Researchers studied 425 pregnant women with gestational diabetes (a type of diabetes that develops during pregnancy) to understand how a condition called PCOS affects pregnancy outcomes. PCOS is a hormonal condition that makes it harder for the body to control blood sugar. The study found that women with both PCOS and gestational diabetes had babies with slightly higher rates of jaundice (yellowing of the skin), but otherwise had similar pregnancy outcomes to women with just gestational diabetes. Importantly, a special diet designed to help control blood sugar worked equally well for both groups, suggesting that managing blood sugar levels may be more important than having PCOS itself.

The Quick Take

  • What they studied: Whether women who have both PCOS and gestational diabetes have worse pregnancy outcomes than women with only gestational diabetes, and whether a special diet works differently for each group.
  • Who participated: 425 pregnant women from eight hospitals in the UK who had gestational diabetes and were overweight (BMI of 25 or higher). Of these, 50 women had PCOS and 375 did not.
  • Key finding: Women with PCOS and gestational diabetes had similar pregnancy outcomes to those with only gestational diabetes, except their babies had higher rates of jaundice (24.4% versus 8.9%). Both groups responded equally well to a reduced-calorie diet.
  • What it means for you: If you have PCOS and develop gestational diabetes during pregnancy, your pregnancy outcomes should be similar to someone with just gestational diabetes. A structured diet can help manage your blood sugar effectively. However, you should be aware that your baby may have a slightly higher chance of jaundice, which is usually treatable. Talk to your doctor about monitoring for this condition.

The Research Details

This was a randomized controlled trial, which is considered one of the strongest types of medical research. Researchers divided 425 pregnant women into two groups: one group followed a reduced-calorie diet (1,200 calories per day) while the other group followed a standard diet (2,000 calories per day). The women were followed from around 29 weeks of pregnancy until delivery. The researchers then compared pregnancy outcomes between women who had PCOS and those who didn’t, looking at factors like weight gain, blood sugar control, and baby health.

The study was “double-blind,” meaning neither the women nor the researchers knew which diet group each woman was in until the study ended. This helps prevent bias in the results. The women came from eight different hospitals across the UK, which makes the findings more representative of different populations.

Researchers measured many things throughout the pregnancy, including how much weight the mothers gained, their blood sugar levels, what they ate, and their babies’ health at birth. They used statistical tests to compare outcomes between the PCOS and non-PCOS groups.

This research design is important because it allows researchers to determine cause-and-effect relationships rather than just associations. By randomly assigning women to different diets and following them carefully, the researchers could see whether PCOS itself causes worse outcomes or whether other factors (like higher blood sugar or more weight gain) are responsible. This helps doctors understand what to focus on when treating pregnant women with PCOS and gestational diabetes.

This study has several strengths: it’s a randomized controlled trial (the gold standard for research), it includes a reasonably large sample size (425 women), it was conducted across multiple hospitals, and it carefully measured many different outcomes. The study was published in a highly respected medical journal. However, the number of women with PCOS was relatively small (50 out of 425), which means some findings about the PCOS group should be interpreted cautiously. The study only included women in the UK with a BMI of 25 or higher, so results may not apply to all pregnant women with gestational diabetes.

What the Results Show

The main finding was surprising: women with PCOS and gestational diabetes had very similar pregnancy outcomes compared to women with only gestational diabetes. Their blood sugar control was comparable, they gained similar amounts of weight during pregnancy, and their babies had similar birthweights. Both groups of women responded equally well to the reduced-calorie diet, meaning that having PCOS didn’t make the diet less effective.

The one notable difference was in neonatal jaundice (yellowing of a newborn’s skin). Babies born to mothers with PCOS had jaundice more often (24.4% of cases) compared to babies born to mothers without PCOS (8.9% of cases). This difference was statistically significant, meaning it’s unlikely to have happened by chance.

When researchers adjusted their analysis to account for other factors like how high the mothers’ blood sugar was and their BMI, PCOS was still not associated with worse outcomes for most measures. This suggests that the severity of blood sugar problems and weight may be more important than having PCOS itself.

The dietary intervention results were particularly interesting: women in both the reduced-calorie and standard-calorie diet groups had similar outcomes, and this was true whether or not they had PCOS. This suggests that structured dietary guidance may be helpful regardless of which specific calorie level is recommended.

