Rates of unintended pregnancy in US at historic low

March 16, 2016

Data from the National Center Health Statistics (NCHS) show that rates of unintended pregnancy in the United States have a hit a 3-decade low.

Data from the National Center Health Statistics (NCHS) show that rates of unintended pregnancy in the United States have a hit a 3-decade low. In 2011, 45% of pregnancies (2.8 million) were unintended compared with 51% in 2008 and the authors of a new report in The New England Journal of Medicine  believe that changes in contraceptive use, particularly long-acting methods, may have contributed to the downward trends.

To calculate the incidence of unintended pregnancy in 2011, researchers from The Guttmacher Institute used US data on pregnancy intentions released in December 2014 by NCHS. They estimated the total number of pregnancies that ended in birth, miscarriage, and inducted abortion and calculated the percentages of each of the outcomes that were unintended and then divided the total number of unintended pregnancies by the population of women and girls aged 15 to 44.

Pregnancy intention was based on a woman’s answers to questions on a retrospective survey about the desire to become pregnant right before each pregnancy occurred. A pregnancy was considered mistimed if a woman wanted to become pregnant in the future but not when the current pregnancy occurred. A pregnancy was unwanted if a woman did not want to become pregnant at any time. Unintended pregnancies comprised those that were mistimed or unwanted.

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The rate of unintended pregnancy, the researchers found, declined by 18% over the period from 2008 to 2011, the first substantial decline since 1981. At the same time, the rate of intended pregnancy increased from 51 to 53 per 1000 women and the overall rate of pregnancy decreased from 106 to 98 per 1000 women.

In 2011, women aged 20 to 24 had the highest rates of unintended pregnancy, followed by those aged 18 to 19 and aged 25 to 29. Rates of unintended pregnancy declined across most demographic groups, with the largest reduction in Hispanics. The higher a woman’s income and the greater her educational level, the less likely she was to have an unintended pregnancy. No substantial variation was seen in rates of abortion of unintended pregnancies by age group, although among girls aged 15 to 17, the percentage did increase.

Commenting on the reasons for the trends, the authors noted that “overall use of any method of contraception among women and girls at risk for unintended pregnancy increased slightly between 2008 and 2012. More important, the use of highly effective long-acting methods, particularly intrauterine devices, among U.S. females who used contraception increased from 4% to 12% between 2007 and 2012.” They also speculated that during the recession, some women may have postponed childbearing and then had intended pregnancies between 2008 and 2011.

NEXT: Does labor induction in older women increase cesarean risk?

 

Does labor induction in older women increase cesarean risk?

Results of a recent UK randomized controlled trial published in The New England Journal of Medicine suggest that inducing labor at 39 weeks’ gestation in women aged 35 or older may not increase the risk of cesarean delivery.

Researchers assessed outcomes in 619 primigravidas aged 35 or older but the trial, which was conducted at 38 hospitals and 1 Primary Care Trust organization in UK, was not powered to look at the effects of labor on stillbirth. The women were randomly assigned to either labor induction between 39 weeks 0 days and 39 weeks 6 days gestation or to expectant management. In most participating institutions, induction was with prostaglandin followed, if necessary, by amniotomy and oxytocin infusion.

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Following an intention-to-treat analysis, researchers found no significant differences in the number of cesarean deliveries between the 2 groups. Of the 304 women in the induction group, 98 had cesarean deliveries versus 103 of the 314 women in the expectant management group (relative risk [RR], 0.99; 95% confidence interval [CI], 0.87 to 1.14). In addition, no significant difference was seen between the 2 groups in use of forceps or vacuum during vaginal delivery (115 of 304 induction versus 104 of 314 expectant management group [RR, 1.30; 95% CI, 0.96 to 1.77]). No maternal or infant deaths were recorded and no significant difference between the two groups was seen in the frequency of adverse events.

The researchers concluded that inducing labor at 39 weeks’ gestation in women aged 35 or older does not appear to have a significant impact on the rate of cesarean delivery nor does it adversely affect short-term maternal or neonatal outcomes. They noted, however, that the results may not be generalizable to older multiparas or apply to all nulliparas aged 35 and older because only nulliparas who did not have high-risk pregnancies were enrolled. 

NEXT: Does prenatal vitamin D boost bone in neonates?

 

Does prenatal vitamin D boost bone in neonates?

A study by UK researchers shows that taking 1000 IU/day of vitamin D is safe and effective for pregnant women but does not increase bone mineral content (BMC) in their offspring. However, the results of dual-energy x-ray absorptiometry (DXA) in the infants also hint at the intriguing possibility that babies born during the winter may get some benefit from the supplements taken by their mothers.

Published in The Lancet, the findings are from the Maternal Vitamin D Osteoporosis Study (MAVIDOS), a multicenter, double-blind, randomized, placebo-controlled trial performed at three sites in UK. The women who participated were aged 18 or older and had singleton gestations <17 weeks and serum 25-hydroxyvitamin D (252[OD]D) concentrations of 25-100 nmol/L at 10 to 17 weeks’ gestation.

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Randomization was to either 1000 IU/day of vitamin D or placebo, taken orally from 14 weeks’ gestation (or as soon as possible before 17 weeks’ gestation) until delivery. The whole-body BMC of the women’s offspring was assessed within 2 weeks of birth with DXA. The authors also assessed the safety of the vitamin supplementation.

A total of 1134 women participated in the study, 565 of whom received vitamin D and 569 of whom received placebo. DXA scans were performed on 367 (65%) of the infants born to the women in the vitamin D group and 370 (65%) of the infants born to the women in the placebo group.

No significant differences were seen between the BMC of infants whose mothers had taken vitamin D and those who mothers took placebo (61.6 g [95% CI 60.3-62.8] vs 60.5 g [95% CI 59.3-61.7], respectively; P=0.21). More women in the placebo group (96 [17%]) than in the vitamin D group (65 [12%]) had severe postpartum hemorrhage but there were no other differences in safety outcomes. 

In a secondary analysis, interestingly, the authors found an interaction between the effect of supplementation with vitamin D and the season in which the infants were born. “For births in the winter,” the researchers said, “neonatal BMC, bone area, BMD, and body fat, but not birthweight or birth length, were greater in offspring of mothers who had received cholecalciferol than in the offspring of mothers who had not.” The finding, they said, is biologically plausible and consistent with previous data but further study in larger populations is necessary to determine its public health significance.