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Open Access Research article

Hyperemesis gravidarum and pregnancy outcomes in the Norwegian mother and child cohort – a cohort study

Åse V Vikanes1*, Nathalie C Støer2, Per Magnus1 and Andrej M Grjibovski34

Author Affiliations

1 Department for Genes and Environment, Division for Epidemiology, Norwegian Institute of Public Health, Nydalen, P.O. Box 4404, Oslo 0403, Norway

2 Department of Mathematics, University of Oslo, Oslo, Norway

3 Department for International Public Health, Norwegian Institute of Public Health, Oslo, Norway

4 International School of Public Health, Northern State Medical University, Arkhangelsk, Russia

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BMC Pregnancy and Childbirth 2013, 13:169  doi:10.1186/1471-2393-13-169

Published: 3 September 2013

Abstract

Background

Hyperemesis gravidarum (HG) characterized by excessive nausea and vomiting in early pregnancy, is reported to be associated with increased risks for low birthweight (LBW), preterm birth (PTB), small-for-gestational-age (SGA) and perinatal death. Conflicting results in previous studies underline the necessity to study HG’s potential effect on pregnancy outcomes using large cohorts with valid data on exposure and outcome measures, as well as potential confounders. This study aims to investigate associations between HG and adverse pregnancy outcomes using the Norwegian Mother and Child Cohort Study (MoBa).

Methods

All singleton pregnancies in MoBa from 1998 to 2008 were included. Multivariable regression was used to estimate relative risks, approximated by odds ratios, for PTB, LBW, SGA and perinatal death. Linear regression was applied to assess differences in birthweight and gestational age for children born to women with and without HG. Potential confounders were adjusted for.

Results

Altogether, 814 out of 71,468 women (or 1.1%) had HG. In MoBa HG was not associated with PTB, LBW or SGA. Babies born to women with HG were born on average 1 day earlier than those born to women without HG; (−0.97 day (95% confidence intervals (CI): -1.80 - -0.15). There was no difference in birthweight when maternal weight gain was adjusted for; (23.42 grams (95% CI: -56.71 - 9.86). Babies born by women with HG had lower risk for having Apgar score < 7 after 1 minute (crude odds ratio was 0.64 (95% CI: 0.43 - 0.95)). No differences between the groups for Apgar score < 7 after 5 minutes were observed. Time-point for hospitalisation slightly increased differences in gestational age according to maternal HG status.

Conclusions

HG was not associated with adverse pregnancy outcomes. Pregnancies complicated with HG had a slightly shorter gestational length. There was no difference in birth weight according to maternal HG-status. HG was associated with an almost 40% reduced risk for having Apgar score < 7 after 1 minute, but not after 5 minutes. The clinical importance of these statistically significant findings is, however, rather limited.

Keywords:
Hyperemesis gravidarum; The Norwegian Mother and Child Cohort Study; Birth weight; Gestational age; Preterm birth; Low birthweight; Small for gestational age; Apgar score; Perinatal death; Maternal weight gain