Minimal Interpregnancy Interval to Reduce Complications
The optimal interpregnancy interval to reduce maternal and fetal complications is at least 18 months between birth and the beginning of a subsequent pregnancy. 1, 2
Understanding Interpregnancy Interval (IPI)
Interpregnancy interval (IPI) refers to the time between a live birth and the beginning of a subsequent pregnancy. Both short and long intervals are associated with different types of complications:
Short IPI (<18 months) risks:
- Increased risk of preterm birth (35% higher risk with IPI <18 months) 3
- Higher rates of small for gestational age infants 3
- Increased risk of perinatal deaths (3.83 times higher risk) 3
- Higher risk of placenta previa (2.58 times higher odds) 4
- Increased risk of premature rupture of membranes 4
- Higher risk of fetal malposition (OR 3.84) and fetal growth restriction (OR 2.06) 5
- Increased risk of hypertensive disorders (OR 1.86) 5
Long IPI (≥60 months) risks:
- Higher risk of preterm labor (OR 3.82) 5
- Increased risk of oligohydramnios (OR 2.54) 5
- Higher rates of gestational diabetes (OR 2.19) 5
- Increased risk of maternal anemia (OR 1.45) 5
Recommendations Based on Patient Factors
General Population:
- Aim for an interpregnancy interval of at least 18 months after a live birth before conceiving again 2
- This represents a shift from previous WHO recommendations of 24 months 2
Special Populations:
After Cesarean Delivery:
- Longer intervals (≥24 months) are particularly important to reduce the risk of uterine rupture in subsequent pregnancies 2
Advanced Maternal Age (≥35 years):
- Shorter intervals may be acceptable due to declining fertility with age 2
- Balance the risks of short IPI against the risks of delayed childbearing
After Pregnancy Loss:
- After spontaneous or induced abortion, shorter intervals may be acceptable 2
- No need to delay conception after early pregnancy loss
Bariatric Surgery:
- Postpone pregnancy until weight stabilization is achieved 1
- Typically 1 year after sleeve gastrectomy or gastric bypass procedures 1
- 2 years after adjustable gastric banding 1
Contraception Strategies to Achieve Optimal Spacing
Immediate Postpartum Period:
- All women have low risk of pregnancy in first 3 weeks postpartum 6
- By 4 weeks postpartum, fertility may return in non-breastfeeding women 6
Contraceptive Options:
- Long-acting reversible contraception (LARC) methods are highly effective:
- IUDs can be inserted within 10 minutes after delivery of placenta 6, 1
- Implants can be inserted immediately postpartum 6
- Progestin-only pills can be started immediately postpartum 6
- Combined hormonal methods become safer options after 42 days postpartum if no additional risk factors for thrombosis are present 6
Breastfeeding Considerations:
- Lactational Amenorrhea Method (LAM) provides <2% risk of pregnancy in first 6 months if:
Clinical Implications
- Approximately 33% of pregnancies in the US are conceived within 18 months of a previous birth 4
- In Ethiopia, about 9% of preterm births, 21% of term low birth weight, and 41% of perinatal deaths could be prevented by avoiding IPI <18 months 3
- Women with previous pregnancy complications have higher absolute risks but may have lower relative risks with short IPI compared to women without previous complications 7
Common Pitfalls to Avoid
- Assuming infertility during breastfeeding - Pregnancy can occur even before first postpartum menses 6
- Misunderstanding LAM criteria - All three criteria must be met for effectiveness 6
- Ignoring changes in breastfeeding patterns - Supplemental feeding increases pregnancy risk 6
- Delaying too long between pregnancies - Long intervals (≥60 months) carry their own risks 5
- One-size-fits-all approach - Consider individual factors like maternal age and previous pregnancy outcomes 2
By counseling patients about optimal interpregnancy intervals and providing effective contraception in the postpartum period, healthcare providers can help reduce the risk of adverse maternal and fetal outcomes in subsequent pregnancies.