Nausea, vomiting and nutrition in pregnancy

Glenda Lindseth, PhD, RN, RD, FADA, Marlene Buchner, MS, RN, Patti Vari, MS, RN, April Gustafson, RN
University of North Dakota, College of Nursing, Grand Forks, North Dakota, U.S.A.

This study was funded in part by the National Institutes of Health NICHD Grant #HD33991

Introduction

Of the approximately five million pregnancies annually in the United States, 50% to 80% of these women could be expected to experience nausea or vomiting during the pregnancy.1-3 Nausea and vomiting in pregnancy (NVP) have been recorded as early as 2000 B.C.; yet, even today the majority of women still suffer some form of nausea or vomiting in early pregnancy.4 As many as 20% of pregnant women continue with nausea or vomiting into late pregnancy.5,6 More than 50,000 women each year in the United States (U.S.) alone are hospitalised because standardised suggestions for NVP fail to work.7 Despite their frequency and potential effects, the phenomena are often ignored. While nausea and vomiting in pregnancy are typically not life threatening, the nutritional effects of the phenomena of nausea and vomiting in pregnancy on the maternal dietary habits may be significant to foetal development and diminish the mother's sense of well-being.8

A void is found in the literature on the relationship between NVP and nutrient intakes in pregnancy.8-10 Hook and the Institute of Medicine have stated that the nutritional implications of NVP are virtually unknown.4,10 Therefore, the purpose of this study was to conduct a descriptive analysis of pregnant women to examine the relationship of nutrient intakes and related variables to nausea and vomiting in pregnancy.

Methods

Design and sampling
This descriptive, correlational study was guided by Orem's Theory of Self-Care. Subjects were selected from populations of primarily Native American and Caucasian pregnant women in the north central U.S. who may or may not have been experiencing NVP upon entry into the study. Considerations for selection were to include samples of pregnant women who were receiving care from consenting prenatal clinics and that reflected the cultural diversity that existed within vulnerable populations of the proposed study sites. One hundred thirty-three subjects were entered into the study, with nine women turning down the opportunity to participate. Eighty-eight percent of the pregnant women completed the study. Twenty-four percent (33) of the women were Native American, 72% (92) were Caucasian, and 4% other. Pregnant women were considered eligible for participation in the study according to the following sample selection criteria: (1) have a confirmed, positive test for pregnancy; (2) have given consent to participate in the study; (3) have consent of the obstetrician; (4) be 18 to 40 years in age; (5) be able to read, understand and speak English; and (6) be within the first trimester of pregnancy, as confirmed by the obstetrician.

Procedure
The pregnant women were targeted for observation during their early pregnancy (£ 20 weeks) at 12-16 weeks and during the late pregnancy (> 20 weeks) at the 26-30 week time frame. Subjects who signed the consent forms to participate completed questionnaires for measurements of self-care agency and for demographic information. The women wrote down their dietary intakes and recorded their nausea and vomiting distress symptoms for three days in early pregnancy and for three days in late pregnancy. Anthropometric data were also recorded. Subjects received $10 for the completion of each data collection interview as compensation for participation time in the study, inconvenience, and as an expression of appreciation for contributing to this body of knowledge.

Instrumentation and measurement

The following methods of data collection were completed for the study:

Demographic data were recorded as responses to open-ended questions related to age, vocation, employment status, educational level, marital/social living status, ethnic identification, questions of medication intake and general data related to this pregnancy and prior pregnancy outcomes.

Nausea and vomiting were measured by the Nausea and Vomiting Symptom Distress Adaptation Scale that was originally developed by Rhodes, Watson and Johnson.11 The instrument was selected because it measures duration, frequency and severity distress of both nausea and vomiting, as well as the frequency and distress of dry heaves of the pregnant women. A pilot study by this researcher on a population of pregnant women experiencing nausea and vomiting indicated a Cronbach's coefficient of a = 0.88.

