In a past work position, one part of my job was to review the functional capacities of people relative to injuries, capabilities, etc. Then I would relate those work restrictions to a person’s job to see if work accommodations should be required to allow those people to safely perform their work duties. Sometimes matching functional work capacities to job duties is clear cut, other times it is less so, due to the accuracy of the person’s functional capacity limits or due to the level of physicality of the job.
Today’s post relates to the accuracy of work capacities in pregnancy. Until this article, there was ONLY one guideline available to identify suitable and safe lifting restrictions for pregnant women, the American Medical Association (AMA) guidelines. The guidelines define permissible weight limits ‘that healthy employees with normal uncomplicated pregnancies should be able to perform… without undue difficulty or risk to the pregnancy’. These weights are:
- Lifting more than 23 kg (51 lbs) is permitted repetitively for the first half of pregnancy (up to Week 20) and intermittently through Week 30.
- Between Weeks 20 and 24, repetitive lifting up to 23 kg (51 lbs) is permitted. A weight limit of 11 kg (24 lbs) is specified after Week 24.
- After Week 30, intermittent lifting up to 11 kg (24 lbs) is permitted.
If you think this is a lot to lift, you may be right (read on)…
The researchers were interested in using an in depth tool to determine if the above guidelines could be better. To do so, they applied the National Institute for Occupational Safety and Health’s (NIOSH) recommended lifting levels (RWLs) to pregnant women. They also completed an extensive literature review to ensure that pregnant workers were sufficiently protected from any other risk!
The NIOSH lifting equation is a widely used ergonomic tool that quantifies safe lifting based on:
- Horizontal reach distance
- Vertical height of the lift
- Symmetry (with respect to twisting of the spine during the lift)
- Duration of lifting
- Type of hand holds in the item to be lifted
Guess what? If you said that the existing lifting limits were too much, you were RIGHT!
The researchers found that the original AMA guidelines were substantially higher than the ergonomic calculated limits (using NIOSH lifting equation).
When that person is lifting in non-ideal lifting conditions (for example from above shoulder level) the ideal lifting weights are even lighter. The shear fact of being pregnant, by definition, makes most lifts non-ideal due to the increased horizontal reach distance imposed by increased abdominal girth; due to the growing baby, the horizontal load distance will also substantially increase through the pregnancy. So, the recommended weight limits from the first half of pregnancy will not be protective enough for the second half.
Other pregnancy risk reduction strategies:
- Limit constrained postural demands (ie: prolonged standing, stooping)
- Limit frequent/prolonged back bending (for more than 1 hour / day)
- Limit work overhead
- Limit bending forward
- Limit picking up objects from the floor in the later stages of pregnancy
Also important to note: the recommended weight limits guidelines are violated when the lifting frequency exceeds 3 lifts per minute. Job risk analyses should be completed to consider all risks for the pregnant worker and actions at this point may prohibit lifting or choosing a lifting condition more acceptable may be recommended by a treatment practitioner.
The below recommendations present lifting thresholds that most pregnant workers with uncomplicated pregnancies should be able to perform without increased risk of adverse maternal and fetal health consequences.
Waters, T., MacDonald, L., Hudock, S. & Goddard, D. (2014). Provisional Recommended Weight Limits for Manual Lifting During Pregnancy. Human Factors, 56 (1): 203–214.