Pregnant women are bombarded with advice. Among social media, web searches, direct marketing, family, and friends, it can be difficult for women to navigate the myriad of conflicting recommendations regarding what they should and should not do when they are pregnant. This leads to confusion at best and misinformation at worst regarding nearly all facets of life—eating, drinking, sleeping, working, travel, exercise, and sexual intercourse, to name a few. Women usually turn to their prenatal care providers for direction, but health care providers are also exposed to the same variety of opinions regarding routine advice for pregnancy. This article is meant to be an evidence-based review of common recommendations for pregnant women. It is not meant to be exhaustive nor is it meant to replace more expansive reviews of each topic. As such, a systematic review and meta-analysis were not performed for each topic. Rather, quality systematic reviews are referenced (such as a Cochrane review) as are guidelines from several national or international organizations such as the American College of Obstetricians and Gynecologists (ACOG). Relevant studies are also referenced to support the “bottom line” conclusions of the author (Box 1). It is of course possible that in certain instances others could read the same studies and come to different conclusions in general or for a specific patient. However, the goal of this article is to combine these topics into one source that can be used as a starting point for discussion with pregnant women, and the article itself can be shared with pregnant women as well.
PRENATAL VITAMINS
Prenatal vitamins are designed to meet the daily mineral and vitamin (micronutrient) requirements of most pregnant women. However, except for folic acid and possibly vitamin D and iron, it is unknown whether meeting recommended dietary allowances improves outcomes or whether failing to meet these recommended allowances worsens outcomes. Additionally, for women with well-balanced, nutritious diets that meet the recommended allowances, supplementation is likely not required. If supplementation is required, there is no known best formulation. A simple multivitamin will normally suffice, including nonprescription vitamins.
A Cochrane review of randomized trials in low- and middle-income countries where micronutrient deficiencies are common found that micronutrient supplementation reduced the risk of low birth weight and small for gestational age, but there were no other differences in maternal or neonatal outcomes.1 These trials are likely not generalizable to higher income countries. For this reason, health authorities in the United Kingdom do not recommend supplementation aside from folic acid in the first trimester and vitamin D throughout pregnancy.
Folic acid deficiency is associated with fetal neural tube defects; therefore, women who do not consume at least 400–800 micrograms of folic acid daily should be advised to take folic acid supplementation from prepregnancy until the end of the first trimester.2 Women with a history of a fetal neural tube defect should take 4,000 micrograms (4 mg) daily.2
Iron supplementation is advised as a result of the risk of maternal anemia at birth.3 However, if dietary iron is adequate (30 mg/d) and anemia is part of routine prenatal screening (which it usually is in the United States), there is no known benefit to supplemental iron in the absence of anemia.
Vitamin D deficiency is associated with several adverse outcomes such as preterm birth and preeclampsia, but it is currently unknown whether supplementation improves outcomes.4–6 The National Academy of Medicine (previously known as the Institute of Medicine) recommends that all women younger than 70 years consume 600 international units of vitamin D daily and recommends the same for pregnant women.5 Currently, ACOG does not recommend routine screening for vitamin D deficiency nor does it recommend supplementation beyond the dose