CT: 10 Prenatal and Postpartum Measurements

Effective Date: 08/92 Downloads: PDF Version    Revised Date: 07/14


To determine eligibility, all women will be weighed and measured as part of the certification process. Body Mass Index (BMI) will be determined for all clients. Prenatal client’s weight gain will be plotted on the appropriate weight gain grid.


I.          Measurements

Pregnant women will be measured and weighed at their initial certification and weighed as needed during the prenatal period. Postpartum women will be weighed and measured as part of their certification appointment. To obtain a woman’s height and weight, follow the “Procedures for Weighing and Measuring”.


II.         Calculating BMI

Body Mass Index (BMI) is a tool for indicating weight status in adults. It is a measure of weight for height.

*  Prenatal and Postpartum women <6 months: use prepregnancy weight.

*  Postpartum women > 6 months: use current weight.


For both prenatal and postpartum women calculating BMI is the same and the following methods may be utilized.


A.  Obtain BMI from current certification data entered into the WIC Program.

B.  Using a calculator, determine BMI with the following calculation;


 BMI = Weight (lb) ¸ Stature (in) ¸ Stature (in) ´ 703


 BMI = Weight (kg) ¸ Stature (cm) ¸ Stature (cm) ´ 10,000




English:  Weight 160 lbs.  Height 63 ½ inches.

(160 lbs÷ 63.5in÷ 63.5 in) x 703 = 27.9


Metric: Weight 72 kg. Height 161.29 cm.

(72.72 kg ÷ 161.29 cm÷ 161.29 cm) x 10,000 =27.9


C.  Using the Body Mass Index (BMI) Table for Determining Weight Classification;


When determining height of a participant;


If the woman’s measurement is greater than ½, round up

Example: 67 ½ → rounds up to → 68 inches


If the woman’s measurement is less than ½, round down

Example: 64 ¼ → round down to → 64 inches



Body Mass Index (BMI) Table for Determining Weight Classification for Women





BMI <18.5

Normal Weight

BMI 18.5-24.9


BMI 25.0-29.9


BMI > 30.0

58” <89 89-118 119-142 >142
59” <92 92-123 124-147 >147
60” <95 95-127 128-152 >152
61” <98 98-131 132-157 >157
62” <101 101-135 136-163 >163
63” <105 105-140 141-168 >168
64” <108 108-144 145-173 >173
65” <111 111-149 150-179 >179
66” <115 115-154 155-185 >185
67” <118 118-158 159-190 >190
68” <122 122-163 164-196 >196
69” <125 125-168 169-202 >202
70” <129 129-173 174-208 >208
71” <133 133-178 179-214 >214
72” <137 137-183 184-220 >220


(1) Adapted from the Clinical Guidelines on the Identification, Evaluation and Treatment of Overweight and Obesity in Adults.  National Heart, Lung and Blood Institute (NHLBI), National Institutes of Health (NIH).  NIH Publication No. 98-4083.



III.           Assigning Risk


Once you have obtained a BMI number or determined where the client’s height/weight intersect on the table, place in one of four categories;


Pre-Pregnancy and Non-Pregnant BMI


Underweight BMI <18.5

Normal Weight BMI 18.5-24.9

Overweight BMI 25.0-29.9

Obese BMI ≥ 30.0


Record either the BMI number or corresponding letter on the questionnaire and/or prenatal weight gain grid.


IV.        Selecting a Prenatal Weight Gain Grid


For Normal weight and underweight:


“Prenatal Weight Gain Grid” for normal/underweight


For overweight and obese use:


“Prenatal Weight Gain Grid” for overweight/obese


V.         Determining Weeks Gestation


  1.   In order to determine a woman’s estimated date of delivery, ask the woman:


  • “What is your due date?”


  • “When was the first day of your last menstrual period (LMP)?


  1. Using the gestational wheel:
    • If the clients expected due of confinement ( EDC) is available:
      • point the arrow on the gestational wheel to the (EDC or the 40th week, probable day of delivery)
      • Find today’s date (without turning inner wheel) and read the number of weeks that client is pregnant.
      • Record the number of weeks pregnant ( using appropriate rounding as described in P&P manual) on prenatal weight gain grid and prenatal questionnaire)
    • If the EDC is not available;
      • locate the “first day” of last period so that it points to that day, then locate today’s date and record the number of weeks.



Today’s Date:            March 8

EDC:                           July 13

LMP:                          October 5

Weeks Gestation:    21 weeks



If “today’s date” falls between two weeks; i.e. the 21st and 22nd week of gestation. Use the lower number. This is her last completed week of gestation. In the example above the participant has completed her 21st week of gestation.


VI.        Plotting Prenatal Weight Gain Grids


On the appropriate prenatal weight gain grid complete the following

*  Record the client’s name, EDC, Height, Prepregnancy Weight, and BMI.

*  Circle the letter to indicate which graph line is designated.

*  Record “today’s date” and current weight

*  Subtract the woman’s prepregnancy weight from her current weight to determine current weight gain or loss since the onset of pregnancy;



Current Weight                                    165 lb

(subtract)Prepregnancy Weight       142 lb

Current Weight Gain                            23 lb


*  On the appropriate grid, find the current weight gain/loss on the vertical axis and current week gestation on the horizontal axis. Place a dot at the point where the two intersect.

*  Each time a pregnant woman is weighed, the current week gestation should be calculated and her weight gain plotted as described.