: 8-38%. Majority of women (n=286; 51.6%) got increased BMI in range of 10-20%, while 183 women (33%) had increased BMI in range of 20-30% and 64 women had %EBMIG of more than 30%. Forty- nine women had PD labor for a fre- quency of 8.8%. Two hundred and sixty-one (47.1%) women received induction of labor that resulted in spontaneous unaided vaginal delivery in 83 women, 96 women had instru- mental delivery, while 82 had CS. There was positive significant correla- tion between %EBMIG during preg- nancy and development of PD, re- quirement for labor induction, and augmentation and rate of CS. Kaplan- Meier analysis defined %EBMIG dur- ing pregnancy of 32.7, 25.2, 27.6 and 31.6% as the cutoff points for predic- tion of PD, need for induction of labor, need for labor augmentation and CS. Conclusion: Pregnant women with excessive weight grain during preg- nancy are at a risk of postdated deliv- ery by a frequency of 8.8% and re- quiring induction and augmentation of labor with high frequency. Failure to achieve vaginal delivery and need for CS is a frequent event. Labor-related complications are positively related to the extent of BMI gain during preg- nancy. The %EBMIG of ≥25% could be a cutoff level for prediction of high frequency of labor-related complica- tions.