Placental development and function US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Placental development and function. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Placental development and function US Medical PG Question 1: A 26-year-old woman comes to the emergency department because of a 3-day history of nausea and vomiting. Her last menstrual period was 9 weeks ago. A urine pregnancy test is positive. Ultrasonography shows an intrauterine pregnancy consistent in size with a 7-week gestation. The hormone that was measured in this patient's urine to detect the pregnancy is also directly responsible for which of the following processes?
- A. Development of breast tissue
- B. Preparation of the uterine endometrium for implantation
- C. Inhibition of preterm uterine contractions
- D. Maintenance of the corpus luteum (Correct Answer)
- E. Inhibition of ovulation
Placental development and function Explanation: ***Maintenance of the corpus luteum***
- The hormone measured in the urine pregnancy test is **human chorionic gonadotropin (hCG)**.
- **hCG** acts like **luteinizing hormone (LH)** to maintain the **corpus luteum** in early pregnancy, ensuring continued progesterone production until the placenta takes over.
*Development of breast tissue*
- **Estrogen** and **progesterone** are the primary hormones responsible for the development of breast tissue during pregnancy, preparing the breasts for lactation.
- While hCG indirectly supports these hormones, it does not directly cause breast tissue development.
*Preparation of the uterine endometrium for implantation*
- The **preparation of the uterine endometrium** for implantation is primarily driven by **progesterone**, produced by the corpus luteum initially and later by the placenta.
- hCG’s role is to maintain the corpus luteum, thus indirectly supporting progesterone production.
*Inhibition of preterm uterine contractions*
- **Progesterone** is the main hormone responsible for **inhibiting uterine contractions** during pregnancy to prevent preterm labor.
- While hCG supports progesterone production, it does not directly inhibit uterine contractions itself.
*Inhibition of ovulation*
- High levels of **estrogen** and **progesterone** during pregnancy suppress the hypothalamic-pituitary-gonadal axis, thereby **inhibiting ovulation**.
- While hCG maintains the corpus luteum which produces these hormones, hCG itself is not the direct inhibitor of ovulation.
Placental development and function US Medical PG Question 2: A 30-year-old woman, gravida 2, para 1, at 12 weeks' gestation comes to the physician for a prenatal visit. She feels well. Pregnancy and vaginal delivery of her first child were uncomplicated. Five years ago, she was diagnosed with hypertension but reports that she has been noncompliant with her hypertension regimen. The patient does not smoke or drink alcohol. She does not use illicit drugs. Medications include methyldopa, folic acid, and a multivitamin. Her temperature is 37°C (98.6°F), pulse is 80/min, and blood pressure is 145/90 mm Hg. Physical examination shows no abnormalities. Laboratory studies, including serum glucose level, and thyroid-stimulating hormone concentration, are within normal limits. The patient is at increased risk of developing which of the following complications?
- A. Placenta previa
- B. Abruptio placentae (Correct Answer)
- C. Spontaneous abortion
- D. Polyhydramnios
- E. Uterine rupture
Placental development and function Explanation: ***Abruptio placentae***
- The patient's history of **chronic hypertension** (145/90 mmHg) and her noncompliance with antihypertensive medication significantly increase her risk for **abruptio placentae**. Hypertension is a major risk factor for this condition.
- Abruptio placentae involves the **premature separation of the placenta** from the uterine wall, which can lead to severe maternal hemorrhage, fetal distress, and preterm birth.
*Placenta previa*
- **Placenta previa** is characterized by the placenta covering the cervical os and is primarily associated with risk factors like **previous C-section**, multiple gestations, or advanced maternal age.
- While a serious complication, it is **not directly linked to chronic hypertension** in the same manner as abruptio placentae.
*Spontaneous abortion*
- **Spontaneous abortion** typically occurs in the **first trimester** and is often due to chromosomal abnormalities, endocrine disorders, or uterine anomalies.
- While hypertension could theoretically contribute to some pregnancy complications, it is **not a primary risk factor** for spontaneous abortion at 12 weeks gestation.
*Polyhydramnios*
- **Polyhydramnios** is an excessive accumulation of amniotic fluid, often associated with **maternal diabetes**, fetal anomalies (e.g., GI obstruction, anencephaly), or multiple gestations.
