First Steps to First Kicks: A Sweet Spot for Timing that Next Pregnancy

Some parents may daydream about the life they want to build. It may involve the pitter patter of tiny footsteps on the floor, or maybe it’s the sound of multiple children laughing and playing in the backyard. Creating a family can involve seemingly endless decisions, especially as it relates to timing the next pregnancy. Will the children be close enough in age to play together? Will they get along if they are too close in age? These questions may replay in the minds of parents as they decide what's right for their unique family. With these things considered, parents should also consider the ideal spacing in order to avoid additional pregnancy and birth complications. So, how close is too close? Let's dive into this idea.

Firstly, let's discuss the definition of spacing between pregnancies. The timing between pregnancies is called the interpregnancy interval (IPI) and is the time between pregnancies when a woman is not pregnant. It's not to be confused with the time between birth. For example, if a woman gives birth in January and becomes pregnant the following January, the time between pregnancies would be one year, whereas the age difference between those children would be about 1 year and 9 months.

The American College of Obstetricians and Gynecologists suggests the ideal interpregnancy interval is 18 months or more and that women should avoid getting pregnant within 6 months after the birth of a child.¹ The World Health Organization remains more conservative, advising women to wait at least 24 months after childbirth to attempt a subsequent pregnancy.³ There is debate as to whether the WHO recommendation is applicable to women in the United States or other developed countries, since pregnancy, nutrition, and other variables differ between the US and lower-resource countries.⁶ One exception to the recommended interpregnancy spacing is after miscarriage or induced abortion, where the interval is much smaller and a subsequent pregnancy can be attempted after 6 months.³ Most data looking at pregnancy spacing assesses the risk of spacing pregnancies too closely, but pregnancies spaced too far apart may also pose risks. Intervals of over 5 to 10 years between pregnancies may also be associated with complications.¹

Getting pregnant too soon after having a baby can pose risks to the mother, infant, and may adversely affect other siblings that may still be breastfeeding. Most studies evaluating complications related to pregnancy spacing grouped the spacing by intervals of less than 6 months, 6 - 11 months, and over 18 months. Therefore, there are limitations in interpreting the risks involved with pregnancy spacing outside of those intervals, between 12 and 18 months. 

Several pregnancy-related complications may arise with shorter interpregnancy intervals. Data suggests that risk of preterm birth, or birth of a baby at less than 37 weeks gestation, increases as the IPI decreases.^2,6 Premature rupture of membranes, the rupture of membranes before labor has begun, may occur in women with an IPI of less than 2 years.⁴ In women who have previously undergone a a cesarean section (C-section), the risk of uterine rupture is significantly increased with birth spacing of 18 months, which equates to an approximate IPI of less than 9 months.¹ Further, adverse birth outcomes appear to decrease as the pregnancy spacing increases, where adverse outcomes are highest with an IPI of less than 6 months, lower with an IPI of 6 -11 months, and further reduced with an IPI of 12 -17 months.²

Adverse maternal outcomes may be explained by inadequate repletion of maternal nutrients, insufficient time to lose pregnancy weight, incomplete healing of incision site after cesarean section, and other factors. Placental abruption and gestational diabetes risk is associated with an IPI of less than 6 months, while risk of obesity is increased when intervals less than 11 months. On the other hand, pre-eclampsia risk appears to be reduced with decreasing IPI, and the risk is increased with an IPI greater than 60 months (or 5 years). Dystocia, or difficult labor, also appears to decrease with an IPI less than 24 months. For mothers attempting a vaginal birth after c-section (VBAC), an IPI less than 6 months is associated with increased risk of uterine rupture, increased blood transfusions, and additional complications related to the bladder and bowels.⁵ The risks to a mother are mainly associated with pregnancy spacing less than 6 months or greater than 5 years.

