Physiology of Labor — MCQs
Which of the following options include cardinal movements that occur during labor?
Oxytocin causes all EXCEPT:
What is the expected rate of cervical dilatation per hour during active labor in a primigravida?
Which of the following is consistent with a decision to perform a cerclage?
When a fetus is in an attitude of flexion, which presentation is most likely?
What marks the beginning of the second stage of labor?
The suckling reflex:
Converting frank breech presentation into footling breech presentation within the upper birth canal is called
Palmer sign is related to ?
During delivery of HIV infected women, which of the following are recommended ? 1. Zidovudine (ZDV) is given at the onset of labour. 2. Elective caesarean delivery reduces the risk of vertical transmission. 3. Amniotomy and oxytocin augmentation should be done. 4. Antiretroviral therapy should be given to all neonates. Select the correct answer using the code given below :
Physiology of Labor Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following options include cardinal movements that occur during labor?
- A. Engagement
- B. Descent, Flexion, Internal Rotation (Correct Answer)
- C. Shoulder Dystocia
- D. External Rotation
Explanation: ***Descent, Flexion, Internal Rotation*** - These are three of the **seven cardinal movements** of labor, which ensure the **optimal passage** of the fetus through the birth canal. - The seven cardinal movements are: **Engagement, Descent, Flexion, Internal Rotation, Extension, External Rotation (Restitution), and Expulsion**. - These movements occur sequentially or in combination, adapting the fetal head and body to the **pelvic diameters**. *Engagement* - While engagement is indeed a **cardinal movement** (the first one), the question asks which options include cardinal movements in a broader context. - Engagement alone refers to the **descent of the widest diameter** of the fetal presenting part to a level below the pelvic inlet. *Shoulder Dystocia* - **Shoulder dystocia** is a **complication of labor** where the anterior shoulder impacts behind the maternal pubic symphysis, NOT a cardinal movement. - It requires specific **obstetric maneuvers** to resolve and prevent fetal injury. *External Rotation* - **External rotation (restitution)** is indeed one of the cardinal movements, occurring after delivery of the head when it rotates to align with the shoulders. - However, in the context of this question, Option B provides a more comprehensive representation of multiple sequential cardinal movements.
Question 2: Oxytocin causes all EXCEPT:
- A. Milk ejection
- B. Milk production (Correct Answer)
- C. Induction of labour
- D. Stimulates myoepithelial cells
Explanation: ***Milk production*** - **Oxytocin** is primarily involved in the **milk ejection reflex** (let-down), but prolactin is the hormone responsible for **milk synthesis** or production. - While oxytocin facilitates the release of milk already produced, it does not stimulate the **mammary glands** to produce more milk. *Milk ejection* - Oxytocin causes contraction of the **myoepithelial cells** surrounding the alveoli in the mammary glands, leading to the **ejection of milk** into the ducts. - This reflex is crucial for **breastfeeding** and is often stimulated by the suckling of an infant. *Induction of labour* - **Oxytocin** stimulates rhythmic contractions of the **uterine smooth muscle**, making it a key hormone for initiating and progressing **labor**. - It is often administered exogenously to **induce** or augment labor due to its **uterotonic effects**. *Stimulates myoepithelial cells* - Oxytocin directly acts on the **myoepithelial cells** within the breast to cause their contraction. - This contraction generates pressure that forces milk from the **alveoli** into the **lactiferous ducts**, leading to milk ejection.
Question 3: What is the expected rate of cervical dilatation per hour during active labor in a primigravida?
