How Long Should You Wait between Pregnancies? What Scientific Studies Suggest

Based on the results of 3 studies, it is best that intervals between pregnancy (the interval between the previous live birth and the next pregnancy) are 18 to 23 months to prevent both preterm birth, low birth weight, and small birth size).

Below are the details of the findings:

(1) The interval between pregnancies from 18 to 23 months is able to reduce the odds of pre-term birth and low birth weight.

Otherwise, compared to infants who were conceived 18-23 months later, infants who were conceived less than 6 months later may have 1.3 times lower birth weight, 1.4 times preterm birth, and 1.3 times small size. Infants who were conceived after 120 months or more after the previous live birth have 2 times all of these three adverse outcomes (low birth weight, preterm birth, and small size) after controlling for other factors (such as maternal biological conditions).  

(2) The interval between pregnancies from 18 to 59 months is able to reduce the odds of having premature infants.  

Mothers with intervals between pregnancies of less than 6 months have high risks of having very low birth weight infants (50%-80% increased risk of birth weight below 1.5 kg compared to mothers whose intervals of pregnancies are above 12 months).

Created on December 08 2015 at 04: 56 PM

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Details of Scientific Answers: Click on each bullet to Read References


1: "Effect of the interval between pregnancies on perinatal outcomes ," New England journal of medicine, 1999, by Zhu, B. P., Rolfs, R. T., Nangle, B. E., & Horan, J. M. . (Citations: 329).


1: "Interpregnancy interval and the risk of premature infants," Obstetrics & Gynecology, 2000, by Fuentes-Afflick, E., & Hessol, N. A.. (Citations: 108).


1: "Short interpregnancy intervals and the risk of adverse birth outcomes among five racial/ethnic groups in the United States," American Journal of Epidemiology, 1998, by Khoshnood, B., Lee, K. S., Wall, S., Hsieh, H. L., & Mittendorf, R. . (Citations: 97).

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How Long Should You Wait between Pregnancies? What Scientific Studies Suggest

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