Today on the blog, we're revisiting one of the most popular topics we've covered: How soon is too soon to have another baby?
We’re always interested in digging into new research that relates to perinatal health, so when a new study was released that updates recommendations on inter-pregnancy intervals, we had to dig in.
As a quick refresher, prior research has suggested that an 18 month gap between the birth of one baby and conception of another is ideal for optimal pregnancy outcomes, while other research acknowledges that it may be more important to consider the length of the recuperative interval - the time that a woman is not pregnant or lactating.
This new research calls into question the length of these prior intervals. Below, we take a closer look.
A note to loss mamas: we also cover the research on conceiving again after early pregnancy loss. In presenting this research, we aim to empower you with helpful information, never to make you feel rushed or pressured to try again before you feel physically and emotionally ready. Feel free to skip this post if the topic of loss and conceiving again is a trigger for you. ♥️
Study conclusion
The study concludes that it found insufficient evidence for association between short interpregnancy interval and adverse birth outcomes, except for a slightly elevated odds of spontaneous preterm birth for interpregnancy intervals less than 6 months. The study also concludes that previous recommendations for parents to wait at least 24 months may be unnecessarily long in high-income countries. Conversely, the study found consistently elevated odds of adverse birth outcomes for births following long interpregnancy intervals (in both the 60 - 119 months category and greater than 120 months category) and suggested that recommendations regarding long IPI are required.
The resulting headline?
Women don't have to wait as long between pregnancies.
Study limitations
However, this study has a number of limitations that cause us to take pause before accepting that headline, and updating the research in our prior piece on the topic:
- It does not consider a number of variables that could impact pregnancy outcomes (e.g., length of breastfeeding a first child, nutritional status after a first child, nutritional status during second pregnancy, use of other medications or substances before or during pregnancy, etc.). (“We could not analytically explore a range of time-varying potential covariates such as pre-pregnancy body mass index, diet during pregnancy, maternal medical conditions, and fertility treatment due to lack of complete information in the cohorts across countries.”)
- It measures pregnancy outcomes by preterm birth or small for gestational age babies and uses this to assume nutritional status (“Given the lack of observed associations between overall preterm and small for gestational age with short interpregnancy interval, our findings do not provide support for the maternal depletion hypothesis.”) However, a number of other adverse outcomes could result from compromised nutritional status and shortened interpregnancy interval which are not considered in this study.
- Outcomes measured are short term and do not consider a baby or mother's health status after birth, both of which could be dramatically influenced by the interpregnancy interval, the recuperative interval (the time not breastfeeding), and of course nutrition status. As we know, effects of low nutrition status in pregnancy and postpartum can have serious short- and long-term health effects on both mother and baby that may not become apparent for several years.
- While the data included a large population of women from four high income countries (Australia, Finland, Norway, and United States), the highest proportion of women were between the ages of 20 and 24 years old in the United States, much lower than the current average age for a pregnant woman. However the highest proportion of women in the other countries was between the ages of 25 and 29 years, more representative of the current average pregnancy age.
The takeaway?
As with gestational length, there seem to be heightened risks on either end of "optimal" when it comes to interpregnancy interval. However, there are a number of outcomes other than small for gestational age and preterm birth that should also be considered when evaluating one’s own ideal interval between pregnancies.
In general, we are skeptical of broad headlines that summarize research so broadly and simply, and we will always take the time to dig into the details to understand all of the implications.
A note on conception after loss
Because pregnancy and conception is often not linear, and pregnancy loss is far more common than is often acknowledged, we also wanted to touch on what we know about conception and pregnancy outcomes after early (First Trimester) loss.
Many women may follow a recommendation to wait at least six months following an early loss. However, research suggests that women who begin trying to achieve pregnancy within three months of loss (non-ectopic and non-molar) have just as fast, if not faster, time to pregnancy leading to a live birth, as women who wait until 3-6 months to start trying. The study also found that women with a long intertrying interval (greater than 12 months versus 0–3 or 3–6 months) had significantly lower fecundability (the probability of achieving a pregnancy within one menstrual cycle) after taking into account many confounding factors including a history of subfertility.
While this study didn’t specifically look at pregnancy outcomes, it did find that there was no significantly increased risk for any pregnancy complication (including pregnancy loss, preterm birth, preeclampsia, and gestational diabetes) among women with an intertrying interval 0–3 months versus greater than three months.
Of course, this study did not take into account the emotional aspect of pregnancy loss. For many couples, trying again immediately after loss may be emotionally difficult, and presenting this research certainly isn’t to suggest that a couple should feel pressured or rushed to try again before they are both physically and emotionally ready.
Our conclusion is the same
Ultimately, the best thing you can do to optimize the health of you and all of your babies is to make sure that you’re taking good care of your body throughout the important periods of preconception, pregnancy, postpartum, and pregnancy loss. Getting adequate sleep, minimizing stress, and ensuring proper nutrition through a balanced diet and a comprehensive prenatal vitamin along with Omega-3s and a Probiotic will only improve your chances of a healthy pregnancy, no matter what your journey looks like.
