Women May Not Need to Delay Pregnancy After an Initial Miscarriage by Laurie Barclay, MD

Very interesting study to those that have been affected by miscarriage. Personally, we were usually told that we could begin trying for another pregnancy after one normal menstrual cycle without trying. Due to things out of our control, conception of Abigail occurred approximately 5 months after our last miscarriage. That was the longest length of time between pregnancies for us. Now for the article (feel free to skip down to "Clinical Context" for a little less medical jargon).

August 26, 2010 — Women may not need to delay pregnancy after an initial miscarriage, according to the results of a retrospective, Scottish population–based cohort study reported Online First August 5 in the BMJ.
 
"How long a couple should wait before trying for another pregnancy after a miscarriage is controversial," write Eleanor R. Love, from the University of Aberdeen in Aberdeen, Scotland, and colleagues. "Some clinicians believe that there is little justification for delaying the next pregnancy, as an increased interpregnancy interval is unlikely to improve perinatal outcomes, whereas a new viable pregnancy and the birth of a child could enhance the women's chances of recovery.... Current guidelines from the World Health Organization recommend that women should wait for at least six months before trying again, whereas others suggest a delay of up to 18 months, based on reports that interpregnancy intervals of 18-23 months after a live birth can enhance maternal and perinatal outcomes in the next pregnancy."

The goal of this study was to evaluate the optimal interval to subsequent pregnancy after miscarriage in a first recorded pregnancy. At Scottish hospitals between 1981 and 2000, a total of 30,937 women who had a miscarriage in their first recorded pregnancy and subsequently became pregnant were followed up during the second pregnancy. The main study outcome was miscarriage, live birth, termination, stillbirth, or ectopic pregnancy in the second pregnancy, and secondary endpoints were rates of cesarean and preterm delivery, low birth weight infants, preeclampsia, placenta previa, placental abruption, and induced labor in the second pregnancy.

Compared with an interval of 6 to 12 months between the miscarriage and second conception, an interval less than 6 months was associated with lower risks for repeated miscarriage (adjusted odds ratio [OR], 0.66; 95% confidence interval [CI], 0.57 - 0.77), termination (OR, 0.43; 95% CI, 0.33 - 0.57), and ectopic pregnancy (OR, 0.48; 95% CI, 0.34 - 0.69). The risk for an ectopic second pregnancy was greater with an interpregnancy interval exceeding 24 months (OR, 1.97; 95% CI, 1.42 - 2.72), as was the risk for termination (OR, 2.40; 95% CI, 1.91 - 3.01).
Compared with women who had an interpregnancy interval of 6 to 12 months, those who conceived again within 6 months and had a live birth in the second pregnancy were less likely to have a cesarean delivery (OR, 0.90; 95% CI, 0.83 - 0.98), preterm delivery (OR, 0.89; 95% CI, 0.81 - 0.98), or low-birth-weight infant (OR, 0.84; 95% CI, 0.71 - 0.89). However, they were more likely to have labor induced (OR, 1.08; 95% CI, 1.02 - 1.23).

"Women who conceive within six months of an initial miscarriage have the best reproductive outcomes and lowest complication rates in a subsequent pregnancy," the study authors write.
Limitations of this study include potential lack of uniformity in documenting gestational age and outcomes of interest as well as possible misclassification. This study also evaluated only miscarriages that led to hospital contact, and the findings therefore cannot be generalized to all women with a miscarriage.

"Our research shows that it is unnecessary for women to delay conception after a miscarriage," the study authors conclude. "As such the current WHO [World Health Organization] guidelines may need to be reconsidered. In accordance with our results, women wanting to become pregnant soon after a miscarriage should not be discouraged."

In an accompanying editorial, Julia Shelley, associate professor of health and social development at Deakin University in Melbourne, Australia, discusses some of the methodologic issues regarding this study and earlier studies.

"[A]ll of the studies have selection and measurement biases that cast doubt on the value and generalisability of their findings," Dr. Shelley writes. "Of greatest concern is that women with short interpregnancy intervals are more fertile than those whose subsequent pregnancy occurs later because these women seem to have better pregnancy outcomes and fewer complications. Further research into this question may need to wait for data from more sophisticated linked primary care and hospital datasets or specifically designed research studies that can measure and account for such differences, even if they will not be able to control for them."

This research was partially funded by the Chief Scientist's Office in Scotland. Two of the study authors were employed by the University of Aberdeen at the time of doing this research and are independent from the funders. Ms. Love is a medical student, and another study author is employed by NHS Grampian. Dr. Shelley has disclosed no relevant financial relationships.
BMJ. 2010;341:c3967. Abstract
Additional Resource
Previous guidelines issued on management of early pregnancy loss are published online on the Agency for Healthcare Research and Quality Web site, and guidelines on investigation and medical treatment of recurrent miscarriage were published in the journal of Human Reproduction.

