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Q.The periodic abstinence by a couple for family planning should be from: (A) Day 5 to 10 of menstrual cycle (B) Day 13 to 15 of menstrual cycle (C) Day 10 to 17 of menstrual cycle (D) Day 16 to 20 of menstrual cycle

CBSECBSE Class XII Board 2024MCQ· 1mImportance★★★★★
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Periodic abstinence (the rhythm method) requires avoiding intercourse during the fertile window, which spans ovulation and the viable lifespan of sperm and egg. For a typical 28-day cycle, abstinence should be from day 10 to 17.

The rhythm method relies on understanding when conception is actually possible during the menstrual cycle. A woman can conceive only when a viable egg meets viable sperm, so we need to map out this fertile window with some safety margins.

The biology behind the fertile window

Ovulation typically occurs around day 14 in a standard 28-day cycle (counting from the first day of menstruation). The released ovum remains viable for about 12–24 hours. However, sperm can survive in the female reproductive tract for up to 5 days under favorable conditions in cervical mucus.

This creates a window of fertility that extends before and after ovulation:

  • Sperm deposited 5 days before ovulation can still be alive when the egg is released
  • The egg remains fertilizable for about 1 day after ovulation

So the theoretical fertile period spans roughly 6 days: from 5 days before ovulation through 1 day after.

Calculating the safe period for abstinence

For a 28-day cycle with ovulation on day 14:

  1. Earliest possible fertilization: Intercourse on day 9 → sperm survive 5 days → meet egg on day 14

  2. Latest possible fertilization: Ovulation on day 14 → egg viable until day 15

  3. Adding a safety buffer: Because ovulation timing can vary by ±2 days even in regular cycles, we extend the window:

    • Start abstinence a bit earlier: day 10 (accounting for early ovulation on day 12)
    • End abstinence a bit later: day 17 (accounting for late ovulation on day 16, plus 1 day egg viability)

This gives us the day 10 to 17 window for periodic abstinence.

Watch out

The rhythm method has a relatively high failure rate (13–25% with typical use) because:

  • Cycle length varies between women and even cycle-to-cycle in the same woman
  • Stress, illness, and other factors can shift ovulation timing
  • It requires meticulous tracking and significant self-discipline

Let's verify against the options:

OptionPeriodAssessment
(A)Day 5–10Too early; misses the fertile window entirely
(B)Day 13–15Too narrow; only covers ovulation itself, not sperm survival period
(C)Day 10–17Correct; covers pre-ovulation sperm survival through post-ovulation egg viability
(D)Day 16–20Too late; misses the critical pre-ovulation days when sperm can be deposited
✓Final answer

The correct option is (C) — periodic abstinence should be from day 10 to 17 of the menstrual cycle.

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