BiologyISC Class 12 · Reproductive Health

Contraceptive Methods and How They Work: ISC Class 12 Biology

Updated 15 October 2026 · Fact-checked

Contraceptives prevent pregnancy by stopping sperm and ovum from meeting, by stopping ovulation or by preventing implantation. ISC groups them as natural methods (periodic abstinence, withdrawal, lactational amenorrhoea) and artificial methods (barriers, spermicides, IUDs, oral pills, injectables and implants, and surgical sterilisation such as vasectomy and tubectomy).

Group each method by how it works: blocking the meeting of gametes, stopping ovulation, or preventing implantation in the uterus.

Illustration drawn for QuestionBuddy.

Understand Contraceptive Methods

Why contraception. Better health care and living conditions sharply lowered death rate, maternal mortality rate (MMR) and infant mortality rate (IMR), and raised the number of people of reproductive age, so population grew explosively. Small families ('Hum Do Hamare Do'), raising the legal marriageable age to 18 years for females and 21 for males, incentives for small families and, above all, contraception are the government's tools.

An ideal contraceptive is user-friendly, easily available, effective and reversible, with no or least side effects, and does not interfere with sexual drive, desire or the sexual act.

A. Natural (traditional) methods: avoid the meeting of ovum and sperm; no drugs or devices, so side effects are almost nil, but failure rates are high.
1. Periodic abstinence: avoid coitus from day 10 to 17 of the cycle, the fertile period, when ovulation is expected.
2. Withdrawal (coitus interruptus): the male withdraws the penis before ejaculation to avoid insemination.
3. Lactational amenorrhoea: absence of menstruation during intense breastfeeding after parturition. Ovulation, and therefore the cycle, does not occur while the mother breastfeeds fully, because suckling keeps prolactin high and suppresses GnRH and the gonadotropins (LH, FSH). Effective only up to a maximum of six months after delivery.

B. Barrier methods: physically stop sperm reaching the ovum.

Condoms: thin rubber/latex sheaths covering the penis (male; 'Nirodh' is a popular brand) or the vagina and cervix (female), put on just before coitus. Disposable, self-inserted, private; also protect against STIs and AIDS.
Diaphragms, cervical caps and vaults: rubber barriers inserted to cover the cervix during coitus; reusable.
Spermicidal creams, jellies and foams: used with these barriers to increase efficiency.

C. Intra-uterine devices (IUDs): inserted by doctors or expert nurses into the uterus through the vagina.

Non-medicated: Lippes loop.
Copper-releasing: CuT, Cu7, Multiload 375.
Hormone-releasing: Progestasert, LNG-20.
Action: IUDs increase phagocytosis of sperms within the uterus; Cu ions suppress sperm motility and the fertilising capacity of sperms; hormone-releasing IUDs also make the uterus unsuitable for implantation and the cervix hostile to sperms.
Ideal for women who want to delay pregnancy or space children; one of the most widely accepted methods in India.

D. Oral pills: small doses of progestogens or progestogen-oestrogen combinations. Taken daily for 21 days, starting preferably within the first five days of the cycle, then a 7-day gap (menstruation occurs), then repeated. They inhibit ovulation and implantation and alter cervical mucus to prevent or retard sperm entry. Saheli, developed at the Central Drug Research Institute (CDRI), Lucknow, is a non-steroidal, once-a-week pill with very few side effects and high contraceptive value.

E. Injectables and implants: progestogens alone or with oestrogen, given as injections or implants under the skin; act like pills but for much longer.

Emergency contraception: progestogens or progestogen-oestrogen combinations, or IUDs, within 72 hours of coitus, after rape or casual unprotected intercourse.

F. Surgical methods (sterilisation): terminal methods that block gamete transport. Vasectomy (male): a small part of the vas deferens is removed or tied through a small incision on the scrotum. Tubectomy (female): a small part of the fallopian tube is removed or tied through a small incision in the abdomen or through the vagina. Highly effective, but reversibility is very poor.

Cautions. A method should be chosen only with advice from qualified medical professionals. Contraceptives are not regular requirements for maintaining reproductive health: they are used against a natural event (conception), for personal reasons, to avoid, delay or space pregnancy. They have done much to check population growth, but the side effects reported for some methods, such as irregular or breakthrough bleeding, nausea, abdominal pain and even breast cancer, are uncommon yet should not be ignored.

Where each method acts (flow chart). semen deposited (stopped by withdrawal, condom) → sperm through cervix (stopped by diaphragm, cap, hostile mucus from pills or hormone IUD) → sperm in uterus (phagocytosed, immobilised by Cu ions) → ovum released (stopped by pills, implants, lactation) → gametes meet in oviduct (stopped by tubectomy; vasectomy keeps sperm out of semen) → implantation (stopped by pills, hormone IUD).

