# 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. Her hemoglobin was 12.4 g/dL (124 g/L) at registration. At 26 weeks it is 11.1 g/dL (111 g/L), although she takes her supplements daily and has no symptoms. Which statement BEST explains this change?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=629568  
> language: ko  
> 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.

Her hemoglobin was 12.4 g/dL (124 g/L) at registration. At 26 weeks it is 11.1 g/dL (111 g/L), although she takes her supplements daily and has no symptoms. Which statement BEST explains this change?

## 보기

1. Her total blood volume has risen by about 40 to 50 percent.
2. Her iron intake is falling short of the needs of pregnancy.
3. Her red cell mass has fallen as the fetus takes up her iron.
4. Her plasma volume has risen more than her red cell mass. **✔ 정답**

**정답: 4**

## 해설

Plasma volume rises more than red cell mass in pregnancy, so hemoglobin falls by dilution and is lowest in the second trimester. At 26 weeks she is in the second trimester, where a hemoglobin of 10.5 g/dL (105 g/L) or more is normal, so 11.1 g/dL (111 g/L) is expected and does not indicate iron deficiency. A rise in total blood volume alone would not lower the concentration; the imbalance between plasma and red cells does.

## 심화 해설

Why hemoglobin falls in mid-pregnancy

The drop from 12.4 g/dL to 11.1 g/dL between 12 weeks and 26 weeks is a physiologic change, not a sign of worsening iron status. In a normal singleton pregnancy, maternal plasma volume and red cell mass both expand, but they do so at different rates and with different timing. Plasma volume increases more than red cell mass, and this disproportionate expansion dilutes hemoglobin, producing a fall in concentration even though total circulating hemoglobin is actually rising. The dilutional effect is greatest in the second trimester, which is exactly where this client is at 26 weeks.

Hemodilution is the term for this process. The hemoglobin concentration falls because the denominator—plasma volume—grows faster than the numerator—red cell mass. This is not anemia caused by iron deficiency; it is a relative, dilutional lowering of the measured value. Key point! A hemoglobin of 11.1 g/dL at 26 weeks is above the second-trimester threshold of 10.5 g/dL and is therefore expected, not abnormal.

| Option | Why it is incorrect or incomplete |
| --- | --- |
| 1. Total blood volume has risen by 40–50% | True as a physiologic fact, but a rise in total volume alone would not lower hemoglobin concentration. The fall requires an imbalance between plasma and red cell expansion. |
| 2. Iron intake is falling short | Not supported. The client takes supplements daily and has no symptoms. At 26 weeks, 11.1 g/dL is within the normal second-trimester range, so iron deficiency is not the best explanation. |
| 3. Red cell mass has fallen | Incorrect. Red cell mass actually increases in pregnancy, just less than plasma volume. It does not fall because the fetus takes up iron. |
| 4. Plasma volume has risen more than red cell mass | Correct. This disproportionate expansion is the mechanism of physiologic hemodilution and the resulting fall in hemoglobin concentration. |

Serum ferritin is the most reliable marker of iron stores in the first trimester, but its interpretation becomes less straightforward after about 20 weeks because plasma dilution also lowers ferritin. Watch out! A falling hemoglobin in the second trimester does not by itself justify a diagnosis of iron deficiency anemia. The diagnosis requires a hemoglobin below the trimester-specific threshold, ideally supported by ferritin or other iron studies.

The timing matters for clinical reasoning. Negative iron balance tends to develop in the latter half of pregnancy, so true iron deficiency anemia is more characteristic of the third trimester, not the second. At 26 weeks, a hemoglobin of 11.1 g/dL is still within the expected range because hemodilution peaks around the late second to early third trimester. The fetal demand for iron is real, but it does not cause maternal red cell mass to fall; it increases the total iron requirement for both maternal hemoglobin mass expansion and fetal growth.

## 임상 시나리오

Physiologic Anemia of PregnancyHemodilution in the Second Trimester
In normal pregnancy, plasma volume rises more than red cell mass, causing a dilutional fall in hemoglobin concentration. This effect is greatest in the second trimester.

At 26 weeks, a hemoglobin of 10.5 g/dL (105 g/L) or more is normal, so 11.1 g/dL (111 g/L) is expected and does not indicate iron deficiency.

CautionA rise in total blood volume alone would not lower hemoglobin concentration; the fall requires an imbalance between plasma and red cell expansion.

## 핵심 개념

- **Hemodilution** — Physiologic dilutional lowering of hemoglobin concentration during pregnancy due to plasma volume expanding more than red cell mass.
- **Plasma volume expansion** — Increases by about 40-50% during pregnancy, exceeding the rise in red cell mass and causing hemodilution.
- **Second-trimester hemoglobin threshold** — A hemoglobin of 10.5 g/dL (105 g/L) or more is considered normal in the second trimester.
- **Red cell mass** — Total volume of circulating red blood cells; it increases during pregnancy but less than plasma volume.
- **Physiologic anemia of pregnancy** — A normal dilutional fall in hemoglobin concentration, most pronounced in the second trimester, not caused by iron deficiency.

## 같은 주제 문제

- [Situation: A 26-year-old woman comes to the Rural Health Unit (RHU) for her first prenatal…](https://mymerci.kr/pages/nclex_q.php?qn_id=629366)
- [Situation: A 26-year-old woman comes to the Rural Health Unit (RHU) for her first prenatal…](https://mymerci.kr/pages/nclex_q.php?qn_id=629367)
- [Situation: A 26-year-old woman comes to the Rural Health Unit (RHU) for her first prenatal…](https://mymerci.kr/pages/nclex_q.php?qn_id=629368)
- [Situation: A 26-year-old woman comes to the Rural Health Unit (RHU) for her first prenatal…](https://mymerci.kr/pages/nclex_q.php?qn_id=629369)
- [Situation: A 30-year-old primigravida at 30 weeks' gestation attends a prenatal check-up a…](https://mymerci.kr/pages/nclex_q.php?qn_id=629370)
- [Situation: A 30-year-old primigravida at 30 weeks' gestation attends a prenatal check-up a…](https://mymerci.kr/pages/nclex_q.php?qn_id=629371)
- [Situation: A 30-year-old primigravida at 30 weeks' gestation attends a prenatal check-up a…](https://mymerci.kr/pages/nclex_q.php?qn_id=629372)
- [Situation: A 30-year-old primigravida at 30 weeks' gestation attends a prenatal check-up a…](https://mymerci.kr/pages/nclex_q.php?qn_id=629373)

---

More free questions: [기출문제](https://mymerci.kr/)

_학습 참고용입니다. 실제 임상은 최신 지침과 소속 기관 프로토콜을 따르세요._