- Maternal hypertension is **not a direct risk factor** for polyhydramnios.
*Uterine rupture*
- **Uterine rupture** is a rare but catastrophic event, most commonly associated with a **previous uterine scar** (e.g., from a prior C-section or myomectomy).
- The patient's history of a prior vaginal delivery and absence of uterine surgery means she is **not at increased risk** for uterine rupture at this stage.
Placental development and function US Medical PG Question 3: A 36-year-old woman, gravida 2, para 1, at 30 weeks' gestation comes to the physician for evaluation of increased urinary frequency. She has no history of major medical illness. Physical examination shows no abnormalities. Laboratory studies show an increased serum C-peptide concentration. Ultrasonography shows polyhydramnios and a large for gestational age fetus. Which of the following hormones is predominantly responsible for the observed laboratory changes in this patient?
- A. Human placental lactogen (Correct Answer)
- B. Adrenocorticotropic hormone
- C. Human chorionic gonadotropin
- D. Progesterone
- E. Estrogen
Placental development and function Explanation: ***Human placental lactogen***
- **Human placental lactogen (hPL)**, also known as **chorionic somatomammotropin**, is produced by the placenta and has **anti-insulin effects**, increasing maternal blood glucose to prioritize fetal nutrient supply.
- This **insulin resistance** leads to increased maternal insulin production (reflected by **elevated C-peptide**) to compensate, and if inadequate, results in **gestational diabetes mellitus (GDM)**, which explains the **polyhydramnios** and **large for gestational age fetus**.
*Adrenocorticotropic hormone*
- **ACTH** stimulates the **adrenal cortex** to produce **cortisol**, which also has diabetogenic effects.
- However, **hPL** is the primary hormone responsible for the **insulin resistance** of pregnancy and the associated elevated C-peptide and GDM features (polyhydramnios and large for gestational age fetus) in this context.
*Human chorionic gonadotropin*
- **hCG** is crucial for maintaining the **corpus luteum** in early pregnancy, stimulating **progesterone** production, and is used as a marker for pregnancy.
- It does not directly cause the **insulin resistance** or significantly elevate C-peptide that leads to the observed findings of **polyhydramnios** and a **large for gestational age fetus**.
*Progesterone*
- **Progesterone** is essential for maintaining pregnancy by promoting **endometrial growth** and suppressing uterine contractions.
- While it plays a role in some metabolic changes during pregnancy, it is not the primary hormone responsible for the **insulin-antagonistic effects** that lead to the elevated C-peptide and signs of GDM described.
*Estrogen*
- **Estrogen** promotes uterine growth, maintains the **endometrium**, and plays a role in fetal development and the development of maternal secondary sexual characteristics.
- While it contributes to metabolic changes in pregnancy, it is not the main hormone responsible for the **insulin resistance** and related features like elevated C-peptide, polyhydramnios, and a large for gestational age fetus seen in this patient.
Placental development and function US Medical PG Question 4: A 31-year-old G3P2 who is at 24 weeks gestation presents for a regular check-up. She has no complaints, no concurrent diseases, and her previous pregnancies were vaginal deliveries with birth weights of 3100 g and 4180 g. The patient weighs 78 kg (172 lb) and is 164 cm (5 ft 5 in) in height. She has gained 10 kg (22 lb) during the current pregnancy. Her vital signs and physical examination are normal. The plasma glucose level is 190 mg/dL after a 75-g oral glucose load. Which of the listed factors contributes to the pathogenesis of the patient’s condition?
- A. Decrease in insulin gene expression
- B. Insulin antagonism of human placental lactogen (Correct Answer)
- C. Production of autoantibodies against pancreatic beta cells
- D. Decrease in insulin sensitivity of maternal tissues caused by alpha-fetoprotein
- E. Point mutations in the gene coding for insulin
Placental development and function Explanation: ***Insulin antagonism of human placental lactogen***
- The patient's elevated plasma glucose indicates **gestational diabetes mellitus (GDM)**, a condition characterized by **insulin resistance** that emerges during pregnancy.
