The Optimal Prepregnancy Body Mass Index for Lactation in Japanese Women with Neonatal Separation as Analyzed by a Differential Equation.

We used a differential equation to identify the biological relationship between the maternal prepregnancy body mass index (BMI) and lactation on postpartum day 4 in Japanese women with neonatal separation. This retro-spective observational study included 252 mothers (135 primiparas, 117 multiparas) whose singleton neonates were admitted to a neonatal ICU. We formulated hypotheses based on breast anatomy to analyze the relation-ship between the expressed milk obtained on postpartum day 4 and the maternal prepregnancy BMI with the following differential equation: y'(x) = k y(x)/x, where k is the constant, x is the prepregnancy BMI, and y is the expressed milk volume. The formula was then obtained as y(x) = axk, where a is the constant. The Akaike information criterion (AIC) was used to estimate the regression equation with the maximum likelihood for primiparas and multiparas. The best criteria for BMI determined by the AIC were 20.89 kg/m2 in primiparas and 20.19 kg/m2 in multiparas. These were the optimal BMI values for lactation, coinciding with the median prepregnancy BMI in the study population (20.78 kg/m2 in primiparas and 20.06 kg/m2 in multiparas). The formula based on biomathematics might help establish the biological relationship between prepregnancy BMI and breastmilk volume.

High-intensity breastfeeding improves insulin sensitivity during early post-partum period in obese women with gestational diabetes.

AIM: To investigate whether high-intensity breastfeeding (HIB) reduces insulin resistance during early post-partum period in women with gestational diabetes (GDM), independent of post-partum weight change (PWC). MATERIALS AND METHODS: In this multicentre prospective study, we included Japanese women with GDM who underwent a 75-g oral glucose tolerance test (OGTT) during early post-partum. We measured plasma insulin during OGTT to obtain a homeostasis model of assessment of insulin resistance (HOMA-IR). We defined the condition in which infants were fed by breastfeeding alone or greater than or equal to 80% of the volume as HIB, and other statuses, including partial and nonbreastfeeding, as non-HIB. We investigated the association between post-partum HOMA-IR and the breastfeeding status after adjusting for confounders including PWC. RESULTS: Among 222 women with GDM who underwent the OGTT at 7.9 ± 2.3 weeks post-partum with a PWC of -7.8 ± 3.4 kg, although the rate of abnormal glucose tolerance (prediabetes and diabetes) did not differ between the groups (33% vs 32%), the HOMA-IR in the HIB women (n = 166) was significantly lower than that in the non-HIB women (n = 56) (1.12 ± 0.85 vs 1.72 ± 1.43, P = 0.0002). The effect of the HIB was independently associated with lower HOMA-IR after adjusting for confounders including PMC. However, the subgroup analysis according to their pre-pregnancy obesity states showed that the effect was seen only in the obese subjects (BMI ≥ 25). CONCLUSIONS: In obese Japanese women with GDM, HIB has a significant effect in reducing insulin resistance during early post-partum, independent of the post-partum weight loss.