# Situation: A 22-year-old primigravida registers at the Rural Health Unit (RHU) at 12 weeks' gestation. Before pregnancy she weighed 42 kg, and her height is 152 cm. She has no medical conditions and a single fetus. Using her prepregnancy body mass index (BMI) and the Institute of Medicine (IOM) weight gain guidelines, what total weight gain should the nurse recommend? Round the BMI to one decimal place.

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> subject: Nursing Practice II — Maternal and Child Health Nursing

## 문제

Situation: A 22-year-old primigravida registers at the Rural Health Unit (RHU) at 12 weeks' gestation. Before pregnancy she weighed 42 kg, and her height is 152 cm. She has no medical conditions and a single fetus.

Using her prepregnancy body mass index (BMI) and the Institute of Medicine (IOM) weight gain guidelines, what total weight gain should the nurse recommend? Round the BMI to one decimal place.

## 보기

1. 12.5 to 18 kg **✔ 정답**
2. 11.5 to 16 kg
3. 7 to 11.5 kg
4. 17 to 25 kg

**정답: 1**

## 해설

BMI = weight in kg ÷ (height in m)²: 42 ÷ (1.52 × 1.52) = 42 ÷ 2.3104 = 18.2. A BMI below 18.5 is underweight, for which the recommended total gain is 12.5–18 kg. Weight loss or restriction is not advised in pregnancy.

## 심화 해설

BMI Calculation and Classification

The first step is to compute the prepregnancy body mass index. Using the formula weight in kilograms divided by height in meters squared, the calculation is 42 ÷ (1.52 × 1.52) = 42 ÷ 2.3104 = 18.2. A BMI below 18.5 places this client in the underweight category, which directly determines the recommended gestational weight gain range.

IOM Weight Gain Recommendation for Underweight Women

The Institute of Medicine guideline specifies a total weight gain of 12.5 to 18 kg for women who begin pregnancy underweight. This range is intentionally higher than the recommendation for normal-weight women because the mother must support both fetal growth and her own depleted energy reserves. A systematic review and meta-analysis confirmed that weight gain consistent with these IOM thresholds is associated with more favorable maternal and infant outcomes, whereas gain below the guideline increases risk for small-for-gestational-age infants and preterm birth [1].

Why Underweight Women Need a Higher Gain Target

Underweight women often enter pregnancy with limited subcutaneous fat and lean body mass. The physiologic demands of pregnancy include expansion of maternal blood volume, uterine and breast tissue growth, and deposition of fat stores that will later support lactation. When prepregnancy BMI is below 18.5, the recommended gain of 12.5 to 18 kg reflects the need to build these tissues while still providing adequate substrate for fetal growth [1][2]. A study examining underweight women found that gestational weight gain within the IOM-defined range was linked to better fetal growth parameters, reinforcing that restriction of weight gain in this group is not appropriate [2].

Differentiating the BMI Categories

The IOM guidelines assign distinct weight gain ranges according to prepregnancy BMI classification. These categories are a frequent source of confusion on licensure examinations, so the following comparison clarifies the boundaries.

| Prepregnancy BMI Category | BMI Cut-Point | Recommended Total Weight Gain |
| --- | --- | --- |
| Underweight | Below 18.5 | 12.5 to 18 kg |
| Normal weight | 18.5 to 24.9 | 11.5 to 16 kg |
| Overweight | 25.0 to 29.9 | 7 to 11.5 kg |
| Obese | 30.0 or greater | 5 to 9 kg |

The client’s BMI of 18.2 falls just below the underweight threshold, so the correct recommendation is 12.5 to 18 kg. The option of 11.5 to 16 kg corresponds to normal-weight women, while 7 to 11.5 kg is for overweight women and 17 to 25 kg is not a recognized IOM category.

Clinical and Examination Considerations

Key point! The BMI classification determines the IOM weight gain target, not the woman’s current pregnancy weight or her subjective perception of appropriate gain. A common error is selecting the normal-weight range when the BMI is close to 18.5, but the cutoff is strict: below 18.5 is underweight and requires the higher gain range.

Watch out! Weight loss or intentional restriction of gestational weight gain is never advised for underweight women. The nursing role includes nutritional counseling, monitoring weight at each antenatal visit, and reinforcing that the higher gain target protects fetal growth and maternal reserve [1][2].

Although some populations may use adjusted BMI cut-points or country-specific weight gain targets, the question specifies the IOM guideline, and the IOM classification remains the standard reference for this calculation . The nurse should document the BMI as 18.2, classify the client as underweight, and recommend a total gain of 12.5 to 18 kg.References (research sources)

- [1]Association of Gestational Weight Gain With Maternal and Infant Outcomes: A Systematic Review and Meta-analysis.Meta-analysis/systematic reviewGoldstein RF, Abell SK, Ranasinha S, Misso M, Boyle JA, Black MH (2017) · DOI: 10.1001/jama.2017.3635

- [2]Gestational weight gain and fetal growth in underweight women.Research articleZanardo V, Mazza A, Parotto M, Scambia G, Straface G (2016) · DOI: 10.1186/s13052-016-0284-1

## 임상 시나리오

Underweight Pregnancy Weight GainIOM Target for BMI < 18.5
Calculate prepregnancy BMI: 42 kg ÷ (1.52 m)² = 18.2. A BMI below 18.5 is underweight.

For underweight women, the IOM recommended total gestational weight gain is 12.5 to 18 kg. This higher range supports fetal growth and replenishes maternal reserves.

CautionDo not advise weight loss or restriction during pregnancy. Gain below the IOM range increases risk for SGA and preterm birth.

## 핵심 개념

- **Body Mass Index (BMI)** — Weight in kg divided by height in meters squared; used to classify nutritional status.
- **Underweight BMI** — BMI below 18.5; associated with higher recommended gestational weight gain.
- **IOM Gestational Weight Gain Guidelines** — Institute of Medicine recommendations for total weight gain based on prepregnancy BMI category.
- **Primigravida** — A woman who is pregnant for the first time.
- **Small-for-gestational-age (SGA)** — Infant born smaller than expected for gestational age; risk increases with inadequate weight gain.

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