Grand Rounds

Does Daily Marijuana Use in Pregnancy Impair Fetal Growth?

BACKGROUND AND PURPOSE:

Brar et al. (Journal of Maternal-Fetal & Neonatal Medicine, 2019) studied the effect of daily marijuana use on fetal sonographic growth parameters and placental perfusion

Retrospective cohort study (2013 to 2017)
Participants
- Confirmed viable pregnancy on ultrasound | Between 18 and 52 years of age | Singleton and non-syndromic
- Self-identified daily marijuana users or nonusers
- Exclusion: Other risk factors for FGR
Study design
- Daily marijuana users were gestational aged matched to controls
- Comparisons included
  - Maternal demographics
  - Fetal biometry
  - Nuchal translucency
  - Umbilical artery Dopplers
- Intrauterine growth restriction: Defined as EFW <10^th percentile

442 pregnant women | 55 first trimester daily marijuana users | 195 second trimester daily marijuana users | 192 third trimester daily marijuana users
First trimester
- CRL: No difference
- NT: No difference
Second trimester
- Biometry: No differences
- Umbilical artery S/D ratios: Higher in marijuana users (4.02 vs 3.92; p = 0.024)
Third trimester:
- HC: Smaller head circumference, measured in percentile, found in marijuana users (37.55 vs 51.49; p < 0.0001) | Similar finding for AC
- Growth restriction: Higher number in the marijuana users group (26/192 vs 6 6/192; p=0 .002)
Umbilical artery SD ratios: Higher in marijuana users (3.52 vs 3.12; p = 0.0001)
- Four cases of absent and reversed end diastolic flow were observed in marijuana users, while no cases were observed in controls

Daily marijuana use is associated with impaired fetal growth and placental vascular resistance compared to non-users in the 2^nd and 3^rd trimesters
These findings confirm current recommendations that “marijuana use in pregnancy should be discouraged due to its association with harmful effects on the pregnancy”

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