Is the nausea and vomiting of early pregnancy really feto-protective?

Health care providers and popular press articles frequently advise women that nausea and vomiting of early pregnancy (NVP) portends a favorable fetal outcome.

To investigate the claim that NVP protects against adverse fetal outcomes and improves placental and fetal growth.

Data were collected on a prospective cohort of 849 Ecuadorian prenatal patients beginning in early gestation until postpartum. A questionnaire collected information on NVP and other maternal characteristics. Fetal outcomes and placental characteristics were examined using anthropometry and physical examination. Multivariate statistical methods controlled for potential confounders.

Women with nausea only (AOR = 0.45; 95% CI = 0.22-0.94) or nausea with vomiting (AOR = 0.66; 95% CI = 0.46-0.99) had significantly decreased miscarriage risk although the strength of the protection appeared less than that reported for other populations. NVP was not associated with low birth weight, preterm delivery, congenital anomaly, or other outcomes excepting slightly increased mean infant thigh skinfold (P = 0.024), mid-upper arm circumference (P = 0.049), and placental weight (P = 0.034).

The data did not support the common belief that NVP protects against multiple adverse outcomes. Placental weight was slightly increased in women with NVP but this difference was not reflected in higher birth weights or other types of fetal growth except of marginally increased limb fat.