Nutrient intakes were documented by the Three-Day Food Diaries, selected for convenience, validity, and ease of dietary intakes recordings by the pregnant women. This food recording method is often used for assessment of actual or usual nutrient intakes of individuals in the 18 to 40 year-old age group.12 Quantitatively, nutrient values for the women were measured for relationship to the NVP scores.

Self-care agency of the pregnant women was measured using the Exercise of Self-Care Agency (ESCA) Instrument developed by Kearney and Fleischer.13 Self-care agency is the capability enabling the pregnant women to control or manage their prenatal health, including nausea and vomiting, and ultimately their nutritional status, to promote positive pregnancy outcomes. The instrument is a 43-item questionnaire for measurement of clients' beliefs regarding their self-care ability. Responses are rated on a five-point Likert-type scale, eliciting responses ranging from "very characteristic of me" to "very uncharacteristic of me." A Cronbach's alpha coefficient indicated a reliability of this tool as a = 0.81 in prior studies.14

Anthropometric measurements that were recorded for these women included serial weights and heights. Basal Metabolic Indexes (BMIs) were calculated for the weight-for-height measures. Weights were taken using a portable strain-gauge, electronic scale. Heights were measured by using a portable height board.

Subjective well-being was measured to determine how the pregnant women perceived their life quality during certain items in pregnancy when they may have been experiencing nausea and vomiting. In this study of pregnant women experiencing nausea and vomiting, the alpha coefficient was a = 0.81. The seven-point scale was used to assess the subjective well-being of the pregnant women that asks respondents to evaluate "their life as a whole."15

Analysis

Data were analysed using the Statistical Analysis System (SAS). Nutrient analyses of the three-day diet records were completed by a nutrition analysis system, the Food Processor-Deluxe.16 Frequencies were tabulated for responses to the measurements of nutrient intakes, food frequencies, demographic questions, self-care abilities, anthropomorphic data, nausea and vomiting, and well-being assessments. ANOVAs and t-tests were used to determine significant differences between dietary intakes/nutritional data and related variables of the pregnant women experiencing NVP and those women asymptomatic for NVP. Relationships of demographic variables and nutrient intakes to the pregnant women's NVP experience scores were determined through the use of multiple regression analyses. An alpha level of a £ 0.05 was the identified criterion for significance.

Results

Sample characteristics
The mean age of the pregnant women upon enrollment in this study was 26.3 years. When the anthropometric measures of the women were calculated, BMI was 26.5. The typical pregnant woman was 13.5 weeks into pregnancy on the first observational visit and had 13.3 years of education. Self-care agency scores were 119 out of a possible 172 points, with more points indicating strong opinions on caring for oneself; the subjective well-being score was a 10.9 score out of a possible 14. A score of 14 would indicate a "most satisfied" feeling. Table 1 reports means for the demographic variables of the pregnant women.

Table 1 - Characteristics of the sample (n = 133)

 

NVP experience scores
Scores were calculated for the pregnant women's severity, frequency and duration of their NVP experiences in early pregnancy and late pregnancy. Scores of "0" indicated no discomforts of nausea and vomiting; and "8" indicated the most severe experience. Seventy percent of the women experienced nausea and vomiting in early pregnancy (£ 20 weeks) and 32% of the women were sick in late pregnancy (> 20 weeks). As Table 2 shows, there were no significant differences when comparing NVP experience scores between the Native American and Caucasian women in early pregnancy. However, in late pregnancy, Caucasian women had higher (more severe) NVP experience scores. In both early and late pregnancy, t-test differences indicated that the longer the women used oral contraceptives just prior to their pregnancies, the more severe the NVP experiences for the women. Women who exercised more also had significantly higher NVP experience scores than those who reported exercising less.

Table 2 - Nausea and vomiting experience scores and ethnicity

 

Relationship of dietary intakes to NVP
From the food diaries, nutritional analyses were calculated for those women who experienced NVP and for those women asymptomatic for NVP. Table 3 illustrates a comparison of the dietary intakes and the Recommended Dietary Allowances (RDA) for pregnant women.

