## 2 Methods
### Exposure and Field Measurements  
Details of reverberating chambers are described by [PERSON] et al. [24]. Briefly, RF-EMF exposures were performed in 3 reverberation chambers commercialized by ITIS Foundation (Zurich, Switzerland) [25]. A signal generator (SMIQ02B generator, Rohde and Schwarz Munich, Germany) produced a 900 MHz band RF-EMF (continuous waves). It was coupled with amplifiers (700 MHz-2200 MHz TE UMS 015 AA, Zurich, Switzerland) and with 3 log-periodic antennas manufactured by SPEAG. The antennas were directed to one of the two stirrs (vertical and horizontal) for good RF-EMF signal homogeneity. The exposure to the electromagnetic field (EMF) was monitored with two probes (ER3 DVS, SPEAG, Zurich, Switzerland). The rats were free to move in their cages during the 900 MHz RF-EMF exposure from the generator. ITIS Foundation performed  
Figure 1: Experimental design. From gestational day (GD 8 until postnatal day (PND) 17, the rats were daily exposed to 900 MHz radiofrequency (RF) from 11:00 a.m. to 7:00 p.m. of 0 (sham-exposed group), 30.2 V/m electric field and 0.08 W/kg (PuM: whole-body limits of the general public applied to mother rats), or 67.5 V/m electric field and 0.4 W/kg (OcM: whole-body occupational limits applied to mother rats). The dam’s body weight was assessed from GD 8 until PND 22, and food consumption was assessed from GD 9 until PND 20.  
the dosimetry using the finite difference time domain (FDTD) method as previously described [26]. Exposures were off anytime the investigators had to open the exposure apparatus doors to manipulate, weigh, check the rats, and check the system (before 11 a.m. or after 7 p.m.). To determine the SAR in rats at mobile phone frequencies, a simplified 12-plane wave model for the average exposure in a reverberation chamber was used in conjunction with a variety of anatomical rat model within the FDTD solver in SEMCAD X (SPEAG, Switzerland). The measurement indicates a variation of 0.2 dB standard deviation for the E-Field strength.  
Exposure was set at 30.2 V/m and 67.5 V/m EF to reach 0.08 W/kg (PuM group) and 0.4 W/kg (OcM group) for the wbSAR of a 330 g adult rat. The corresponding postnatal pups wbSAR were deduced from extraction from the exposure software with theoretical weights (Figure 2) or from the approximation formula from [PERSON] et al. [27] with measured weight of pups or mothers (Figures 2 and 3). The wbSAR of a 10 g pump was approximately 0.12 W/kg and 0.024 W/kg when its 330 g mother was exposed at 0.4 W/kg (EF: 67.5 V/m) or 0.08 W/kg (EF: 30.2 V/m), respectively. The wbSAR then grew with the body weight and reached, respectively, 0.4 or 0.08 W/kg when the pups weighed 45 g around the age of 14 days. The wbSAR peak for the pups was reached at PND 27 (weight around 100 g) with approximately 0.90 W/kg and 0.20 W/kg, respectively, for the OcM and PuM groups.  
Figure 3: Effects of pre- and postnatal 900 MHz exposure on the mothers’ body weight (**a**) and on the litter food intake (**b**). * \(p\) < 0.05 between the OcM and sham group, \({}^{\circ}\)_p_ < 0.05 between the PuM and sham group. n = 8–9/group. wbSAR was calculated numerically with an approximation formula. Left Y axis indicates the weight in grams for the sham, PuM, and OcM groups. Right Y axis indicates the wbSAR evolution in W/kg.  
Figure 2: Estimate of the wbSAR in the pups and mothers showed linear growth before a peak at 100 g body weight (around PND 27) followed by a linear decrease with 0.4 W/kg and 0.08 W/kg attained for 330 g body weight. The wbSAR was calculated for the pups (**a**) and mothers (**b**) on a “coupling factor” dependent on the animal’s body weight.