(197) Association Between Morning Sickness and Having a Girl – Myth or Fact?

Publication Number: 528

Background: According to an old wives’ tale, more severe nausea and vomiting in pregnancy (NVP) is a sign that the baby will be a girl.

Objectives: To investigate the relationship between being pregnant with a female fetus and the severity of NVP.

Methods: In a cohort study, we linked data from nationwide registers on pregnancies, prescriptions, and primary and secondary healthcare from 2004 to 2020 in Norway. Singleton pregnancies with recorded information on sex and resulting in termination, stillbirth or live birth were included. NVP was identified from a diagnosis or the dispensing of antiemetic drugs in first trimester, when its symptoms usually are most severe.

Severity of NVP was classified in two ways. First, by the level of care at which the diagnosis for NVP was recorded: 1) primary care, 2) outpatient secondary care and 3) inpatient secondary care. Second, according to the recommended treatment pyramid for the dispensing of antiemetic drugs in pregnancy: 1) antihistamines, 2) dopamine antagonists, 3) ondansetron and 4) methylprednisolone. Using Poisson regression, we estimated risk ratios (RR) with 95% confidence intervals (CI) for a diagnosis at each level of healthcare and the dispensing of a drug from each level of the antiemetic drug treatment pyramid for women pregnant with a female compared to a male fetus. No adjustments were made.

Results: We included 961,790 pregnancies, 48.6% with females and 51.4% with males. A diagnosis of NVP and an antiemetic drug dispensing was made in 156,483 and 66,931 pregnancies, respectively. Of these, 43,820 pregnancies had both a diagnosis and a dispensing. The RR for receiving a diagnosis of NVP in primary care was 1.05 (95% CI 1.05-1.06) for women pregnant with a female versus a male fetus, while it was respectively 1.07 (95% CI 1.03-1.12) and 1.13 (95% CI 1.10-1.16) for receiving a diagnosis in outpatient and inpatient secondary care. For antiemetic drugs, the corresponding RRs increased from 1.08 (95% 1.06-1.10) for antihistamines and 1.08 (1.07-1.10) for dopamine antagonists to 1.11 (1.06-1.16) for ondansetron and 1.14 (95% 0.90-1.44) for methylprednisolone.

Conclusions: Being pregnant with a female fetus was associated with an increased risk of being diagnosed with NVP and dispensed an antiemetic drug during first trimester. The risk was stronger for more severe NVP, i.e. higher levels of healthcare and antiemetic drug treatment.