- A. 1.0 cm (Correct Answer)
- B. 1.5 cm
- C. 2 cm
- D. 1-7 cm per hour
Explanation: ***1.0 cm*** - Historically, the **minimum expected rate** of cervical dilatation during the active phase of labor for a primigravida has been accepted as **1.0 cm per hour**. - This rate is often used to define **protraction disorders** in labor, when dilatation falls below this threshold. *1.5 cm* - This rate is typically associated with the expected cervical dilatation in **multiparous women** during active labor, who often progress faster than primigravidae. - While some primigravidae may dilate at this rate, it is not the traditionally accepted **minimum expected rate** for the entire group. *1-7 cm per hour* - This range is too broad and does not represent a specific, expected minimum rate, but rather a **wide spectrum of possible dilatation speeds**. - While actual dilatation can vary significantly, the question asks for the **expected rate**, which implies a more defined minimum or average. *2 cm* - A dilatation rate of 2 cm per hour is considered **very rapid** and, while beneficial, is not the minimum expected or average rate for a primigravida in active labor. - Such a fast rate would indicate excellent labor progression, rather than the baseline expectation.
Question 4: Which of the following is consistent with a decision to perform a cerclage?
- A. Gestation of 26 weeks
- B. Uterine bleeding
- C. Uterine contractions
- D. Cervix dilated to 3 cm (Correct Answer)
Explanation: ***Cervix dilated to 3 cm*** - In the context of **mid-trimester cervical dilation** (before 24 weeks) without contractions or bleeding, this represents **cervical insufficiency** - a potential indication for **emergency (rescue) cerclage**. - While 3 cm dilation is at the **upper limit** and somewhat controversial, emergency cerclage may still be considered if membranes are intact, there are no contractions, and gestational age is <24 weeks. - This is the **only option** that represents a clinical scenario where cerclage might be performed, as the other three options are **absolute contraindications**. - Note: Most clinicians prefer cervical dilation **<2 cm** for rescue cerclage, but individual cases at 2-3 cm may be considered based on clinical judgment. *Gestation of 26 weeks* - Cerclage is typically placed between **12-14 weeks** (prophylactic) or up to **23-24 weeks** (emergency). - At **26 weeks**, cerclage is **contraindicated** - the risks (membrane rupture, infection, preterm labor) outweigh benefits at this advanced gestation. - This is an **absolute contraindication** regardless of cervical findings. *Uterine bleeding* - **Active uterine bleeding** is an **absolute contraindication** to cerclage placement. - Bleeding increases risks of **infection, membrane rupture, and preterm labor**. - Must rule out **placental abruption, placenta previa**, or other complications before considering any cervical intervention. *Uterine contractions* - **Active uterine contractions** are an **absolute contraindication** for cerclage. - Placing cerclage during contractions can precipitate **preterm labor and delivery**. - Contractions indicate the cervix may be responding to labor stimuli, making cerclage ineffective and potentially harmful.
Question 5: When a fetus is in an attitude of flexion, which presentation is most likely?
- A. Brow
- B. Cephalic (Correct Answer)
- C. Face
- D. Transverse
Explanation: ***Cephalic*** - An **attitude of flexion** is the normal fetal attitude where the head is flexed onto the chest, with the chin tucked, and the limbs are flexed towards the body. This attitude is characteristic of a **cephalic presentation**. - In a cephalic presentation, the **head is the presenting part** to the maternal pelvis, aligning with the fetus being in a flexed attitude. *Brow* - In a brow presentation, the fetal head is **partially extended**, with the brow being the presenting part. This is an abnormal attitude, not one of complete flexion. - This presentation often leads to **labor dystocia** due to the larger presenting diameter of the head. *Face* - A face presentation involves **complete extension** of the fetal head, with the occiput touching the fetal back. The face is the presenting part. - This is an abnormal variation of cephalic presentation and is incompatible with a flexed attitude. *Transverse* - A transverse lie means the fetus is positioned horizontally across the uterus, with the **shoulder being the presenting part**. - This presentation concerns the fetal lie, not the attitude of flexion or extension of the head relative to the body.
Question 6: What marks the beginning of the second stage of labor?
