Study question:
Is there any association between mode of conception or IVF-related variables and nausea and vomiting of pregnancy (NVP)?
Summary answer:
Conception by means of IVF is not associated with NVP but the stage of the transferred embryo may affect NVP development.
What is known already:
The exact cause of NVP is unknown but risk factors including increased hormonal levels, maternal distress and anxiety disorders, also described in IVF populations, have been reported. There are only a few studies exploring NVP in IVF samples. A population-based study examining the characteristics of women who suffered from a severe form of NVP, it was reported that women with severe NVP had more often conceived through assisted reproduction techniques. So far, the relationship between NVP and IVF or different treatment related parameters in the IVF population in relation to NVP remains unclear.
Study design, size, duration:
The study is a longitudinal, matched - cohort, pilot study including 630 pregnant women with singletons without malformations, recruited during the pregnancy ultrasound in gestational week 17 (GW 17). The study was conducted between 2010-2016 at the University Hospital of Uppsala, Sweden.
Participants/materials, setting, methods:
The study population comprised 210 women with IVF conceived pregnancies and 420 age and parity matched women with spontaneous pregnancies. All participants self-reported sociodemographic and pregnancy-related information. IVF treatment data were obtained after scrutinization of the medical records. The outcome, NVP at GW 17, was divided into: 1) absence of NVP, 2) NVP not requiring medications and 3) NVP requiring medications. NVP was then studied in relation to exposure and to different IVF treatment-associated variables.
Main results and the role of chance:
The mean age of the participants was 33.7 years with 2/3 of the participants being primipara. IVF pregnant women reported more frequently comorbidities (such as hypertension, diabetes, migraine etc) (59.1% vs 49.9%), but less frequently alcohol consumption (38.4% vs 48.7%) compared to women with spontaneous pregnancies. Clinical and sociodemographic characteristics such as education, employment, smoking habits, maternal BMI, depression history, delivery fear and newborn gender, were otherwise similar between the groups. NVP with or without medications was not associated with mode of conception (p=0.889); 11.4% of women who conceived through IVF suffered from NVP requiring medications and 62.4% from unmedicated NVP vs 10.8% and 64.3% respectively of women with spontaneous pregnancies. Absence of NVP was reported by 26.2% of IVF and 24.9% of spontaneously pregnant women. However, in a subgroup analysis in the group of women who conceived through IVF, NVP was more frequently seen in the group who received cleavage stage embryos vs blastocysts (p=0.019). We could not however find any significant difference in the rate of NVP with or without medications between fresh (69.4%) or frozen/thawed embryo transfers (78.5%), nor between IVF(72.3%) and intracytoplasmic sperm injection(ICSI)(77.4%) treatments. Lastly, there was no significant difference between infertility diagnosis and NVP.
Limitations, reasons for caution:
The study had limited power to detect differences in NVP in relation to mode of conception. In addition, there was a missing rate of 30.5% in the reported embryo stage variable. Finally, the rate of blastocyst-transfers during that period was lower than otherwise expected with current statistics.
Wider implications of the findings:
It is still unclear whether IVF has an impact on the risk of NVP. However, transfer of a blastocyst may decrease the risk of developing NVP.