Table 3 - Kilocalorie and nutrient intakes of pregnant women with and without NVP

 

When comparing for differences in dietary intakes of the Native American and Caucasian pregnant women during the early pregnancy visits (£ 20 weeks) there were no significant differences in dietary intakes. However, in the late pregnancy (> 20 weeks) dietary intakes of vitamin A (t = 2.37, df 100, p = 0.03) and thiamine (t = 1.99, df 100, p 0.02) were significantly different when comparing the dietary intake differences of the women with and without NVP. In late pregnancy the dietary intakes of iron were significantly lower for Native American women (23.5 mg) than for Caucasian women (32 mg), (t = 2.46, df 100, p = 0.04). Likewise, intakes of calcium were significantly lower for the Native American women (826 mg) than for the Caucasian women (1276 mg), (t = 2.56, df 100, p < 0.03).

An analysis using multiple regression statistics of nutritional intakes by the women revealed that fats (r = -0.24, p = 0.01), carbohydrates (r = -0.29, p < 0.01), vitamin B6 (r = -0.22, p < 0.02), thiamine (r = -0.27, p < 0.01), riboflavin (r = -0.23, p < 0.01), niacin (r = -0.23, p = 0.01), and kilocalories (r = -0.29, p < 0.01) had significant relationships to the women's NVP scores. Table 4 shows the relationships of micronutrient intakes and NVP experience correlations.

Table 4 - Correlations among macro-nutrient intakes and NVP experience scores

 

NVP and related factors
Quality of life and well-being scores of the pregnant women were analysed for relationships with NVP scores. Having a history of motion or airsickness correlated significantly with higher NVP scores for the women (r = 0.19, p = 0.05). Table 5 illustrates the correlations.

Table 5 - Correlating NVP and related factors

 

There were no significant correlations when comparing well-being scores with NVP scores for the women with and without NVP. Nausea and vomiting had a significant but negative relationship with self-care agency scores for the pregnant women (r = -0.23, p = 0.02).

Discussion and conclusion

In support of previous studies that showed 50 to 80% of pregnant women could be expected to experience nausea and vomiting in early pregnancy, 70% of the pregnant women in this study experienced nausea and vomiting in early pregnancy. Researchers have speculated that nutritional relationships might be significant when pregnant women experience nausea and vomiting;4,5,10 however, correlations in this study indicated that dietary intakes of kilocalories, carbohydrates, fats, thiamine, riboflavin, niacin and vitamin B6 intakes had significant negative relationships to the NVP scores (p < 0.05). This may be of concern because the pregnant woman and foetus are so dependent upon optimal nutritional intakes.

While approximately 20% of pregnant women will go on to experience NVP in late pregnancy, in this study 32% of the women experienced NVP in late pregnancy. A comparison of NVP experiences for the Native American and Caucasian women indicated that Native American women had significantly less NVP in late pregnancy. The Native American women also had lower dietary intakes of iron and calcium. Therefore, health care providers need to be aware of dietary needs as well as be culturally sensitive to pregnant women so that positive prenatal outcomes can be facilitated to maximise the quality of life for women experiencing conditions such as NVP. Because increased use of oral contraceptives correlated with NVP experience scores, this could indicate that hormones are a factor in NVP occurrences. Therefore, women using oral contraception may be counselled to use a substitute contraception prior to the planned cessation of all contraceptives in order to reduce the NVP experience. The dietary results, along with the fact that increased minutes of daily exercise correlate with increased NVP, might prompt the health care provider to suggest that increased rest might be advisable to decrease pregnant women's NVP experiences. With additional information gained from clinical trials to test nutritional relationships to NVP, women may feel that they have some recourse to the NVP so that their beliefs regarding self-care ability may increase.

Further research is needed on NVP occurring in late pregnancy, the hormonal relationships to NVP, and clinical trials to test nutritional relationships to NVP.

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