Curtin School of Population Health, Curtin University, Perth, Western Australia, Australia.
School of Public Health, University of Adelaide, Adelaide, South Australia, Australia.
PLoS One. 2021 Jul 19;16(7):e0255000. doi: 10.1371/journal.pone.0255000. eCollection 2021.
Most evidence for interpregnancy interval (IPI) and adverse birth outcomes come from studies that are prone to incomplete control for confounders that vary between women. Comparing pregnancies to the same women can address this issue.
We conducted an international longitudinal cohort study of 5,521,211 births to 3,849,193 women from Australia (1980-2016), Finland (1987-2017), Norway (1980-2016) and the United States (California) (1991-2012). IPI was calculated based on the time difference between two dates-the date of birth of the first pregnancy and the date of conception of the next (index) pregnancy. We estimated associations between IPI and preterm birth (PTB), spontaneous PTB, and small-for-gestational age births (SGA) using logistic regression (between-women analyses). We also used conditional logistic regression comparing IPIs and birth outcomes in the same women (within-women analyses). Random effects meta-analysis was used to calculate pooled adjusted odds ratios (aOR).
Compared to an IPI of 18-23 months, there was insufficient evidence for an association between IPI <6 months and overall PTB (aOR 1.08, 95% CI 0.99-1.18) and SGA (aOR 0.99, 95% CI 0.81-1.19), but increased odds of spontaneous PTB (aOR 1.38, 95% CI 1.21-1.57) in the within-women analysis. We observed elevated odds of all birth outcomes associated with IPI ≥60 months. In comparison, between-women analyses showed elevated odds of adverse birth outcomes for <12 month and >24 month IPIs.
We found consistently elevated odds of adverse birth outcomes following long IPIs. IPI shorter than 6 months were associated with elevated risk of spontaneous PTB, but there was insufficient evidence for increased risk of other adverse birth outcomes. Current recommendations of waiting at least 24 months to conceive after a previous pregnancy, may be unnecessarily long in high-income countries.
大多数关于妊娠间隔（interpregnancy interval，IPI）和不良出生结局的证据来自于那些容易受到不同女性之间混杂因素不完全控制的研究。将妊娠与同一女性进行比较可以解决这个问题。
我们进行了一项国际纵向队列研究，纳入了来自澳大利亚（1980-2016 年）、芬兰（1987-2017 年）、挪威（1980-2016 年）和美国加利福尼亚州（1991-2012 年）的 3849193 名女性的 5521211 次妊娠。IPI 是根据两次妊娠之间的时间差（第一次妊娠的出生日期和下一次（索引）妊娠的受孕日期）计算的。我们使用逻辑回归（基于女性的分析）来估计 IPI 与早产（PTB）、自发性早产（spontaneous PTB）和小于胎龄儿（small-for-gestational age births，SGA）之间的关系。我们还使用条件逻辑回归比较了同一女性的 IPI 与出生结局（基于女性的分析）。随机效应荟萃分析用于计算汇总调整后的优势比（adjusted odds ratio，aOR）。
与 IPI 为 18-23 个月相比，IPI<6 个月与总体 PTB（aOR 1.08，95%CI 0.99-1.18）和 SGA（aOR 0.99，95%CI 0.81-1.19）之间的关联证据不足，但在基于女性的分析中，自发性 PTB 的发生风险增加（aOR 1.38，95%CI 1.21-1.57）。我们观察到与 IPI≥60 个月相关的所有出生结局的发生风险增加。相比之下，基于女性的分析显示，IPI<12 个月和>24 个月与不良出生结局的发生风险升高有关。
我们发现较长的 IPI 后不良出生结局的发生风险持续升高。IPI<6 个月与自发性 PTB 的风险增加相关，但目前尚无足够证据表明其他不良出生结局的风险增加。目前建议在前次妊娠后至少等待 24 个月再怀孕，这在高收入国家可能是不必要的。