 

Clinical Context

Miscarriage, or spontaneous pregnancy loss before 24 weeks of gestation, affects 1 in 5 pregnancies. Women who have miscarried are more likely to experience threatened miscarriage, preterm birth, induced labor, and postpartum hemorrhage in the second pregnancy. However, the best interpregnancy interval for maternal and fetal outcomes after a first miscarriage is not well known. The World Health Organization recommends a wait of 6 months before attempting a next pregnancy after miscarriage; longer waits have also been recommended.
This is a retrospective cohort study of women with a first miscarriage who went on to a second pregnancy to examine the association between interpregnancy interval and outcomes of a second pregnancy.

 

Study Highlights

• The investigators conducted this study on data from the Information Services Division of the National Health Service of Scotland, United Kingdom, using anonymized patient data.
• They used a retrospective cohort design extract data on all women with a first miscarriage between 1981 and 2000 and who went on to a second pregnancy, as identified by internal linkage of datasets using probability matching.
• Women who had twin or multiple pregnancies and improbable interpregnancy intervals were excluded.
• Women were divided into 5 groups by interpregnancy interval: less than 6 months, 6 to 12 months, 12 to 18 months, 18 to 24 months, and more than 24 months.
• Admission dates less than 4 weeks apart for the first and second pregnancy events were assumed to be related to the same event.
• The primary endpoint was reproductive outcome in the second pregnancy, including miscarriage, ectopic pregnancy, termination, stillbirth, and live birth.
• Confounding factors accounted for were maternal age and socioeconomic status.
• Only 57.2% of women had smoking status recorded.
• Preterm birth was defined as occurring at 36 completed weeks or less of gestation and very preterm birth as less than 32 weeks of gestation.
• Of 34,845 women with data available, 30,937 were included for analysis, of whom 12,744 (41.2%) conceived again within 6 months, 7791 (25.2%) between 6 and 12 months, 2958 (9.6%) between 12 and 18 months, 1995 (6.4%) after 18 to 24 months, and 5449 (17.6%) after 24 months.
• Older women and those with higher social class had shorter interpregnancy intervals.
• Women with interpregnancy intervals of less than 6 months were more likely to be older (26 vs 23.9 years) and were less likely to have ever smoked.
• Live birth rates were highest among women with intervals of less than 6 months (85.2%) and lowest in women with intervals of more than 24 months (73.3%).
• Termination rates had a similar pattern.
• Adverse outcomes were more likely to occur with longer intervals.
• Compared with women with interpregnancy intervals of 6 to 12 months, those with intervals of less than 6 months were less likely to experience another miscarriage (OR, 0.66; 95% CI, 0.57 - 0.77), termination (OR, 0.43; 95% CI, 0.33 - 0.57), or ectopic pregnancy (OR, 0.48; 95% CI, 0.34 - 0.69).
• Women with the longest interpregnancy intervals were more likely to experience an ectopic pregnancy (OR, 1.97; 95% CI, 1.42 - 2.72) or termination (OR, 2.40; 95% CI, 1.91 - 3.01).
• Women with interpregnancy intervals of less than 6 months were less likely to have a cesarean delivery, preterm delivery before 36 weeks, or an infant of low birth weight (< 2500 g) vs women with intervals of 6 to 12 months.
• Women with an interpregnancy interval of more than 24 months were most likely to have a preterm delivery (OR, 1.21; 95% CI, 1.07 - 1.36) or very preterm delivery (OR, 1.40; 95% CI, 1.11 - 1.70) vs women with intervals of 6 to 12 months.
• No association was found between interpregnancy interval and preeclampsia, placenta previa, or placental abruption in the second pregnancy.
• The authors concluded that the best pregnancy outcomes with lowest complication rates after a first miscarriage occurred for short interpregnancy intervals of less than 6 months. They recommended that it was unnecessary for women to delay conception after miscarriage.
• The authors also recommended that unless there were indications preventing a second conception soon after miscarriage, women should be counseled about potential negative effects of waiting more than 18 to 24 months before the next pregnancy, after a first miscarriage.

 

Clinical Implications

• An interpregnancy interval of less than 6 months vs a 6- to 12-month interval after a first miscarriage and subsequent pregnancy is associated with lower risk for ectopic pregnancy, cesarean delivery, and another miscarriage. However, at less than 6 months, labor induction was more likely.
• An interpregnancy interval of more than 24 months vs an interval of less than 6 months or 6 to 12 months after a first miscarriage and subsequent pregnancy is associated with increased risk for preterm birth and low birth weight for a second pregnancy.