Safety of caffeine consumption during pregnancy is controversial. Some studies suggest that modest caffeine intake of less than two average cups (defined below) of coffee per day presents a slight risk to the embryo or fetus, but others do not. There is stronger evidence that larger daily amounts of caffeine during pregnancy may increase the risks of miscarriage, preterm delivery and low birth weight, but no solid proof.

High caffeine intake during pregnancy should be avoided. Individual sensitivity to caffeine may vary for both pregnant women and developing fetuses, and risks of moderate caffeine consumption are not clear. Women trying to become pregnant may conceive sooner if they limit caffeine intake to moderate amounts. To minimize infants’ exposures to caffeine, breastfeeding women can avoid very high caffeine intake.

General Effects of Caffeine
Caffeine is a stimulant that is naturally produced by a variety of plants. Natural or synthetic caffeine is present in many foods and beverages, and some medications.

Caffeine usually enters the central nervous system within fifteen minutes of consumption. It slightly increases both blood pressure and heart rate. Caffeine also stimulates urination and thus reduces body fluid levels – an effect considered undesirable during pregnancy, when adequate hydration is important.

Caffeine in Coffee, Tea and Other Products
The caffeine content of a serving of coffee or tea depends on the beans or leaves used, serving size, and the method of preparation.  An 8-oz. cup of  brewed coffee averages 150 milligrams (mg) of caffeine. Instant coffee contains less. Black tea averages 80 mg per 8-oz. cup. Green tea contains less. A 12-oz. caffeinated soft drink may contain 30-60 mg. (See the table below for more specific values.)

Other sources of caffeine include chocolate, chocolate syrup, hot cocoa, and certain medications. Amounts differ greatly from one such source to another. Chocolate or cocoa generally has very low caffeine content. Medications containing caffeine include some formulations for pain relief, migraine, the common cold, diuretic purposes, and delaying sleep. Unlike foods and beverages, FDA-approved medications carry labels that say how much caffeine they contain. Some “dietary supplements” may contain caffeine, but are not required to say how much.

Caffeine’s Effects on Fertility
Some studies have found a link between high levels of caffeine consumption by women and delayed conception. Those who consumed more than 300 mg of caffeine per day were twice as likely to have conception delayed for a year or more.¹ Another study also linked high caffeine intake to delayed conception, but only in women consuming 500 mg or more (about four cups of coffee) per day.²

Caffeine’s Effects on the Developing Fetus
Caffeine easily passes from mother to fetus through the placenta. A developing fetus may have higher, sustained blood levels of caffeine than its mother because of immature metabolism.³ A few studies have shown that even moderate caffeine consumption affects fetal heart rate and movement patterns.³ A pregnant woman’s ability to metabolize caffeine slows as pregnancy progresses, so some of its effects may increase later in pregnancy.

Some studies have found that pregnant women who consumed large quantities of caffeine (five or more cups of coffee a day) were twice as likely to miscarry as those who consumed less, while fewer or no effects were seen at lower levels of caffeine consumption.^{4, 5} A detailed analysis of caffeine's reported effects on pregnancy outcome can be found at motherisk.org.

Caffeine’s Effects on Newborns and Infants
High caffeine consumption during pregnancy may shorten gestation and lower birth weight.⁶ Both effects appear modest in terms of days and ounces, but may be important to an infant already compromised by prematurity or fetal growth restriction. Such effects have not been consistently linked to moderate consumption.⁷

A reported link between heavy maternal caffeine intake during pregnancy and increased risk of SIDS⁸ has not been supported by further studies.⁹

Breast milk can transfer caffeine from mother to baby. Very high caffeine intake by a nursing mother may make her baby irritable, with disturbed sleep cycles, but this is not known to occur from ordinary food and beverage caffeine intake, or without use of medications containing caffeine.

1 Hatch EE, Bracken MB (1993). Association of delayed conception with caffeine consumption. American Journal of Epidemiology, 138(12), 1082-092.

2 Bolumar F, Olsen J, Rebagliato M, Bisanti L, and the European Study Group on Infertility and Subfecundity (1997). Caffeine intake and delayed conception: a European multicenter study on infertility and subfecundity. American Journal of Epidemiology, 145(4), 324-334.

3 Eskenazi B (1999). Caffeine – filtering the facts. The New England Journal of Medicine, 341(22), 1688-689.

4 Klebanoff MA, Levine RJ, DerSimonian R, Clemens JD, Wilkins DG (1999). Maternal serum paraxanthine, a caffeine metabolite, and the risk of spontaneous abortion. The New England Journal of Medicine, 341(22), 1639-1644.

5 Cnattingius S, Signorello LB, Anneren G, Clausson B, Ekbom A, Ljunger E, Blot W, McLaughlin JK, Petersson G, Rane A, Granath F (2000). Caffeine intake and the risk of first-trimester spontaneous abortion. The New England Journal of Medicine, 343(25), 1839-845.

6 Eskenazi B,  Stapleton AL,  Kharrazi M,  Chee WY (1999). The associations between maternal decaffeinated and caffeinated coffee consumption and fetal growth and gestational duration. Epidemiology, 10(3), 242-49.

7 Clausson B, Granath F, Ekbom A, Lundgren S, Nordmark A, Signorello LB, Cnattingius S (2002). Effect of caffeine exposure during pregnancy on birth weight and gestational age. American Journal of Epidemiology, 155(5), 429-436.

8 Ford RP, Schluter PJ, Mitchell EA, Taylor BJ, Scragg R, Stewart AW (1998). Heavy caffeine intake in pregnancy and sudden infant death syndrome: New Zealand Cot Death Study Group. Archives of Disease in Childhood, 78(1), 9-13.

9 Alm B, Wennergren G, Norvenius G, Skjaerven R, Øyen N, Helweg-Larsen K, Lagercrantz H, et al (1999). Caffeine and alcohol as risk factors for sudden infant death syndrome.  Archives of Disease in Childhood, 81(2), 107-111.

10 Adapted from Kansas State University table