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Shorter interpregnancy intervals may increase risk of adverse outcomes

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Counseling of women over 35 years differs from that of younger women

While the findings of Schummers et al. appear to encourage pregnancy spacing among women of all ages, women who are 35 or older should be counseled differently than women aged 20-34 years, Stephanie B. Teal, MD, MPH, and Jeanelle Sheeder, MSPH, PhD, wrote in a related editorial.

“Clinicians should understand that women delivering at age 35 years or later may desire more children and may wish to conceive sooner than recommended,” the authors wrote.

Women who are 35 years old or older may not have 6-12 months to delay pregnancy, the authors explained, and thus should be counseled differently than younger patients. Delaying pregnancy in older women may increase the risk of miscarriage and chromosomal abnormalities, and may cause families to miss out on their desired family size. In addition, spacing out births up to 24 months apart does not significantly diminish the risk of fetal or infant risk among women 35 years and older as it does for younger women, which may make short interpregnancy intervals in this group a “rational choice.”

“Simply telling older women to delay conception is not likely to improve health outcomes, as women are aware of their ‘biological clocks’ and many will value their desire for another child over their physician’s warnings,” Dr. Teal and Dr. Sheeder noted. “Clinicians should use patient-centered counseling and shared decision-making strategies that respect women’s desires for pregnancy, possibly at short intervals in women 35 years or older, and adequately discuss fetal, infant, and maternal risks in this context.”

Dr. Teal and Dr. Sheeder are in the division of family planning in the department of obstetrics and gynecology at the University of Colorado in Aurora. Their their comments were made in an editorial in JAMA Internal Medicine (2018 Oct 29. doi: 10.1001/jamainternmed.2018.4734 ). They reported no conflicts of interest.



Short interpregnancy intervals carry an increased risk of adverse pregnancy outcomes for women of all ages and increased adverse fetal and infant outcome risks for women between 20 and 34 years old, according to research published in JAMA Internal Medicine.

“This finding may be reassuring particularly for older women who must weigh the competing risks of increasing maternal age with longer interpregnancy intervals (including infertility and chromosomal anomalies) against the risks of short interpregnancy intervals,” wrote Laura Schummers, SD, of the department of epidemiology at Harvard T. H. Chan School of Public Health, Boston, and her colleagues.

The researchers examined 148,544 pregnancies of women in British Columbia who were younger than 20 years old at the index (5%), 20-34 years at the index birth (83%), and 35 years or older (12%). The women had two or more consecutive singleton pregnancies that resulted in a live birth between 2004 and 2014 and were recorded in the British Columbia Perinatal Data Registry. There was a lower number of short interpregnancy intervals, defined as less than 6 months between the index and second pregnancy, among women in the 35-years-or-older group, compared with the 20- to 34-year-old group (4.4% vs. 5.5%); the 35-years-or-older group instead had a higher number of interpregnancy intervals between 6 and 11 months and between 12 and 17 months, compared with the 20- to 34-year-old group (17.7% vs. 16.6%, and 25.2% vs. 22.5%, respectively).

The risk for maternal mortality or severe morbidity was higher in women who were a minimum 35 years old with 6 months between pregnancies (0.62%), compared with women who had 18 months (0.26%) between pregnancies (adjusted relative risk [aRR], 2.39). There was no significant increase in those aged between 20 and 34 years at 6 months, compared with 18 months (0.23% vs. 0.25%; aRR, 0.92). However, the 20- to 34-year-old group did have an increased risk of fetal and infant adverse outcomes at 6 months, compared with 18 months (2.0% vs. 1.4%; aRR, 1.42) and compared with women in the 35-years-or-older group at 6 months and 18 months (2.1% vs. 1.8%; aRR, 1.15).

There was a 5.3% increased risk at 6 months and a 3.2% increased risk at 18 months of spontaneous preterm delivery in the 20- to 34-year-old group (aRR, 1.65), compared with a 5.0% risk at 6 months and 3.6% at 18 months in the 35-years-or-older group (aRR, 1.40). The researchers noted “modest increases” in newborns who were born small for their gestational age and indicated preterm delivery at short intervals that did not differ by age group.

The authors reported no conflicts of interest. Dr Schummers was supported a National Research Service Award from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, and received a grant from the Canadian Institutes for Health Research and the Public Health Agency of Canada Family Planning Public Health Chair Seed Grant. Two of her coauthors were supported by various other awards.

SOURCE: Schummers L et al. JAMA Intern Med. 2018 Oct 29. doi: 10.1001/jamainternmed.2018.4696.

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