Factors associated with short interpregnancy interval among women treated with in vitro fertilization

The effect of interpregnancy interval on preterm birth and low birth weight in singleton pregnancies conceived without assistance or by infertility treatments

OBJECTIVE

To determine the association of interpregnancy interval on perinatal outcomes and whether this was influenced by mode of conception.

DESIGN

Retrospective cohort.

SETTING

Centers for Disease Control and Prevention's natality national database.

PATIENT(S)

Patients who had an index singleton live birth with a preceding live birth. Index pregnancies from 2016 to 2019 were conceived with in vitro fertilization (IVF) (n = 32,829) or ovulation induction/intrauterine insemination (OI/IUI) (n = 23,016) or without assistance (n = 7,564,042).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The primary outcomes evaluated were preterm birth (<37 weeks) and low birth weight (<2,500 g). Multivariable logistic regression was performed to evaluate the association of interpregnancy intervals with perinatal outcomes stratified by mode of conception. Adjusted odds ratios and 95% confidence intervals (CIs) were presented.

RESULT(S)

Compared with the interpregnancy interval reference group of 12 to <18 months, a <12 month interpregnancy interval was associated with an increase in preterm birth (<37 weeks) for pregnancies conceived with OI/IUI or without assistance (aOR, 1.42; 95% CI, 1.16-1.74, and aOR, 1.14; 95% CI, 1.13-1.15, respectively), whereas IVF was not associated with an increase (aOR, 0.90; 95% CI, 0.77-1.04). A <12 month interpregnancy interval was associated with an increase in low birth weight for pregnancies conceived with IVF or OI/IUI or without assistance (aOR, 1.34; 95% CI, 1.09-1.64; aOR, 1.33; 95% CI, 1.01-1.76; and aOR, 1.26; 95% CI, 1.24-1.27, respectively).

CONCLUSION(S)

An interpregnancy interval of at least 12 months reduces adverse perinatal outcomes for pregnancies conceived with and without infertility treatment.

Conception after early IVF pregnancy loss: should we wait?

RESEARCH QUESTION

Is the interval length between an early pregnancy loss and the following treatment cycle a predictor for achieving clinical pregnancy among IVF patients?

DESIGN

This retrospective cohort study of 257 women who reinitiated treatment after first-trimester IVF pregnancy loss was conducted at a tertiary, university-affiliated medical centre between 1 January 2014 to 1 January 2018. Women aged 18-40 years, with normal uterine cavity, who experienced first-trimester pregnancy loss at less than 14 weeks after IVF, were included. Miscarriages were classified as spontaneous, biochemical, medical or surgical.

RESULTS

Among 257 women, interval to subsequent IVF treatment was not associated with achieving pregnancy. Patients after biochemical pregnancy (72.7 ± 56.4, median 60 days) or spontaneous miscarriage (97.7 ± 93.1, median 66 days) had shorter intervals to next cycle, compared with medical (111.9 ± 103.2, median 65 days) or surgical (123.4 ± 111.1, median 84 days) (Kaplan-Meier, P = 0.03) miscarriages. Logistic regression analysis showed that the chance of subsequent pregnancy was affected by the number of embryos transferred (P = 0.009) and the type of miscarriage. Medical (P = 0.005) and surgical (P = 0.017) miscarriages were related to lower likelihood of pregnancy compared with biochemical pregnancy (reference group). When pregnancy was achieved in the first post-miscarriage cycle, the chance of live birth increased with shorter intervals (median 57.5 days), whereas second miscarriage was related to longer intervals (median 82.5 days) between miscarriage and subsequent IVF cycle (P = 0.03).

CONCLUSION

On the basis of this cohort, IVF should not be postponed after pregnancy loss, as shorter intervals were associated with greater likelihood of live birth.