The role of zinc during pregnancy is very difficult to determine because there is no consistent way to measure zinc levels in an individual; further, what may constitute zinc deficiency is not known. Therefore, all research regarding zinc deficiency during pregnancy is preliminary and estimated.
Although zinc deficiency has been linked to decreased immune function and potentially preterm birth, supplementation may only help prevent problems if women are deficient; zinc supplementation likely has no benefit otherwise.
Zinc is a popular ingredient in cold lozenges and related medications, and research does indicate that zinc may lessen symptoms after a cold has appeared, but zinc will likely not prevent or cure a common cold.
Pregnant women need to talk to their health care provider (HCP) before taking any zinc-containing medication or supplements. It is very easy to take too much, as even just three to four times the daily limit could cause negative effects.
Background
Zinc is a nutrient found throughout the body; it plays a role in metabolism and immune function, protein synthesis, wound healing, cognitive function, bone health, DNA and RNA synthesis, cell division, and proper sense of taste and smell.
Zinc is very popular as a potential cold remedy and is found in lozenges and over-the-counter cold medications (cough and throat drops).
It is important to note that zinc does not help prevent colds, although it has been linked to the shortened duration and severity of cold symptoms when taken within 24 hours of symptoms appearing. Overall, however, studies are inconsistent.
Further, the optimal dosage, duration, and type of preparation (lozenge, syrup, etc.) that is most beneficial with fewest side effects is not known, and it may be possible to take too much zinc with the use of these products (read Cold Medications).
Pregnancy
Zinc research, statistics, and its effects on pregnancy is difficult to determine as there is no reliable way to measure zinc status in humans.
HCPs currently use indirect indicators to determine zinc deficiency to include the prevalence of anemia, iron deficiency, and plasma zinc concentrations.
Despite the above, it is currently assessed that zinc requirements are increased during pregnancy; therefore, women starting their pregnancy with borderline zinc status are likely at an increased risk of zinc deficiency.
Animal studies have indicated it is possible zinc deficiency may negatively impact fetal development, leading to possible pregnancy loss, congenital malformations, intrauterine growth restriction, reduced birth weight, prolonged labor, and/or preterm or post-term deliveries.
However, similar changes have not been observed in pregnant women most likely due to humans requiring much less zinc that rats (zinc is a trace mineral, and is only needed by humans in small amounts).
Regardless, zinc deficiency is being considered a potential factor in various infections during pregnancy that may lead to preterm birth, based on its assessed impact on the immune system.
Deficiency
It is suggested that even moderate zinc deficiency can negatively impact immune system function and make certain individuals susceptible to infection; however, the reverse is not clear. It has not been strongly shown that additional zinc supplementation (more than required for daily function) prevents infection (even if deficiency causes it).
Further – there is no definitive way to determine if a person is suffering from a zinc deficiency as there is no reliable lab test, which greatly inhibits research regarding this aspect of zinc.
While, overt zinc deficiency is uncommon in North America, it can occur with chronic diarrhea, sickle cell disease, alcoholism, ulcerative colitis, Crohn’s disease, celiac disease, short bowel syndrome, kidney disease, diabetes, and the use of thiazide diuretics for blood pressure.
Zinc deficiency can also cause loss of appetite, poor growth, hair loss, dermatitis, alopecia, frequent diarrhea, upper respiratory tract infection, and eye and skin lesions – all of which further associate zinc deficiency with immune system dysfunction.
Supplementation
It is estimated that over 80% of pregnant women worldwide do not get enough zinc, and consume, on average, 9.6 milligrams (mg)/day (11 mg is recommended daily for pregnant women). However, this shortfall can be overcome with better targeted food intake rather than supplementation.
A varied diet should be all that is needed to meet zinc requirements during pregnancy, therefore routine supplementation of zinc for any specific purpose during pregnancy is not recommended:
A March 2021 review of 25 randomized controlled trials involving over 18,000 women and their babies determined there is not enough evidence that zinc supplementation during pregnancy results in improvements in maternal or neonatal outcomes.
For women who do take zinc supplements:
Zinc supplementation can affect the absorption of certain antibiotics; taking an antibiotic at least 2 hours before, or 4 to 6 hours after taking a zinc supplement can improve absorption. Women who are concerned about their zinc status or are taking antibiotics should speak to their HCP.
Acute (short term, high concentration) adverse effects of high zinc intake (hundreds of mg) include nausea, vomiting, loss of appetite, abdominal cramps, diarrhea, and headaches – possibly within as few as 30 minutes.
Long-term zinc supplementation over the tolerable upper intake level (40 mg/d for adults) may lead to copper deficiency (which is why some zinc dietary supplements also contain copper).
Sources
Food sources of zinc include oysters (higher than any other food), chicken, red meat, beans, crab, lobster, dairy, pork chop, beef, yogurt, and fortified breakfast cereals.
Vegetarians may require as much as 50% more zinc than non-vegetarians, as phytates in whole grains and legumes can inhibit zinc’s absorption.
Zinc content can be increased by soaking beans, grains, and seeds in water for several hours before cooking and allow them to sit after soaking until sprouts form.
Action
While zinc is a popular "cold remedy", pregnant women should keep in mind the daily recommended requirement is estimated to be 11 mg, and the upper recommended limit is estimated to be 40 mg. Each dose certain over-the-counter medications could contain 10 mg of zinc or more. Additionally, no optimal dose/timing has been determined regarding zinc supplementation and shortening the duration of cold symptoms.
Women who are concerned about their zinc status or are taking antibiotics should speak to their HCP. Women should also speak to their HCP prior to taking or using any supplements, lozenges, or over-the-counter medications that contain zinc.
Pregnant women can also use the opportunity to speak with their HCP about their overall diet and nutrition. HCPs are trained to look for areas in which pregnant women may be lacking in certain nutrients.
Resources
Zinc Fact Sheet (Oregon State University, Micronutrient Information Center)