Moving to a new residence during the first three months of pregnancy is linked to a heightened risk of premature birth and low birthweight, as well as a slightly higher risk of a smaller-than-expected-size baby, according to new research from the University of Washington School of Public Health published online July 30 in the Journal of Epidemiology & Community Health.

Still, it’s too soon to raise warning flags.

“I don’t think we have enough information to make any specific recommendations about moving during pregnancy at this point, but I’m hopeful that our study will draw attention to moving as a risk factor worth investigating in more detail,” said Julia Bond, the lead author who conducted the research as a PhD student in the Department of Epidemiology at the School.

Little is known about the potential health impact of a house move during pregnancy. To try to rectify this, the researchers analyzed birth certificate data for babies born in Washington state between 2007 and 2014 to mothers who were 18 or older.

The researchers randomly selected 30,000 women who had moved during the first three months of pregnancy, known as the first trimester, and compared them with 120,000 randomly selected women of the same birth year, but who hadn’t moved during early pregnancy. The first trimester was chosen because previous research has suggested that major stressors during early pregnancy have a greater impact on the health of the baby than those experienced later on in the pregnancy.

The final analysis included 28,011 women who had moved early in pregnancy and 112,451 who hadn’t. Women who moved early in pregnancy were likely to be younger, to be less educated, to have lower levels of household income and to have had other children than women who hadn’t moved. Researchers noted that this cohort also was more likely to be unmarried and to have smoked during their pregnancy.

These circumstances and behaviors are all potential risk factors for the outcomes the researchers were looking at: low birthweight; premature birth; and smaller–than-expected-size babies.

After taking account of these potentially influential factors, a house move during the first three months of pregnancy was associated with a 37 percent heightened risk of low birthweight and a 42 percent heightened risk of premature birth compared with those who didn’t move during this period. A house move in the first trimester was also associated with a slightly increased risk of giving birth to a smaller-than-expected-size baby.

These differences were seen across women in all social and economic strata that was analyzed. As an observational study, researchers can’t establish cause. The researchers were not able to explore the potential reasons behind their findings, but interruptions to health care, the physical strain of moving, disruptions to social support systems, and a biological stress reaction may all be possible triggers, according to the report. Although the study included a large number of women, the researchers weren’t able to establish the reasons for the participants’ moves or whether they moved into more or less desirable areas, which may have influenced the results.

“Despite these limitations, our results yield important insights regarding moving during pregnancy,” the researchers write in the report. “Regardless of whether the negative impact of moving is driven by the stress from the move itself, stressful situations leading to a move, or disruption of care because of the move, asking patients about plans to move and using that as an opportunity to counsel patients on stress-mitigating techniques and care continuity may be beneficial.”

Co-authors on the study include graduate students Amanda Mancenido, Divya Patil and Seth Rowley, as well as faculty Alyson Littman and Jack Goldberg, all of the UW.