Short interpregnancy intervals can also have negative implications for the infant, yet most of these effects were limited to scenarios where the IPI was less than 6 months.⁶ Some adverse infant outcomes were associated with infants conceived between 6-11 months after a sibling, but the association was not as strong. Infants conceived less than 6 months after the birth of an older sibling had a marginally increased risk of being small-for-gestation (<10th percentile), an increased risk of preterm birth, and was associated with neonatal death (death <4 weeks after birth), although the data on neonatal death was inconsistent. Stillbirth was not significantly associated with an IPI of less than 6 months.⁶ Pregnancy spacing less than 6 months appears to be associated with most adverse outcomes affecting infants, while spacing less than 12 months may pose those same risks, but to a lesser extent.⁵

Mothers who become pregnant shortly after giving birth may still be breastfeeding. Breastfeeding during pregnancy does not seem to harm an unborn child, nor is it correlated with preterm labor, although milk supply generally decreases 4 - 5 months into a pregnancy.⁹ However, mothers considered at-risk for premature labor may want to discontinue breastfeeding by the 3rd trimester as a precaution.¹⁰ Breastfeeding during pregnancy is considered acceptable as long at the mother receives adequate nutrition and has sufficient caloric intake, while getting a reasonable amount of sleep.¹⁰ After the baby is born from a subsequent pregnancy, a mother may tandem nurse - feeding both children during the same timeframe. This method of nursing is not known to harm breastfeeding children.⁹ The main consideration when planning to become pregnant while breastfeeding is that milk supply may be reduced 4 or 5 months into the pregnancy.

All things considered, the evidence points towards waiting at least 6 months between pregnancies, but it may not be necessary to wait 18 months for mothers who had a previous uncomplicated vaginal birth. Mothers who have undergone a C-section may choose to wait at least 9 months to avoid potential complications and ensure healing of the incision site. Further, mothers who are breastfeeding may want to wait 12 months before attempting a subsequent pregnancy, in order to focus on providing adequate breast milk to their current child (or children).

• References

  1. American College of Obstetricians and Gynecologists. (2019). Interpregnancy care. Obstetrics & Gynecology, 133(1), e51–e72

  2. Thoma, M. E., Copen, C. E., & Kirmeyer, S. E. (2016, April). Short interpregnancy intervals in 2014: Differences by maternal demographic characteristics. NCHS Data Brief, (240). Centers for Disease Control and Prevention. https://www.cdc.gov/nchs/products/databriefs/db240.htm

  3. World Health Organization. (2006) Birth Spacing - report from  WHO technical consultation. Department of Reproductive Health and Research. https://iris.who.int/bitstream/handle/10665/73710/RHR_policybrief_birthspacing_eng.pdf

  4. Lin, D., Hu, B., Xiu, Y., Ji, R., Zeng, H., Chen, H., & Wu, Y. (2024). Risk factors for premature rupture of membranes in pregnant women: a systematic review and meta-analysis. BMJ open, 14(3), e077727. https://doi.org/10.1136/bmjopen-2023-077727

  5. Hutcheon, J. A., Nelson, H. D., Stidd, R., Moskosky, S., Ahrens, K. A., & the Office of Population Affairs. (2019). Short interpregnancy intervals and adverse maternal outcomes in high-resource settings: An updated systematic review. Paediatric and Perinatal Epidemiology, 33(1), O48–O59. https://doi.org/10.1111/ppe.12518

  6. Ahrens, K. A., Nelson, H., Stidd, R. L., Moskosky, S., & Hutcheon, J. A. (2019). Short interpregnancy intervals and adverse perinatal outcomes in high-resource settings: An updated systematic review. Paediatric and perinatal epidemiology, 33(1), O25–O47. https://doi.org/10.1111/ppe.12503

  7. Dewey, K. G., & Cohen, R. J. (2007). Does birth spacing affect maternal or child nutritional status? A systematic literature review. Maternal & child nutrition, 3(3), 151–173. https://doi.org/10.1111/j.1740-8709.2007.00092.x

  8. Source about breastfeeding

  9. La Leche League International. (n.d.). Breastfeeding during pregnancy and tandem nursing. La Leche League International. https://llli.org/breastfeeding-info/breastfeeding-pregnancy-tandem-nursing/

  10.  Stalimerou, V., Dagla, M., Vivilaki, V., Orovou, E., Antoniou, E., & Iliadou, M. (2023). Breastfeeding During Pregnancy: A Systematic Review of the Literature. Maedica, 18(3), 463–469. https://doi.org/10.26574/maedica.2023.18.3.463

Created April 2025.

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