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Reproductive Health Set-3

Practice Important MCQs for Reproductive Health — Biology, Class 12.

“Reproductive Health” is a high-yield CBSE/competitive chapter because it connects core reproductive physiology with real-world public-health concepts such as contraception, sexually transmitted infections, infertility management, and assisted reproductive technologies (ART). Questions from this chapter often test both biological understanding (processes like fertilization, implantation, and implantation success) and application-based reasoning (risk assessment, success probability, and interpretation of clinical/diagnostic measures), making it important for boards as well as JEE/NEET-style problem solving.

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Q1. (Assume the probability of pregnancy after a single unprotected sexual act is $5\%$ . A contraceptive method reduces the per‑act risk by $95\%$ . If a couple has $10$ independent acts of intercourse using this contraceptive, what is the probability that they will experience at least one pregnancy during these $10$ acts?)

(A)

( $A$ ) $1-(1-0.05)^{10}$

(B)

( $B$ ) $1-(1-0.0025)^{10}\approx2.47\%$

(C)

( $C$ ) $1-(1-0.0475)^{10}\approx38.6\%$

(D)

( $D$ ) $(1-0.0025)^{10}\approx97.53\%$

Q2. (In an IVF cycle $6$ mature oocytes are retrieved. Each oocyte has a $60\%$ chance of fertilization; given fertilization, the embryo has a $50\%$ chance of surviving to a transferable blastocyst; and each transferable blastocyst has a $30\%$ chance of successful implantation. Assuming independence of these events and that all transferable blastocysts are available for implantation, what is the probability that the cycle results in at least one established pregnancy?)

(A)

( $A$ ) $6\times(0.6\times0.5\times0.3)=54\%$

(B)

( $B$ ) $1-(1-0.6\times0.5)^{6}=1-(1-0.3)^{6}$

(C)

( $C$ ) $1-(1-0.6\times0.5\times0.3)^{6}=1-(1-0.09)^{6}\approx43.2\%$

(D)

( $D$ ) $(0.6\times0.5\times0.3)^{6}=(0.09)^{6}$

Q3. (In a community of $1000$ sexually active couples the baseline annual pregnancy probability per couple without contraception is $0.8$ . Strategy I: $70\%$ of couples adopt method P which reduces pregnancy risk by $95\%$ (remaining $30\%$ use no contraception). What is the expected number of pregnancies per $1000$ couples per year under Strategy I?)

(A)

( $A$ ) $700\times\big(0.8\times(1-0.95)\big)+300\times0.8=268\ \text{pregnancies/year}$

(B)

( $B$ ) $700\times\big(0.8\times(1-0.8)\big)+300\times0.8=352\ \text{pregnancies/year}$

(C)

( $C$ ) $700\times(0.8\times0.95)+300\times0.8=772\ \text{pregnancies/year}$

(D)

( $D$ ) $700\times(0.8\times(1-0.95))=28\ \text{pregnancies/year}$

Q4. (A rapid HIV screening test used in antenatal clinics has sensitivity $Se=99.5\%$ and specificity $Sp=99.0\%$ . If HIV prevalence in the screened pregnant population is $0.5\%$ , calculate the positive predictive value (PPV) and state the practical implication.)

(A)

( $A$ ) $PPV=\dfrac{Se\times Prev}{Se\times Prev+(1-Sp)\times(1-Prev)}\approx99.5\%$ ; a positive rapid test almost certainly indicates infection — start treatment immediately.

(B)

( $B$ ) $PPV\approx67\%$ ; repeat the same rapid test once and act if both positives.

(C)

( $C$ ) $PPV\approx0.5\%$ ; false positives dominate so screening is not useful.

(D)

( $D$ ) $PPV=\dfrac{0.995\times0.005}{0.995\times0.005+0.01\times0.995}\approx33\%$ ; in a low‑prevalence antenatal population a positive rapid test will include a substantial proportion of false positives, therefore all positives require confirmatory testing and counselling before diagnosis.