- A. Complete cervical dilation (Correct Answer)
- B. Beginning of fetal descent
- C. Expulsion of placenta
- D. Internal rotation during labor
Explanation: ***Complete cervical dilation*** - The **second stage of labor** officially begins once the cervix is **fully dilated to 10 centimeters**, allowing for the passage of the fetal head. - This stage is characterized by the mother's active pushing efforts and culminates in the birth of the baby. *Beginning of fetal descent* - While fetal descent occurs during labor, it is an ongoing process that starts before **complete cervical dilation**. - Significant fetal descent is a feature of the second stage, but not its defining start point. *Expulsion of placenta* - The expulsion of the placenta marks the **third stage of labor**, which follows the birth of the baby. - This event signals the completion of the birthing process, not the beginning of the second stage. *Internal rotation during labor* - **Internal rotation** is a mechanism of labor that occurs as the fetal head descends through the pelvis, typically during the first and early second stages. - It is a fetal movement for optimal fit within the maternal pelvis, rather than a marker for the onset of a specific labor stage.
Question 7: The suckling reflex:
- A. Increases the release of dopamine from the arcuate nucleus
- B. Increases placental lactogen secretion
- C. Triggers the release of oxytocin by stimulating the supraoptic nuclei
- D. Has afferent neuronal and efferent hormonal components (Correct Answer)
Explanation: ***Correct: Has afferent neuronal and efferent hormonal components*** - The **suckling reflex** is a classic **neuroendocrine reflex** with both neural and hormonal components. - **Afferent pathway**: Mechanoreceptors in the nipple send sensory signals via **spinal nerves** to the hypothalamus. - **Efferent pathway**: Hormonal responses include **oxytocin release** (milk ejection) and **prolactin release** (milk production). - This represents the complete physiological description of the suckling reflex mechanism. *Incorrect: Triggers the release of oxytocin by stimulating the supraoptic nuclei* - While partially true, this is **anatomically imprecise**. - Oxytocin for milk ejection is primarily synthesized in the **paraventricular nuclei**, not the supraoptic nuclei. - The **supraoptic nucleus** primarily produces **vasopressin (ADH)**, though both nuclei produce some oxytocin. - This option is too specific and emphasizes the wrong nucleus. *Incorrect: Increases the release of dopamine from the arcuate nucleus* - The suckling reflex **decreases dopamine release** from the arcuate nucleus (tuberoinfundibular neurons). - Since dopamine acts as **prolactin-inhibiting factor (PIF)**, decreased dopamine leads to **increased prolactin secretion**. - This disinhibition mechanism is essential for milk production during lactation. *Incorrect: Increases placental lactogen secretion* - **Human placental lactogen (hPL)** is secreted by the **placenta during pregnancy**, not postpartum. - It prepares mammary glands during pregnancy but does not respond to suckling. - After delivery, the placenta is expelled and hPL secretion ceases.
Question 8: Converting frank breech presentation into footling breech presentation within the upper birth canal is called
- A. Displacement
- B. Relaxation
- C. Decomposition (Correct Answer)
- D. Conversion
Explanation: ***Decomposition*** - **Decomposition** is the correct obstetric term for the maneuver of converting a frank breech presentation into a footling breech presentation. - This involves bringing down one or both feet from the extended position, making them accessible for **assisted breech delivery**. - The term specifically refers to "breaking down" or altering the configuration of the breech presentation within the birth canal. - This maneuver is part of **breech extraction techniques** and may be performed during vaginal breech delivery. *Displacement* - **Displacement** in obstetrics typically refers to pushing the presenting part upward or to the side. - Commonly used in cases of **cord prolapse** where the presenting part is displaced to relieve cord compression. - It does not describe the conversion between different types of breech presentation. *Relaxation* - **Relaxation** is a general term referring to the absence of uterine contractions or muscular tension. - It does not describe any specific obstetric maneuver or presentation change. *Conversion* - **Conversion** is a broader term that can refer to changing one presentation to another (e.g., **external cephalic version** to convert breech to cephalic). - However, the specific technical term for converting frank breech to footling breech is **decomposition**, not conversion.
