Pregnancy Prevention
Senior 2 · Biology
Pregnancy Prevention
Lesson 2 of 4
24 min
Natural methods of family planning use no devices and no medicines, cost nothing, and are accepted by every major religion. Many couples in Rwanda choose them. But they work only if the user understands the menstrual cycle well enough to know which days are fertile. This lesson teaches that understanding, and it is exactly the biology examiners test.
Cycles vary. Anything from about 21 to 35 days is normal for adults, and the cycles of teenagers are often irregular for the first few years.
An egg lives for only 12 to 24 hours after ovulation, but sperm can live in the woman's body for up to about five days. So intercourse can lead to pregnancy on about six days of each cycle: the five days before ovulation and the day of ovulation. All natural methods try to identify this window and avoid intercourse during it.
This calendar-based method uses a fixed rule. It works only for women whose cycles are always between 26 and 32 days long.
CycleBeads are a ring of coloured beads that make the rule easy to follow. A red bead marks day 1; brown beads mark the days when pregnancy is unlikely; and white beads mark the fertile days 8 to 19. The user moves a small rubber ring one bead forward each day. With typical use, about 12 in 100 women using this method become pregnant in a year.
The cervix produces mucus that changes during the cycle. The woman checks the sensation and appearance of the mucus every day and records it on a chart.
After ovulation, progesterone raises the body's resting temperature by about 0.2 to 0.5 °C, and it stays higher until the next period (see the top of the diagram). The woman measures her temperature every morning before getting up. After three days in a row at the higher level, ovulation has passed and the fertile window is over for that cycle. The temperature rise confirms that ovulation has already happened; it cannot give warning in advance.
Frequent breastfeeding delays the return of ovulation after childbirth. LAM is more than 98% effective, but only while all three conditions are true:
As soon as any condition stops being true, the mother needs another method.
Over six months, Keza's cycles lasted 27, 30, 28, 29, 31 and 28 days. Her latest period began on 3 March. Can she use the Standard Days Method, and which days are fertile?
Tip
The number 14 counts backwards. Ovulation is about 14 days before the next period, not always on day 14. In a 32-day cycle, ovulation is around day 32 − 14 = 18.
LAM needs all three: baby under 6 months, fully breastfed, and no periods.
A woman has a regular 30-day cycle. On about which day does she ovulate, and which days make up her fertile window?
Answer: Ovulation is about 30 − 14 = day 16. The fertile window is the five days before ovulation plus the day itself: about days 11 to 16.
Describe the cervical mucus on a fertile day, and explain why it has these properties.
Answer: It is wet, clear, slippery and stretchy, like raw egg white. Rising oestrogen before ovulation causes this; the mucus helps sperm survive and swim through the cervix.
A mother's baby is four months old and fully breastfed, but her periods returned last week. Can she rely on LAM? Explain.
Answer: No. All three conditions must be true, and her periods have returned, which shows that ovulation may have restarted. She needs another method now.
Give two reasons why natural methods are not reliable for most teenagers.
Answer: Teenagers' cycles are often irregular, so the fertile days cannot be predicted; the methods need careful daily records and long periods of abstaining; and they give no protection against STIs, including HIV.
Remember
Sources and credits
This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.
