ACOG advises people to avoid interpregnancy intervals shorter than six months and to be counseled about the risks and benefits of conceiving again sooner than 18 months. That is not the same as saying everyone must wait exactly 18 months. Age, prior infertility, C-section history, pregnancy complications, recovery, and family goals all belong in the decision.
The clock starts at birth, not when your period returns
What is an interpregnancy interval?
It is the time from one delivery to the beginning of the next pregnancy — not the time between two due dates and not the age gap between children.
So an 18-month interpregnancy interval produces a sibling age gap of more than two years.
Why very short intervals get attention
Observational studies have associated very short intervals with higher risks of some adverse outcomes. ACOG notes that the strongest concern is for intervals under six months, while data under 18 months show more modest associations and have important methodological limitations.
Possible explanations include nutritional recovery, uterine healing, residual inflammation, breastfeeding demands, chronic disease recovery, and social factors.
Why 18 months is counseling, not a universal commandment
ACOG specifically says patients should be counseled about the risks and benefits of pregnancy sooner than 18 months.
That wording matters.
A 39-year-old who required treatment to conceive the first child faces a different tradeoff from a 24-year-old with no fertility concerns. Someone with severe preeclampsia, major postpartum anemia, pelvic-floor injury, or a complicated C-section may also need a different recovery plan.
Breastfeeding does not automatically prevent pregnancy
Ovulation can return before the first postpartum period. If you are not ready to conceive again, use a contraception strategy rather than assuming breastfeeding will indefinitely suppress fertility.
Our breastfeeding and fertility guide explains the strict conditions under which lactational amenorrhea can work as contraception.
What if you had infertility before the first pregnancy?
ACOG says spacing recommendations generally should not automatically differ for people with prior infertility, but it acknowledges that age and the use of assisted reproduction can change the practical timing conversation.
That means “wait 18 months no matter what” may be too simplistic for somebody whose fertility is time-sensitive.
What should be recovered before the next pregnancy?
Depending on your first pregnancy and delivery, review:
- anemia and iron status
- blood pressure
- diabetes or gestational diabetes follow-up
- thyroid disease
- pelvic-floor symptoms
- mental health
- nutrition and prenatal-vitamin plan
- C-section history
- medications
Frequently asked questions
Does ACOG say everyone must wait 18 months?
No. ACOG advises avoiding intervals shorter than six months and counseling about risks and benefits when conception occurs sooner than 18 months.
Can I get pregnant before my first postpartum period?
Yes. Ovulation occurs before menstruation, so conception can happen before the first period returns.
Does prior infertility mean I should ignore birth-spacing guidance?
No. It means fertility timing should be part of an individualized discussion rather than applying one calendar rule without context.