Contraceptive Methods: key facts

Natural methods: $periodic abstinence (days 10-17) ∣ withdrawal ∣ lactational amenorrhoea (up to 6 months)$; No side effects, high failure.
IUD types: $non-medicated: Lippes loop; Cu: CuT, Cu7, Multiload 375; hormone: Progestasert, LNG-20$; Multiload 375, not 365.
IUD actions: $↑ phagocytosis of sperms + Cu^{2 +} ↓ motility and fertilising capacity + (hormone: uterus unsuitable, cervix hostile)$; Give any two for a 2-mark item.
Pill schedule: $21 days pills (start within days 1-5) + 7 days gap \to repeat$; Saheli: once a week, non-steroidal.
Emergency contraception: $progestogen or progestogen-oestrogen, or IUD, within 72 h$; After rape or casual unprotected intercourse.

How to answer Contraceptive Methods questions

ISC questions name a device and ask its mode of action, ask reasons (lactational amenorrhoea), or ask you to recommend a method for a situation.

1Identify the category: natural, barrier, IUD, hormonal (pill, injection, implant), emergency or surgical.
2State the mode of action precisely: barrier stops sperm; Cu ions suppress motility and fertilising capacity; pills inhibit ovulation and implantation and alter cervical mucus.
3For lactational amenorrhoea, give the hormonal reason: high prolactin during intense breastfeeding, low GnRH, LH and FSH, so no ovulation; limit six months.
4For recommendations, match the need: spacing → IUD; temporary and STD protection → condom; no more children → vasectomy or tubectomy; unprotected coitus → emergency contraception within 72 hours.
5Spell device names exactly (Multiload 375, Progestasert, LNG-20).
6When asked for 'two ways', give two different mechanisms, not two devices.

Contraceptive Methods in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Matching a contraceptive to a family's needs

Suppose a couple has one child aged four months, whom the mother breastfeeds fully. They want a second child after about three years and, after that, no more children.

Suggest suitable methods for each stage, with reasons.

Try it first, then show the solutionSolution

Now: lactational amenorrhoea gives some protection while she breastfeeds fully, because high prolactin suppresses ovulation, but it works only up to about six months after delivery, so they should start another method soon.
For the three-year gap: an IUD such as a CuT or Multiload 375 is ideal for spacing; Cu ions suppress sperm motility and fertilising capacity, and it can be removed when they want the second child.
Condoms can be used alongside if protection from STDs is also needed.
After the second child: a terminal method, vasectomy for the husband or tubectomy for the wife, chosen with medical advice, because its reversibility is very poor.

Answer: Lactational amenorrhoea briefly (up to six months), then an IUD for spacing, then vasectomy or tubectomy once the family is complete.

Memory hook: Breastfeed briefly, IUD to space, surgery to close the chapter.

Tricks to remember Contraceptive Methods

Short memory aids. Say each one aloud once, then use it on a question the same day.

Copper Cuts Motility
Cu = 'Cuts' sperm motility and fertilising capacity.
Use it when: Mode of action of copper IUDs.
Ten to seventeen, stay clean
Periodic abstinence: avoid coitus from day 10 to 17.
Use it when: Fertile period numbers.
Vas-ectomy for the vas, Tub-ectomy for the tube
The name tells you which duct is cut.
Use it when: Surgical methods.

Contraceptive Methods: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Copper IUDs · 2 marks · Short answerBoard level

A woman has a CuT fitted after the birth of her first child. Name one other copper-releasing IUD, and explain two ways in which such a device prevents conception. (A question on Cu-releasing IUDs was set in 2024.)

Try it first, then show the solutionSolution

Other copper-releasing IUDs: Cu7 or Multiload 375 (1 mark).
They increase phagocytosis of sperms within the uterus; the Cu ions released suppress sperm motility and fertilising capacity (1 mark).

Answer: Cu7 (or Multiload 375); increased phagocytosis of sperms, and Cu ions suppress sperm motility and fertilising capacity.

Example 2: Sorting the methods · 2 marks · Short answerBoard level

Classify these methods as natural, barrier, IUD, oral pill/implant or surgical: withdrawal, cervical cap, Multiload 375, Saheli, tubectomy, lactational amenorrhoea, implant under the skin, vault.

Try it first, then show the solutionSolution

Natural: withdrawal, lactational amenorrhoea. Barrier: cervical cap, vault (1 mark).
IUD: Multiload 375. Oral pill/implant: Saheli, implant under the skin. Surgical: tubectomy (1 mark).

Answer: Natural: withdrawal, lactational amenorrhoea; barrier: cervical cap, vault; IUD: Multiload 375; pill/implant: Saheli, implant; surgical: tubectomy.

Example 3: Lactational amenorrhoea · 2 marks · Short answerHarder board level

A mother who has fed her baby only on breast milk has had no periods for four months since delivery. Explain the hormonal basis of this, and say whether she can rely on it for contraception for another four months.

