Vitamin D deficiency increases the risk of complicated deliveries, states study
A research team at Uppsala University has identified a clear link between osteomalacia – a form of bone softening commonly caused by vitamin D deficiency – and a fivefold increased risk of emergency caesarean sections or the need for vacuum-assisted delivery. The study is based on a prospective cohort of pregnant women in Sweden and is published in the journal Bone.
“Our findings suggest that osteomalacia, in which vitamin D deficiency is a key underlying cause, may influence the course of labour in ways that increase the need for urgent obstetric interventions,” says Paul Kalliokoski, Specialist General Practitioner, Senior Lecturer and first author of the study.
The study examined 52 Somali and 71 Swedish women registered at the maternity health centre in Borlänge, on two occasions. The aim was to analyse the impact of osteomalacia – a serious complication of vitamin D deficiency – on the risk of vacuum-assisted delivery or emergency caesarean section in women at high risk of vitamin D deficiency, compared with women expected to have higher vitamin D levels.
Suction cup and emergency cesarean section
On the first occasion, during pregnancy, blood samples, questionnaires and clinical examination were carried out. Two years later, registry data were collected, with diagnostic codes for delivery methods. Women with miscarriages, stillbirths or who had moved away from the region were excluded. Osteomalacia was confirmed by diagnostic criteria and was based on a non-invasive, non-radiation protocol. Associations between osteomalacia and delivery outcomes were analysed using multinomial logistic regression, adjusted for a minimal sufficient set of confounders.
Of the participants, 20 women, 19 Somali and one Swedish, were diagnosed with osteomalacia.
Muscle weakness may explain
To isolate the effect of osteomalacia from other factors, the researchers employed a causal analysis strategy using Directed Acyclic Graphs (DAGs). The study is the first of its kind to specifically examine suction cup (vacuum-assisted) delivery as a primary outcome in relation to osteomalacia.
As muscle weakness is a cardinal symptom of osteomalacia – resulting from a relative deficiency of calcium required for normal muscle function – this, together with potential effects on pelvic bone structure, may be a possible explanation for the increased need for emergency obstetric interventions observed in the study.
Reduce risks and suffering
The results may have implications for both maternal healthcare and public health strategies, particularly in populations where vitamin D deficiency is prevalent.
“We have long known that osteomalacia can be effectively treated with sunlight, vitamin D and calcium. Therefore, there is a potential opportunity to reduce the risks and suffering of both women and babies during childbirth if we can identify osteomalacia early in pregnancy,” says Kalliokoski.
Reference:
Paul Kalliokoski, Thomas Torstensson, Per Kristiansson, Biochemical osteomalacia reaffirmed by signs and symptoms and perinatal outcome. A prospective cohort study of women in Sweden, Bone, Volume 202, 2026, 117679, ISSN 8756-3282, https://doi.org/10.1016/j.bone.2025.117679.
