Validating a “Term BMI” using Mode of Delivery, Estimated Blood Loss, and Neonatal Weight

Diana Garretto, MD & Erin Stevens, MD State University of New York at Stony Brook University Medical Center Department of Obstetrics, Gynecology, & Reproductive Medicine

Background

Among non-pregnant women age 20-39, 25% of them are overweight and 28% are obese, and 6% have a BMI >= to 40. Issues begin with pre-conception with infertility etc to antepartum issues including GDM and anomalies through intrapartum problems. Postpartum issues include increased risk for venous thrombosis, etc.

Objective

To validate using a “Term BMI” instead of pre-pregnancy BMI to evaluate for risk of blood loss, LGA fetus, and cesarean section on day of delivery.

Study Design

In non-pregnant populations, underweight is a BMI <18.5, normal weight is a BMI 18.5-24.9, overweight is a BMI 25-29.9, and obese is a BMI>30. The “Term BMI” was calculated by adding the respective IOM weight gain recommendations of each category to each pregnancy at term.

A single institution retrospective chart review was then performed of patients who delivered at term (>=37 weeks) from July 2009 to January 2010 was performed to validate the use of a Term BMI. Data included height, pre-pregnancy weight, maternal blood loss.

delivery weight, mode of delivery, neonatal weight, and estimated

Results

Based on the IOM guidelines, a patient would be considered underweight if the BMI at term was <23.5, normal weight if the BMI at term was 23.5-29.9, overweight if the BMI at term was 30-33.5 and obese if the BMI at term was >33.5. These were used as the “Term BMI” categories.

1,031 patients met inclusion criteria. The data was analyzed using the Jonckheere Terpstra Test. There was a significant increase in risk of cesarean section with increasing BMI in both the pre-pregnancy and Term BMI groups (Table 1). There was also BMI groups.

a significant increase in estimated blood loss (Table 2) and neonatal weight (Table 3) with increasing BMI in both the pre-pregnancy and Term

Conclusions

Using the “Term BMI” at the time of delivery may be an easier and more accurate way to objectively assess risks of obesity at term than pre-pregnancy weight or BMI alone.

The “Term BMI” allows calculation of a woman’s BMI the actual day of delivery and can help to predict complications associated with delivery including mode of delivery, neonatal weight, and estimated blood loss.

Table 1 Table 2 Table 3 Tables

BMI Normal Weight Overweight Obese P-value C-Section Rate Pre-pregnancy 27.79% 31.87% 42.27% 0.0026

C-Section Rate Term 28.64% 28.93% 40.5% 0.0033

BMI Normal weight Overweight Obese P-value EBL Mean Pre-pregnancy 589 636 727 0.0002

EBL Mean Term 573 627 731 <0.0001

BMI Normal weight Overweight Obese P-value Neonatal weight Mean Pre-pregnancy 3405 3420 3466 0.0168

Neonatal weight Mean Term 3366 3436 3510 <0.0001