Try it first, then show the solutionSolution

During intense breastfeeding, suckling keeps prolactin high, which suppresses GnRH and hence LH and FSH; follicles do not mature and ovulation does not occur, so there is no cycle and no menstruation (1 mark).
No: the method is effective only up to about six months after parturition, and only while the mother breastfeeds fully; four more months would take her to eight months, and ovulation may return before her first period, so she should start another method (1 mark).

Answer: High prolactin suppresses GnRH, LH and FSH, so there is no ovulation; she cannot rely on it for four more months, as it works only up to about six months with full breastfeeding.

Example 4: Pills and Saheli · 3 marks · Short answerHarder board level

Describe the schedule and mode of action of combined oral contraceptive pills. How is Saheli different?

Try it first, then show the solutionSolution

Pills of progestogen or progestogen-oestrogen are taken daily for 21 days, starting within the first five days of the cycle, followed by a 7-day gap when menstruation occurs, then repeated (1 mark).
They inhibit ovulation and implantation and alter cervical mucus to prevent or retard the entry of sperms (1 mark).
Saheli, developed at CDRI Lucknow, is non-steroidal and taken once a week, with very few side effects and high contraceptive value (1 mark).

Answer: 21 days on, 7 off; inhibit ovulation and implantation and thicken cervical mucus; Saheli is a non-steroidal once-a-week pill.

Example 5: Hormone IUD versus copper IUD · 3 marks · Short answerHarder board level

What additional actions does a hormone-releasing IUD such as LNG-20 have compared with a copper IUD? Why are IUDs regarded as ideal for spacing children?

Try it first, then show the solutionSolution

Both increase phagocytosis of sperms in the uterus (½ mark).
Hormone-releasing IUDs, in addition, make the uterus unsuitable for implantation and the cervix hostile to sperms (1½ marks).
They are long-acting, need no daily attention, and fertility returns after removal, so they suit women who want to delay pregnancy or space children (1 mark).

Answer: Hormone IUDs also block implantation and make the cervix hostile to sperms; IUDs are long-acting and reversible.

Example 6: After vasectomy · 3 marks · Short answerHOTS / competency

Suppose a man undergoes vasectomy. (a) Will his semen volume change much, and will it contain sperms? (b) Will his testosterone level fall? (c) Why is he advised to use another method for some time after the operation? Explain each.

Try it first, then show the solutionSolution

(a) Volume changes little because most seminal plasma comes from the seminal vesicles, prostate and bulbourethral glands beyond the cut; but sperms from the testis cannot pass the cut vas deferens, so the semen lacks sperms (1 mark).
(b) No: testosterone from Leydig cells enters the blood, not the vas deferens (1 mark).
(c) Sperms already stored in the ducts beyond the cut can still be ejaculated for a while, so pregnancy is possible until they are cleared (1 mark).

Answer: Semen without sperms but similar volume; hormones unaffected; stored sperms beyond the cut need time to clear.

Where students lose marks in Contraceptive Methods

The slips examiners see most often, and what to write instead.

Mistake: Naming only one device or misnaming it
In 2024 examiners noted that candidates named only one Cu-releasing IUD or wrote 'Multiload 365' instead of 375.
Do this: Learn the three names exactly: CuT, Cu7, Multiload 375.
Usually costs: ½ to 1 mark.
Mistake: Describing barrier action for an IUD
Examiners (2024) found the functions of mechanical or barrier methods written for copper IUDs.
Wrong working
Cu-T blocks the sperm from entering the uterus.
Right working
Cu-T increases phagocytosis of sperms and its Cu ions suppress sperm motility and fertilising capacity.
Do this: An IUD sits inside the uterus; it acts on sperms there, not as a gate.
Usually costs: 1 mark.
Mistake: Repeating 'no menstruation' without the hormonal reason
In 2025 examiners reported that candidates restated the lactational amenorrhoea statement without linking it to suppression of ovulation by high prolactin.
Do this: Write: high prolactin during intense lactation → low GnRH, LH, FSH → no ovulation → no cycle.
Usually costs: The whole 1-mark reason.
Mistake: Claiming IUDs or pills prevent STDs
A common slip carried over from barrier methods.
Do this: Only condoms (and other barriers) reduce STD transmission.
Usually costs: 1 mark.

Exam tips

Classify the method first, then give its mode of action in one precise line.
Quote NCERT figures: day 10-17, six months, 21 + 7 days, 72 hours, Multiload 375.
In 'two ways' questions, give two mechanisms, not two names.
Mention reversibility: IUDs and pills reversible; sterilisation practically irreversible.
Use British spelling in answers: oestrogen, amenorrhoea, sterilisation.

