Mediterranean diet adherence shows reduction in adverse pregnancy outcomes

Researchers in a 2022 study found that women with high adherence to the Mediterranean diet show a reduction in adverse pregnancy outcomes.

The Mediterranean diet has been associated with numerous health benefits, but its impact on preventing adverse pregnancy outcomes isn’t clear.

Makarem et al. (2022), in their multicenter prospective cohort study, assessed the impact of the Mediterranean diet as part of their regular diet on adverse pregnancy outcomes among 7,798 women in the US, as part of the nuMoM2b-HHS study (Nulliparous Pregnancy Outcomes Study- Monitoring Mothers-to-Be-Heart Health Study).

The nuMoM2b-HHS study aimed to better understand and predict adverse pregnancy outcomes of women in their first pregnancy, who were followed through delivery. It enrolled over 10,000 racially diverse women in the US between 2010 and 2013 at 8 medical centers. As of 2022 there have been 11 papers on a variety of topics relating to adverse pregnancy outcomes published using the nuMoM2b-HHS study (you can read more about it on clinicaltrials.gov).

Key points:

Participants answered the Block 2005 Food Frequency Questionnaire at 6-13 weeks of pregnancy.
Diet was assessed for the 3 month period before pregnancy. This questionnaire addressed their regular diet, there was no intervention to encourage them to adhere to the Mediterranean diet.
Participants were given a score, which reflected the intake of vegetables (excluding potatoes), fruits, nuts, whole grains, legumes, fish, monounsaturated to saturated fat ratio, red and processed meats, and alcohol.
Scores were assigned based on median values. For example, in the case of vegetable intake, participants who ate more vegetables than the median were given 1 point (if less they got 0 points).
Red meat was scored the opposite, so eating more red meat than the median gave 0 points. Alcohol intake was limited to 1 drink a day, and any less or more than this resulted in 0 points.
The points were added up to give an “aMed score.” The higher the aMed score, the more adherence to the Mediterranean diet. A low score was 0-3, a moderate score was 4-5 and a high score was 6-9.

Baseline characteristics were compared for those with a low, moderate and high aMed score and were different in terms of age, educational level, race and ethnicity, marital status, obesity, smoking, and family history of cardiovascular disease. All of these confounders were statistically adjusted in their analysis.

Women with a higher aMed score were more likely to be older, non-Hispanic White, married, never smokers, have a higher level of education and less likely to be obese.

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High adherence to the Mediterranean diet before pregnancy led to lower adverse pregnancy outcomes

They looked at the odds for developing any of the following adverse pregnancy outcomes, and for each individual outcome:

Preeclampsia or eclampsia
Gestational hypertension
Gestational diabetes
Preterm birth–composite
Preterm birth–iatrogenic
Preterm birth–spontaneous
Small size for gestational age
Stillbirth

Any adverse outcome. Women with high adherence to the Mediterranean diet had a 21% reduction in the odds of developing any adverse pregnancy outcome compared to those with low adherence (adjusted odds ratio [95% CI]: 0.79 [0.68-0.92]).

Preeclampsia or eclampsia. Women with high adherence to the Mediterranean diet had a 28% reduction in the odds of developing preeclampsia or eclampsia compared to those with low adherence (adjusted odds ratio [95% CI]: 0.72 [0.55-0.93]).

Gestational diabetes. Women with high adherence to the Mediterranean diet had a 28% reduction in the odds of developing gestational diabetes compared to those with low adherence (adjusted odds ratio [95% CI]: 0.63 [0.44-0.90]).

There were no statistically significant differences in the development of other adverse pregnancy outcomes, including gestational hypertension, preterm birth–composite, preterm birth–iatrogenic, preterm birth–spontaneous, small size for gestational age and stillbirth.

There were no statistically significant differences between moderate and low adherence to the Mediterranean diet, only high adherence was significant. Another analysis refined the scores more and found that there was a benefit for aMed scores of 5 for any adverse outcome and preeclampsia or eclampsia. An aMed score of 5 is the higher end of the “moderate” score that’s examined above.

Some components of the Mediterranean diet are more important than others in reducing adverse pregnancy outcomes

This study included a questionnaire that evaluated intake of vegetables (excluding potatoes), fruits, nuts, whole grains, legumes, fish, monounsaturated to saturated fat ratio, red and processed meats, and alcohol.

Diets that were high in vegetables, fruits, legumes or fish had significantly lower adverse pregnancy outcomes:

A high vegetable diet reduced adverse pregnancy outcomes by 17% (adjusted odds ratio [95% CI]: 0.83 [0.74-0.93]).
A high fruit diet reduced adverse pregnancy outcomes by 11% (adjusted odds ratio [95% CI]: 0.89 [0.80-1.00]).
A high legumes diet reduced adverse pregnancy outcomes by 23% (adjusted odds ratio [95% CI]: 0.77 [0.69-0.86]).
A high fish diet reduced adverse pregnancy outcomes by 14% (adjusted odds ratio [95% CI]: 0.86 [0.77-0.96]).

The other components of the diet showed no statistical significance in reducing adverse pregnancy outcomes.

Women with advanced age had improved benefit with Mediterranean diet in reducing adverse pregnancy outcomes

Next they performed a subgroup analysis among women of different age, BMI, race and ethnicity.

For women ≥35, there was a 48% reduction in adverse pregnancy outcomes (adjusted odds ratio [95% CI]: 0.52 [0.33-0.81]), while in women <35 the reduction was 15% (adjusted odds ratio [95% CI]: 0.85 [0.73-0.99]). This means that women ≥35 show a greater benefit to adherence to the Mediterranean diet compared to younger women (but it was significant in both groups).

There were no differences in terms of BMI, race or ethnicity, meaning that all these groups can benefit from the diet.

Conclusions

This study found that women who had high adherence to the Mediterranean diet as part of their regular diet had a reduction adverse pregnancy outcomes, specifically preeclampsia or eclampsia and gestational diabetes. Women who were 35 or older seemed to benefit the most from this diet.

In general, high adherence to the Mediterranean diet showed a reduction in adverse pregnancy outcomes compared to low adherence. This is based off of aMed scores, which is based off of the median values that the researchers obtained from the questionnaires. So it really isn’t possible to know exactly what their diets looked like, only that their diets contained more than what 50% of the group (the median) was eating for each category.

This study compared adverse pregnancy outcomes in women based on their regular diet, and was an observational study (they didn’t intervene and have the participants follow the Mediterranean diet). Because of this, they can’t say that the Mediterranean diet caused a reduction in adverse outcomes, only that there was an association. To establish causality, future studies need to be done that compare groups that follow this diet vs those that do not.

Reference

Makarem N, Chau K, Miller EC, Gyamfi-Bannerman C, Tous I, Booker W, Catov JM, Haas DM, Grobman WA, Levine LD, McNeil R, Bairey Merz CN, Reddy U, Wapner RJ, Wong MS, Bello NA. Association of a Mediterranean Diet Pattern With Adverse Pregnancy Outcomes Among US Women. JAMA Netw Open. 2022 Dec 1;5(12):e2248165. doi: 10.1001/jamanetworkopen.2022.48165. PMID: 36547978; PMCID: PMC9857221.

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About Embryoman

Embryoman (Sean Lauber) is a former embryologist and the founder of Remembryo, an IVF research and fertility education website. After working in an IVF lab in the US, he returned to Canada and now focuses on making fertility research more accessible. He holds a Master’s in Immunology and launched Remembryo in 2018 to help patients and professionals make sense of IVF research. Sean shares weekly study updates on Facebook, Instagram, and Reddit regularly. He also answers questions on Reddit or in his private Facebook group.