Is lifting heavy loads in work harmful to pregnancy?

This paper studied the association between women lifting heavy loads in work and preterm birth and fetal deaths. 

Among pregnant women who work, many can be involved in physically demanding work and have to lift heavy weights. The risk of miscarriage (death of fetus) and preterm birth (birth before the 37th week of pregnancy) associated with heavy lifting has been studied previously. However previous studies had various limitations such as not studying women who lifted more than 200 kg per day.  

68,086 women who worked were studied. They were asked about the loads they carried each day through a telephone interview at the 16th week of pregnancy. 

48% of women lifted more than 15kg of weight a day.

There was no relationship between lifting of increasingly heavier loads and increased risk of fetal death when other factors were taken into consideration. However, women with a history of prior fetal death and who lifted more than 200 kg/day had a 2.87 times increased risk of fetal death.

There were a total of 3,128 preterm births. It was found that an increased total load lifted per day was associated with an increased risk of preterm birth. Women who lifted 101-975 kg/day were 25% more at risk of preterm birth. Specifically,  women in their first pregnancy who lifted more than 200 kg/day were 43% more at risk of preterm birth. 

The authors concluded that even though lifting of heavy loads was not associated with high risks, pregnant women should limit levels of heavy occupational lifting.

Data about the load women lifted was only collected once, but this load might change during the course of the study and affect results. 

Lifting of heavy loads in work could affect your pregnancy and should be avoided where possible.