- **Human placental lactogen (hPL)**, secreted by the placenta, is a key hormone that **antagonizes maternal insulin**, contributing significantly to the insulin resistance seen in GDM.
*Decrease in insulin gene expression*
- A decrease in insulin gene expression would lead to **reduced insulin production**, which is not the primary mechanism of insulin resistance in GDM.
- While pancreatic beta cells compensate by increasing insulin secretion in GDM, the underlying problem is the **tissue's reduced response** to insulin.
*Production of autoantibodies against pancreatic beta cells*
- This mechanism is characteristic of **Type 1 diabetes**, where the immune system destroys insulin-producing beta cells, leading to absolute insulin deficiency.
- GDM is primarily a condition of **insulin resistance**, not autoimmune destruction of beta cells.
*Decrease in insulin sensitivity of maternal tissues caused by alpha-fetoprotein*
- **Alpha-fetoprotein (AFP)** is primarily involved in fetal development and is not known to directly cause a decrease in maternal insulin sensitivity.
- The main placental hormones contributing to insulin resistance are **hPL**, progesterone, and cortisol, not AFP.
*Point mutations in the gene coding for insulin*
- **Point mutations** in the insulin gene are rare and would typically manifest as forms of monogenic diabetes or insulin-related disorders, not characteristic GDM.
- GDM is generally a polygenic or multifactorial condition influenced by pregnancy hormones and pre-existing insulin resistance.
Placental development and function US Medical PG Question 5: A 3175-g (7-lb) male newborn is delivered at 39 weeks' gestation to a 29-year-old primigravid woman following a spontaneous vaginal delivery. Apgar scores are 8 and 9 at 1 and 5 minutes, respectively. Cardiac examination in the delivery room shows a continuous machine-like murmur. An echocardiogram shows a structure with blood flow between the pulmonary artery and the aorta. This structure is most likely a derivate of which of the following?
- A. 4th aortic arch
- B. 1st aortic arch
- C. 6th aortic arch (Correct Answer)
- D. 2nd aortic arch
- E. 3rd aortic arch
Placental development and function Explanation: ***6th aortic arch***
- The description of a "continuous machine-like murmur" and a structure with blood flow between the pulmonary artery and the aorta is characteristic of a **patent ductus arteriosus (PDA)**.
- The **ductus arteriosus** is a remnant of the **6th aortic arch**, connecting the pulmonary artery to the aorta in fetal life.
*4th aortic arch*
- The **4th aortic arch** contributes to the formation of the **aortic arch** itself on the left side and the proximal **right subclavian artery** on the right.
- Abnormalities of the 4th arch can lead to conditions like **coarctation of the aorta** or **vascular rings**, which do not typically present as a PDA.
*1st aortic arch*
- The **1st aortic arch** largely disappears, but its remnants contribute to the formation of the **maxillary artery** and the **external carotid artery**.
- It is not involved in developmental anomalies of the major vessels between the pulmonary artery and aorta.
*2nd aortic arch*
- The **2nd aortic arch** also largely regresses, but its remnants contribute to the **stapedial artery** and part of the **hyoid artery**.
- It does not play a role in the formation of the ductus arteriosus or other major arteries of the heart.
*3rd aortic arch*
- The **3rd aortic arch** develops into the common carotid arteries and the proximal internal carotid arteries.
- Genetic disorders and malformations involving this arch typically affect the carotid system, not the connection between the pulmonary artery and aorta.
Placental development and function US Medical PG Question 6: Thirty minutes after normal vaginal delivery of twins, a 35-year-old woman, gravida 5, para 4, has heavy vaginal bleeding with clots. Physical examination shows a soft, enlarged, and boggy uterus. Despite bimanual uterine massage, administration of uterotonic drugs, and placement of an intrauterine balloon for tamponade, the bleeding continues. A hysterectomy is performed. Vessels running through which of the following structures must be ligated during the surgery to achieve hemostasis?
- A. Suspensory ligament
- B. Round ligament
- C. Ovarian ligament
- D. Uterosacral ligament
- E. Cardinal ligament (Correct Answer)
Placental development and function Explanation: ***Cardinal ligament***
- The **uterine artery** and **uterine vein**, which supply the uterus, run through the **cardinal ligament** (also known as the transverse cervical ligament).
