Once you resume sex after birth, use contraception — breastfeeding is not contraception; if you want another pregnancy, wait at least 18 months

You can conceive again as early as 3 weeks after birth, even while breastfeeding and before periods return. Breastfeeding only blocks pregnancy when all three hold: exclusive breastfeeding, no period yet, and the child under 6 months. Conceiving again within half a year after birth raises the next child’s preterm risk by about four tenths. The World Health Organization advises waiting at least two years after birth before trying again.

Cost

A box of condoms is a few dozen yuan. An IUD or an implant means a hospital visit; prices vary by place. The hard part is postpartum chaos leaving no room for this

Benefit

The UK National Health Service (NHS) says you can conceive again as early as 3 weeks after birth, even while breastfeeding and before periods return. Unless you want another pregnancy right away, use contraception every time you have sex. Relying on breastfeeding is the lactational amenorrhea method; it needs all three at once: breast milk only, no period yet, and the child under 6 months. Done by the rules, it blocks over 99%. When that standard is not met, about 2 in every 100 people conceive within 6 months. Switch to another method if any of these appear: the child passes 6 months, formula or complementary food or a pacifier is introduced, a period returns (even light bleeding counts), night feeds stop, or feed frequency falls. One pool merged 67 studies and adjusted for maternal age and household circumstances. Using 18 to 23 months from prior birth to next conception as the reference, intervals under 6 months had preterm OR 1.40 (95% CI 1.24–1.58, the plausible range), about 40% higher; low birth weight 1.61 (1.39–1.86); child small for gestational age 1.26 (1.18–1.33). Intervals of 6 to 17 months and over 59 months were also higher on these three. A Canadian study of more than 148000 pregnancies compared a 6-month interval with an 18-month interval. For mothers 35 and older, death or serious illness was 0.62% versus 0.26%, aRR 2.39 (2.03–2.80), about 2.4 times. For mothers 20 to 34 there was no difference (0.92, 0.83–1.02). For children of mothers 20 to 34, combined stillbirth, death, extreme smallness, or extreme prematurity was 2.0% versus 1.4%, aRR 1.42 (1.36–1.47). A 2005 WHO expert meeting advised waiting at least 24 months after a live birth before trying the next pregnancy. Experts agreed that conception under 18 months should be avoided. After miscarriage or induced abortion, wait at least 6 months

Notes

Controversial. How long is enough differs by voice. One WHO expert camp wants 18 months, another 27 months; 24 months is the compromise. The NHS says at least 12 months. An Australian study compared two intervals within the same 40441 mothers and got a different picture. For intervals of 0 to 5 months, preterm OR 1.07 (0.86–1.34), low birth weight 1.03 (0.79–1.34), both showing no clear difference. Comparing across different mothers, preterm was 1.41. So part of the short-interval risk may come from the mother’s own circumstances. Contraception itself is not in dispute; the dispute is only how long to wait. Per the NHS, condoms and implants can be used right after birth, including while breastfeeding. Combined hormonal pills for breastfeeding people usually wait until at least 6 weeks postpartum. Which method to use, discuss with the doctor at the 42-day postpartum checkup; see Item 16 (the 42-day postpartum checkup). The “medium” benefit rating is a judgement call, with the reasoning in the verification record. The benefit falls on you and the next child

Sources · 6

1. NHS. Sex and contraception after birth. nhs.uk/baby/support-and-services/sex-and-cont…
2. NHS. Natural family planning. nhs.uk/contraception/methods-of-contraception…
3. Conde-Agudelo A, Rosas-Bermúdez A, Kafury-Goeta AC (2006). Birth spacing and risk of adverse perinatal outcomes: a meta-analysis. JAMA, 295(15), 1809. doi.org/10.1001/jama.295.15.1809
4. Schummers L, Hutcheon JA, Hernandez-Diaz S, et al. (2018). Association of Short Interpregnancy Interval With Pregnancy Outcomes According to Maternal Age. JAMA Internal Medicine, 178(12), 1661. doi.org/10.1001/jamainternmed.2018.4696
5. World Health Organization (2007). Report of a WHO Technical Consultation on Birth Spacing, Geneva, 13–15 June 2005（WHO/RHR/07.1）. who.int/publications/i/item/WHO-RHR-07.1
6. Ball SJ, Pereira G, Jacoby P, de Klerk N, Stanley FJ (2014). Re-evaluation of link between interpregnancy interval and adverse birth outcomes: retrospective cohort study matching two intervals per mother. BMJ, 349, g4333. doi.org/10.1136/bmj.g4333（备注里的反方研究）