Practice questions on Contraceptive Methods

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
Which of these is a hormone-releasing IUD?
(a) Lippes loop (b) Multiload 375 (c) LNG-20 (d) Cu7
Hint
Progestasert is another.
Answer
(c) LNG-20.
Q2 · 2 marks · Short answerBoard level
Distinguish between vasectomy and tubectomy.
Hint
Which duct, which sex, where the incision is.
Answer
Vasectomy is male sterilisation: a small part of the vas deferens is removed or tied through a small incision on the scrotum. Tubectomy is female sterilisation: a small part of the fallopian tube is removed or tied through a small incision in the abdomen or through the vagina.
Q3 · 1 mark · Assertion-reasonHarder board level
Assertion (A): Diaphragms are used with spermicidal jellies.
Reason (R): Spermicides increase the contraceptive efficiency of barriers.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Hint
Why add a cream to a barrier?
Answer
(a).
Q4 · 2 marks · Short answerHarder board level
Explain periodic abstinence. Why is the period from day 10 to day 17 called the fertile period, and why does this method often fail?
Hint
Ovulation timing varies.
Answer
Couples avoid coitus from day 10 to 17 of the cycle, when ovulation is expected and chances of fertilisation are very high, hence the fertile period. It often fails because the timing of ovulation varies between cycles and depends on correct counting and strict abstinence.
Q5 · 2 marks · Short answerHarder board level
What is emergency contraception? Name two methods and the time limit within which they must be used.
Hint
After rape or unprotected coitus.
Answer
Contraception used after coitus to avoid possible pregnancy after rape or casual unprotected intercourse. Progestogens or progestogen-oestrogen combinations, or an IUD, used within 72 hours of coitus.
Q6 · 2 marks · Short answerHarder board level
List three possible ill effects of contraceptive use mentioned for some methods, and explain why contraceptives are said not to be a regular requirement of reproductive health.
Hint
They act against a natural event.
Answer
Nausea, abdominal pain, breakthrough bleeding, irregular menstrual bleeding or even breast cancer (any three). They are used against a natural reproductive event (conception) for personal reasons, to prevent, delay or space pregnancy; reproductive health itself does not depend on them.
Q7 · 3 marks · Short answerHOTS / competency
Suppose a new contraceptive implant releases a progestogen that keeps the cervical mucus thick but, in a few women, does not fully stop ovulation. (a) By which action will it still prevent pregnancy in them? (b) Name one more action expected from progestogens. (c) Why is an implant more convenient than a daily pill?
Hint
Pills and implants share their mode of action.
Answer
(a) Thick cervical mucus prevents or retards the entry of sperms, so fertilisation is unlikely even if an ovum is released. (b) It makes the uterus unsuitable for implantation (pills and implants inhibit implantation). (c) An implant works for a much longer period without daily action, so missed doses do not occur.
Q8 · 3 marks · Case-basedHOTS / competency
Read and answer.
Suppose a health worker meets three women: Leela wants no more children after three; Rani wants to delay her first pregnancy by two years and is in a stable relationship with a tested partner; Meena had unprotected intercourse 36 hours ago and fears pregnancy.
(a) Suggest the most suitable method for each. (2)
(b) Which of the methods you suggested is practically irreversible? (1)
Hint
Terminal, spacing, emergency.
Answer
(a) Leela: tubectomy (or vasectomy for her husband). Rani: an IUD such as CuT or Multiload 375 (or oral pills). Meena: emergency contraception, progestogen or progestogen-oestrogen pills, or an IUD, since she is within 72 hours. (b) Tubectomy (and vasectomy): reversibility is very poor.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.Name a non-medicated IUD.Show answer
Lippes loop.
2.What is Saheli?Show answer
A once-a-week, non-steroidal oral contraceptive pill developed at CDRI, Lucknow.
3.Within how many hours must emergency contraception be used?Show answer
72 hours.
4.Which part is cut or tied in tubectomy?Show answer
A small part of the fallopian tube.
5.Up to how long after parturition is lactational amenorrhoea effective?Show answer
A maximum of about six months.
6.Name two hormone-releasing IUDs.Show answer
Progestasert and LNG-20.

Contraceptive Methods: frequently asked questions

How does a copper IUD prevent pregnancy?

It increases phagocytosis of sperms in the uterus, and the copper ions suppress sperm motility and fertilising capacity.

Why is there no menstruation during lactational amenorrhoea?

High prolactin during intense breastfeeding suppresses GnRH, LH and FSH, so ovulation and the cycle do not occur.

How do oral contraceptive pills work?

They inhibit ovulation and implantation and alter cervical mucus so that sperms cannot enter easily.

What are the natural methods of contraception?

Periodic abstinence (days 10-17), withdrawal (coitus interruptus) and lactational amenorrhoea.

Which contraceptive methods are terminal?

Surgical sterilisation: vasectomy in men and tubectomy in women.