- Ligation of these vessels is crucial during a hysterectomy to control bleeding from the uterus.
*Suspensory ligament*
- The **suspensory ligament of the ovary** contains the **ovarian artery** and vein, which primarily supply the ovaries and fallopian tubes.
- While these may be ligated during a hysterectomy if the ovaries are removed, they are not the primary vessels causing uterine bleeding in postpartum hemorrhage.
*Round ligament*
- The **round ligament of the uterus** extends from the uterus to the labia majora and contains relatively small vessels, primarily contributing to uterine support.
- Ligation of this ligament alone would not effectively control heavy uterine bleeding.
*Ovarian ligament*
- The **ovarian ligament** connects the ovary to the uterus and contains small vessels that mainly supply the ovary.
- It does not house the major blood supply to the uterus itself.
*Uterosacral ligament*
- The **uterosacral ligaments** primarily provide support to the uterus by connecting it to the sacrum and contain small nerves and vessels.
- Ligation of these ligaments would not control the main arterial supply to the uterus.
Placental development and function US Medical PG Question 7: A 26-year-old woman comes to the physician because she has not had a menstrual period for 5 weeks. Menarche was at the age of 14 years and menses occurred at regular 30-day intervals. She reports having unprotected sexual intercourse 3 weeks ago. A urine pregnancy test is positive. Which of the following best describes the stage of development of the embryo at this time?
- A. Fetal heart is beating, but cardiac activity is not yet visible on ultrasound
- B. Limb buds have formed, but fetal movements have not begun
- C. Sexual differentiation has begun, but fetal movement has not started
- D. Neural crest has formed, but limb buds have not yet formed (Correct Answer)
- E. Implantation has occurred, but notochord has not yet formed
Placental development and function Explanation: ***Neural crest has formed, but limb buds have not yet formed***
- At **5 weeks gestational age (3 weeks post-fertilization)**, neurulation is completing or recently completed
- **Neural crest cells** migrate from the neural folds during weeks 3-4 post-fertilization and are definitely present by this time
- **Limb buds** appear later, around week 4-5 post-fertilization (week 6-7 gestational age), making this the most accurate description for the current developmental stage
*Fetal heart is beating, but cardiac activity is not yet visible on ultrasound*
- The primitive heart tube begins contracting around day 22-23 post-fertilization (early week 4)
- At 3 weeks post-fertilization (5 weeks gestational age), the heart may just be starting to beat, but this timing is less precise
- Cardiac activity becomes visible on transvaginal ultrasound around 5.5-6 weeks gestational age, so this option is close but less precise than the correct answer
*Limb buds have formed, but fetal movements have not begun*
- **Limb buds** typically appear around week 4-5 post-fertilization (week 6-7 gestational age)
- This is **too advanced** for 3 weeks post-fertilization
- While fetal movements aren't perceptible to the mother until 16-20 weeks, they begin much later than the current stage
*Sexual differentiation has begun, but fetal movement has not started*
- **Sexual differentiation** of the gonads begins around week 7 post-fertilization (week 9 gestational age)
- External genitalia differentiation occurs even later (weeks 9-12 post-fertilization)
- This stage is **far too advanced** for the current 3-week post-fertilization timeframe
*Implantation has occurred, but notochord has not yet formed*
- **Implantation** occurs 6-12 days after fertilization, which is approximately 2-3 weeks before a positive pregnancy test
- The **notochord** forms during gastrulation in the **3rd week post-fertilization** (5th week gestational age)
- By the time of this positive pregnancy test (5 weeks gestational age), the notochord has **already formed**, making this statement incorrect
Placental development and function US Medical PG Question 8: A 32-year-old woman, gravida 2, para 1, at 20 weeks' gestation comes to the physician for a prenatal visit. She feels well. Her first pregnancy was uncomplicated and the child was delivered vaginally. Medications include folic acid and an iron supplement. Her temperature is 37°C (98.6°F), pulse is 98/min, respirations are 18/min, and blood pressure is 108/76 mm Hg. Abdominal examination shows a uterus that is consistent with a 20-week gestation. The second-trimester scan shows no abnormalities. The patient intends to travel next month to Mozambique to visit her grandmother. Which of the following drugs is most suitable for pre-exposure prophylaxis against malaria?