Q5. (A semen analysis reports ejaculate volume $2.5\ \mathrm{mL}$ , sperm concentration $20\times10^{6}\ \mathrm{mL}^{-1}$ , total motility $50\%$ and normal morphology $4\%$ . Estimate the number of motile normal sperm in the ejaculate and assess fertility implication using a threshold of $5\times10^{6}$ motile normal sperm for reasonable fertility.)

(A)

( $A$ ) Total sperm $=2.5\times20\times10^{6}=50\times10^{6}$ ; motile normal $=50\times10^{6}\times0.5\times0.04=1\times10^{6}$ , which is below $5\times10^{6}$ — suggests increased risk of subfertility.

(B)

( $B$ ) Motile normal $=50\times10^{6}\times0.5=25\times10^{6}$ (ignoring morphology) — appears adequate for fertility.

(C)

( $C$ ) Motile normal $=50\times10^{6}\times0.04=2\times10^{6}$ (ignoring motility) — below the threshold, suggesting increased risk of subfertility.

(D)

( $D$ ) Motile normal $=2.5\times20\times10^{6}=50\times10^{6}$ (ignoring motility and morphology) — appears excellent fertility.

Q6. During an IVF cycle 12 mature oocytes were retrieved; 75% fertilized and 66% of zygotes reached blastocyst stage. Two blastocysts were transferred and each has an independent implantation probability of $p=0.30$ . What is the probability that at least one embryo implants? (Use $P(\text{at least one})=1-(1-p)^n$ .)

(A)

$49\%$

(B)

$51\%$

(C)

$30\%$

(D)

$60\%$

Q7. A couple's semen analysis shows volume $V=3\ \text{mL}$ , sperm concentration $C=15\times10^6\ \text{mL}^{-1}$ and progressive motility $=40\%$ . A clinic guideline states: perform IUI if total progressive motile sperm count (TPMSC) satisfies $TPMSC = V\times C\times(\% \text{motility}) \ge 20\times10^6$ , otherwise proceed to IVF/ICSI. Calculate TPMSC and select the appropriate ART.

(A)

Intrauterine insemination (IUI)

(B)

Expectant management (monitor natural conception)

(C)

Donor insemination

(D)

IVF/ICSI

Q8. A subdermal contraceptive implant releases progestin at rate $R(t)=R_0 e^{-kt}$ (µg day $^{-1}$ ). If $R_0=120\ \mu\text{g day}^{-1}$ , $k=0.1\ \text{month}^{-1}$ and ovulation suppression requires $R(t)>20\ \mu\text{g day}^{-1}$ , after approximately how many months can ovulation be expected to resume?

(A)

$\approx 18\ \text{months}$

(B)

$\approx 9\ \text{months}$

(C)

$\approx 36\ \text{months}$

(D)

$\approx 24\ \text{months}$

Q9. Each embryo transferred in an IVF attempt implants independently with probability $p=0.30$ . The probability of a multiple pregnancy (≥2 implantations) when $n$ embryos are transferred is given by $1-\big[(1-p)^n + n p (1-p)^{\,n-1}\big]$ . To keep the multiple-pregnancy risk $\le 10\%$ , what is the largest integer $n$ the clinic should transfer?

(A)

$n=1$

(B)

$n=3$

(C)

$n=2$

(D)

$n=4$

Q10. A couple, both carriers of the same autosomal recessive mutation, underwent preimplantation genetic diagnosis (PGD) using single-cell PCR on a blastomere. An embryo reported as mutation‑negative was transferred but the resulting child was born affected by the disorder. Which is the most likely explanation?

(A)

A de novo mutation occurred in the embryo after PGD

(B)

Allelic dropout during single‑cell PCR caused a false‑negative PGD result

(C)

Maternal uniparental disomy produced homozygosity for the mutant allele

(D)

A postzygotic somatic mutation in the embryo created mosaic affected tissues

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