Question 9: Palmer sign is related to ?
- A. Increased pulsations in uterine arteries
- B. Bluish discoloration of cervix and vagina
- C. Softening of the cervix during pregnancy
- D. Uterine contractions palpable through rectum during labor (Correct Answer)
Explanation: ***Uterine contractions palpable through rectum during labor*** - **Palmer sign** refers to the palpation of **uterine contractions** through the rectum, particularly during the early stages of labor or even in simulated labor pains. - This sign is an indicator used to assess uterine activity, especially when vaginal examination might be less informative or desired. *Softening of the cervix during pregnancy* - This describes **Goodell's sign**, which is caused by increased vascularity and edema of the cervix during early pregnancy. - While an important sign of pregnancy, it is not referred to as Palmer sign. *Bluish discoloration of cervix and vagina* - This phenomenon is known as **Chadwick's sign**, resulting from increased blood flow to the reproductive organs during pregnancy. - It is an early indication of pregnancy but distinct from the uterine contraction palpation. *Increased pulsations in uterine arteries* - This is known as **Osiander’s sign** or **uterine souffle**, characterized by a soft blowing sound over the uterus due to increased blood flow through the uterine arteries. - It is a vascular sign of pregnancy and not related to uterine contractions felt rectally.
Question 10: During delivery of HIV infected women, which of the following are recommended ? 1. Zidovudine (ZDV) is given at the onset of labour. 2. Elective caesarean delivery reduces the risk of vertical transmission. 3. Amniotomy and oxytocin augmentation should be done. 4. Antiretroviral therapy should be given to all neonates. Select the correct answer using the code given below :
- A. 1 and 2 only (Correct Answer)
- B. 2, 3 and 4
- C. 1, 2 and 4
- D. 1, 2 and 3
Explanation: ***1 and 2 only*** - **Zidovudine (ZDV)** is administered intravenously to the mother at the onset of labor and during delivery as part of the **PMTCT (Prevention of Mother-to-Child Transmission)** protocol. It reduces viral load and provides pre-exposure prophylaxis to the fetus, significantly decreasing the risk of **vertical HIV transmission**. - **Elective cesarean section** is recommended for HIV-infected women with **viral loads >1,000 copies/mL** or unknown viral loads near term (performed at 38 weeks). This reduces neonatal exposure to maternal blood and genital tract secretions during vaginal delivery, thereby **reducing perinatal HIV transmission risk by approximately 50%** compared to vaginal delivery in women not on effective antiretroviral therapy. - Statement 3 is **incorrect**: **Amniotomy (artificial rupture of membranes) and oxytocin augmentation are contraindicated** in HIV-infected women as these procedures increase fetal exposure to maternal blood and bodily fluids, thereby **increasing the risk of vertical transmission**. Guidelines recommend avoiding invasive obstetric procedures. - Statement 4 is **incorrect**: While **antiretroviral prophylaxis** (typically zidovudine syrup) is given to all neonates born to HIV-infected mothers for 4-6 weeks, **full antiretroviral therapy (ART)** is only initiated if the infant tests positive for HIV. The statement incorrectly uses "therapy" instead of "prophylaxis." *1, 2 and 3* - This option incorrectly includes statement 3. **Amniotomy and oxytocin augmentation should be avoided**, not recommended, in HIV-infected women as they increase the risk of vertical transmission through increased fetal exposure to maternal blood. *2, 3 and 4* - Statement 3 is **incorrect** as amniotomy and oxytocin augmentation are **contraindicated** in HIV management during labor. - Statement 4 is **incorrect** as all neonates receive **prophylaxis**, not full antiretroviral **therapy**. *1, 2 and 4* - While statements 1 and 2 are correct, statement 4 is **incorrect** because neonates receive **antiretroviral prophylaxis** (not therapy). Full **ART** is reserved for confirmed HIV-positive infants.
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