- A. Mefloquine (Correct Answer)
- B. Primaquine
- C. Chloroquine
- D. Doxycycline
- E. Proguanil
Placental development and function Explanation: ***Mefloquine***
- **Mefloquine** is the **most appropriate antimalarial prophylaxis** for pregnant women traveling to **chloroquine-resistant areas** such as Mozambique, particularly after the first trimester.
- Mozambique has **widespread chloroquine-resistant *P. falciparum* malaria**, making mefloquine the preferred choice according to CDC and WHO guidelines.
- While mefloquine is avoided in the first trimester due to limited safety data, it is considered **safe in the second and third trimesters** of pregnancy.
- Though neuropsychiatric side effects can occur, the benefits outweigh risks when traveling to high-risk malaria areas during pregnancy.
*Primaquine*
- **Primaquine** is *contraindicated* in pregnancy because it can cause **hemolytic anemia** in the fetus if the fetus has **glucose-6-phosphate dehydrogenase (G6PD) deficiency**.
- It is used primarily for the **radical cure** of *P. vivax* and *P. ovale* malaria (to eradicate liver hypnozoites), not as a primary prophylactic agent.
*Chloroquine*
- While **chloroquine** is safe in pregnancy and preferred for **chloroquine-sensitive malaria** areas, it is *not appropriate for Mozambique*.
- Mozambique has **high rates of chloroquine-resistant *P. falciparum* malaria**, making chloroquine ineffective for prophylaxis in this region.
- Chloroquine would only be suitable for travel to areas with confirmed chloroquine-sensitive malaria (e.g., Central America west of Panama Canal, parts of the Middle East).
*Doxycycline*
- **Doxycycline** is *contraindicated* in pregnancy and in children under eight years old due to its potential to cause **permanent dental discoloration**, **enamel hypoplasia**, and inhibition of **bone growth** in the developing fetus.
*Proguanil*
- **Atovaquone-proguanil** (Malarone) has limited safety data in pregnancy and is generally not recommended as a first-line option when other proven alternatives are available.
- While some data suggest it may be safe, **mefloquine** is preferred for chloroquine-resistant areas during pregnancy due to more extensive safety documentation in the second and third trimesters.
Placental development and function US Medical PG Question 9: A 29-year-old woman is brought to the emergency room for seizure-like activity. Her husband reports that they were in bed sleeping when his wife began complaining of “hot flashes.” Several minutes later, her right arm began to twitch, and she did not respond to his calls. The whole episode lasted for about 5 minutes. She denies any prior similar episodes, tongue biting, loss of bowel or urinary control, new medications, or recent illness. She reports a family history of epilepsy and is concerned that she might have the same condition. Urine pregnancy test is positive. If this patient is prescribed phenytoin, during which of the following weeks is the fetus most sensitive to its side effects?
- A. Week 18
- B. Weeks 1-2
- C. Weeks 10-12
- D. Week 14
- E. Weeks 3-8 (Correct Answer)
Placental development and function Explanation: ***Weeks 3-8***
- This period marks the **embryonic stage**, crucial for organogenesis, when the fetus is highly susceptible to **teratogenic effects** from drugs like phenytoin.
- Exposure during weeks 3-8 can lead to **Fetal Hydantoin Syndrome**, characterized by features like craniofacial abnormalities, digital hypoplasia, and growth deficiency.
*Week 18*
- By week 18, most major organ systems have largely formed, making the fetus less vulnerable to the **initial teratogenic effects** of phenytoin.
- While some developmental issues can still occur, the risk of severe structural malformations caused by initial exposure is significantly lower compared to the embryonic period.
*Weeks 1-2*
- During weeks 1-2 (peri-implantation period), the embryo is generally resilient to teratogens, following an "all or none" principle where exposure either causes **fetal demise** or no effect.
- Major **organogenesis** has not yet begun, so the specific structural malformations associated with Fetal Hydantoin Syndrome are unlikely to occur from exposure during this very early stage.
