Short & Long Interpregnancy Intervals

Posted On: March 21, 2017 By Nathan D. Fox, MD

Interpregnancy interval (IPI) refers to the time between the birth of one child and conception of the next.  Both short and a long IPI’s have been associated with increased risks in the second pregnancy, including preterm birth, low birth weight, and preeclampsia.

Practically, this information is sometimes used to advise women how to best plan their following pregnancies, and many authorities recommend that women wait at least 18-24 months after the birth of a child before conceiving again.

However, the research supporting a link between IPI and pregnancy outcomes is complex.  Ideally, the best type of study would take a large group of women who just delivered and randomly assign each of them to either get pregnant quickly, or wait 18-24 months and then compare outcomes between these two groups.  For many reasons, this study has not been done and would be very difficult to do.  Since this is the case, the studies on this topic are only descriptive.  Meaning, they compared outcomes between women with different IPI’s, but the researchers had no control over the IPI.  This opens the possibility that the women who got pregnant early are somehow different from women who waited 18-24 months. Any differences in outcomes seen between the groups of women may be due to the baseline differences, and not due to the different IPI’s.  For example, women who got pregnant quickly may not have good access to healthcare and contraceptive options.

To illustrate this, several studies examining IPI’s that controlled for baseline differences between the groups of women did not find a strong correlation between short and long IPI’s and adverse pregnancy outcomes. However, one recent study showed that a short IPI was associated with starting the second pregnancy at a higher weight, which also led to higher rates of gestational diabetes. This finding makes sense as a short IPI might not give women enough time between pregnancies to lose the weight they gained in the first pregnancy.

So, what is the ideal time to wait between pregnancies?  Nobody knows for sure and the decision needs to be individualized. Certainly, it is best to enter any pregnancy in good overall health, and at a healthy weight (not too low and not too high).  If waiting for a few more months can achieve that goal, it is probably worthwhile.  However, for a healthy woman with a normal weight, it is not clear if waiting 18-24 months is truly necessary.  For more information, visit our blog page or contact us today!

Carnegie Imaging for Women blogs are intended for educational purposes only and do not replace certified professional care. Medical conditions vary and change frequently. Please ask your doctor any questions you may have regarding your condition to receive a proper diagnosis or risk analysis. Thank you!

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