Beyond the main findings, the study looked at several other outcomes. Maternal weight changes during pregnancy were similar between the PCOS and non-PCOS groups. Continuous glucose monitoring data (which measures blood sugar throughout the day) showed comparable patterns in both groups. The study also examined physical activity and dietary adherence, and these were similar between groups. Infant birthweight, which is an important indicator of baby health, did not differ significantly between the two groups.

Previous research suggested that PCOS might increase the risk of worse pregnancy outcomes in women with gestational diabetes because PCOS is associated with insulin resistance (the body’s difficulty using insulin effectively) and higher body weight. This study’s findings are somewhat reassuring because they suggest that when blood sugar levels and weight are similar, having PCOS alone doesn’t necessarily lead to worse outcomes. However, the finding about increased jaundice in babies of mothers with PCOS is new and suggests there may be specific mechanisms related to PCOS that affect newborn health in ways not fully explained by blood sugar or weight alone.

Several limitations should be considered when interpreting these results. First, only 50 women in the study had PCOS, which is a relatively small number. This means some findings about the PCOS group may not be as reliable as findings about the larger non-PCOS group. Second, all participants were from the UK and had a BMI of 25 or higher, so results may not apply to pregnant women in other countries or those with lower BMI. Third, the study only included women who were enrolled around 29 weeks of pregnancy, so it doesn’t tell us about earlier pregnancy outcomes. Finally, while the study found an association between PCOS and neonatal jaundice, it doesn’t explain why this happens, so more research is needed to understand this connection.

The Bottom Line

If you have PCOS and develop gestational diabetes during pregnancy, you should follow the same dietary and medical management recommendations as women with gestational diabetes alone. Working with a dietitian to manage your diet and blood sugar is important. You should be aware that your baby may have a slightly higher risk of jaundice, so discuss this with your healthcare provider and ensure your newborn is monitored for this condition after birth. The evidence suggests that controlling blood sugar levels and managing weight gain are the most important factors for good outcomes. (Confidence level: Moderate - based on a well-designed study, but with a relatively small PCOS group)

This research is most relevant to: pregnant women with PCOS who develop gestational diabetes, healthcare providers caring for these women, and women planning pregnancy who have PCOS. Women with PCOS but without gestational diabetes may find this information interesting but it’s less directly applicable. The findings are less relevant to women without PCOS or those with PCOS who don’t develop gestational diabetes during pregnancy.

If you implement dietary changes to manage gestational diabetes, you may see improvements in blood sugar control within days to weeks. Weight changes typically become noticeable over several weeks. The benefits for your baby’s health develop throughout the remainder of your pregnancy, so consistent management from the time of diagnosis until delivery is important. Neonatal jaundice, if it occurs, typically appears within the first few days after birth and can be treated effectively.

Want to Apply This Research?

  • Track daily blood sugar readings (fasting and after meals), daily weight, and dietary intake (especially carbohydrate portions). For women with PCOS and gestational diabetes, monitoring these three metrics together helps identify patterns and shows whether dietary changes are working effectively.
  • Use the app to log meals and snacks at consistent times each day, aiming for the calorie target recommended by your healthcare provider. Set reminders for blood sugar testing at the same times daily. Track your weight weekly at the same time of day. This creates accountability and helps you see how food choices affect your blood sugar.
  • Over the long term, use the app to identify which foods and meal patterns keep your blood sugar most stable. Share weekly summaries with your healthcare provider to adjust your plan if needed. After delivery, continue tracking for a few weeks to monitor for postpartum changes. If you plan future pregnancies, this historical data will be valuable for your healthcare team.

This research summary is for educational purposes only and should not replace professional medical advice. If you have PCOS, are pregnant, or have been diagnosed with gestational diabetes, consult with your obstetrician, endocrinologist, or healthcare provider before making any changes to your diet, exercise routine, or medical treatment. The findings from this study apply specifically to pregnant women with gestational diabetes and BMI ≥25 kg/m² and may not apply to all individuals. Neonatal jaundice, while more common in babies of mothers with PCOS in this study, is generally treatable and should be monitored by your healthcare team. Always follow your healthcare provider’s individualized recommendations for your specific situation.