*Weeks 10-12*
- By weeks 10-12, the basic structures of most organs are established, reducing the risk of **major congenital malformations** typically seen with early embryonic exposure.
- While developmental and functional impairments can still arise from drug exposure, the critical period for *inducing* severe structural defects due to phenytoin has generally passed.
*Week 14*
- Similar to week 18, by week 14, **organogenesis** is largely complete, and the fetus is less susceptible to the type of gross structural defects caused by phenytoin during earlier embryonic development.
- Exposure at this stage is more likely to cause **functional deficits** or subtle anomalies rather than the severe malformations associated with **Fetal Hydantoin Syndrome**.
Placental development and function US Medical PG Question 10: A 30-year-old primigravid woman at 16 weeks' gestation comes to the emergency department because of vaginal bleeding. She has had spotting for the last 2 days. She has had standard prenatal care. A viable uterine pregnancy was confirmed on ultrasonography during a prenatal care visit 2 weeks ago. She reports recurrent episodes of pain in her right wrist and both knees. Until pregnancy, she smoked one pack of cigarettes daily for the past 11 years. Pelvic examination shows an open cervical os and blood within the vaginal vault. Laboratory studies show:
Hemoglobin 9.6 g/dL
Leukocyte count 8,200/mm3
Platelet count 140,000/mm3
Prothrombin time 14 seconds
Partial thromboplastin time 46 seconds
Serum
Na+ 136 mEq/L
K+ 4.1 mEq/L
Cl- 101 mEq/L
Urea nitrogen 12 mg/dL
Creatinine 1.3 mg/dL
AST 20 U/L
ALT 15 U/L
Ultrasonography shows an intrauterine pregnancy and no fetal cardiac activity. Which of the following is the most likely explanation for this patient's examination findings?
- A. Subchorionic hematoma
- B. Placental thrombosis
- C. Hyperfibrinolysis
- D. Preeclampsia
- E. Chromosomal abnormalities (Correct Answer)
Placental development and function Explanation: ***Chromosomal abnormalities***
- The combination of **vaginal bleeding**, an **open cervical os**, and the absence of **fetal cardiac activity** in a previously confirmed viable pregnancy at 16 weeks gestation is highly suggestive of an **inevitable or incomplete abortion**. The most common cause of spontaneous abortion, particularly in the first trimester and early second trimester, is **chromosomal abnormalities**.
- While the patient's history of smoking and recurrent joint pain (potentially indicative of an autoimmune condition like lupus, which could be associated with antiphospholipid syndrome) could increase the risk of pregnancy complications, **chromosomal anomalies** remain the leading cause of early pregnancy loss.
*Subchorionic hematoma*
- A **subchorionic hematoma** is a collection of blood between the chorion and the uterine wall and can cause **vaginal bleeding**.
- However, while it can pose a risk to pregnancy, the presence of an **open cervical os** and **absent fetal cardiac activity** points more strongly toward a spontaneous abortion rather than just a hematoma in isolation.
*Placental thrombosis*
- **Placental thrombosis** can lead to fetal demise and often presents with **vaginal bleeding**.
- It is more commonly associated with conditions like **antiphospholipid syndrome** or thrombophilias, which could be suggested by recurrent joint pain (though not definitively diagnosed). However, chromosomal abnormalities are statistically a more frequent cause for this presentation.
*Hyperfibrinolysis*
- **Hyperfibrinolysis** would present with generalized bleeding tendencies and abnormal coagulation parameters (e.g., shortened PT/aPTT, decreased fibrinogen), which are not evident in this patient's lab results (normal PT, slightly prolonged aPTT but not dramatically so, platelet count is low but not critically low for hyperfibrinolysis).
- The primary issue here is pregnancy loss, not a primary bleeding disorder as the cause of fetal demise.
*Preeclampsia*
- **Preeclampsia** is a hypertensive disorder of pregnancy, typically presenting after 20 weeks gestation, characterized by **hypertension** and **proteinuria**.
- This patient is at 16 weeks gestation, and there is no mention of hypertension or proteinuria, making preeclampsia an unlikely cause for her current presentation.
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