In our study population, a significant number of women with EOT2D experienced CMO or CFO, emphasizing that almost half of women with CMO also had CFO. Interestingly, pregnant women with EOT2D but without CMO were prone not to have newborns with CFO. Analyzing social determinants of pregnant women with EOT2D and CMO, the majority of them lived in suburban areas. Regarding metabolic parameters, pregnant women with EOT2D and CMO had worse HbA1c both in preconception and in the first trimester of pregnancy. Focusing on CFO in pregnant women with EOT2D, we observed unsatisfactory metabolic control from preconception until second trimester and higher GWG in late pregnancy. Furthermore, regression analysis revealed that level of pHbA1c and HbA1c in first in conjunction with second trimester and type of community were predictors of CMO. Moreover, pHbA1c and occurrence of CMO were also identified as predictors of CFO in pregnant women with EOT2D.

Interestingly, it has been shown that pregnancies complicated by T2D may have comparable rates of the most common adverse maternal and fetal pregnancy outcomes as seen in T1D [19], while prior published meta-analyses indicated lower incidence of certain outcomes, except perinatal mortality in pregnancy complicated by T2D.

In our study, almost half of the pregnant women with EOT2D had some form of CMO, CFO, or even both, while the frequency of adverse pregnancy outcomes was almost comparable to the results of previous studies. In contrast, a large UK-based cohort study, which included a more substantial sample size, reported a lower incidence of PD and a higher percentage of LGA babies compared with our findings. While perinatal mortality is a key concern in pregnancies complicated by T2D, our study did not detect any cases, likely owing to the small sample size.

According to our findings, the majority of women with EOT2D and CMO lived in suburban areas, while those without CMO predominantly lived in rural communities. While previous research indicates that unfavorable social determinants may influence adverse pregnancy outcomes [20, 21], we did not conduct a more detailed analysis. It could be speculated whether socioeconomic deprivation predisposes individuals to poor pregnancy outcomes per se or exacerbates them owing to higher metabolic risk.

Moreover, previous studies have shown that preconception obesity is associated with increased rates of GH, PE, E, PD, CS, macrosomia, and LGA in pregnant women with T2D [22, 23]. Other studies suggest that pregnant women with T2D and overweight and obesity are more prone to having only LGA newborns [24, 25]. In our study, preconception obesity did not emerge as an independent predictor in the regression analysis or group analysis, which may reflect the current sample size.

It has been shown that GWG plays an important role in the risk of adverse outcomes in T2D pregnancies. A recent study demonstrated an association between excessive GWG and a higher risk of GH, CS, and macrosomia. Nevertheless, most studies analyze absolute GWG in the context of excessive, recommended, or insufficient throughout pregnancy, without trimester-specific estimation [25,26,27]. Having this in mind, we aimed to report the trimester-specific GWG from preconception to delivery, with limitations related to potential confounders. In this respect, GWG in the second and third trimesters of pregnancy was higher among pregnant women with EOT2D and CFO.

A prior study showed that the first and the last trimester HbA1c were the main critical factors related to maternal and fetal outcomes in women with T2D [24]. In that context, our results partially differ by indicating preconception HbA1c and first and second trimester HbA1c as predictors of CMO in women with EOT2D. In contrast, women with EOT2D and CFO had continuously worse glycemic control from preconception until the third trimester, which might help assessing the risk at the time of delivery.

It has been reported that poor preconception HbA1c in pregestational T2D is a predictor of impairment of glycemic control during pregnancy and associated with some of the adverse pregnancy outcomes (PD and lower birth weight) [28]. In our study, preconception glycemic control was important for both CMO and CFO, in contrast to glycemic control during the trimesters. However, we can assume that on the basis of the odds ratio, the value of pHbA1c could be more significant in prediction of CFO than CMO in women with EOT2D.

There is limited evidence regarding trimester-specific effects of hyperglycemia on maternal and fetal outcomes in pregnant women with EOT2D. It is important to emphasize that we estimated metabolic control by trimester, unlike other studies on this topic that most often evaluated the percentage of pregnant women with T2D who achieved target metabolic control [25]. We sought to clarify whether there are differences in the length of exposure to hyperglycemia on adverse maternal and fetal outcomes separately in pregnancies complicated by EOT2D. According to Pederson’s hypothesis, hyperglycemia in pregnancy may have short- and long-term effects on fetal outcomes through “fuel-mediated teratogenesis” [29, 30]. It was previously confirmed that poor glycemic control in the first trimester increases the risk for the development of congenital malformations, while hyperglycemia in late pregnancy leads to unfavorable anthropometric and metabolic outcomes [24, 28, 31]. Bearing in mind that in our study we analyzed not separate fetal entities but CFO, it is not surprising that women with EOT2D and CFO had worse metabolic control throughout the first and second trimesters of pregnancy.

Although it was not possible to analyze the effect of different antihyperglycemic treatment on CMO and CFO due to sample size, more than half of the women with EOT2D were on metformin monotherapy before conception, and over two-thirds of pregnant women required intensification of insulin therapy during pregnancy.

Our study has limitations, including the rather small sample size and study design. Moreover, we acknowledge all the disadvantages related to HbA1c as a metabolic parameter in pregnancy. However, the major strength of our pilot study is the longitudinal follow-up of women with EOT2D from preconception until delivery.