Animal studies have not been performed with the combination product. There are no controlled data in human pregnancy.
Guaifenesin: Animal studies are not available. A monitoring study including 197 mother-child pairs that had first trimester guaifenesin exposure showed an increase in inguinal hernias; 1336 any time pregnancy exposures showed no association with malformations.

Phenylephrine: A monitoring study including 1249 mother-child pairs that had first trimester phenylephrine exposure showed an increase in malformation, with association greater with minor defects than major defects (8 eye and ear defects, 6 syndactyly, 4 preauricular skin tags, and 3 clubfoot cases); 4149 any time pregnancy exposures were associated with 15 congenital dislocation of the hip, 6 umbilical hernia, and 4 other musculoskeletal defects. Placental transfer is likely with phenylephrine's low molecular weight (about 167).

AU TGA pregnancy category B2: Drugs which have been taken by only a limited number of pregnant women and women of childbearing age, without an increase in the frequency of malformation or other direct or indirect harmful effects on the human fetus having been observed. Studies in animals are inadequate or may be lacking, but available data show no evidence of an increased occurrence of fetal damage.

US FDA pregnancy category Not Assigned: The US FDA has amended the pregnancy labeling rule for prescription drug products to require labeling that includes a summary of risk, a discussion of the data supporting that summary, and relevant information to help health care providers make prescribing decisions and counsel women about the use of drugs during pregnancy. Pregnancy categories A, B, C, D, and X are being phased out.

Safety has not been established during pregnancy; use should be avoided during the third trimester of pregnancy.

AU TGA pregnancy category: B2
US FDA pregnancy category: Not assigned

Comments:
-There is no data on use in pregnant women to know this drugs risks, including the risk of fetal harm or reproductive effects.
-Available data do not indicate developmental toxicity with guaifenesin.
-Phenylephrine is a sympathomimetic used in emergencies to treat hypotension and alleviate eye and ear allergic symptoms.
-Phenylephrine could cause constriction in uterine vessels (that are normally maximally dilated during pregnancy), reducing uterine blood flow, potentially causing fetal hypoxia.
-Phenylephrine may interact with oxytocic or ergot derivatives to cause persistent maternal hypertension; cerebral vessel rupture is possible.
-Sympathomimetic amines are teratogenic in some animal models, but are not suspected to cause human teratogenicity.

See references

The manufacturer makes no recommendation regarding use during lactation.

Excreted into human milk: Data not available (guaifenesin, phenylephrine)
Excreted into animal milk: Data not available (guaifenesin, phenylephrine)

Comments:
-There is no information regarding this drug on the presence in human milk, the effects on a breastfed infant, or effects on milk production.
-Guaifenesin from breast milk is not expected to adversely affect nursing infants at normal parental doses.
-Phenylephrine oral bioavailability is about 40%, making it unlikely an infant would receive large doses from breast milk.
-Phenylephrine may decrease milk production.
-Products with high alcohol content should be avoided during while breastfeeding.

See references