Prenatal Nutritional Strategies to Reduce the Risk of Preterm Birth

Editor(s): Karen Patricia Best, Judith Gomersall, Maria Makrides .

Key insights

Preterm birth (PTB) is one of the most challenging problems in obstetric and neonatal care. Because of its complex etiology, the causes of PTB are unclear and there are currently no reliable strategies for prevention or treatment. Maternal nutrition before and during pregnancy plays a critical role in providing the necessary nutrients for fetal growth and may be an important modifiable risk factor for the prevention of PTB. Current evidence indicates that the use of omega-3 polyunsaturated fatty acids (PUFA) may be a promising approach for PTB prevention.

Current knowledge

A normal human pregnancy lasts around 40 weeks, with most babies delivered at 37–42 weeks’ gestation. The World Health Organization (WHO) defines PTB as all births occurring before 37 weeks’ gestation. Worldwide, PTB is the second leading cause of
death in children under 5 years of age. An estimated 15 million babies are born preterm each year; among these, 20% are born before 34 weeks (referred to as early preterm birth [EPTB]). Infants born early preterm may require extended periods in hospital intensive care and some exhibit developmental problems that can last a lifetime, including problems with their lungs, gut, immune system, vision, and hearing. Furthermore, developmental difficulties may emerge in early childhood, with later societal and economic impacts caused by low educational achievement, high unemployment, and deficits in social and emotional well-being.

Practical implications

The homeostatic balance between the metabolites of omega- 3 and omega-6 fatty acids play a vital role in the maintenance of normal gestational length, cervical ripening, and the initiation of labor. The standard Western diet is generally low in omega-3 but high in omega-6 fatty acids. Based on the available evidence, omega-3 supplementation during pregnancy to prevent EPTB should be targeted towards women with low omega-3 status in early pregnancy. Women with replete omega-3 levels in early pregnancy should continue their current dietary practices to maintain their status. Correcting low maternal omega-3 levels through supplementation (such as the use of low-dose fish oil supplements) may reduce the risk of EPTB.

Recommended reading

Samuel TM, Sakwinska O, Makinen K, Burdge GC, Godfrey KM, Silva-Zolezzi I. Preterm birth: a narrative review of the current evidence on nutritional and bioactive solutions for risk reduction. Nutrients. 2019;11(8):1811.


Key Messages

• Cost-effective primary prevention strategies to reduce preterm birth (PTB) are required to reduce the ∼ 15 million preterm babies born every year worldwide. Nutritional interventions may offer a promising solution.
• The strongest evidence to date for a nutritional solution to reduce PTB exists for omega-3 long-chain polyunsaturated fatty acids and suggests that women with low levels of omega-3 in early pregnancy may benefit from supplementation.
• Recent findings suggest that determining an individual woman’s polyunsaturated fatty acid status in early pregnancy may be a precise way to inform recommendations to reduce her risk of PTB.


Preterm birth · Nutrition · Pregnancy · Omega-3 ·
Prevention · Supplementation · Prematurity


Worldwide, around 15 million preterm babies are born annually, and despite intensive research, the specific mechanisms triggering preterm birth (PTB) remain unclear. Cost-effective primary prevention strategies to reduce PTB are required, and nutritional interventions offer a promising alternative. Nutrients contribute to a variety of mechanisms that are potentially important to preterm delivery, such as infection, inflammation, oxidative stress, and muscle contractility. Several observational studies have explored the association between dietary nutrients and/or dietary patterns and PTB, often with contrasting results. Randomized trial evidence on the effects of supplementation with zinc, multiple micronutrients (iron and folic acid), and vitamin D is promising; however, results are inconsistent, and many studies are not adequately powered for outcomes of PTB. Large-scale clinical trials with PTB as the primary outcome are needed before any firm conclusions can be drawn for these nutrients. The strongest evidence to date for a nutritional solution exists for omega-3 long-chain polyunsaturated fatty acids (LCPUFAs), key nutrients in fish. In 2018, a Cochrane Review (including 70 studies) showed that prenatal supplementation with omega-3 LCPU- FAs reduced the risk of PTB and early PTB (EPTB) compared with no omega-3 supplementation. However, the largest trial of omega-3 supplementation in pregnancy, the Omega-3 to Reduce the Incidence of Prematurity (ORIP) trial ( n = 5,544), showed no reduction in EPTB and a reduction in PTB only in a prespecified analysis of singleton pregnancies. Exploratory analyses from the ORIP trial found that women with low baseline total omega-3 status were at higher risk of EPTB, and that this risk was substantially reduced with omega-3 supplementation. In contrast, women with replete or high baseline total omega-3 status were already at low risk of EPTB and additional omega-3 supplementation increased the risk of EPTB compared to control. These findings suggest that determining an individual woman’s PUFA status may be the most precise way to inform recommendations to reduce her risk of PTB.